WSA Yorkton 517 and 519
WSA Yorkton 517 and 519 and a lake level monitoring station were constructed in 1974 near the shore of York Lake to observe natural groundwater and lake level fluctuations and to study the interrelationship between the lake and groundwater. WSA Yorkton 517 was completed to a depth of 40.23 metres in a sand and gravel aquifer resting on the surface of a bedrock depression trending beneath the lake. The bedrock surface is formed by the Piere Shale. WSA Yorkton 519 was completed to 6.52 metres in tills of the overlying aquitard.
The hydrograph for WSA Yorkton 517 shows annual water level fluctuations of a metre or more with seasonal highs typically in late spring/early summer and the lows in the late winter. The record low water level of about 509.6 metres occurred in in 1991, while record peaks of just over 512.5 metres occurred in 2011 and 2012. Water levels in the well remain high.
The WSA Yorkton 519 hydrograph suggests that seasonal water levels follow a similar trend to those in WSA Yorkton 517. Seasonal variations can reach 2 metres and are generally at least half a metre. Following the onset of monitoring in the spring of 1975, a very sharp increase in water levels occurred over the next year. This saw the water level rise from its record low of about 507.5 metres to just over 510.5 metres in the summer of 1976. The water level hit a record high peak of about 512.4 metres in 2011 and water levels remain high.
The hydrographs for WSA Yorkton 517 and 519 show a lot of similarities except for the period of 1975 - 1981. During this time water levels in 517 were higher than in 519, but were declining while levels in 519 were rising. During the balance of the record, water levels have been similar, but there is some variation in the magnitude and direction of the vertical gradient. The relationship between the water levels in the two wells and the lake is very complex and is still not well understood.
Water from WSA Yorkton 517 is of the magnesium/calcium/sodium-sulphate/bicarbonate type with a sum of ions concentration of approximately 1820 mg/L. No samples have been obtained from WSA Yorkton 519.
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