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In arid and semiarid areas, the issues of water security, ecological security, and food security are tightly interlinked. Understanding the water‐ecosystem‐agriculture (WEA) nexus in such areas is critical to their sustainable development. This study presents a basin‐scale integrated ecohydrological model and a paradigm for analyzing the WEA nexus through physically based modeling. The integrated model is successfully applied to the Heihe River Basin (HRB), the second largest endorheic river basin in China. A system analysis of the WEA nexus in the HRB is performed using the validated model. The major findings are as follows. First, reducing the amount of irrigation water applied to the midstream of the HRB produces widely varying effects on the water balance of the basin. Second, a threshold of 11.5 × 108 m3/yr is found for the streamflow from the midstream region to the downstream region, beyond which the contribution of the streamflow to the recovery of vegetation is trivial in the short term. Third, the trade‐off among water conservation, ecosystem protection, and food production in the HRB is strong, and it is highly sensitive to the water management strategy employed. Evaporative water‐saving practices are more desirable than direct water‐saving regulation of irrigation water from the perspective of the WEA nexus. Overall, the results of the study provide insights into the allocation of water resources, ecosystem conservation, and agricultural development in the vast arid and semiarid areas of the world.

Integrated surface water–groundwater (SW–GW) models could be used to assess the impacts of climate change or variability on the hydrological cycle. However, the damping effects of the hydrological system have rarely been explored via integrated SW–GW modeling. This paper presents an integrated modeling study in a typical humid area, the Miho catchment in Korea, using an integrated model called Groundwater and Surface-water FLOW (GSFLOW). The major findings of this study are as follows: (1) The simulated results from 2005 to 2014 indicate that the temporal variability in the streamflow, stream-groundwater interactions and groundwater recharge are dominated by the precipitation, while the temporal variability in the evapotranspiration (ET) is controlled by the energy conditions; (2) Damping effects can affect the hydrological cycle across different temporal and spatial scales. At the catchment scale, the soil zone and aquifer play a dominant role in damping the precipitation on monthly and annual time scales, respectively; (3) Variability in the capacity to buffer earlier precipitation is found at small spatial scales, such as streams, and larger spatial scales, such as the whole catchment. This variability could affect the water balance at larger spatial scales and affect the hydrography recession at smaller spatial scales.

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