Shallow Aquifer

The water balance for the shallow aquifer is:

$aq_{sh,i}=aq_{sh,i-1}+w_{rchrg,sh}-Q_{gw}-w_{revap}-w_{seep}-w_{pump,sh}$ 2:4.2.1

where $aq_{sh,i}$ is the amount of water stored in the shallow aquifer on day $i$ (mm H$_2$O), $aq_{sh,i-1}$ is the amount of water stored in the shallow aquifer on day $i-1$ (mm H$_2$O), $w_{rchrg,sh}$ is the amount of recharge entering the shallow aquifer on day $i$ (mm H$_2$O), $Q_{gw}$ is the groundwater flow, or base flow, into the main channel on day $i$ (mm H$_2$O), $w_{revap}$ is the amount of water moving into the soil zone in response to water deficiencies on day $i$ (mm H$_2$O), $w_{seep}$ is seepage from the shallow aquifer to the deep aquifer on day $i$ (mm H$_2$O) and $w_{pump,sh}$ is the amount of water removed from the shallow aquifer by pumping on day $i$ (mm H$_2$O).