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

ANSWER:

Given,

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.

I hope you appreciate my spending an hour in the blazing sun to dig this hole at the beach. It is a great way to illustrate the concept of how, below a certain depth, the ground, if it is permeable enough to hold water, is saturated with water. The upper surface of this zone of saturation is called the water table. The saturated zone beneath the water table is called an aquifer, and aquifers are huge storehouses of water. What you are looking at in this picture is a "well" that exposes the water table, with an aquifer beneath it. Of course, I am cheating here, as at the beach, the level of the water table is always at the same level as the ocean, which is just below the surface of the beach.

Groundwater is one of our most valuable resource—even though you probably never see it or even realize it is there. As you may have read, most of the void spaces in the rocks below the water table are filled with water. But rocks have different porosity and permeability characteristics, which means that water does not move around the same way in all rocks below ground.

Related Questions

Navigate

• Browse (All)
• Browse 4
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.