Groundwater Recharge Modelling at Godagari using the Soil and Water Assessment Tool (SWAT)

Abstract Accurate groundwater recharge assessment is a prerequisite for efficiently managing groundwater resources. In places with low rainfall, especially in arid regions, the level of groundwater is consistently decreasing. As a result, there is a shortage of groundwater resources, which significantly impacts the economy, particularly in relation to irrigation. One of the bottlenecks in evaluating groundwater resources is determining the rate of aquifer recharge. Unlike simpler water balance models, SWAT utilizes physical equations to represent key hydrological processes governing recharge. This allows for a more realistic simulation of recharge based on factors like soil properties, vegetation cover, and topography. Thus, this project aims to create a model using the SWAT model at Godagari, which is situated in the northern region of Bangladesh, to estimate groundwater recharge, aiming to reduce uncertainties and errors in the recharge assessment to the greatest extent possible. The ArcSWAT extension of SWAT version 2009 was used for setting up the model. The model was set up from 1991 to 2022 using weather data, a digital elevation model, a soil map, and a land use and land cover map. The maps were prepared using ArcGIS version 10.7.1. The SWAT model simulation results indicate that out of the total average annual rainfall of 1272.72 mm, only 119.01 mm replenishes the groundwater, 678.09 mm contribute to surface runoff, and 473.20 mm are lost through evapotranspiration. The simulated annual recharge varied from 83.89 to 194.78 mm, indicating a relatively low recharge. The comparison of yearly observed and SWAT simulated recharge showed that the Nash-Sutcliffe coefficient of effectiveness or efficiency (NSE) and coefficient of determination (R2) for the calibration period (1993–2012) and the validation period (2013–2022) are 0.76, 0.69, and 0.81, 0.86, respectively. These results show that the model's performance was satisfactory. SWAT modeling is a feasible option over field-scale approaches for assessing groundwater recharge. The assessments of groundwater recharge using the SWAT model can provide information for developing policies to ensure the sustainable management of water resources in dry areas like the Barind region of Bangladesh. Implementing measures such as zoning and water harvesting that are based on recharge patterns may ensure aquifer replenishment. We can protect groundwater resources and promote long-term water security by prioritizing recharge evaluations in policy creation.