# Research on the Jiamusi Area's Shallow Groundwater Recharge Using Remote Sensing and the SWAT Model
## 4 Results
### Calculation of Groundwater Recharge in the Jianusi Area by the SWAT Model
#### 4.2.3 Calculation of Groundwater Resources Based on SWAT
The yearly runoff was 981 million m\({}^{3}\) in 2014 (\(p\) = 50%) and 1.216 billion m\({}^{3}\) in 2016 (\(p\) = 25%). The recoverable amount of groundwater was computed in average years. This paper computed the natural recharge of the groundwater system in the watershed using the groundwater runoff modulus approach. Prior to calculating the natural recharge of each sub-basin, the output of each sub-basin in a typical year that the model simulated was determined. The average runoff of each sub-basin was then translated into the groundwater runoff modulus of each sub-basin. Moreover, the groundwater exploitable amount \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**A Given Year**} & \multicolumn{2}{c}{**Supply Term**} & \multicolumn{2}{c}{**Excretion Term**} & \multirow{2}{*}{**Subtotal**} & \multirow{2}{*}{**\(\Delta\)**Sgw**} \\ \cline{2-2} \cline{5-6}  & **PERC** & & & & & \\ \hline
**2010** & 35.70 & 3.6 & 26.15 & 12.51 & 6.56 & \(-\)6.56 \\
**2011** & 26.40 & 3.41 & 31.2 & 17.61 & 25.82 & \(-\)25.82 \\
**2012** & 42.50 & 2.07 & 30.41 & 1.52 & 8.5 & 8.5 \\
**2013** & 33.54 & 0.42 & 35.64 & 2.00 & 4.34 & \(-\)4.34 \\
**2014** & 35.42 & 0.23 & 39.09 & 1.83 & 5.73 & \(-\)5.73 \\
**2015** & 29.77 & 0 & 33.08 & 1.75 & 5.13 & \(-\)5.13 \\
**2016** & 51.59 & 0.11 & 35.76 & 1.56 & 14.16 & 14.16 \\
**Mean value** & 36.41 & 1.40 & 33.04 & 5.54 & 3.57 & \(-\)3.57 \\
**Excretion item** & - & 3.50 & 82.64 & 13.85 & - & - \\
**percentage/\%** & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Groundwater storage variables in Jiamusi area. Unit: 10\({}^{8}\) m\({}^{3}\). Figure 9: Spatial distribution map of water volume in phreatic beds in sub-basins ((a) is basin No. 1, (b) is basin No. 2, Unit: 10\({}^{8}\)\(\times\) m\({}^{3}\)). in typical years of each sub-basin was estimated using the exploitable coefficient approach in order to determine the groundwater exploitable amount in the basin at the scale of the research region. The average mining coefficient (\(\rho\) = 0.45) of the several hydrogeological zones in Jiamusi City was calculated in order to increase the estimation's accuracy. It can be seen from the calculation that the groundwater recharge in the No. 1 basin was about 384,925,200 cubic meters in the dry year, about 46,580,908,600 cubic meters in the normal year, and 4,801,663,100 cubic meters in the wet year; therefore, the groundwater recharge in the wet year was 1.25 times that in the dry year. The trend of groundwater recharge in the No. 2 basin was similar to that in the No. 1 basin. The groundwater recharge in the dry year was 841,353,600 cubic meters, the groundwater recharge in the normal year was about 1,883,781,800 cubic meters, and the groundwater recharge in the wet year was about 2,350,304 million cubic meters; therefore, the groundwater recharge in the wet year was about 2.54 times that in the dry year. Detailed results are shown in Tables 11 and 12 and Figure 1