# Solution to Exercise 9

9) A confined aquifer underlies a 10 km2 area. The average water level in a number of wells penetrating the confined system rose 2.5 m from April through June. An overlying unconfined aquifer showed an average water table rise of 2.5 m over the same period of time.
Assume the storativity for the confined system is 3.6 × 10-5, and specific yield is 0.12 for the unconfined system. How much water (in m3) recharged each aquifer based on the responses of each potentiometric surface?

Assume the storativity, S, for the confined system is 3.6 × 10-5, and specific yield, Sy, is 0.12 for the unconfined system. How much water (in m3) recharged each aquifer based on the responses of each potentiometric surface?

Unconfined aquifer
Applying Equation 48 in this book to compute the volume of water recharged:

 Volume of Unconfined Water for a change in head = SyA∆h Unconfined Volume =

Confined aquifer
Applying Equation 50 in this book to compute the volume of water recharged:

 Volume of Confined Water for a change in head = SAΔh Confined Volume =

The unconfined aquifer received 3,333 times as much water as the confined aquifer.