Hill & Neary figured out the net groundwater exchange $($groundwater discharge and recharge added together$)$ in each month based on the following data for net precipitation $(($:$P_n\},$ surface water runoff inflow $,$ equivalent to $S_i$ in your textbook$),$ change in storage volume over time $(\frac{?}{{?}_{\frac{?}{?}}S},$ equivalent to $\frac{V}{}t),$ and evapotranspiration $($PET$-$E $E_c,$ equivalent to $ET).($We assume there is no surface water outflow and no tidal influence in this wetland.$)$

Table I Summary of water budget for $10$ months in $2004$ and $2005$ with ponded surface water

$\backslash$table$[[,$Month,$P_n(m^3),\backslash$table$[[R_i(m^3)$