Water Management: A Complex Balancing Act

Transcription

1 Water Management: A Complex Balancing Act Chandra A. Madramootoo Dean, Agricultural and Environmental Sciences McGill University Montreal, Canada Presentation to the Caribbean Week of Agriculture October, Georgetown, Guyana

2 Water and Land Resource Management Develop and test innovative water conservation and modern irrigation practices to conserve water and reduce agrochemical contamination of soil and water Implement irrigation scheduling techniques to enhance water use efficiency

3 Field Research Sites Guyana Black Bush Polder Parika St Kitts Mansion Stapleton St Lucia Black Bay

4 Soil characteristics of project sites Project sites St. Kitts Black Bush Polder (GUY) Parika (GUY) Particle Size distribution Sand Silt Clay Field Capacity Perm Wilting Point Available Water Content Trigger value % of AWC Soil Classification % % % % % % Sandy loam (Monkey Hill Loam)* Clay (Corentyne Clay )** Silty clay (Mara Series) ** Source: *, Soil and Land-Use Surveys No. St. Kitts and Nevis ** NAREI

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8 Crop yield Kg/ha) Parika Crop Yields (Kg/ha) Tomato Irrigated Not irrigated Bora

9 Madramootoo Lab Soil Water Plant Dynamics Model Surface runoff Return flows (Q,L) IRRIG, PRECIP ET Active root zone Capillary fluxes Soil Water Reservoir Capillary fringe Leaching Fraction Interflow Percolation GW accretion Upward GW movement Subsurface drainage Return flows (Q,L)

10 Soil Water Balance Model McGill-IRRIMOD Sw i = Soil water balance in mm SW (i-) = Soil water balance content in the root zone at the end of the previous day, i (mm) ETc i = Actual Crop Evapotranspiration on day i (mm) DP= Deep percolation in mm I i = Irrigation applied depth on day i (mm) Reff i is the Effective rainfall of the day in mm

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12 Crop Evapotranspiration (ET c ) ETo= reference evapotranspiration Kc = crop coefficient

13 ETcrop = ETo * Kc

14 Determination of the Soil Water Retention Curve Pressure plate apparatus Soil Water Plant Dynamics Lab

15 % VWC. Soil Water Retention Curve BBP_- BBP_-... %sand %silt %clay BBP_- BBP_- BBP_-. BBP_-. BBP_-. BBP_-. BBP_-. - Pressure applied (bars) Average values

16 % VWC. Soil Water Characteristics Curve low range pressure Avg-. Avg-. Avg-.. Field Capacity at. bars Pressure applied (bars) Avg- Avg-

17 mm of Water St. Kitts - Water Balance Model Simulation Results- annual rainfall Rainfall Surplus Deficit Etc

18 mm of Water Parika - Water Balance Model Simulation Results annual rainfall Rainfall Surplus Deficit Etc

19 Depth (mm) Depth (mm) St Kitts wettest year ( mm of Rainfall) Water Balance January to February Water Balance September to October deficit Surplus Water Balance Field Capacity Lower Trigger deficit Surplus Water Balance Field Capacity Lower Trigger Sep Oct Jan Feb Driest month: January Rainfall: mm Wettest month: October Rainfall: mm

20 Depth (mm) Depth (mm) Parika - wettest year ( mm of Rainfall) Water Balance September to October deficit Surplus Soil Moisture Field Capacity Lower Trigger Water Balance January to February deficit Surplus Soil Moisture Field Capacity Lower Trigger Sep Oct Dec Jan Feb Driest month: October Rainfall mm Wettest month: February Rainfall mm

21 Depth (mm) Depth (mm) Black Bush Polder - driest year ( mm of Rainfall) Water Balance September to October Water Balance January to February deficit Surplus Water Balance Field Capacity Lower Trigger Sep Oct Dec Jan Feb deficit Surplus Driest month: September Rainfall mm Wettest month: January Rainfall mm

22 Depth (mm) Depth (mm) Black Bush Polder - wettest year ( mm of Rainfall) Water Balance November to December deficit Surplus Water Balance Field Capacity Lower Trigger Nov Dec Water Balance November to December deficit Surplus Water Balance Field Capacity Lower Trigger Nov Dec Driest month: November Rainfall mm Wettest month: December Rainfall mm

23 Crop yield (Kg/ha) St. Kitts - Crop Yields (Kg/ha) Irrigated Not irrigated

24 Crop yield Kg/ha) Black Bush Polder - Crop Yields (Kg/ha) Tomato Eggplant Red beans Sweet peppers (BBP_GUY) Irrigated Not irrigated

25 Conclusions Drip irrigation significantly increased crop yields in St Kitts There was increased diversity in cropping systems and year crop production in St Kitts; This production was used to partially supply the dietary needs of the School Meals Program; Small farmers, particularly women, had increased incomes; Yield increases were not as significant in Guyana due to wetter soil conditions, heavier soil types and the rainfall patterns; Soil water simulation modelling enabled precise calculation of the daily crop water requirements, and is useful in explaining crop response to either soil water surpluses or deficits; Automated soil moisture sensors can support irrigation scheduling practices, provided the soil water holding capacity is known.

26 IDRC Acknowledgment This work was carried out with the aid of a grant from the International Development Research Center (IDRC), Ottawa, Canada, and with financial support from the Government of Canada, provided through Foreign Affairs, Trade and Development Canada (DFATD),

27 THANK YOU

28 By inputting climatological data into the soil water balance model (McGill-IRRIMOD ), the amount of irrigation water to be applied daily was calculated. Reff - Effective rainfall (mm) -rainfall lower than mm is not considered as a effective rainfall. The trigger values for the irrigation scheduling simulation were based on soil water retention curve for each region. For the days when the combined soil moisture and rainfall exceeds Field Capacity the excess is considered as surface runoff. The computation of the soil moisture for the following day assumes that the soil was at field capacity the previous day. For the days when the combined soil moisture and rainfall is lower than trigger value (% of AWC), the lack of water is consider as a deficit. The computation of the soil moisture for the following day assumes that the soil was at field capacity on the previous day.

29 Sr. Kitts Water Balance Model Annual values Rainfall Etc Surplus Deficit mm mm mm mm Parika (Guyana) Water Balance Model Annual values Rainfall Etc Surplus Deficit mm mm mm mm Black Bush Polder (Guyana) Water Balance Model Annual Values Rainfall Etc Surplus Deficit mm mm mm mm

30 Rainfall (mm). Monthly rainfall between - at Albion (Black Bush Polder) JAN FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC - -

31 Rainfall (mm). Monthly rainfall between - at Uitvlugt (Parika) JAN FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC - -

32 mm of Water Black Bush Polder - Water Balance Model Simulation Results - annual rainfall Rainfall Surplus Deficit Etc

33 Depth (mm) St. Kitts driest year ( mm of Rainfall) Water Balance March to April deficit Surplus Water Balance Field Capacity Lower Trigger Mar Apr Driest month: April Rainfall. mm Wettest month in : October Rainfall : mm

34 Depth (mm) Depth (mm) Water Balance September to October deficit Surplus Water Balance Field Capacity Lower Trigger Sep Parika - driest year ( mm of Rainfall) Oct Water Balance January to February deficit Surplus Water Balance Field Capacity Lower Trigger Dec Jan Feb Driest month: September Rainfall mm Wettest month of year: January Rainfall mm