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.

Salinization is one of the significant factors that impede agricultural development, threaten ecological security, and hinder sustainable development. This study successfully achieved precise and expeditious identification of salinization grades by integrating optical satellite data with other geospatial information. It effectively enhanced the accuracy of salinization inversion, with a recognition rate of 85.34%. The salinization in the Hexi irrigation area showed a decreasing trend from 2014 to 2023, with no and slight salinization increasing by 8.37% and 3.54%, while moderate and severe salinization decreased by 17.23% and 19.11%. This was mainly due to changes in hydrological processes, shown by a 5.6% and 6.8% decrease in water diversion and drainage, and a roughly 0.45 m rise in groundwater depth. Through the analysis of the relationship between salinization and groundwater depth, it is found that the further north the area is, the more severe the salinization. And the shallower the groundwater depth, the more difficult it is to maintain the groundwater depth at the threshold to prevent salinization. It is primarily due to obstructed drainage in the northern region, leading to salinization. Through exploring the reasons for drainage obstruction, the causes of salinization in different regions were identified. This research aims to provide some reference for the investigation, regulation, and management of regional salinization.

The runoff levels of the major hydrological stations in the Weihe river basin (WRB) have been found to present decreasing trends. However, the conspicuous spatial differences in the hydro-meteorological conditions have led to variations in the rainfall–runoff pattern in each of the sub-basin areas. The aims of this research study were to reveal the main factors contributing to the runoff changes in the different regions—and it has significance in the water resources rational allocation and protection in the different regions. Three statistical methods were used to analyze the law of precipitation and runoffs of five hydrological stations. The SWAT (Soil and Water Assessment Tool) model was used to reconstruct the runoff in the impact period. The effects of climate change and human activity on runoff were separated by comparing measured runoff and reconstructed runoff. The results show that the closer the proximity to the downstream hydrological station, the more the runoff decreased. In the tributaries and upstream hydrological stations (Zhuanhtou (ZT), Zhangjiashan (ZJS), and Linjiacun (LJC)), from 1970 to 2016, the dominant factor of the runoff reduction was determined to be climate change, and accounted for 148.2%, 98.9%, and 90.5%, respectively. In the hydrological stations of middle and lower reaches (Xianyang (XY) and Huaxian (HX)), the contributions of the climate change to the runoff reduction were 49.7% and 44.3%, respectively, and the impacts of human activity accounted for 50.3% and 55.7%. The impacts of human activity on the runoff reduction were slightly greater than that of the climate change. Due to the different leading factors affecting runoff change in the basin, in response to future climate change, for tributaries and upstream areas, land use should be rationally planned to achieve the optimal balance of water volume in each part of the basin, which is of great significance to the protection and utilization of water resources. As for the middle and downstream regions, reasonable planning should also be focused on the amount of water withdraw, water resource allocations, and water conservancy project construction. According to the factors affecting runoff, corresponding strategies are proposed for different regions, which have important research significance for the protection and sustainable development of watershed water resources.

Agricultural economy is usually studied by total factor analysis, while it is uncertain what factors affect agricultural production in the perspective of water utilization. The aim of this study was to investigate driving forces of agricultural economy related to water utilization effects in Ningxia during 2007 to 2017. The logarithmic mean Divisia index (LMDI) method was selected to decompose the driving forces of agricultural production value. Results showed that the agricultural production value increased significantly in 2007–2017 in all of Ningxia and in each city. In terms of the whole region, the effect of agriculture water efficiency played a leading and positive role in the increase of the agricultural production value. The effects of water stress, water utilization structure, and water resource endowment all showed a negative driving force, while population exerted a positive effect. For five cities, the effect of agriculture water efficiency and water utilization structure showed no spatial difference; whereas the other effects expressed different driving forces between cities in the northern plain area and southern hilly area due to varied natural conditions and agricultural activities. The results of this research suggested that the first and foremost strategy of agricultural development and water resource management in Ningxia should be to promote water-saving irrigation and optimize agricultural structure.

Water conservation is imperative for alleviating water shortages and fostering the establishment of a water-saving society. However, the implementation of water-saving measures caused an increase in the depth to groundwater, resulting in ecological issues. Therefore, reasonable water saving should consider the appropriate depth to groundwater and its evolution trend. This study focuses on the Helan irrigation area in Ningxia as the research subject, aiming to establish thresholds for agricultural water-saving measures while considering constraints by depth to groundwater. The evolution trend of depth to groundwater from 1995 to 2018 was analyzed using the k-Shape cluster and complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) methods. Then, the thresholds of agricultural water-saving measures involved comparing groundwater numerical simulation results for water-saving scenarios, with the control area of ecological groundwater table depth and water shortage rate serving as the evaluation indices. The thresholds for implementing agricultural water-saving measures are as follows: the canal water utilization coefficient is set at 0.62; the proportion of water-efficient irrigation areas to effective irrigation areas should be 40% in the Yellow River irrigation area and 90% in the pumps-up Yellow River irrigation area; additionally, a reduction of 75% in the rice planting area is targeted.

Irrigated areas are major vectors of agricultural development and components of ecosystems. The groundwater level maintains the irrigated areas’ ecology safety and sustainable development. Under the influence of irrational irrigation practices—such as flood irrigation or extreme water saving without consideration of ecological impact—different areas within an irrigation district may experience anomalies in groundwater levels (either too deep or too shallow). It is of great significance to carry out research on water resource allocation and future water-saving strategies, taking into consideration groundwater depths. In this study, a method for the optimal allocation of irrigation water resources that considered groundwater level was used to regulate irrational irrigation practices and to reveal the future direction of water saving. Helan County in Ningxia province, an ecologically fragile and arid irrigated area, was selected as a case study. Multiple scenarios of different water use and different degrees of water-saving were analyzed. The results showed that non-engineering water-saving measures (such as adjusting the planting structure and controlling the amount of irrigation for rice) had better benefits compared to engineering measures (such as efficient water-saving irrigation and channel lining). When implementing only one water-saving measure, the strategy of replacing 75% of the rice area with corn yielded the best results. This approach can reduce the irrigation water shortage rate to 11% and increase by 4.58% the acreage where the groundwater level is reasonable. When multiple water-saving measures are implemented together, the most effective strategy for future water-saving efforts involves the joint implementation of several measures: replacing 75% of the rice area with corn, limiting irrigation for rice to no more than 11.85 thousand m³/ha, adopting high-efficiency water-saving irrigation in 90% of the pump-diverted water irrigation region and 40% of the channel-diverted water irrigation region, and maintaining the channel’s water utilization coefficient at 0.62. This strategy can keep the irrigation water shortage below 3.66% and increase the acreage where the groundwater level is reasonable, by 4.58% per year. The conclusions and research approaches can provide references for the formulation of water-saving measures for irrigated areas’ sustainable development.