The following problems use the hydrogeologic cross section of an area in northwe
ID: 1732678 • Letter: T
Question
The following problems use the hydrogeologic cross section of an area in northwest Indiana. Site-specific field data indicate that the transmissivity of the confined aquifer is approximately 13,000 ft2/day, and the coefficient of storage is 0.000043. Well 16-1 is an irrigation well that is used periodically during the growing season.
1. The storativity of the Jordan Aquifer (a regional confined aquifer) is 5x10-4 and the porosity is 0.3. The thickness of the aquifer is 200 ft.
a. The Jordan has been pumped for several decades, yet remains fully saturated. Explain where the water is coming from.
b. If the head in the Jordan has been pumped down by 100 ft in recent times, how much water in cubic feet has been pumped out of storage for an area of 100 sq mi?
Mostly sand and gravel Mostly clay Shale bedrock Well 800T 1 mi 1 km 6Explanation / Answer
a) Storativity : it is the volume of water released from aquifer per unit decline in hydraulic head in the aquifer, per unit area of the aquifer. Here the storativity of field aquifer is more than the Jordan aquifer and( 43×10^(-4) more than 5×10^(-4)) Jordan aquifer located in the field. So as of my understanding Jordan aquifer can get the water from field aquifer. So this is the reason for its long term saturation condition.
b) volume of water pumped V = S × A × ??h
S- storativity of aquifer
A- area of aquifer
??h - Chang in head
V = 5×10^(-4) × 278784 × 10^(4) × 100
= 139392000 cubic feet
( 100 Sq.miles = 2787840000 Sq. ft)
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