Performance evaluation and verification of groundwater balance using WA + as a new water accounting system

In this study, to increase the accuracy of determining the parameters of groundwater balance and finally the aquifer reservoir deficit, WA + as a new water accounting system has been applied by calculating six sheets in the Plasjan basin, central Iran. According to the results, the volume of rainfall and transfer flow to the basin was 548.8 MCM in the water year 2016–2017, which entered the hydrological cycle as input. Moreover, the results of FAO’s Water Productivity Open-Access Portal (WaPOR) product showed that evapotranspiration was equal to 465 MCM, of which 345 and 120 MCM belonged to green water and blue water, respectively, at the basin level. The results of the WaPOR product showed that 264 MCM of evapotranspiration was beneficial, while the rest was non-beneficial in the basin. Finally, investigating the runoff and utilization of water resources showed that the return flow to surface water and groundwater resources was 35.5 MCM and 62 MCM, respectively. Therefore, the aquifer deficit was estimated to be 56.3 MCM based on the results of the WA + system. By calculating the evapotranspiration using remote sensing in WA + , the return water flow was estimated at 28%, being more accurate compared to the classical groundwater balance. Consequently, the amount of aquifer deficit calculated by the WA + method was accurate according to the balance and the aquifer hydrograph. The findings of this study show that as a suitable tool, the water accounting system can reduce the uncertainty of groundwater balance calculations. Graphical abstract