SOME ASPECTS OF THE SPATIAL AND TEMPORAL VARIABILITY OF CLIMATE IN ONTARIO AND ITS EFFECT ON GROUNDWATER

Transcription

1 SOME ASPECTS OF THE SPATIAL AND TEMPORAL VARIABILITY OF CLIMATE IN ONTARIO AND ITS EFFECT ON GROUNDWATER Presented to the OWWA/OMWA Joint Annual Conference May 6, 2014 Mezmure Haile-Meskale, Ph.D., P.Geo

2 Topics of this Presentation Spatial & Temporal variability of climate Spatial & Temporal variability of depth to SWL s Discussion on the possible factors that have affected the measured SWL s Discussion on the significance of the overall effect on the groundwater users of Southern Ontario

3 DATA SOURCES Groundwater data: MOE water well information system (WWIS) Climate data: - NASA (National Aeronautics and Space Administration) - Environment Canada METHODOLOGY GIS and statistical analysis

4 Similarities and Differences Between Data From WWIS and From Monitoring Wells WWIS Initial Measurement just after well construction. Conventional Monitor Initial measurement after well stabilization One time Several. WWIS economical, high resolution due to high density (over 540,000 data points used for this study) 4

5 Grid Based Climatic Data Source from NASA SOUTHERN ONTARIO 46 0 Lat. WESTERN ONTARIO SOUTHCENTRAL AND EASTERN ONTARIO 23 years ( )

6 Climatic Data Sources From Environment Canada Thiessen Polygons For the Weather Station in Ontario Southern Ontario Northern Ontario Km Km 6

7 TEMPERATURE - MONTHLY AVERAGED FROM

8 PRECIPITATION - MONTHLY AVERAGED FROM

9 9 SUNSHINE HOURS - MONTHLY AVERAGED FROM

10 10 Climatic Regions of Ontario

11 The difference in T and PPT between 43 Years ( ) mean and the mean of each year 11 Long term averages were compared with yearly means. The graphs show the difference between the two. Note: increase of T in recent years, low PPT, in the 70 s and variable PPT afterwards

12 Years of quasi similar climate (wet-cold, hot-dry, variable) affecting groundewater levels Wells drilled in the Southern Ontario when PPT was mostly wet and T was mild PPT was moderate and T was hot Before to <= 1965:- Climate not characterised PPT was mostly variable, T was cold to mild. PPT was mostly dry and T was mild to hot

13 Spatial variability PPT AET for relatively dry-hot and wet-cold years For example, here 3 or more spatially variable areas in micro climate:- Niagara Scarp, the Oak Ridges Moraine, the Frontenach Arch, and St Lawrence Platform to the east

14 Temporal Variations of the depth to SWL s From Drilled Wells Depth to water Well depth The overall trend Before

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16 Spatial comparison of SWL s for different time intervals bedrock wells

17 Spatial comparison of swl s for different time intervals overburden wells 1948 to to 1989

18 The integrated maps the lower parts of the previous maps

19 Measurement started in 1992 Difference in Groundwater Levels Between Wells Drilled in 1990 to 1996 and wells drilled in 1997 to 2002

20 The Vulnerability of Wells and Aquifers to Drought SO WHAT? Vulnerability of overburden aquifers and the respective wells V OA/W = S (f 1 Wpd + f 2 Wd + f 3 Wwd + f 4 Pwwd + f 5 RDAC + f 6 LTWC) Vulnerability of bedrock aquifers and the respective wells V BA/W = S (f 1 Wpd + f 2 Wd + f 3 Wwd + f 4 Pwwd + f 5 RDAC + f 6 LTWC + f 7 T) Where f 1 to f 7 are arbitrary factors of multiplications, Wpd = well point density, Wd = well depth, Wwd = well water depth, Pwwd = Percent of well water depth, RDAC = relative degree of aquifer confinement, LTWC = long term well capacity, and T = transmissivity (for bedrocks only)

21 Well point density D Overburden Wells C B Legend Number of wells 1 0 A 2 1-2, ,375-7,121 Vulnerability Score 4 5 7,122-16,021 16, ,313 D C Bedrock Wells B Legend Number of wells 0 A 1-1,208 1,209-4,429 4,430-14,897 14, ,666

22 Well depth It is highly probable that, in most cases, deep wells survive drought conditions, while shallow wells dry up.

23 Well water depth (column)

24 Percentages of water column relative to well depths

25 The relative degree of aquifer confinement

26 The estimated long term well capacity

27 The transmissivity of the bedrocks

28 THE INTEGRATED FACTORS AFFECTING VULNERABILITY OF QUIFERS AND WELLS TO DROUGHT

29 Previously Dug Wells Density Map and Other Wells Points

30 THE INTEGRATED SENSITIVE AREAS TO GROUNDWATER LEVEL FLUCTUATIONS AND VULNERABLE AQUIFERS AND WELLS TO DROUGHT

31 Conclusions Having observed the spatial variability of climate and the measured depth to water levels, some correlations were observed between the two. Apart from climate, other factors, such as aquifer characteristics, well construction details and groundwater usage could have affected the measured SWL s. The effect of climate in isolation may be most probable in rural areas, where there is no groundwater use The measured depth to SWL s variations appear to be more pronounced in overburden wells than in the bedrock wells. In the event of drought, certain areas could be more vulnerable than others. Hence, it would be advisable to make use of such general understanding and focus on specific areas that could pose a problem in the future.

32 The end Thank You