Agricultural water and land resources are key elements of human production and their unbalanced distribution has threatened the sustainable development of agriculture and regional food security. This study is aiming to investigate the spatial–temporal changes of matching characteristics between agricultural water and land resources in Ningxia during 2007 to 2017. The agricultural irrigation water (AIW), farmland area (FA) and effective irrigated area (EIA) were selected as quantity parameters for agricultural water and land resource. Results show that the gravity centers of AIW and EIA both moved in the southeast direction, while the gravity center of FA moved northwestward, which indicated a better spatial matching degree between AIW and EIA. According to the Gini coefficient and total spatial mismatch index, the spatial mismatch between AIW and FA of Ningxia was remedied and that of AIW and EIA was worse. Counties with sufficient and insufficient AIW were distributed in the north and the south of Ningxia, respectively. The sensitivity of agricultural irrigation water to land resources remarkably increased in the study period, particularly for the counties in northern area of Ningxia. The findings may provide implications for effective management of regional agricultural water and land resources.

The Yangtze River Estuary (YRE) is the largest estuary in China, with three-order bifurcations and four outlets into the sea. In recent years, issues of saltwater intrusions have received increased attention due to the increased levels and frequencies of the intrusions. The saltwater intrusions into the YRE resulting from river discharges were investigated in this study based on river discharge levels at the Datong station. A hydrodynamic and salinity transport model (MIKE21) was used to quantify the influences of the river discharges on the saltwater intrusions in the YRE. The model was effectively validated through observational data of the tidal and salinity levels. The 25%, 50% and 70% frequencies of the river discharges during the dry seasons were determined to be 18,112, 16,331 and 14,832 m³/s, respectively. A multi-year averaged river discharge of 27,856 m³/s was used to simulate the salinity level changes resulting from the different river discharges. The results revealed the following: (1) the salinity of the South Branch (SB) was distributed as “high–low–high”; and the changes in the salinity levels were greatly affected by the river discharges. A strong correlation was found between the salinity and flow in the North Branch (NB) and SB of between 0.917 and 1; (2) the changes in the river discharges had major impacts on the changes in the salinity levels in the SB. When the runoff was 27,856 m³/s, the salinity excessive area rate (the ratio between salinity excessive area (>0.45‰) and the SB area) less than 10%. However, when the river discharges were reduced to 16,331 m³/s, the salinity excessive area rate is more than 50%; (3) As the river discharges decreased, the amplification line (0.2‰) also rapidly decreased, and the amplification lines (0.45‰, 2‰) increased. At points far from the river’s entrance, the effects of the runoff were observed to be weakened, such as the amplification lines gradually becoming reduced; (4) the changes in the river discharges were observed to have significant impacts on the freshwater reservoir water withdrawal. When the river discharges were maintained at 27,856 m³/s, the salinity of the Baogang, Chenhang, and Qingcaosha Reservoirs remained below 0.45‰. The salinity levels of the four reservoir locations examined in this study were found to exceed the Chinese drinking water standard (0.45‰) for more than 23 days in the 14,832 m³/s river discharge scenario, which negatively affected the drinking water of the population living near the YRE.

Water resource shortages, water environmental deterioration, and water ecological degradation are becoming increasingly prominent in the Haihe River Basin under the effects of global climate change and intense human activity. Finding ways to solve these problems reasonably is an urgent task in basin water resources management. The water cycle describes the formation and transformation of every water drop, while it interacts with associated water ecology and water environment processes. Therefore, to fundamentally solve the above problems, the three processes must be combined and the evolutionary trends of the ecology and water environment driven by the water cycle must be determined. To comprehensively diagnose and solve the problems of water resources, ecology and water environment in the basin, an integrated simulation platform of the dualistic water cycle and its associated processes in the Haihe River Basin was established by fully analyzing the “natural-social” dualistic characteristics of the evolution of the basin water cycle in this study. Accordingly, it is a supporting tool to evaluate the future trends of water resources, ecology and the water environment by setting scenarios based on the predictions of a climate mode and water control conditions. The results show that with climate change, the water consumption, groundwater overexploitation, and the amount of water flowing to the sea could develop soundly and satisfy the requirements of national economic growth in the future planning year 2030 through the implementation of water consumption control management and the South-North Water Diversion Project. Meanwhile, associated water environmental deterioration can be alleviated, and a growing trend for production capacities of the natural ecosystem and agro-ecosystem is seen. The above results provide a foundation for implementing basin water resources regulation and the most strict water resources management.