Assessing the effect of urbanization on regional-scale surface water-groundwater interaction and nitrate transport

Abstract

Identifying regional-scale surface water-groundwater interactions (SGI) is vital for predicting anthropogenic effects on surface water bodies and underlying aquifers. However, large-scale water and nutrient flux studies rely on surface water or groundwater-focused models. This study aims to model the effect of urbanization, which is usually accompanied by high groundwater abstraction and surface water pollution, particularly in the developing world, on a regional-scale SGI and nitrate loading. In the study area, the urban expansion increased by over 3% in the last decade. The integrated SWAT-MODFLOW model, Soil and Water Assessment Tool (SWAT) and Modular Finite-Difference Groundwater Flow (MODFLOW) coupling code, was used to assess SGI. By coupling SWAT-MODFLOW with Reactive Transport in 3-Dimensions, the nutrient loading to the river from point and non-point sources was also modeled. Basin average annual results show that groundwater discharge declined with increasing groundwater abstraction and increased with Land use/Land cover (LULC) changes. Groundwater recharge decreased significantly in the Belge season (February to May), and the river seepage and groundwater discharge decreased correspondingly. High spatiotemporal changes in SGI and nitrate loading were found under the combined LULC and groundwater abstraction scenarios. The water yield decreased by 15%. In a large part of the region, the nitrate loading increased by 17–250%. Seasonally controlled groundwater abstraction and water quality monitoring are essential in this region.

Assessment of Nitrate in Groundwater from Diffuse Sources Considering Spatiotemporal Patterns of Hydrological Systems Using a Coupled SWAT/MODFLOW/MT3DMS Model

“…The lack of a better fit is due to the limited information and the uncertainty associated with the use of the model as a third stage, which did not allow for better results. The calibration performed in MODFLOW and MT3DMS presented a lower error than the present study [117,131,137,138], with acceptable results [132].…”

“…The implementation of the SWAT model, as a tool to evaluate this interrelation of the hydrological system, presents a great advantage in water resources management. In addition, as observed in previous works [115,136], the calibrated parameters are related to the interrelationship that occurs in the subsoil [117,118,137], towards the recharge in order to make the coupling with MODFLOW. However, in this study, in addition to calibrating these parameters, soil characteristics were calibrated, as shown in Table 1.…”

“…The following proposed method was used to assess nitrate concentration in groundwater by quantifying the spatiotemporal patterns of groundwater-surface water interaction with limited information. It is presented as a methodology, since according to studies [93,94,[117][118][119][120][121], the coupling of SWAT/MODFLOW/MT3DMS and SWAT/MODFLOW models is performed by calibrating parameters associated with recharge and the passage of water through the subsurface (plant available soil water capacity, curve number, surface runoff lag coefficient, deep aquifer percolation fraction, and others). However, in the present study, in addition to these parameters associated with recharge, it is calibrated using the characteristics of a single soil type.…”

Calibration and uncertainty analysis of integrated SWAT-MODFLOW model based on iterative ensemble smoother method for watershed scale river-aquifer interactions assessment

“…Coupled Groundwater and Surface-Water Flow (GSFLOW) (Markstrom et al 2008) and SWAT-MODFLOW (Kim et al 2008;Bailey et al 2016) are widely used iteratively coupled models. This coupling method is less computationally intensive and has been increasingly used in regional-scale studies (Markstrom et al 2008; Sur eet and Tullos 2013; Chung et al 2014;Yifru et al 2022).…”

Seasonal variation in landcover estimates reveals sensitivities and opportunities for environmental models

“…This has prompted popular hydrological models such as the Soil and Water Assessment Tool (SWAT) 16 to include seasonal cycles for factors like leaf area and crops 17 . SWAT is one of the most popular water quality models worldwide 18 and has been used for many recent environmental studies [19][20][21][22] . Further, to account for the coarse temporal resolution of traditional LULC datasets (e.g.…”