Water-saving potential analysis of irrigation districts with conjunctive use of groundwater and surface water based on the concept of groundwater safety: A case study of Zhangjiakou section in the Yongding River Basin
Agricultural water-saving potential plays an important role in the determination of the development direction of water-saving irrigation and the solution of water shortage problems. In order to explore the water-saving potential of irrigation districts with conjunctive use of groundwater and surface water in Zhangjiakou section of the Yongding River Basin, the agricultural water-saving potential was divided into two categories, namely, management water-saving potential and engineering water-saving potential. To avoid the risk of groundwater over-exploitation in the irrigation districts after they fulfilled their full water-saving potential, the groundwater safety test method was introduced to establish an analysis method that met the groundwater safety requirements. The results showed that the current water consumption of the large and medium-sized irrigation districts in the Zhangjiakou section of the Yongding River Basin totalled 1.62×108 m3, the surface water-saving potential estimated by conventional method was 0.805 9×108 m3, and then revised to 0.795 4×108 m3 after the consideration of groundwater safety, of which the management water-saving potential and engineering water-saving potential were 0.610 5×108 m3 and 0.185 0×108 m3, accounting for 76.7% and 23.3%, respectively. The management water-saving potential accounted for a larger proportion. The phenomenon of heavy engineering construction and light irrigation management in the large and medium-sized irrigation districts of Zhangjiakou section of the Yongding River Basin must be addressed in order to tap the management water-saving potential to a greater extent. The proportion of management water-saving potential and engineering water-saving potential of the irrigation districts with conjunctive use of groundwater and surface water can be accurately evaluated using the proposed analysis method under the premise of groundwater safety, and the research results have practical guiding significance for the future planning and construction of irrigation projects in the irrigation districts.