Modeling surface water-groundwater interaction in arid and semi-arid regions with intensive agriculture Yong Tian, Yi Zheng * , Bin Wu, Xin Wu, Jie Liu, Chunmiao Zheng Center for Water Research, College of Engineering, Peking University, Beijing 100871, China article info Article history: Received 10 March 2014 Received in revised form 10 October 2014 Accepted 13 October 2014 Available online Keywords: Surface water-groundwater interaction Integrated modeling GSFLOW SWMM Heihe River Basin abstract In semi-arid and arid areas with intensive agriculture, surface water-groundwater (SW-GW) interaction and agricultural water use are two critical and closely interrelated hydrological processes. However, the impact of agricultural water use on the hydrologic cycle has been rarely explored by integrated SW-GW modeling, especially in large basins. This study coupled the Storm Water Management Model (SWMM), which is able to simulate highly engineered flow systems, with the Coupled Ground-Water and Surface- Water Flow Model (GSFLOW). The new model was applied to study the hydrologic cycle of the Zhangye Basin, northwest China, a typical arid to semi-arid area with significant irrigation. After the successful calibration, the model produced a holistic view of the hydrological cycle impact by the agricultural water use, and generated insights into the spatial and temporal patterns of the SW-GW interaction in the study area. Different water resources management scenarios were also evaluated via the modeling. The results showed that if the irrigation demand continuous to increase, the current management strategy would lead to acceleration of the groundwater depletion, and therefore introduce ecological problems to this basin. Overall, this study demonstrated the applicability of the new model and its value to the water resources management in arid and semi-arid areas. © 2014 Elsevier Ltd. All rights reserved. Software availability Name: GSFLOW-SWMM Program language: Fortran and C Developers: Dr. Yong Tian (yongtian@pku.edu.cn) and Dr. Yi Zheng (yizheng@pku.edu.cn), Center for Water Research, College of Engineering, Peking University, Beijing 100871, China Availability: Contact the developers 1. Introduction In arid and semi-arid regions, interaction between surface water (SW) and groundwater (GW) plays an important role in the eco- hydrological system (Sophocleous, 2002; Gilfedder et al., 2012). The interaction is often complicated by agricultural activities including surface water diversion, groundwater pumping and irri- gation, as they could significantly alter the flow regimes of both surface water and groundwater (Barlow et al., 2000; McCallum et al., 2013; Shah, 2014; Siebert et al., 2010). Understanding the complex behavior of the integrated SW-GW system is very important to the regional water resources management (Rassam et al., 2013), and integrated modeling is a highly desired approach. A number of integrated SW-GW models have been developed, such as GSFLOW (Markstrom et al., 2008), HydroGeoSphere (Brunner and Simmons, 2012; Therrien et al., 2010), ParFlow (VanderKwaak and Loague, 2001), MIKE SHE (Graham and Butts, 2005), MODHMS (Panday and Huyakorn, 2004) and SWATMOD (Sophocleous et al., 1999). Some of these models incorporate MODFLOW (Harbaug, 2005), a classic 3-D groundwater simulator, as their subsurface module. For example, GSFLOW integrates Pre- cipitation Runoff Modeling System (PRMS) (Leavesley et al., 1983) with MODFLOW; SWATMOD couples the widely applied Soil Water Assessment Tool (SWAT) (Arnold et al., 1998) model with MOD- FLOW; and MODHMS introduces 2-D diffusion wave routing for surface water into MODFLOW. The existing models have been applied to address different water resources issues, including irri- gation management (e.g., P erez et al., 2011), SW-GW interactions (e.g., Huntington and Niswonger, 2012; Niswonger et al., 2008; Werner et al., 2006), land use and climate change (e.g., Graham and Butts, 2005; Markstrom, 2012), water quality (e.g., Borah and Bera, 2003) and so on. However, few studies (Demetriou and Punthakey, 1998) have investigated the hydrologic impacts of agricultural water use in the context of integrated SW-GW modeling, especially for large river * Corresponding author. E-mail address: yizheng@pku.edu.cn (Y. Zheng). Contents lists available at ScienceDirect Environmental Modelling & Software journal homepage: www.elsevier.com/locate/envsoft http://dx.doi.org/10.1016/j.envsoft.2014.10.011 1364-8152/© 2014 Elsevier Ltd. All rights reserved. Environmental Modelling & Software 63 (2015) 170e184