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7.3 WATER LEVELS IN WELLS ~ _ ,r? <br />t; <br />Water Levels in Wells are Determined by <br />Aquifer Properties and Indicate the <br />Direction of Ground-Water Flow <br />The degree of aquifer confinement and <br />the ability of an aquifer to transmit <br />water affect water levels in wells. <br />TAn dr~fenawca ,N, yJ~l,y~be*r,esw. ~~C w.~taR~RM.sp q...C~fA.~- P^++Zu.a~w~~^~'c.Aa. a <br />- _welli indicateSthe degree of aquifer confinvvement. <br />If an aquifer is confined between impermeable or less permeable layers, <br />ground water is under artesian p=essure, which increases in proportion <br />• 'to the thickness of the overlying layer. The level to which water <br />rises in a well penetrating a confined aquifer indicates the amount <br />of artesian pressure on the aquifer. In figure 7.3-1, the artesian <br />pressure on the Trinidad Sandstone increases from well A to wells B and <br />NeJa.e~ <br />C as the thickness of tie less permeable ~Lesa~jo-a~xd-itatorr-Formations <br />overlying the Trinidad Sandstone increases. In Huerfano County, Colorado <br />and Colfax County, New Mexico, wells drilled through several hundred <br />feet of impermeable Cretaceous shale to obtain water from the Dakota <br />Sandstone flow (Griggs, 1948, p. 53; McLaughlin, 1965, p. 65). In <br />unconfined aquifers, i.e. aquifers not overlain by less permeable or <br />impermeable formations, ground water is under atmospheric pressure, <br />and water levels in wells coincide with the top of the zone of saturation <br />(well A, fig. 7.3-1). <br />• <br />58 <br />