Estimation of Annual and Seasonal Water Surplus for Five New Regions in Ontario to Identify Critical Regions for Water Quality Monitoring

Transcription

1 Estimation of Annual and Seasonal Water Surplus for Five New Regions in Ontario to Identify Critical Regions for Water Quality Monitoring SES Tech Memo

2 Estimation of Annual and Seasonal Water Surplus for Five New Regions in Ontario to Identify Critical Regions for Water Quality Monitoring H. Dadfar, D.J. Fallow, D.M. Brown, G.W. Parkin, J.D. Lauzon and R. J. Gordon School of Environmental Sciences, O.A.C. University of Guelph Guelph, Ontario. N1G 2W1 July, 2010 School of Environmental Sciences Technical Memo No ii

3 Copies of this publication are available for $15.00 per hard copy, or $5.00 per CD copy from: School of Environmental Sciences, OAC University of Guelph Guelph, Ontario N1G 2W1 or from the School of Environmental Sciences website digital data bank under Soil Water Balance. Published by the- School of Environmental Sciences, OAC University of Guelph Guelph, Ontario N1G 2W1 SES Contribution No Cover Credits: The water balance diagram was constructed by Humaira Dadfar, Research Associate, School of Environmental Sciences, O.A.C., University of Guelph. The two agricultural land surface photographs were provided by Dr. R.L. Thomas, retired from the former Dept. of Land Resource, O.A.C., University of Guelph. The image of the flooding caused by Hurricane Hazel supplied by Dr H. Whiteley, retired from the School of Engineering, University of Guelph. iii

4 Table of Contents Introduction 1 Description and General Inputs for the SHAW and DRAINMOD Models 2 DRAINMOD Model Background Site Characteristic Inputs Soil Temperature Inputs Volumetric Water Content Inputs Climate Inputs Crop Inputs Drainage System Design Site Specific Inputs 4 Site Specific Soil Inputs Soil Characteristics of a Pontypool Sand Site Specific Climate Inputs Site Specific Drainage System Design Site Specific Crop Inputs Data Output and Presentation 11 DRAINMOD Water Balance File Data Presentation Results and Discussion 12 Annual Water Balance Comparison of Annual Water Balance for Two Different Soil Types Monthly Values of Water Balance Components Comparison of the Year to Year Water Balance Components between Two Soil Types Comparison in the differences of Water Balance Components between the Two Soils for Individual Years ) Two years with similar total annual precipitation but contrasting monthly precipitation and water balance components ) Comparison of the water balance components for the two soils for two years with considerable differences in total annual precipitation 33 Variability in Water Surplus Seasonal Water Surplus Some Limitations of the two Models used in this study iv

5 Summary and Conclusions 43 References 44 Appendices Appendix A Appendix B Appendix C Appendix D Appendix E List of Tables Table 1 A comparison of the main attributes of SHAW and DRAINMOD... 2 Table 2 Location and Ontario climate region of the study sites Table 3 Horizon depths, hydraulic properties and percentage of each texture class for each horizon of the typical soil type in the area of the five study sites, a) through e). a) London... 6 b) Peterborough c) Renfrew d) Vineland e) Wiarton Table 4 Soil series, profile and soil hydraulic properties for a Pontypool sand... 7 Table 5 The average dates of occurrence of key stages in growth of corn at each of the study locations Table 6 Maximum values of crop height, leaf width, leaf area index, root depth and average accumulated crop heat units (AACHU) used as DRAINMOD model inputs for each study site Table 7 Maximum dry biomass used for year 2001 and the intercept value for the linear relationship shown from 1954 to 2001 in Figure 2 for the five study sites used as inputs for the SHAW Model.. 9 Table 8 Average ± standard deviation of annual measured precipitation, and water balance components derived from the SHAW and DRAINMOD models for a typical soil profile at each of the five sites Table 9 Average ± standard deviation of annual water balance components derived from the DRAINMOD model for a Pontypool sand profile at five sites in Ontario.. 20 v

6 Table 10 Table 11 Table 12 Number of years that measured precipitation and DRAINMOD model estimated deep drainage and runoff exceeded the specified limits at five Ontario sites for the typical and Pontypool sand soil types for 1954 to 2001 period Average seasonal totals for measured precipitation, and DRAINMOD model simulated evapo-transpiration, deep drainage, runoff and total water surplus for the typical soil type at all sites for the 48-year study period Average seasonal totals for measured precipitation, and DRAINMOD model simulated evapo-transpiration, deep drainage, runoff and total water surplus for the Pontypool sand soil type at all sites for the 48- year study period.. 41 Appendix A Table A-1 Table A-2 Table A-3 Table A-4 Table A-5 Table A-6 Location where climate elements were recorded at each of the primary climate sites Summary corn growth cycle inputs for the SHAW and DRAINMOD models for London Summary corn growth cycle inputs for the SHAW and DRAINMOD models for Peterborough Summary corn growth cycle inputs for the SHAW and DRAINMOD models for Renfrew Summary corn growth cycle inputs for the SHAW and DRAINMOD models for Vineland Summary corn growth cycle inputs for the SHAW and DRAINMOD models for Wiarton Appendix B Table B-1a Table B-1b Table B-2a Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for London for a typical soil profile Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for London for a Pontypool sand soil profile Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Peterborough for a typical soil profile vi

7 Table B-2b Table B-3a Table B-3b Table B-4a Table B-4b Table B-5a Table B-5b Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Peterborough for a Pontypool sand soil profile Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Renfrew for a typical soil profile Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Renfrew for a Pontypool sand soil profile Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Vineland for a typical soil profile Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Vineland for a Pontypool sand soil profile Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Wiarton for a typical soil profile Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Wiarton for a Pontypool sand soil profile Appendix C Table C-1 Summary of monthly averages ( ) of measured precipitation, and DRAINMOD estimated evapo-transpiration, deep drainage, runoff and water surplus for a typical soil and a Pontypool sand for London. a) London monthly precipitation b) London monthly estimated evapo-transpiration with a typical soil profile.. 70 c) London monthly estimated deep drainage with a typical soil profile.. 70 d) London monthly estimated runoff with a typical soil profile e) London monthly estimated water surplus with a typical soil profile f) London monthly estimated evapo-transpiration with a Pontypool sand soil profile g) London monthly estimated deep drainage with a Pontypool sand soil profile vii

8 Table C-2 Table C-3 h) London monthly estimated runoff with a Pontypool sand soil profile.. 71 i) London monthly estimated water surplus with a Pontypool sand soil profile.. 71 Summary of monthly averages ( ) of measured precipitation, and DRAINMOD estimated evapo-transpiration, deep drainage, runoff and water surplus for a typical soil and a Pontypool sand for Peterborough. a) Peterborough monthly precipitation b) Peterborough monthly estimated evapo-transpiration with a typical soil profile c) Peterborough monthly estimated deep drainage with a typical soil profile d) Peterborough monthly estimated runoff with a typical soil profile e) Peterborough monthly estimated water surplus with a typical soil profile.. 72 f) Peterborough monthly estimated evapo-transpiration with a Pontypool sand soil profile g) Peterborough monthly estimated deep drainage with a Pontypool sand soil profile h) Peterborough monthly estimated runoff with a Pontypool sand soil profile.. 73 i) Peterborough monthly estimated water surplus with a Pontypool sand soil profile Summary of monthly averages ( ) of measured precipitation, and DRAINMOD estimated evapo-transpiration, deep drainage, runoff and water surplus for a typical soil and a Pontypool sand for Renfrew. a) Renfrew monthly precipitation b) Renfrew monthly estimated evapo-transpiration with a typical soil profile.. 74 c) Renfrew monthly estimated deep drainage with a typical soil profile.. 74 d) Renfrew monthly estimated runoff with a typical soil profile e) Renfrew monthly estimated water surplus with a typical soil profile.. 74 f) Renfrew monthly estimated evapo-transpiration with a Pontypool sand soil profile viii

9 Table C-4 Table C-5 g) Renfrew monthly estimated deep drainage with a Pontypool sand soil profile h) Renfrew monthly estimated runoff with a Pontypool sand soil profile.. 75 i) Renfrew monthly estimated water surplus with a Pontypool sand soil profile Summary of monthly averages ( ) of measured precipitation, and DRAINMOD estimated evapo-transpiration, deep drainage, runoff and water surplus for a typical soil and a Pontypool sand for Vineland. a) Vineland monthly precipitation b) Vineland monthly estimated evapo-transpiration with a typical soil profile c) Vineland monthly estimated deep drainage with a typical soil profile d) Vineland monthly estimated runoff with a typical soil profile e) Vineland monthly estimated water surplus with a typical soil profile f) Vineland monthly estimated evapo-transpiration with a Pontypool sand soil profile g) Vineland monthly estimated deep drainage with a Pontypool sand soil profile h) Vineland monthly estimated runoff with a Pontypool sand soil profile.. 77 i) Vineland monthly estimated water surplus with a Pontypool sand soil profile Summary of monthly averages ( ) of measured precipitation, and DRAINMOD estimated evapo-transpiration, deep drainage, runoff and water surplus for a typical soil and a Pontypool sand for Wiarton. a) Wiarton monthly precipitation b) Wiarton monthly estimated evapo-transpiration with a typical soil profile c) Wiarton monthly estimated deep drainage with a typical soil profile.. 78 d) Wiarton monthly estimated runoff with a typical soil profile e) Wiarton monthly estimated water surplus with a typical soil profile ix

10 f) Wiarton monthly estimated evapo-transpiration with a Pontypool sand soil profile g) Wiarton monthly estimated deep drainage with a Pontypool sand soil profile h) Wiarton monthly estimated runoff with a Pontypool sand soil profile.. 79 i) Wiarton monthly estimated water surplus with a Pontypool sand soil profile Appendix D Table D-1 Table D-2 Table D-3 Table D-4 Table D-5 Summary of differences in DRAINMOD model estimated annual totals of water balance components for a Pontypool sand soil profile as compared to the typical soil type at London Summary of differences in DRAINMOD model estimated annual totals of water balance components for a Pontypool sand soil profile as compared to the typical soil type at Peterborough Summary of differences in DRAINMOD model estimated annual totals of water balance components for a Pontypool sand soil profile as compared to the typical soil type at Renfrew Summary of differences in DRAINMOD model estimated annual totals of water balance components for a Pontypool sand soil profile as compared to the typical soil type at Vineland Summary of differences in DRAINMOD model estimated annual totals of water balance components for a Pontypool sand soil profile as compared to the typical soil type at Wiarton.. 90 Appendix E Table E-1a Table E-1b Table E-1c Annual precipitation and DRAINMOD model estimated water balance components for the winter months (December, January, February and March) for London Annual precipitation and DRAINMOD model estimated water balance components for the spring months (April and May) for London Annual precipitation and DRAINMOD model estimated water balance components for the summer months (June, July and August) for London.. 96 x

11 Table E-1d Table E-2a Table E-2b Table E-2c Table E-2d Table E-3a Table E-3b Table E-3c Table E-3d Table E-4a Table E-4b Table E-4c Table E-4d Annual precipitation and DRAINMOD model estimated water balance components for the fall months (September, October and November) for London.. 97 Annual precipitation and DRAINMOD model estimated water balance components for the winter months (December, January, February and March) for Peterborough Annual precipitation and DRAINMOD model estimated water balance components for the spring months (April and May) for Peterborough Annual precipitation and DRAINMOD model estimated water balance components for the summer months (June, July and August) for Peterborough Annual precipitation and DRAINMOD model estimated water balance components for the fall months (September, October and November) for Peterborough Annual precipitation and DRAINMOD model estimated water balance components for the winter months (December, January, February and March) for Renfrew Annual precipitation and DRAINMOD model estimated water balance components for the spring months (April and May) for Renfrew Annual precipitation and DRAINMOD model estimated water balance components for the summer months (June, July and August) for Renfrew Annual precipitation and DRAINMOD model estimated water balance components for the fall months (September, October and November) for Renfrew Annual precipitation and DRAINMOD model estimated water balance components for the winter months (December, January, February and March) for Vineland Annual precipitation and DRAINMOD model estimated water balance components for the spring months (April and May) for Vineland. 113 Annual precipitation and DRAINMOD model estimated water balance components for the summer months (June, July and August) for Vineland Annual precipitation and DRAINMOD model estimated water balance components for the fall months (September, October and November) for Vineland xi

12 Table E-5a Table E-5b Table E-5c Table E-5d Annual precipitation and DRAINMOD model estimated water balance components for the winter months (December, January, February and March) for Wiarton Annual precipitation and DRAINMOD model estimated water balance components for the spring months (April and May) for Wiarton Annual precipitation and DRAINMOD model estimated water balance components for the summer months (June, July and August) for Wiarton Annual precipitation and DRAINMOD model estimated water balance components for the fall months (September, October and November) for Wiarton List of Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Map of the five new locations with the five original Southern Ontario locations Yearly corn dry biomass values in Ontario from 1908 to 2000 (OMAF, 2001) Averages of annual measured precipitation and annual water balance components derived from the DRAINMOD model for a typical soil profile at five sites in Ontario.. 13 Percentage of the total annual measured precipitation and DRAINMOD model values for evapo-transpiration, runoff and deep drainage for a typical soil profile at five sites in Ontario. [The actual model estimated values of water (in mm) appear in each bar with the total average annual precipitation (in mm) provided in brackets below the site name.] Annual measured precipitation and DRAINMOD simulated evapotranspiration, deep drainage and runoff for the 1954 to 2001 period using the typical soil type at London. The arrow on the y-axis indicates the mean annual precipitation for the site xii

13 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Annual measured precipitation and DRAINMOD simulated evapotranspiration, deep drainage and runoff for the 1954 to 2001 period using the typical soil type at Peterborough. The arrow on the y-axis indicates the mean annual precipitation for the site Annual measured precipitation and DRAINMOD simulated evapotranspiration, deep drainage and runoff for the 1954 to 2001 period using the typical soil type at Renfrew. The arrow on the y-axis indicates the mean annual precipitation for the site Annual measured precipitation and DRAINMOD simulated evapotranspiration, deep drainage and runoff for the 1954 to 2001 period using the typical soil type at Vineland. The arrow on the y-axis indicates the mean annual precipitation for the site Annual measured precipitation and DRAINMOD simulated evapotranspiration, deep drainage and runoff for the 1954 to 2001 period using the typical soil type at Wiarton. The arrow on the y-axis indicates the mean annual precipitation for the site Averages of annual measured precipitation and annual water balance components derived from the DRAINMOD model for a Pontypool Sand soil profile at five sites in Ontario.. 21 Percentage of the total annual measured precipitation and DRAINMOD model values for evapo-transpiration, runoff and deep drainage for a Pontypool sand soil profile at five sites in Ontario. The actual model estimated values of water (in mm) appear in each bar with the total average annual precipitation (in mm) provided in brackets below the site name.. 22 Comparison of the average monthly evapo-transpiration (a), deep drainage (b) and runoff (c) for the typical soil and the Pontypool soil profile at London. The yearly averages are given in brackets beside soil type in the legend.. 23 Comparison of the average monthly evapo-transpiration (a), deep drainage (b) and runoff (c) for the typical soil and the Pontypool soil profile at Peterborough. The yearly averages are given in brackets beside soil type in the legend Comparison of the average monthly evapo-transpiration (a), deep drainage (b) and runoff (c) for the typical soil and the Pontypool soil profile at Renfrew. The yearly averages are given in brackets beside soil type in the legend Comparison of the average monthly evapo-transpiration (a), deep drainage (b) and runoff (c) for the typical soil and the Pontypool soil profile at Vineland. The yearly averages are given in brackets beside soil type in the legend xiii

14 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Comparison of the average monthly evapo-transpiration (a), deep drainage (b) and runoff (c) for the typical soil and the Pontypool soil profile at Wiarton. The yearly averages are given in brackets beside soil type in the legend Effective profile saturated hydraulic conductivities for the five typical soils and the Pontypool sand soil profile. Name and surface texture of soil profile used with effective saturated hydraulic conductivity in brackets Monthly recorded precipitation for 1959 and 2000, and DRAINMOD model estimated evapo-transpiration for the typical soil (Renfrew silty clay) and a Pontypool sand for 1959 (b) and 2000 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend.. 30 Monthly recorded precipitation for 1959 and 2000, and DRAINMOD model estimated deep drainage for the typical soil (Renfrew silty clay) and a Pontypool sand for 1959 (b) and 2000 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend Monthly recorded precipitation for 1959 and 2000, and DRAINMOD model estimated runoff for the typical soil (Renfrew silty clay) and a Pontypool sand for 1959 (b) and 2000 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend. 32 Monthly recorded precipitation for 1972 and 2001, and DRAINMOD model estimated evapo-transpiration for the typical soil (Renfrew silty clay) and a Pontypool sand for 1972 (b) and 2001 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend.. 34 Monthly recorded precipitation for 1972 and 2001, and DRAINMOD model estimated deep drainage for the typical soil (Renfrew silty clay) and a Pontypool sand for 1972 (b) and 2001 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend.. 35 Monthly recorded precipitation for 1972 and 2001, and DRAINMOD model estimated runoff for the typical soil (Renfrew silty clay) and a Pontypool sand for 1972 (b) and 2001 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend. 36 Appendix D Figure D-1 Differences in annual DRAINMOD model simulated evapotranspiration, deep drainage and runoff for 1954 to 2001 period for a Pontypool sand soil profile as compared to the typical soil type at London xiv

15 Figure D-2 Figure D-3 Figure D-4 Figure D-5 Differences in annual DRAINMOD model simulated evapotranspiration, deep drainage and runoff for 1954 to 2001 period for a Pontypool sand soil profile as compared to the typical soil type at Peterborough Differences in annual DRAINMOD model simulated evapotranspiration, deep drainage and runoff for 1954 to 2001 period for a Pontypool sand soil profile as compared to the typical soil type at Renfrew Differences in annual DRAINMOD model simulated evapotranspiration, deep drainage and runoff for 1954 to 2001 period for a Pontypool sand soil profile as compared to the typical soil type at Vineland Differences in annual DRAINMOD model simulated evapotranspiration, deep drainage and runoff for 1954 to 2001 period for a Pontypool sand soil profile as compared to the typical soil type at Wiarton Appendix E Figure E-1a Figure E-1b Figure E-1c Figure E-1d Figure E-2a Figure E-2b Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the winter months (December, January, February and March) during 1954 to 2001 using the typical soil type at London Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the spring months (April and May) during 1954 to 2001 using the typical soil type at London.. 92 Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the summer months (June, July and August) during 1954 to 2001 using the typical soil type at London Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the fall months (September, October and November) during 1954 to 2001 using the typical soil type at London Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the winter months (December, January, February and March) during 1954 to 2001 using the typical soil type at Peterborough Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the spring months (April and May) during 1954 to 2001 using the typical soil type at Peterborough xv

16 Figure E-2c Figure E-2d Figure E-3a Figure E-3b Figure E-3c Figure E-3d Figure E-4a Figure E-4b Figure E-4c Figure E-4d Figure E-5a Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the summer months (June, July and August) during 1954 to 2001 using the typical soil type at Peterborough.. 99 Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the fall months (September, October and November) during 1954 to 2001 using the typical soil type at Peterborough Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the winter months (December, January, February and March) during 1954 to 2001 using the typical soil type at Renfrew Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the spring months (April and May) during 1954 to 2001 using the typical soil type at Renfrew Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the summer months (June, July and August) during 1954 to 2001 using the typical soil type at Renfrew Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the fall months (September, October and November) during 1954 to 2001 using the typical soil type at Renfrew Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the winter months (December, January, February and March) during 1954 to 2001 using the typical soil type at Vineland Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the spring months (April and May) during 1954 to 2001 using the typical soil type at Vineland Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the summer months (June, July and August) during 1954 to 2001 using the typical soil type at Vineland Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the fall months (September, October and November) during 1954 to 2001 using the typical soil type at Vineland Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the winter months (December, January, February and March) during 1954 to 2001 using the typical soil type at Wiarton xvi

17 Figure E-5b Figure E-5c Figure E-5d Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the spring months (April and May) during 1954 to 2001 using the typical soil type at Wiarton Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the summer months (June, July and August) during 1954 to 2001 using the typical soil type at Wiarton Measured precipitation and DRAINMOD model simulated evapotranspiration, deep drainage and runoff for the fall months (September, October and November) during 1954 to 2001 using the typical soil type at Wiarton xvii

18 Acknowledgments Financial support provided by the Innovation and Risk Management Branch, Ontario Ministry of Agriculture, Food and Rural Affairs and Syngenta Crop Protection was greatly appreciated. Our gratitude is extended to M. Adamson, N. MacDonald, V. Mather, J. Passmore, C. Roberts, and S. Wong. for their carefulness in assisting in updating the climate data for the five sites and in documenting the locations from which climate data were substituted for the missing data at each site. The authors also thank Sandy Radecki at Environment Canada for her assistance in collecting the climate data for this project. Peter von Bertoldi of School of Environmental Sciences, University of Guelph provided excellent computing support. xviii

19 Abstract The variability in annual and seasonal surplus water in five regions of Ontario is estimated and analyzed in this publication. Surplus water is that water resulting from precipitation (P) that runs off the land surface or drains through the soil profile eventually reaching the groundwater table. Surplus water, as either runoff (RO) or deep drainage (DD), may carry pollutants that could lead to surface water or groundwater contamination. Knowledge of the timing, amount and partitioning of surplus water in a given region of Ontario would assist in the prediction of when surface water and groundwater are more susceptible to contamination. For example, this information could potentially be used by farmers as related to their nutrient management practices. One-dimensional, deterministic models that simulated water flow in soil, including plant uptake by evapo-transpiration (ET), and freeze/thaw conditions were used to estimate the water surpluses. The two models, referred to as the Simultaneous Heat and Water (SHAW) and DRAINMOD, were applied to daily climate data from January 1, 1954 to December 31, 2001 for the recording sites in each of five climate regions. The recording sites were London, Peterborough, Renfrew, Vineland and Wiarton. A corn crop and the typical soil profile conditions for each region, with the hydraulic properties for the typical soil and a sandy soil were used as inputs for each model. The seasons were divided into winter (December, January, February and March); spring (April and May); summer (June, July and August); and fall (September, October and November). There were substantial differences in average annual and seasonal water surpluses among the five regions. The variability from year to year was great enough to warrant caution when using long-term annual values for policy formulation, etc. Most of the annual surplus water occurred in the winter and spring seasons, and in some years the surplus exceeded the precipitation in the spring season. The latter could be due to winter snow accumulations lasting into the spring season before melting. For the typical soil profile in each region most of the average water surplus in the winter and spring seasons was estimated to be RO, except DD exceeded runoff at London and Peterborough in the spring season. DD exceeded RO at all locations in the winter and spring seasons when the Pontypool sand soil type was assumed except at Renfrew in the winter season. Neither the average DD or RO were significant in the summer or fall seasons for either soil type, although some water surplus was estimated to occur in these seasons when rainfall exceeds about 300 mm. Due to the adjustments to the lower boundary water content and soil temperature conditions and the assumption of a sandy soil profile in this study, soil type had an influence on the water balance that was not as apparent in our previous studies. The most critical regions for monitoring water surplus occur in the snow-belt region east of Lake Huron and Georgian Bay, and in areas where sandy soils predominate. xix

20 Introduction Spatial and temporal variations in precipitation and soil type can result in considerable differences in water surpluses. These variations lead to fluctuations in the amount of infiltrating water moving through the soil profile to depth resulting in groundwater recharge, as well as the quantity of water ending up as surface runoff. Both of these factors influence the transport of chemicals, and their concentration in groundwater and surface waters. Studies of the chemical pollution and biological contamination of groundwater, streams and lakes require analyses of the variability in water surpluses. Most studies that describe the climate of specific geographic regions include maps of the average water surplus, which are usually based on the water balance method developed by Thornthwaite (1948). Water surplus maps have been published for regions in Canada (Chapman and Brown, 1966; Sanderson and Phillips, 1967) and for Southern and Northern Ontario (Brown et al.,1968; Chapman and Thomas, 1968; Sanderson and Phillips, 1967). A recent study by Fallow et al. (2003), used yearly climate data and the Simultaneous Heat and Water (SHAW) model (Flerchinger and Saxton, 1989a and b) to calculate the temporal variation in total flux of water through a specific depth of the soil profile for seven sites in Ontario (Emo, Guelph, Harrow, Kapuskasing, Mount Forest, Ottawa and Smithfield). Soil freezing and thawing plays an important role in determining the amount of water that drains through the soil profile and flows over the surface in Ontario, prompting the selection of the SHAW model which contains algorithms describing these phenomena. Hayhoe (1994) found fairly good agreement between SHAW estimated and observed winter soil temperatures (at specific depths), liquid and total water contents for both snow-covered and snow-cleared sites, as well as estimates of snow depth and timing and rate of snow melt. For the present study the monthly and seasonal water surplus data were estimated using the DRAINMOD computer model as a comparison of the DRAINMOD and SHAW models by Parkin et al. (2007) provided nearly identical total water surplus data for 12 sites in Ontario, and the DRAINMOD model doesn t require as much climatic data to estimate evapotranspiration (ET) as the SHAW model. The annual values of ET, deep drainage, runoff and total water surplus are based on the SHAW model output, as these values were in the Parkin et al. (2007) report and are included here for completeness. The objective of this study was to evaluate the temporal variability of water surpluses for five additional regions in southern Ontario, using the SHAW/DRAINMOD models to expand the work of Fallow et al. (2003). The climate locations selected to represent these regions were: London in the South Slopes; Vineland in the Niagara Fruit Belt; Wiarton in the Lake Huron Georgian Bay region; Peterborough in the Simcoe and Kawartha Lakes region; and Renfrew in the Renfrew region. (These regions are those named in Figure 2 in Climatological Studies # 5 by Brown et al., 1968). In the current study, the corn growth and development parameters were determined yearly based on climate data at each site. As well, the boundary input files were adjusted to contain more information from the region being studied. The daily climate data through the entire year for 48-years ( ) was used as input for these model runs in this study. 1

21 Description and General Inputs for the SHAW and DRAINMOD Models A comparison of the main attributes of SHAW and DRIANMOD models are presented in Table 1. Both models have freezing and thawing, and snowmelt components, making them suitable for use in cold regions/seasons. Table 1: A comparison of the main attributes of SHAW and DRAINMOD. Model Snow accumulation Runoff Lower boundary SHAW Modified Penman Yes P > I + DS* Variable water content Potential Evapotranspiration Water retention model Brooks- Cory (1966) DRAINMOD User input or Thornthwaite Yes P > I + DS* Impermeable boundary Brooks- Cory (1966) * I is infiltration and DS is soil surface depression storage. The description and general inputs for the SHAW model can be found in LRS Tech Memo (Fallow et al., 2003), whereas for the DRAINMOD model is presented in the following sections. DRAINMOD Model Background DRAINMOD (Skaggs, 1978) is a field scale deterministic hydrologic model based on the water balance technique for the soil surface and for a section of soil located midway between the adjacent drains extending from the soil surface to an impermeable layer. It estimates infiltration, evapo-transpiration, runoff, subsurface drainage, and seepage on hourly and daily bases for long periods of climatological record (e.g. 50 years). Recently the model was modified to include freezing and thawing, and snowmelt components to enhance its application in cold conditions (Luo et al., 2000, 2001). The model has been successfully tested and used in a wide variety of soil and climatic conditions (Gupta et al., 1993; Shukla et al., 1994; Brevé et al., 1997a; Brevé et al., 1997b; Yang, 2008; Ale et al., 2010), including cold climates (Wang et al., 2006; Yang et al., 2007; Dayyani et al., 2009). The DRAINMOD 6.0 model was used in this simulation. These simulations require climate, soil, crop, water management system design, and trafficability input parameters. Site Characteristic Inputs The saturated hydraulic conductivity (K sat ), soil water characteristic (h(θ)), and Green-Ampt equation parameters of each horizon above the restricting layer are important inputs in 2

22 DRAINMOD. The h(θ) data are used in determining the relationship between water table depth and drainage volume, upward flux, etc. In addition to the soil information file used in the hydrologic simulations, water table depth versus volume drained data for each soil layer is required by DRAINMOD-N. These files were created, based on soil water characteristics data of each site, using the soil preparation program of DRAINMOD. Soil Temperature Inputs Application of DRAINMOD for cold regions requires input data for an initial soil temperature profile, a base temperature as the lower boundary condition, diurnal phase lag of sinusoidal air temperature curve, rain/snow dividing temperature, snowmelt base temperature, degree day coefficient for snow melting, critical ice content above which infiltration stops, and the freezing characteristic curve for the top layer of the profile. These inputs were obtained from examples given with the DRAINMOD package. Volumetric Water Content Inputs Soil hydrology parameters and soil profiles used in DRAINMOD for each region are the same as those used in SHAW as given in Table 2 for the five regions. Other inputs such as maximum surface water storage to a depth of 5 mm before runoff initiation was also made equivalent to those for SHAW (Fallow et al., 2003). Climate Inputs DRAINMOD input climate data includes daily values of precipitation, maximum and minimum temperature. The climate inputs files were assembled to include daily values from January 1, 1954 to December 31, 2001, giving a climate record of 48 years for each site. The model uses the Thornthwaite (1948) method of estimating potential evapotranspiration (PET) based on input data of maximum and minimum daily air temperature. In addition to the temperature data, the parameters controlling PET values are the Thornthwaite heat index and monthly PET calibration factors. The actual evapotranspiration (AET) estimated by DRAINMOD depends on daily crop inputs and the availability of sufficient soil water storage. Monthly PET calibration factors in DRAINMOD were all set equal to 1, since these data are not available for each region. The Thornthwaite heat index was then adjusted until the average annual AET from DRAINMOD matched the SHAW derived average annual AET for the typical soil used at each site. This calibration was performed so that the average annual water surplus for DRAINMOD would be the same as that estimated by SHAW at each site. 3

23 Crop Inputs The main crop input data in DRAINMOD is the relationship between effective rooting depth and time, maximum root depth, desired planting date, and growing degree-days. Relative crop yield is estimated as a product of relative crop yields (actual yield/potential yield) resulting from excess water, drought and delayed planting stress on crop production. Drainage System Design The input data for drainage system parameters include drain spacing, depth, effective drain radius and depression storage. Site Specific Inputs The Ontario sites selected for this study were: London, Peterborough, Renfrew, Vineland, and Wiarton. The location of each site is provided in Figure 1 and Table 2. Figure 1: Map of the five new locations with the five original Southern Ontario locations. 4

24 Table 2: Location and Ontario climate region of the study sites. Site Latitude (N) Longitude (W) Elevation (m.a.s.l.) Climatic region* London 43º 01 81º m South Slopes Peterborough 44º 13 78º m Simcoe and Kawartha Lakes Renfrew 45º 29 76º m Renfrew Vineland 43º 10 79º m Niagara Fruit Belt Wiarton 44º 45 81º m Lake Huron Georgian Bay * As defined in Climate of Southern Ontario, (Brown et al.,1968). Site Specific Soil Inputs A typical soil type was selected and characterized for each study site in Table 3. The soil profile for each site was divided into three main horizons: A, B and C. Depths to the bottom of each horizon were estimated based on Table 2 of Webber and Tel (1966), Selirio et al. (1978), and based on soil survey reports as follows: 1) London from Hagerty and Kingston (1992); 2) Peterborough from Gillespie and Acton (1981); 3) Renfrew from Gillespie et al. (1964); 4) Vineland from Kingston and Presant (1989); 5) Wiarton form Hoffman and Richards (1954); and Gillespie and Richards (1954). The lowest depth considered in this application was 1.25 m. Soil hydraulic properties including the saturated hydraulic conductivity (K sat ), pore size distribution index (p.s.d.i.), air entry value, and bulk density (ρ b ) were also required for each soil horizon. Moisture release parameters were obtained from the HYDRUS 2D (Simunek et al., 1996) package based on the textural data for the van Genuchten (1980) moisture release function, and were converted to the equivalent Brooks and Corey parameters. For more information see Fallow et al. (2003) The saturated hydraulic conductivity values (K sat ) were again derived based on the typical soil type specified for each region using Webber and Tel (1966) and the HYDRUS 2D soil texture and K sat data set. The specific values for the soil layers of the typical soil profile at each site are provided in Table 3. 5

25 Table 3: Horizon depths, hydraulic properties and percentage of each texture class for each horizon of the typical soil type in the area of the five study sites, a) through e). Note: p.s.d.i. K sat ρ b pore size distribution index saturated hydraulic conductivity bulk density a) London: Bryanston Silt Loam Horizon Depth (m) p.s.d.i. Air entry (m) K sat (m s -1 ) ρ b (kg m -3 ) Porosity Sand (%) Silt (%) Clay (%) A p B m C k b) Peterborough: Otonabee Loam Horizon Depth (m) p.s.d.i. Air entry (m) K sat (m s -1 ) ρ b (kg m -3 ) Porosity Sand (%) Silt (%) Clay (%) A h B m B c C c) Renfrew: Renfrew Silty Clay Horizon Depth (m) p.s.d.i. Air entry (m) K sat (m s -1 ) ρ b (kg m -3 ) Porosity Sand (%) Silt (%) Clay (%) A h Ae B cg B t C l C k d) Vineland: Oneida Clay Horizon Depth (m) p.s.d.i. Air entry (m) K sat (m s -1 ) ρ b (kg m -3 ) Porosity Sand (%) Silt (%) Clay (%) Ap Bmj B tj C k

26 e) Wiarton: Harkaway Silt Loam Horizon Depth (m) p.s.d.i. Air entry (m) K sat (m s -1 ) ρ b (kg m -3 ) Porosity Sand (%) Silt (%) Clay (%) Ah B B C Soil Characteristics of Pontypool Sand The effects of soil type on the water balance components at each location was studied by running the DRAINMOD model with a Pontypool sand soil profile using the climate data from the five study sites. The input files for soil temperature, climate and crop were the same as used for the typical soil. The site file soil parameters were altered to incorporate the Pontypool sand soil profile properties (Table 4). A Pontypool sand soil type was selected because the typical soil types at all sites were either loam, silt loam or clay, hence using the sand soil provides new information on the surplus water for each site. Table 4: Soil series, profile and soil hydraulic properties for a Pontypool sand. Horizon Depth (m) p.s.d.i. Air entry (m) K sat (m s -1 ) ρ b (kg m -3 ) Porosity Sand (%) Silt (%) Clay (%) A h Ae B B tj C Site Specific Climate Inputs Climate records obtained from the Environment Canada archives were not complete for every day of the simulation period ( ) at all five study sites. Missing data for one or two days were estimated using data from surrounding climate stations and averages of preceding and following days were used as a last resort. Longer term missing data (on the scale of weeks to years) was estimated with data from the nearest climate recording location (Fallow et al., 2003). The location where climate data were recorded and used at each of the five sites are summarized in Appendix A, Table A-1. 7

27 Site Specific Drainage System Design At all sites the profile effective depth to impermeable layer was set to1.2 m. The drain spacing was set to 15 m. Since DRAINMOD produces estimates of tile drainage and SHAW deep drainage, the depth to tile drains in DRAINMOD was set at 100 cm, which is close to the depth of the bottom of the soil profile used in SHAW (125 cm below ground surface). Standard 4 in. (10 cm) corrugated plastic drain tubing was chosen for this modeling as it is typically used throughout Ontario. It has been shown experimentally to offer the same resistance to inflow as a completely open tube with an effective radius between 5 mm and 20 mm, depending on opening area (Mohammed and Skaggs, 1983). As given in DRAINMOD s help file, the effective radius for 4 in. (10 cm) corrugated plastic drain tubing is 1.1 cm. In this study, the height of tile drain above the impermeable layer was 20 cm and the initial water table depth was arbitrarily assigned as 65 cm since it will have little effect on the results of this long-term modeling study. In DRAINMOD, no seepage due to field slope, vertical deep seepage, or due to lateral deep seepage was selected due to the difficulty in determining appropriate seepage parameters for each region. Hence, all of the deep drainage occurred as tile drainage. Site Specific Crop Inputs The DRAINMOD simulations were conducted with a representative corn crop at each site over a climate record of 48 ( ) years. The average initial date of planting each year was estimated from a starting point in the spring season of a daily mean temperature of 10 C at each location and the planting date was the last day of three consecutive days with a daily mean temperature equal to or greater than 12.8 C (after Brown and Bootsma, 1993) (Fallow et al., 2003; Parkin et al., 2007). The complete details of the Site Specific Crop Inputs that were entered into the SHAW and DRAINMOD computer models can be found in LRS Tech Memo (Fallow et al., 2003). Other inputs such as root growth were also made equivalent to those for SHAW; average dates of crop growth stages were used in DRAINMOD as given in Tables 5 and 6. A linear increase in root depth was assumed beginning at the average emergence date and reaching the maximum root depth of 0.9 m at the full crop cover date for all 5 regions. Harvest occurred on the average season-ending date for each region. Many of the parameter values were not available for each region, so DRAINMOD model defaults were selected (Parkin et al. 2007). For SHAW, the maximum dry biomass allowed for each year was determined through a relationship of the changes in dry biomass that occurred from year to year in Ontario as shown in Figure 1 (OMAF, 2001). A best-fit linear equation was used to account for the increasing trend in corn biomass from 1954 to The same slope was used in each case (m = ); however, the intercept was adjusted so that the maximum dry biomass values for each site in 2001 was in accordance to the growth conditions at each site (Table 7) (Fallow et al., 2003). 8

28 Table 5: The average dates of occurrence of key stages in growth of corn at each of the study locations. Site London Peterborough Renfrew Vineland Wiarton Planting day (day of year) May 11 (131) May 12 (132) May 13 (133) May 10 (130) May 17 (137) Emergence (day of year) May 23 (143) May 25 (145) May 24 (144) May 23 (143) June 1 (152) Full crop cover (day of year) July 31 (212) August 2 (214) July 31 (212) July 29 (210) August 11 (223) Beginning of senescence (day of year) September 10 (253) September 7 (250) September 2 (245) September 14 (257) September 19 (262) Season ending Date (day of year) October 7 (280) September 28 (271) September 21 (264) October 15 (288) October 18 (291) Table 6: Maximum values of crop height, leaf width, leaf area index, root depth and average accumulated crop heat units (AACHU) used as DRAINMOD or SHAW model inputs for each study site. Site Crop height (m) Leaf width (m) Leaf area index Maximum root depth (m) (AACHU) London Peterborough Renfrew Vineland Wiarton * The complete details of the Site specific Crop Inputs that were entered into the SHAW and DRAINMOD-N computer models can be found in LRS Tech. Memo (Fallow et al., 2003). Table 7: Maximum dry biomass used for year 2001 and the intercept value for the linear relationship shown from 1954 to 2001 in Figure 2 for the five study sites used as inputs for the SHAW model. Site Intercept value (kg m -2 ) Maximum dry biomass value for 2001 (kg m -2 ) London Peterborough Renfrew Vineland Wiarton

29 Figure 2: Yearly corn dry biomass values in Ontario from 1908 to 2000 (OMAF, 2001). 10

30 Data Output and Presentation DRAINMOD Water Balance File The DRAINMOD model produces daily (DAY), monthly (MON) and annual (YR) files for water balance components for the defined system. The output files contain information such as precipitation, infiltration, evapo-transpiration, drainage, runoff, depth of water stored on the surface, daily water leaving outlet, depth of water in outlet ditch, and amount of water irrigated. Data Presentation The DRAINMOD output data were arranged and summarized into bar charts, graphs and tables for different time periods. Annual totals of precipitation as well as the SHAW estimates of annual evapo-transpiration and DRAINMOD estimates of deep drainage (water in tile drains), runoff and water surplus (deep drainage + runoff) for the typical soil profile are presented graphically and in table form for each site. These results are discussed in the Annual Water Balance section, where a table of averages and standard deviations, two bar charts showing the averages for each site and the proportional distribution of annual precipitation are presented. In order to separate the effect of climate from that of soil type, each site was run again with the Pontypool sand soil profile. Water balance components are presented for comparison of the climate effects, and contrast the effect of soil type; however, values for the typical soil are more representative of the water surplus for each region. Tables of annual totals for each year are presented for all sites for this soil type. Tables of monthly totals with charts are also included to permit a closer look at the difference between the typical soil type and the Pontypool sand soil profile. Charts of the differences in evapo-transpiration, deep drainage, runoff and water surplus between the typical soil profile and the Pontypool sand soil profile are presented. Data are also summarized for the four seasons of the year. The seasons used in this study were defined as follows: Winter- Dec., Jan., Feb. and March; Spring- April and May; Summer- June, July and Aug.; and Fall- Sept., Oct. and Nov. 11

31 Results and Discussion Annual Water Balance The 48-year ( ) averages and standard deviations of annual measured precipitation (P), and SHAW and DRAINMOD estimated evapo-transpiration (ET), deep drainage (DD), runoff (RO) and water surplus for the soil type typical of the area of the climate station site for the five sites are summarized in Table 8. The DRAINMOD data are also presented in bar charts in Figure 3. The water surplus is the total of DD and RO. The 48-year average annual precipitation varied from 792 mm at Peterborough to 1002 mm at Wiarton; where the precipitation during the fall and winter seasons are very different, 215 mm in fall and 224 mm in winter at Peterborough and 301 mm in fall and 332 mm in winter at Wiarton. The SHAW model estimated more deep drainage and less runoff at Renfrew and Wiarton compared to DRAINMOD (Table 8); whereas these differences were smaller at London; no difference at Vineland; and reversed at Peterborough. These differences between the SHAW and DRAINMOD models were likely due to the way in which each model treats certain conditions as a function of texture in the soil profile. The texture of the soil types used for the London, Renfrew and Wiarton sites was a silt loam, whereas it was a loam for Peterborough and a clay for Vineland. Differences between SHAW and DRAINMOD, in terms of dividing surplus water between runoff and deep drainage, could be due to differences in infiltration calculations, freeze\thaw equations, and bottom boundary conditions. The method used for calibration of PET in DRAINMOD may also have influenced the differences between the two models shown in Table 8. The average annual estimated evapo-transpiration ranged from 572 mm at Renfrew to 711 mm at Vineland, which was related to the difference (~27 days) in the length of the growing season at Vineland. The total water surplus ranged from 133 mm at Vineland to 292 mm at Wiarton for the typical soil type in each area. Table 8: Average ± standard deviation of annual measured precipitation, and water balance components derived from the SHAW and DRAINMOD models for a typical soil profile at each of the five sites. Location Precipitation Evapotranspiration Deep drainage Runoff Water surplus London S* 954 ± ± ± ± ± 107 D** 954 ± ± ± ± ± 122 Peterborough S 792 ± ± ± ± ± 115 D 792 ± ± ± ± ± 102 Renfrew S 810 ± ± ± ± ± 70 D 810 ± ± ± ± ± 67 Vineland S 846 ± ± ± ± ± 75 D 846 ± ± ± ± ± 74 Wiarton S 1002 ± ± ± ± ± 127 D 1002 ± ± ± ± ± 101 *SHAW model; **DRAINMOD model 12

32 Water Precipitation Evapo-transpiration Deep drainage Runoff Water surplus London Peterborough Renfrew Vineland Wiarton Figure 3: Averages of annual measured precipitation and annual water balance components derived from the DRAINMOD model for a typical soil profile at five sites in Ontario. The DRAINMOD-estimated annual water balance components are presented as a percentage of the average annual precipitation for each site in Figure 4. Estimated ET accounted for: 84% of the average annual precipitation at Vineland; 76% at Peterborough; and near 70% at the other sites. The percentage of precipitation resulting in water surplus at all sites ranged from 16 % to 29 %, with the lowest value for Vineland and highest value for Renfrew and Wiarton. Of the five sites covered in this study, the potential risk of surface water contamination is greatest in the Renfrew area, where 26% of average annual precipitation resulted in runoff and only 2% resulted in deep drainage. The greater risk at this site is related to the relatively slow hydraulic conductivity of the typical soils in the area and the relatively high amount of excess water in the water budget. The Bonnchere River, located in the vicinity of Renfrew County may be at risk of contamination by runoff. For Vineland 12% (101 mm) of average annual precipitation resulted in runoff and 4% (32 mm) resulted in deep drainage. The higher runoff may be a potential risk of water contamination for Lake Ontario. In terms of over all risk of surface water contamination from a combination of runoff and tile drainage the order from greatest risk to least risk is Wiarton > London > Renfrew > Peterborough > Vinland (Fig. 4). It is worth mentioning that the variability in annual totals of water balance components from year to year at all sites is very high as shown in Figures 5 though 9 and in Appendix B, Tables B-1a through B-5a. A region with a low estimated average potential of surface and ground water contamination, may have large runoff or deep drainage amounts in some years that present a higher potential risk than would normally be attributed to that region. 13

33 100% 90% 80% 70% % 50% 40% 30% % 10% 0% London (954) Peterborough (792) Renfrew (810) Vineland (846) Wiarton (1002) Evapo-transpiration Deep drainage Runoff Figure 4: Percentage of the total annual measured precipitation and DRAINMOD model values for evapo-transpiration, run off and deep drainage for a typical soil profile at five sites in Ontario. [The actual model estimated values of water (in mm) appear in each bar with the total average annual precipitation (in mm) provided in brackets below the site name.] 14

34 Figure 5: Annual measured precipitation and DRAINMOD simulated evapotranspiration, deep drainage and runoff for the 1954 to 2001 period using the typical soil type at London. The arrow on the y-axis indicates the mean annual precipitation for the site. 15

35 Figure 6: Annual measured precipitation and DRAINMOD simulated evapotranspiration, deep drainage and runoff for the 1954 to 2001 period using the typical soil type at Peterborough. The arrow on the y-axis indicates the mean annual precipitation for the site. 16

36 Figure 7: Annual measured precipitation and DRAINMOD simulated evapotranspiration, deep drainage and runoff for the 1954 to 2001 period using the typical soil type at Renfrew. The arrow on the y-axis indicates the mean annual precipitation for the site. 17

37 Figure 8: Annual measured precipitation and DRAINMOD simulated evapotranspiration, deep drainage and runoff for the 1954 to 2001 period using the typical soil type at Vineland. The arrow on the y-axis indicates the mean annual precipitation for the site. 18

38 Figure 9: Annual measured precipitation and DRAINMOD simulated evapotranspiration, deep drainage and runoff for the 1954 to 2001 period using the typical soil type at Wiarton. The arrow on the y-axis indicates the mean annual precipitation for the site. 19

39 Comparison of Annual Water Balance for Two Different Soil Types The 48-year averages and the standard deviations of the annual water balance for the Pontypool sand soil profile at the five sites are summarized in Table 9, and are shown as bar charts in Figure 10. The average annual ET ranged from 560 mm at Peterborough to 657 mm at Vineland when the Pontypool sand was used in DRAINMOD instead of the typical soil profile at all sites. There was a decrease in ET and RO and an increase in DD at all sites for the Pontypool sand compared to the typical soil for the area (Tables 8 and 9). For example, in London the average annual ET decreased by 60 mm and RO decreased by 131 mm, while DD increased by 195 mm when Pontypool sand soil profile was assumed to occur instead of Bryanston silt loam soil profile. The largest differences in the water surplus components were observed at Wiarton, where RO decreased by 157 mm, and DD increased by 224 mm when a Pontypool sand soil profile was assumed to occur instead of Harkaway silt loam soil profile. These results indicate that the components of water surplus, RO and DD are very dependent on soil type. The potential risk of surface and ground water contamination is affected by changes in the components of water surplus. An increase in deep drainage causes the potential risk of groundwater contamination to increase, and with a decrease in surface runoff the potential risk of surface water, and groundwater if preferential flow paths are present, decreases. The results of this study indicate that when the soil has a coarser texture the potential risk of ground water contamination increases, due to greater deep drainage, so this potential risk would increase if the Pontypool sand soil profile predominated in all five regions where the sites occurred. Although we have chosen the typical soil for each region there will be other soils such as sandy and clay soils which will influence the relative amounts of deep drainage and runoff. Table 9: Average ± standard deviation of precipitation and annual water balance components derived from the DRAINMOD model for typical soil and a Pontypool sand profiles at five sites in Ontario. Location Precipitation Evapotranspiration Deep drainage Runoff Water surplus London T* 954 ± ± ± ± ± 122 P** 954 ± ± ± ± ± 128 Peterborough T 792 ± ± ± ± ± 102 P 792 ± ± ± ± ± 102 Renfrew T 810 ± ± ± ± ± 67 P 810 ± ± ± ± ± 74 Vineland T 846 ± ± ± ± ± 74 P 846 ± ± ± ± ± 90 Wiarton T 1002 ± ± ± ± ± 101 P 1002 ± ± ± ± ± 105 *Typical soil; **Pontypool sand 20

40 The relative values for the annual ET, RO and DD at all sites and the differences that occurred due to soil type, can be observed by comparing Figures 4 and 11, which illustrate the proportion of the total annual precipitation for each of the three components on a percentage basis. Comparing these proportional percentages, a 1% decrease in average annual ET was observed for Renfrew, while at other sites there was a 5% to 6% decrease in ET when a Pontypool sand soil type was assumed. A more pronounced change in these proportional percentages occurred in the water surplus components, the DD increased 9% to 22% and the RO decreased 5% to 18% when the typical soil profile at each site was replaced with a Pontypool sand soil profile Water Precipitation Evapo-transpiration Deep drainage Runoff Water surplus London Peterborough Renfrew Vineland Wiarton Figure 10: Averages of annual measured precipitation and annual water balance components derived from the DRAINMOD model for a Pontypool Sand soil profile at five sites in Ontario. Monthly Values of Water Balance Components The average monthly amounts of ET, DD and RO for the typical soils in each area are compared with the Pontypool sand soil profile at each site as shown in Figures 12 to 16. ET was slightly higher in the winter months (Dec., Jan, Feb, March) when the Pontypool sand was assumed at each site. However, in spring (April and May) and in late summer (August) to mid fall (September and October) there was more ET with the typical soil profile as compared to the Pontypool sand soil profile. In the summer months of June and July the ET was similar at most of the sites for the Pontypool sand, except at Wiarton, where the ET in spring through mid-fall was higher for the Pontypool sand soil profile than for the Harkaway silt loam soil type. 21

41 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% London (954) Peterborough Renfrew Vineland Wiarton (792) (810) (846) (1002) Evapo-transpiration Deep drainage Runoff Figure 11: Percentage of the total annual measured precipitation and DRAINMOD model values for evapo-transpiration, run off and deep drainage for a Pontypool Sand soil profile at five sites in Ontario. The actual model estimated values of water (in mm) appear in each bar with the total average annual precipitation (in mm) provided in brackets below the site name. There was a noticeable increase in DD at all sites when the Pontypool sand was assumed, especially in winter and spring months, and there was noticeable decrease in RO using the Pontypool sand soil profile at each of the sites. During summer and fall there was very little deep drainage and runoff and the differences between the two soil types were not noticeable. Deep drainage and runoff mainly take place in winter and spring, and were most pronounced in March and April at all sites. The average monthly precipitation and DRAINMOD model estimated ET, DD, RO and total water surplus using the typical soil profile and the Pontypool sand soil profile for all five sites are provided in Appendix C, Tables C-1 through C-5. 22

42 Water a) Typical soil (690 mm) Pontypool sand (630 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water b) Typical soil (107 mm) Pontypool sand (302 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water c) Typical soil (150 mm) Pontypool sand (19 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 12: Comparison of the average monthly evapo-transpiration (a), deep drainage (b) and runoff (c) for the typical soil and the Pontypool soil profile at London. The yearly averages are given in brackets beside soil type in the legend. 23

43 Water a) Typical soil (599 mm) Pontypool sand (560 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water b) Typical soil (101 mm) Pontypool sand (176 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water c) Typical soil (90 mm) Pontypool sand (52 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 13: Comparison of the average monthly evapo-transpiration (a), deep drainage (b) and runoff (c) for the typical soil and the Pontypool soil profile at Peterborough. The yearly averages are given in brackets beside soil type in the legend. 24

44 Water a) Typical soil (572 mm) Pontypool sand (564 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water b) Typical soil (18 mm) Pontypool sand (179 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water c) Typical soil (214 mm) Pontypool sand (68 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 14: Comparison of the average monthly evapo-transpiration (a), deep drainage (b) and runoff (c) for the typical soil and the Pontypool soil profile at Renfrew. The yearly averages are given in brackets beside soil type in the legend. 25

45 Water a) Typical soil (711 mm) Pontypool sand (657 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water b) Typical soil (32 mm) Pontypool sand (154 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water c) Typical soil (101 mm) Pontypool sand (32 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 15: Comparison of the average monthly evapo-transpiration (a), deep drainage (b) and runoff (c) for the typical soil and the Pontypool soil profile at Vineland. The yearly averages are given in brackets beside soil type in the legend. 26

46 Water a) Typical soil (701 mm) Pontypool sand (644 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water b) Typical soil (130 mm) Pontypool sand (354 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water c) Typical soil (162 mm) Pontypool sand (5 mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 16: Comparison of the average monthly evapo-transpiration (a), deep drainage (b) and runoff (c) for the typical soil and the Pontypool soil profile at Wiarton. The yearly averages are given in brackets beside soil type in the legend. 27

47 Comparison of the Year To Year Water Balance Components between Two Soil Types Differences in annual simulated water balance components for each year between the typical soil and the Pontypool sand soil are shown in Appendix D, Figures D-1 to D-5 and Tables D- 1 to D-5. As seen in these Figures and Tables, there was more deep drainage estimated for the Pontypool sand soil type than for the typical soil at all sites, especially at London, Renfrew and Wiarton. This was due to higher effective saturated hydraulic conductivity in Pontypool sand (Fig. 17) compared to the typical soils. The lower water holding capacity in Pontypool sand resulted in less evapo-transpiration than the typical soil at all sites. There were significant differences between the two soil types in the amount of RO. When the Pontypool sand was assumed to occur there was always less RO, except in 1964 in Wiarton, and just for few years at Peterborough. (There is no good reason to justify this at these two sites). 1 Hydraulic Conductivity (m s -1 ) Smithfield London Peterborough Renfrew Vineland Wiarton Hydraulic conductivity decreases logarithmically in this direction 10-6 Pontypool sand Bryanston silt loam Otonabee loam Renfrew silty clay Oneida clay Harkaway silt loam ( m s -1 ) ( m s -1 ) ( m s -1 ) ( m s -1 ) ( m s -1 ) ( m s -1 ) Figure 17: Effective profile saturated hydraulic conductivities for the five typical soils and the Pontypool (used at Smithfield) sand soil profile. Name and surface texture of soil profile used with effective saturated hydraulic conductivity in brackets. 28

48 Comparison in the differences of Water Balance Components between the Two Soils for Individual Years Since the Pontypool sand was estimated to have a greater effective hydraulic conductivity than that of the Renfrew silty clay (Fig. 17), a comparison of the water balance components on a month by month basis for two individual years for the two soil types was conducted for the Renfrew site. 1) Two years with similar total annual precipitation but contrasting monthly precipitation and water balance components. The two years selected were 1959 and 2000 with nearly identical total annual precipitation of 846 mm and 841 mm, respectively, at Renfrew. Although the monthly precipitation amounts for 1959 and 2000 were quite different (Fig. 18a), the ET followed a very similar trend from month to month for both years and soil types (Figs. 18b and 18c). Monthly ET was nearly identical for both soil types except in April 2000 and in September 1959, when ET was lower for the Pontypool sand soil profile. These differences are hard to explain since there was more precipitation in March and April 2000 and in August and September Perhaps in the summer months there was sufficient water to sustain crop growth, whereas in September Pontypool sand may not have had enough water to sustain maximum evapo-transpiration due to the low hydraulic conductivity of the relatively dry sandy soil by September. These differences in ET between the Renfrew silty clay and Pontypool sand soil profiles may be partially accounted for by the depth to the water table. Typically the water table would be deeper most of the year under sandy soil; however, since an impermeable boundary was imposed below the tile drains the water table may be shallower than anticipated for the sandy soil but not by September. In fall 1958 and winter 1959, there was more precipitation compared to 2000 at Renfrew, so during the spring thaw in April 1959 a large amount of runoff was estimated for the typical soil profile. However, when a Pontypool sand was assumed the estimated amount of runoff became negligible, and considerable deep drainage was estimated in April 1959 (Figs. 19b and 20b). Similarly, in 2000 there was more runoff for the typical soil and more deep drainage for Pontypool sand (Figs. 19c and 20c). These results indicate the effect of soil type on the amounts of deep drainage and runoff in each region especially in the spring season. 29

49 Water a) Precipitation 1959 (846 mm) Precipitation 2000 (841 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water b) 1959 Typical soil (613 mm) Pontypool sand (597 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water c) 2000 Typical soil (598 mm) Pontypool sand (586 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 18: Monthly recorded precipitation for 1959 and 2000, and DRAINMOD model estimated evapo-transpiration for the typical soil (Renfrew silty clay) and a Pontypool sand for 1959 (b) and 2000 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend. 30

50 Water a) Precipitation 1959 (846 mm) Precipitation 2000 (841 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water b) 1959 Typical soil (22 mm) Pontypool sand (245 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water c) 2000 Typical soil (20 mm) Pontypool sand (130 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 19: Monthly recorded precipitation for 1959 and 2000, and DRAINMOD model estimated deep drainage for the typical soil (Renfrew silty clay) and a Pontypool sand for 1959 (b) and 2000 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend. 31

51 Water a) Precipitation 1959 (846 mm) Precipitation 2000 (841 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water b) 1959 Typical soil (247 mm) Pontypool sand (19 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water c) 2000 Typical soil (181 mm) Pontypool sand (84 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 20: Monthly recorded precipitation for 1959 and 2000, and DRAINMOD model estimated runoff for the typical soil (Renfrew silty clay) and a Pontypool sand for 1959 (b) and 2000 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend. 32

52 2) Comparison of the water balance components for the two soils for two years with considerable differences in total annual precipitation The two years selected with considerable differences in total annual precipitation were 1972 (1021 mm) and 2001 (765 mm). May, September and October 2001 had more precipitation, while in most other months 1972 had much more precipitation (Fig. 21a). These differences in precipitation had very little effect on evapo-transpiration. Most of the ET occurred from April through September in both years. Estimated ET was very similar for both soils in each month for both 1972 and 2001 and the totals were nearly identical (Figs. 21b and 21c). Referring back to the average annual amounts of ET for Pontypool sand vs. typical soil (Table 9), there is consistently less ET for Pontypool sand as expected. For 1972 and 2001, the water table under the sandy soil was shallower (data not shown) for most of the two summers, potentially explaining why the same amount of ET occurred under the two different soil types. The extra precipitation in 1972 resulted in more water surplus than in 2001 and the two soils showed the expected differences in deep drainage and runoff. The amount of deep drainage was always significantly higher for the Pontypool sand, while the amount of runoff was always markedly more for the typical soil (Figs. 22 and 23). In 1972 the water surplus (deep drainage plus runoff) mainly occurred in spring (April and May) due to spring thaw with a total water surplus of 277 mm for typical soil and 309 mm for the Pontypool sand. There was some additional water surplus in October through December, with a total water surplus of about 80 mm for typical soil and 85 mm for the Pontypool sand (Figs. 22b and 23b). In 2001 the main water surplus occurred in April due to spring thaw, with a total water surplus of over 180 mm for both soil types. Additionally, in December 2001 typical soil had 19 mm and Pontypool sand had 31 mm of total water surplus (Figs. 22c and 23c). 33

53 Water a) Precipitation 1972 (1021 mm) Precipitation 2001 (765 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water b) 1972 Typical soil (559 mm) Pontypool sand (555 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water c) 2001 Typical soil (610 mm) Pontypool sand (599 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 21: Monthly recorded precipitation for 1972 and 2001 (a), and DRAINMOD model estimated evapo-transpiration for the typical soil (Renfrew silty clay) and a Pontypool sand for 1972 (b) and 2001 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend. 34

54 Water a) Precipitation 1972 (1021 mm) Precipitation 2001 (765 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water b) 1972 Typical soil (33 mm) Pontypool sand (385 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water c) 2001 Typical soil (18 mm) Pontypool sand (208 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 22: Monthly recorded precipitation for 1972 and 2001 (a), and DRAINMOD model estimated deep drainage for the typical soil (Renfrew silty clay) and a Pontypool sand for 1972 (b) and 2001 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend. 35

55 Water a) Precipitation 1972 (1021 mm) Precipitation 2001 (765 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water b) 1972 Typical soil (324 mm) Pontypool sand (9 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Water c) 2001 Typical soil (183 mm) Pontypool sand (7 mm) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 23: Monthly recorded precipitation for 1972 and 2001 (a), and DRAINMOD model estimated runoff for the typical soil (Renfrew silty clay) and a Pontypool sand for 1972 (b) and 2001 (c) at Renfrew. The annual values are given in brackets beside soil type in the legend. 36

56 Variability in Water Surplus In addition to average ± standard deviation of the water balance components derived from the DRAINMOD model for typical soil profile (Table 8) and Pontypool sand (Table 9) at each of the five sites, the year-to-year variability for each of the water balance components is shown in Figures 5 to 9 and tabulated for each year in Appendix B, Tables B-1 through B-5. The number of years that deep drainage and runoff exceeded the specified levels for the two soil types is presented in Table 10. The potential risk of surface and ground water contamination depends on many factors. In this study the sites with a higher frequency and greater amount of deep drainage are seen as having a higher risk of groundwater contamination, whereas the ones with higher quantity and frequency of runoff are seen as having a greater risk of surface water contamination in the regions where the sites are located. Estimated deep drainage did not exceed 300 mm in any year for the typical soil profile at any of the five sites, but exceeded both the 300 mm and 400 mm levels in at least one year at all five sites and for a significant number of years at London and Wiarton for the Pontypool sand profile (Table 10). With the typical soil in each of the five regions the potential risk of groundwater contamination was estimated to be zero for all 48 years. When the Pontypool sand soil profile was assumed to occur in each of the five regions, the number of years with estimated potential risk of groundwater contamination increased and was greatest in the regions where London and Wiarton are located. No doubt this was due to the fact that total annual precipitation exceeded 1000 mm in 33% of years at London, and in 48% of years at Wiarton. At London deep drainage was estimated to exceed 300 mm in 44% of the years and exceed 400 mm in 23% of years, while in Wairton deep drainage was estimated to exceed 300 mm in 69% of the years and exceed 400 mm in 25% of years. Estimated runoff exceeded the 150 mm and 200 mm levels in more years for the typical soil than for the Pontypool sand at all five sites (Table 10). Therefore, the potential risk of surface water contamination was greatest for the typical soil type in each region. This was probably due to the Pontypool sand having a greater saturated hydraulic conductivity than the typical soil in each region (see Figure 17). The regions where London, Renfrew and Wiarton occur were estimated to be at greater risk of surface water contamination with the typical soil type. In Renfrew although the total annual precipitation exceeded 1000 mm in only 4% of years and was below 800 mm in 44 % of years, the runoff exceeded 150 mm in 85% of years and exceeded 200 mm in 60 % of years with a Renfrew silty clay soil profile. The estimated potential risk of surface water contamination for Wiarton and London were similar, where runoff exceeded 150 mm in 52% of years at Wiarton and in 48% of years at London, and exceeded 200 mm in 31% of years at Wiarton and in 29% of years at London. It is worth mentioning that in the presence of preferential flow paths such as cracks and burrows created by decaying crop roots and earthworms there will be potential risk of groundwater contamination even when runoff occurs. DRAINMOD and SHAW models do not consider preferential flow and assume that the runoff water does not enter the soil profile. The results of this study indicate that soil type has a significant influence on surface and ground water contamination. 37

57 Table 10: Number of years that measured precipitation and DRAINMOD model estimated deep drainage and runoff exceeded the specified limits at five Ontario sites for the typical and Pontypool sand soil types for 1954 to 2001 period. Deep Drainage Runoff Precipitation Typical soil Pontypool sand Typical soil Pontypool sand 300 mm 400 mm 300 mm 400 mm 150 mm 200 mm 150 mm 200 mm < 800 mm > 1000 mm London Peterborough Renfrew Vineland Wiarton Seasonal Water Surplus The 48-year averages of measured precipitation, and DRAINMOD simulated ET, DD, RO, and water surplus for each of the four seasons are summarized for the five sites for a typical soil in Table 11, and for the Pontypool sand in Table 12. The year to year variability of water balance components is shown in Appendix E, Figures E-1 through E-5, and Tables E-1 to E-5, where a) represents the winter season (December to March), b) the spring season (April and May), c) the summer season (June to August), and d) the fall season (September to November). On average most of the water surplus occurs in the winter and spring seasons at all sites (Tables 11 and 12). The year to year variability in seasonal precipitation and components of water balance can be seen in Appendix E. Runoff accounted for more than 50% of both winter and spring water surplus for the typical soil in all five regions except for the spring season for the London and Peterborough sites (Table 11). Deep drainage accounted for most of the water surplus that occurred in all seasons when the Pontypool sand was assumed for each site (Table 12). Both deep drainage and runoff were fairly insignificant in the summer and fall seasons at all five sites (Table 11 and 12). In summer, fall, and winter seasons precipitation exceeded the DRAINMOD model estimated water surplus (deep drainage and runoff) in almost all years at all five sites, but in some years the estimated water surplus for the spring season was more than the spring precipitation. For example, at London, in spring of 1960, 1971, and 1978 the water surplus 38

58 was more than precipitation by 94, 77, and 125 mm, respectively, while in all other years the precipitation was more than water surplus (Appendix E). At Peterborough the estimated water surplus for the spring exceeded spring precipitation by 6 to 113 mm in seven years, while in the other 41 spring seasons there was less water surplus than precipitation. At Vineland the seasonal precipitation always exceeded the estimated total seasonal water surplus (deep drainage and runoff) in all four seasons. The number of years when the estimated water surplus in the spring season exceeded the spring precipitation was highest at Wiarton (50% of years). At this site, in 3 springs (6% of years) the estimated runoff exceeded 200 mm and in 9 springs (19 % of years) it exceeded 150 mm, while the spring deep drainage was always less than 200 mm (Appendix E). At Wiarton, on average the amount of spring precipitation was less (139 mm) than the spring water surplus (147 mm), which is expected due to snow melt in the spring in this region. Runoff accounted for more than 50% of both winter and spring water surplus for the typical soil at Wiarton (Table 11). Renfrew is second, with 44% of 48 years (21 springs) having the estimated total water surplus for spring water exceeding precipitation. At this site the estimated deep drainage in spring was always less than 200 mm, while the estimated spring runoff was more than 200 mm in 17% of years (8 springs), and it was more than 150 mm in 31% of years (15 springs) (Appendix E). When the Pontypool sand was assumed to occur, the amount of precipitation in summer and fall seasons was always higher than the DRAINMOD estimated water surplus at all sites (Table 12). In the winter season, the amount of precipitation was more than estimated water surplus nearly every year. However, in the spring the estimated water surplus exceeded precipitation only in 1960 at Vineland, and in several years at the other four sites (Appendix E). On average over the 48 years the amount of precipitation in spring was higher than the estimated water surplus in spring at London, Peterborough and Vineland, while the amount of estimated water surplus exceeded precipitation by 5 mm and 37 mm at Renfrew and Wiarton, respectively (Table 12). At Renfrew in 50% of the years, at Wiarton in about 62 % of years, and at the other 3 sites in less than 19% of years the estimated water surplus was higher than precipitation (Appendix E). At London and Wiarton the amount of spring deep drainage was always higher than the amount of spring runoff, while at other sites in some years the amount of spring runoff exceeded deep drainage when the PontyPool sand was assumed. 39

59 Table 11: Average seasonal totals for measured precipitation, and DRAINMOD model simulated evapo-transpiration, deep drainage, runoff and total water surplus for the typical soil type at all sites for the 48 year study period. Site Winter Spring Summer Fall London Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Perterborough Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Renfrew Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Vineland Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Wiarton Precipitation Evapo-transpiration Deep drainage Runoff Water surplus

60 Table 12: Average seasonal totals for measured precipitation, and DRAINMOD model simulated evapo-transpiration, deep drainage, runoff and total water surplus for the Pontypool sand soil type at all sites for the 48 year study period. Site Winter Spring Summer Fall London Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Perterborough Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Renfrew Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Vineland Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Wiarton Precipitation Evapo-transpiration Deep drainage Runoff Water surplus

61 Some Limitations of the two Models used in this study For this study, comparison of the distribution and amount of water surplus among sites is used to evaluate the sites potential for contamination of surface and groundwater. The risk of ground and surface water contamination depends on many factors such as: soil texture; soil management; intensity, duration and amount of precipitation; crop type; the mass and initial position of contaminant in soil relative to water; and presence of preferential flow paths (Dadfar et al., 2010 a, b). As an example, if a high intensity rainfall occurs in a fine textured soil with subsurface tile drains, it results in runoff. The runoff water can carry dissolved and suspended contaminants to surface water and groundwater (via cracks and earthworm burrows). The surface connected cracks and burrows may also provide a direct pathway for surface applied contaminant transport to subsurface drains, which consequently could transport the contaminant to surface waters. The SHAW and DRAINMOD models do not include preferential flow of water in their calculations. Since this study estimated that the amount of water surplus that occurred as runoff was higher than for deep drainage in nearly all cases at all sites for the typical soil, it indicates a higher potential risk of surface water contamination. However, since preferential flow pathways occur there is risk of groundwater contamination by these pathways as movement of dissolved and suspended agricultural chemicals and waste material in runoff water can flow through these soil cracks and animal burrows (Dadfar et al., 2010 a and b). Soils with high clay content, more than 40% clay, have high likelihood of cracking whenever weather conditions favour soil drying (Dasog et al. 1988; Bronswijk et al. 1995). Comparatively, soils with lower clay content also crack, but to a lower extent, depending upon the clay content (Preston et al. 1997; Kim et al. 2004). The typical soil profile at Renfrew had a very high clay content (Table 3c), thus having a very high likelihood of cracking. On average 94% of water surplus in winter and 91% of water surplus in spring occurred as runoff for the typical soil. Therefore, in addition to risk of surface water contamination there is high likelihood of groundwater contamination by movement of runoff water through soil cracks, especially when the snow falls early and the cracks do not have a chance to close in the fall. The typical soil profile at the other four sites, especially Vineland (Table 3d), is also relatively high in clay content; therefore, there is the likelihood of water flow in cracks at all sites creating the likelihood of groundwater contamination. In addition, Ontario has favorable environmental conditions for Lumbricus terrestris L., a deep burrowing earthworm (Dadfar et al. 2010b). Earthworm burrows connected to the soil surface create a direct route for contaminant transport to groundwater and tile drains. Most of the farmland in Ontario with fine textured soils is tile drained. These fine textured soils have a high likelihood of cracks (Dadfar et al., 2010a) and burrows (Dadfar et al., 2010b), so part of the runoff water may move preferentially through cracks and earthworm burrows and potentially contaminate groundwater or move through the tile drains. No doubt, there is a real probability of these models underestimating ground water contamination for the fine-textured soils. 42

62 Summary and Conclusions Estimated annual and seasonal water surpluses for five climate regions in southern Ontario, from the South Slopes region to the Renfrew region, are assembled in this publication to supplement the information assembled for seven Ontario regions in Fallow et al. (2003). Two models (SHAW and DRAINMOD) were used to estimate the annual water surpluses and DRAINMOD to estimate the seasonal and monthly surpluses and soil type comparisons. Model simulations of evapo-transpiration and water surplus components were performed using daily climate data from each of the five regions for the 48-year period, 1954 to In addition to the local climate, the typical soil profile conditions and a sand soil for each region and the hydraulic properties for each soil type, seasonal growth characteristics for a corn crop in each region were used as input for these models. The major findings of this investigation are: 1) Average annual water surpluses ranged from 133 mm at Vineland in the Niagara Fruit Belt to 292 mm at Wiarton in the Lake Huron-Georgian Bay region, when the typical soil type was assumed for each region (see Table 8). 2) There was significant year-to-year variability in the annual water surplus and therefore for the potential risk of groundwater and surface water contamination at each site with most of the surplus occurring in the winter and spring seasons. 3) For the typical soil profile in each region more of the average water surplus in the winter and spring seasons was estimated to be RO, except DD exceeded RO at London and Peterborough in the Spring season. However, when the Pontypool sand soil type was assumed for each region DD exceeded RO in both seasons at all sites, except at Renfrew in the Winter Season (Tables 11 and 12). 4) Neither the average DD or RO were substantial in the summer or fall seasons for either soil type, although some water surplus occurs in these seasons when rainfall exceeds about 300 mm (see Appendix E). 5) The dominant factors that determined surplus water was when excess precipitation and low ET occurred in any season. 6) More deep drainage occurs in soil types with relatively high hydraulic conductivity, as occurred when Pontypool sand was used in DRAINMOD, whereas soils with high clay content drain very slowly, assuming that preferential flow in macropores is absent as in DRAINMOD. A soil profile that has a coarse texture in the lower layers also provides more opportunity for conduction of water upward into the rooting profile of the crop when the soil is saturated just below the rooting depth and results in more transpiration. 7) Caution needs to be exercised with respect to contaminant transport to groundwater particularly in areas where sandy soils occur, and in the snowbelt regions to the lee of the Great Lakes, as deep drainage was excessive in the wet seasons and wet years in these situations. In other regions, especially if the soil is fine-textured, surface water contamination due to runoff is of greater risk. 43

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66 Webber, L.R. and D. Tel Available moisture in Ontario soils. Department of Land Resource Science Technical Report, University of Guelph. 14 pp. Yang, C.-C., S.O. Prasher, S. Wang, S.H. Kim, C.S. Tan, C. Drury and R.M. Patel Simulation of nitrate-n movement in southern Ontario, Canada with DRAINMOD-N. Agricultural Water Management 87: Yang, X Evaluation and application of DRAINMOD in an Australian sugarcane field. Agricultural water management 95:

67 Appendix A Table A-1: Location where climate elements were recorded at each of the primary climate sites. Table A-2: Summary corn growth cycle inputs for the SHAW model for London. Table A-3: Summary corn growth cycle inputs for the SHAW model for Peterborough. Table A-4: Summary corn growth cycle inputs for the SHAW model for Renfrew. Table A-5: Summary corn growth cycle inputs for the SHAW model for Vineland. Table A-6: Summary corn growth cycle inputs for the SHAW model for Wiarton. 48

68 Table A-1: Location where climate elements were recorded at each of the primary climate sites. Location of primary climate site London Peterborough Element recorded Temperature Precipitation Temperature Precipitation Temperature Precipitation Temperature Precipitation Temperature Precipitation Temperature Precipitation Temperature Precipitation Temperature Precipitation Period of record from which daily/hourly data were obtained from Environment Canada January 1954 to December 2001 Filled in missing data from November March 2001 Site of record from which daily/hourly data were obtained form Environment Canada London Airport: Latitude: 43 1' N Longitude: 81 9' W Elevation: m Woodstock: Latitude: 43 7' N Longitude: 80 46' W Elevation: m Peterborough: Latitude: 44 16' N Longitude: 78 19' W Elevation: m Peterborough Airport: Latitude: 44 13' N Longitude: 78 22' W Elevation: m Filled in missing data from September October 1970 Filled in missing data from March April 1965 Filled in missing data from March November 1970 Filled in missing data from September October 1984 Lindsay: Latitude: 44 21' N Longitude: 78 45' W Elevation: m Peterborough Ontario Hydro: Latitude: 44 19' N Longitude: 78 19' W Elevation: m Peterborough Dobbin TS: Latitude: 44 19' N Longitude: 78 24' W Elevation: m Peterborough Trent University: Latitude: 44 22' N Longitude: 78 18' W Elevation: m 49

69 Table A-1 (continued): Location where climate elements were recorded at each of the primary climate sites. Location of primary climate site Peterborough Renfrew Element recorded Period of record from which daily/hourly data were obtained from Environment Canada Precipitation Filled in missing data for one day in 1961 Temperature Precipitation Temperature Precipitation Temperature Precipitation Temperature Precipitation Temperature Precipitation January August 1959 Filled in missing data from May May 1959 Data also used from September 1959 June 1992 Filled in missing data from July May 1985 July September 1996 Filled in missing data from March 1964-December 1967 October to October 2001 Filled in missing data from September 1960 to December 1963 Precipitation Filled in missing data for March 1964 Temperature Filled in missing data from October 1996 to May 1998 Site of record from which daily/hourly data were obtained form Environment Canada Minden: Latitude: 44 55' N Longitude: 78 43' W Elevation: m Renfrew Sand Point: Latitude: 45 28' N Longitude: 76 25' W Elevation: m Chats Falls: Latitude: 45 28' N Longitude: 76 14' W Elevation: 94 m Renfrew: Latitude: 45 29' N Longitude: 76 42' W Elevation: 99 m Chalk River AECL: Latitude: 46 3' N Longitude: 77 22' W Elevation: m Arnprior: Latitude: 45 26' N Longitude: 76 23' W Elevation: 99 m Chenaux Latitude: 45 58' N Longitude: 76 68' W Elevation: 84.1 m Charteris: Latitude: 45 68' N Longitude: 76 43' W Elevation: 168 m 50

70 Table A-1 (continued): Location where climate elements were recorded at each of the primary climate sites. Location of primary climate site Element recorded Period of record from which daily/hourly data were obtained from Environment Canada Site of record from which daily/hourly data were obtained form Environment Canada Vineland Temperature Precipitation January 1954 to December 1988 Vinland Station: Latitude: 43 10' N Longitude: 79 24' W Elevation: 79.2 m Temperature Precipitation January 1989 to December 2001 Vineland Rittenhouse: Latitude: 43 10' N Longitude: 79 25' W Elevation: 94.5 m Temperature Precipitation Filled in missing data from March 1996 to November 1996 St. Catharines Power Glen: Latitude: 43 7' N Longitude: 79 15' W Elevation: m Temperature Precipitation Filled in missing data from February 1963 to March 1956 St. Catharines CDA: Latitude: 43 10' N Longitude: 79 13' W Elevation: m Wiarton Temperature Precipitation January 1954 to December 2001 Wiarton Airport: Latitude: 44 45' N Longitude: 81 6' W Elevation: m Temperature Precipitation Filled in missing data from October 1979 to November 1979 Goderich Municipal Airport: Latitude: 43 46' N Longitude: 81 42' W Elevation: m Temperature Filled in missing data from September 1982 and August 1985 Saltford: Latitude: 43 45' N Longitude: 81 40' W Elevation: m Temperature Filled in missing data from February 1997 and March 1998 Kincardine: Latitude: 44 10' N Longitude: 81 37' W Elevation: m 51

71 Table A-2: Summary corn growth cycle inputs for the SHAW and DRAINMOD models for London. Year Planting day Emergence Full crop cover Senescence begins First frost day or 12 ºC day (day of the year) (day of the year) (day of the year) (day of the year) (day of the year) Average Stdev

72 Table A-3: Summary corn growth cycle inputs for the SHAW and DRAINMOD models for Peterborough. Year Planting day (day of the year) Emergence (day of the year) Full crop cover (day of the year) Senescence begins (day of the year) First frost day or 12 ºC day (day of the year) Average Stdev

73 Table A-4: Summary corn growth cycle inputs for the SHAW and DRAINMOD models for Renfrew. Year Planting day (day of the year) Emergence (day of the year) Full crop cover (day of the year) Senescence begins (day of the year) First frost day or 12 ºC day (day of the year) Average Stdev

74 Table A-5: Summary corn growth cycle inputs for the SHAW and DRAINMOD models for Vineland. Year Planting day (day of the year) Emergence (day of the year) Full crop cover (day of the year) Senescence begins (day of the year) First frost day or 12 ºC day (day of the year) Average Stdev

75 Table A-6: Summary corn growth cycle inputs for the SHAW and DRAINMOD models for Wiarton. Year Planting day (day of the year) Emergence (day of the year) Full crop cover (day of the year) Senescence begins (day of the year) First frost day or 12 ºC day (day of the year) Average Stdev

76 Appendix B Table B-1a & 1b: Summary of measured precipitation and estimated annual totals of water balance components using the DRAINMOD model for (a) a typical soil profile and (b) the Pontypool sand soil profile for London. Table B-2a & 2b: Summary of measured precipitation and estimated annual totals of water balance components using the DRAINMOD model for (a) a typical soil profile and (b) the Pontypool sand soil profile for Peterborough. Table B-3a &3b: Summary of measured precipitation and estimated annual totals of water balance components using the DRAINMOD model for (a) a typical soil profile and (b) the Pontypool sand soil profile for Renfrew. Table B-4a & 4b: Summary of measured precipitation and estimated annual totals of water balance components using the DRAINMOD model for (a) a typical soil profile and (b) the Pontypool sand soil profile for Vineland. Table B-5a &4b: Summary of measured precipitation and estimated annual totals of water balance components using the DRAINMOD model for (a) a typical soil profile and (b) the Pontypool sand soil profile for Wiarton. 57

77 Table B-1a: Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for London for a typical soil profile. Year Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

78 Table B-1b: Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for London for a Pontypool sand soil profile. Year Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

79 Table B-2a: Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Peterborough for a typical soil profile. Year Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

80 Table B-2b: Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Peterborough for a Pontypool sand soil profile. Year Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

81 Table B-3a: Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Renfrew for a typical soil profile. Year Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

82 Table B-3b: Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Renfrew for a Pontypool sand soil profile. Year Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

83 Table B-4a: Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Vineland for a typical soil profile. Year Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

84 Table B-4b: Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Vineland for a Pontypool sand soil profile. Year Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

85 Table B-5a: Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Wiarton for a typical soil profile. Year Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

86 Table B-5b: Summary of measured precipitation and DRAINMOD model estimated annual totals of water balance components for Wiarton for a Pontypool sand soil profile. Year Precipitation Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

87 Appendix C Summary of monthly averages of (a) precipitation, and DRAINMOD model estimated (b) evapo-transpiration, (c) deep drainage, (d) runoff, and (e) water surplus using the typical soil profile; and DRAINMOD model estimated (f) evapo-transpiration, (g) deep drainage, (h) runoff, and (i) total water surplus using the Pontypool soil profile for all five sites. 68

88 Table C-1: Summary of monthly averages ( ) of measured precipitation, and DRAINMOD estimated evapo-transpiration, deep drainage, runoff and water surplus for a typical soil and a Pontypool sand for London. a) London monthly precipitation : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low b) London monthly estimated evapo-transpiration with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low c) London monthly estimated deep drainage with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low d) London monthly estimated runoff with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low e) London monthly estimated water surplus with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low

89 f) London monthly estimated evapo-transpiration with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low g) London monthly estimated deep drainage with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low h) London monthly estimated runoff with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low i) London monthly estimated water surplus with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low

90 Table C-2: Summary of monthly averages ( ) of measured precipitation, and DRAINMOD estimated evapo-transpiration, deep drainage, runoff and water surplus for a typical soil and a Pontypool sand for Peterborough. a) Peterborough monthly precipitation : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low b) Peterborough monthly estimated evapo-transpiration with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low c) Peterborough monthly estimated deep drainage with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low d) Peterborough monthly estimated runoff with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low e) Peterborough monthly estimated water surplus with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low

91 f) Peterborough monthly estimated evapo-transpiration with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low g) Peterborough monthly estimated deep drainage with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low h) Peterborough monthly estimated runoff with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low i) Peterborough monthly estimated water surplus with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low

92 Table C-3: Summary of monthly averages ( ) of measured precipitation, and DRAINMOD estimated evapo-transpiration, deep drainage, runoff and water surplus for a typical soil and a Pontypool sand for Renfrew. a) Renfrew monthly precipitation : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low b) Renfrew monthly estimated evapo-transpiration with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low c) Renfrew monthly estimated deep drainage with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low d) Renfrew monthly estimated runoff with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low e) Renfrew monthly estimated water surplus with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low

93 f) Renfrew monthly estimated evapo-transpiration with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low g) Renfrew monthly estimated deep drainage with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low h) Renfrew monthly estimated runoff with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low i) Renfrew monthly estimated water surplus with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low

94 Table C-4: Summary of monthly averages ( ) of measured precipitation, and DRAINMOD estimated evapo-transpiration, deep drainage, runoff and water surplus for a typical soil and a Pontypool sand for Vineland. a) Vineland monthly precipitation : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low b) Vineland monthly estimated evapo-transpiration with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low c) Vineland monthly estimated deep drainage with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low d) Vineland monthly estimated runoff with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low e) Vineland monthly estimated water surplus with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low

95 f) Vineland monthly estimated evapo-transpiration with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low g) Vineland monthly estimated deep drainage with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low h) Vineland monthly estimated runoff with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low i) Vineland monthly estimated water surplus with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low

96 Table C-5: Summary of monthly averages ( ) of measured precipitation, and DRAINMOD estimated evapo-transpiration, deep drainage, runoff and water surplus for a typical soil and a Pontypool sand for Wiarton. a) Wiarton monthly precipitation : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low b) Wiarton monthly estimated evapo-transpiration with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low c) Wiarton monthly estimated deep drainage with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low d) Wiarton monthly estimated runoff with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low e) Wiarton monthly estimated water surplus with a typical soil profile : Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low

97 f) Wiarton monthly estimated evapo-transpiration with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low g) Wiarton monthly estimated deep drainage with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low h) Wiarton monthly estimated runoff with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low i) Wiarton monthly estimated water surplus with a Pontypool sand soil profile: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean Stdev High Low

98 Appendix D Differences in annual DRAINMOD model simulated evapo-transpiration, deep drainage and runoff for each year from 1954 to 2001 for a Pontypool sand soil profile as compared to the typical soil type for all five sites. 79

99 Figure D-1: Differences in annual DRAINMOD model simulated evapo-transpiration, deep drainage and runoff for 1954 to 2001 period for a Pontypool sand soil profile as compared to the typical soil type at London. 80

100 Table D-1: Year Summary of differences in DRAINMOD model estimated annual totals of water balance components for a Pontypool sand soil profile as compared to the typical soil type at London. Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

101 Figure D-2: Differences in annual DRAINMOD model simulated evapo-transpiration, deep drainage and runoff for 1954 to 2001 period for a Pontypool sand soil profile as compared to the typical soil type at Peterborough. 82

102 Table D-2: Year Summary of differences in DRAINMOD model estimated annual totals of water balance components for a Pontypool sand soil profile as compared to the typical soil type at Peterborough. Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

103 Figure D-3: Differences in annual DRAINMOD model simulated evapo-transpiration, deep drainage and runoff for 1954 to 2001 period for a Pontypool sand soil profile as compared to the typical soil type at Renfrew. 84

104 Table D-3: Year Summary of differences in DRAINMOD model estimated annual totals of water balance components for a Pontypool sand soil profile as compared to the typical soil type at Renfrew. Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

105 Figure D-4: Differences in annual DRAINMOD model simulated evapo-transpiration, deep drainage and runoff for 1954 to 2001 period for a Pontypool sand soil profile as compared to the typical soil type at Vineland. 86

106 Table D-4: Year Summary of differences in DRAINMOD model estimated annual totals of water balance components for a Pontypool sand soil profile as compared to the typical soil type at Vineland. Evapo-transpiration Deep drainage Runoff Water surplus Average Stdev

107 Figure D-5: Differences in annual DRAINMOD model simulated evapo-transpiration, deep drainage and runoff for 1954 to 2001 period for a Pontypool sand soil profile as compared to the typical soil type at Wiarton. 88