4) (20 pt) Three productive aquifers overlie each other separated by thin aquita

Question

4) (20 pt) Three productive aquifers overlie each other separated by thin aquitards. Extensive pumping in the upper fresh water aquifer by the municipality of Thirsty City, TX, has lowered the average hydraulic head throughout the region. This has created concerns that the pumping may have reversed the natural downward vertical gradient (favoring flow downwards) to upward. Water level measurements indicated that there is still a strong downward gradient owever some private well owners are complaining of brackish water in their shallow wells. a) Determine the orientation (up or down) and magnitude of the vertical hydraulic gradient between the fresh and brackish aquifers, and between the brackish and brine aquifers. b) With the current state of hydraulic heads, how long would it take for brackish water to cross the aquitard separating the fresh and brackish aquifers? c) given the information provided h the urban pumping only began 30 years ago and has been relative constant since, can the urban pumping be responsible for people's wells turning brackish? The thickness of the lower aquitard is 5 m and the K value for both aquitards is 0.001 m/day. ere, if 1 2 3 Fresh Water Aquifer Density = 1,000 Kg/m2 h = 32 m nA Brackish Water Aquifer Density = 1,010 Kg/m3 h =71m ppz z=20m Brine Aquifer Density = 1,050 Kg/m2 "m=82 m

Explanation / Answer

roductive aquifers overlie each other separated by thin aquitards. Extensive pumping in the upper fresh water aquifer by the municipality of Thirsty City, TX, has lowered the average hydraulic head throughout the region. This has created concerns that the pumping may have reversed the natural downward vertical gradient (favoring flow downwards) to upward. Water level measurements indicated that there is still a strong downward gradient owever some private well owners are complaining of brackish water in their shallow wells. a) Determine the orientation (up or down) and magnitude of the vertical hydraulic gradient between the fresh and brackish aquifers, and between the brackish and brine aquifers. b) With the current state of hydraulic heads, how long would it take for brackish water to cross the aquitard separating the fresh and brackish aquifers

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