Groundwater balance

Water enters into an aquifer primarily through the process of recharge from rainfall. Water may also enter into an aquifer by the processes of recharge from canal seepage (R_r), return flow from irrigation field (R_f) , leakage from overlaying and underlying aquifers, i.e. leaky aquifer (Q_li), artificial recharge (Q_r), seepage from streams and lakes (Q_si), inflow from the neighboring basins (Q_i). Water can come out from an aquifer by the process of withdrawal from the groundwater aquifer (Q_p), evapotranspiration from groundwater (E_t), outflow to the neighboring basins (Q_o), seepage to the streams and lakes (Q_so), leakage to overlaying and underlying aquifers (Q_lo), discharge through spring (Q_s).

Considering the various inflows and outflows as mentioned above, the groundwater balance equation can be written as:

(2.1)

Where ΔS is the change in storage. Sometimes, from practical point of view, it may not be possible to compute all the components of the groundwater balance equation. Many times some components are lumped together to get a net response of these components.