Hydrology

River basins constitute a suitable natural territorial unit for the integrated management of natural resources. The El Fuerte River basin (EFRB) in northwestern Mexico is located on the western slope of the Sierra Madre Occidental. Its importance lies in its contribution to irrigation systems in the state of Sinaloa and to hydroelectric power generation, as well as its strong dependence on seasonal precipitation associated with the North American Monsoon (NAM). A reduction in NAM precipitation has been observed in northwestern Mexico. Using CHIRPS precipitation data and ERA5 reanalysis, we analyzed the relationship between precipitation trends and the variability of the Normalized Difference Vegetation Index (NDVI) in the El Fuerte River basin for the 2000–2025 period. Land vegetation cover in EFRB is dominated by Tropical Dry Forest (TDF). The results indicate that the TDF responds directly to precipitation conditions during both the dry and wet seasons. The exceptional drought and a cold wave in 2011 disrupted NDVI values in EFRB, causing an increase in greenness during the post-disturbance recovery period associated with a shift in the basin’s vegetation composition. The decline in NAM precipitation may be linked to multiple factors, including reduced moisture transport due to weakened low-level zonal winds and changes in land vegetation cover. The effects of these changes in precipitation trends and recurrent droughts could drive further changes in vegetation structure, thereby altering the basin’s hydrological cycle.

This study investigates changes in local groundwater carrying status and regional differences under the background of reductions in total groundwater abstraction, using Jiuquan, Jiayuguan, Zhangye, Jinchang, and Wuwei in the Hexi Corridor as study areas. The analysis was conducted from three dimensions: resource base, development pressure, and groundwater-level–storage change. The groundwater abstraction pressure index and net abstraction excess were jointly used to distinguish relative development intensity from the absolute volume exceeding allowable abstraction. Regional differences were further identified using groundwater-depth changes at 515 monitoring stations and shallow groundwater-storage changes. Residual correlations after controlling for month effects and linear trends, together with robustness tests, were used to examine the associations of precipitation, river runoff, and groundwater abstraction with groundwater depth. Results showed that total groundwater abstraction in the five cities decreased by 23.8% from 2018 to 2025, whereas the abstraction pressure index in key overexploitation areas remained between 1.12 and 2.08 in 2024, indicating that regional abstraction reduction and local overexploitation coexisted. Jinchang had the highest relative abstraction pressure, whereas Wuwei had the largest net abstraction excess, demonstrating that relative development intensity and excess abstraction volume correspond to different management priorities. During the study period, groundwater levels declined at 404 monitoring stations, and the cumulative shallow groundwater-storage change was −69.14 × 10⁸ m³. Storage losses were concentrated mainly in Zhangye and Jiuquan and did not correspond to the regional ranking of development pressure, highlighting differences between current development intensity and cumulative storage change. After month effects and linear trends were controlled, the absolute values of 14 of the 15 correlations decreased, and 11 correlations changed from positive to negative, indicating that common seasonal cycles and long-term trends substantially affected the raw contemporaneous associations. By combining diagnosis of relative intensity and water-volume excess, comparison of groundwater-level and storage changes, and temporal-structure adjustment, this study refines regional identification of groundwater carrying status and provides a basis for spatially differentiated abstraction reduction and coordinated surface-water–groundwater management.

Phosphorus (P) contamination in surface water is a major global concern affecting most suburban river catchments worldwide due to the discharge of industrial effluents and urban sewage, a consequence of rapid urbanization and industrialization. The objective of this study was to investigate the concentrations and seasonal patterns of various phosphorus (P) species in water from the Yamato River. Total phosphorus (TP), total particulate phosphorus (TPP), and particulate inorganic phosphorus (PIP) were determined using the molybdenum blue method; particulate organic phosphorus (POP) and total dissolved phosphorus (TDP) were calculated by difference; and particulate phosphorus was fractionated using the sedimentary phosphorus sequential extraction (SEDEX) method. Average TP concentration was 0.31 mg/L (0.14 mg/L–0.77 mg/L), TPP was 0.10 mg/L (0.03 mg/L–0.47 mg/L), PIP was 0.07 mg/L (0.02 mg/L–0.46 mg/L), particulate organic phosphorus (POP) was 0.02 mg/L (0.00 mg/L–0.24 mg/L), and total dissolved phosphorus (TDP) was 0.22 mg/L (0.00 mg/L–0.71 mg/L). There was a decrease in TP levels with increased water levels in summer, possibly due to dilution effects, although other factors may be influencing TP levels. TDP consistently dominated over TPP but was more pronounced in low-flow conditions in winter compared to summer. PIP exceeded POP on most dates, although they both increased with the increased water levels witnessed in the summer. Fe-P was the dominant P species, increasing alongside Ca-P in the summer (irrigation period of paddy fields). The study indicated that the phosphorus pollutants in the river water were inorganic in nature and may have originated from the leaching of inorganic fertilizers from nearby paddy fields, urban surface runoff, wastewater discharge, and construction debris carried as erosion products.