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aquifer is too small to plot in Figure A-3. and the draw- down in the confined aquifer is about 10 feet. Furthermore, a measurable drawdown still occurs in the confined aquifer at a distance of 500,000 feet (about 95 miles) from the pumping well. Considering this information in a spatial sense. the cone of depression (Figure A-4) associated with the pumping well in the confined aquifer is deeper and much more areally extensive compared to the cone of depression in the unconfined aquifer. In fact, the total volume of the cone of depression in the confined aquifer is about 2,000 times larger than the total volume of the cone of depression in the uncon- fined aquifer for this example of a hypothetical infinite aquifer. Water around grains Air ~ '" Figure A-2. Pumping a single welf in an idealized uncon- fined aquifer. Dewatering occurs in cone of depression of unconfined aquifers during pumping by welfs (saturated thickness of aquifer decreases). \ Land \ surface Well discharge Unsaturated zone ./ Water table and original /'" ground-water level (head) before pumping -I _I I -I -I I I . I I I I 1 , I i I I- I- i_ I I- I I Saturated zone Confining unit Tabte A-t. Numerical values of parameters used to calculate drawdowns in ground-water levels in response to pumping in two idealized aquifers, one confined and one unconfined Parameter Hydraulic conductivity, K Aquifer thickness, b Transmissivity, T Storage coefficient, S Duration of pumping, t Rate of pumping, Q Confined aquifer 1 00 feet per day 100 feet 10,000 feet squared per day 0.0001 365 days 192,500 cubic feet per day (1,000 gallons per minute) Unconfined aquifer 100 feet per day 100 feet 10,000 feet squared per day 0.2 365 days 192,500 cubic feet per day (1,000 gallons per minute) ~ 13