Groundwater is one of the most important sources of water for drinking and irrigation in arid and semi-arid regions of the world. In this study, 50 groundwater samples were collected and analyzed for various chemical constituents (pH, TDS, Na⁺, K⁺, Ca²⁺, Mg²⁺, SO₄²⁻, Cl⁻, HCO₃⁻, NO₃⁻, and F⁻) to identify the hydrogeochemical characteristics, and to evaluate its suitability for drinking and irrigation uses in Zhongning area of Northwest China. Results showed that groundwater was slightly alkaline in nature. Fluoride and nitrate concentrations in the groundwater of the study region were much higher than its prescribed limits for drinking purposes. A factor analysis (FA) was implemented to understand the contamination source of groundwater in the region, and the results indicated that rock–water interaction, geogenic, and human-induced contamination were the major factors influencing groundwater chemistry. An entropy-weighted water quality index (EWQI) was employed to evaluate the water quality for drinking purpose. Mg²⁺, Ca²⁺, SO₄^2-, HCO₃⁻, and TDS played the leading roles in influencing the groundwater quality with high weights. Forty-eight percent of groundwater samples were unfit for drinking purpose in the study area, due to poor quality. Elevated concentrations of SO₄²⁻, Cl⁻ and NO₃⁻-N in groundwater caused poor quality and extremely poor quality water, which may be attributed to human activities. According to the calculation of sodium percentage (Na%), sodium adsorption ration (SAR), and permeability index (PI), the majority of the groundwater samples were suitable for irrigation. However, it should be noted that 26% of the samples were unfit for irrigation because of the high salinity in the groundwater. This is mainly attributed to the intense evaporation and the intensified irrigation activities in the region. The findings in this study contribute to a better understanding of groundwater sustainability for supporting water management and protection in the future.

This study focuses on the intensity, duration, and frequency of meteorological droughts in Ningxia, northwest China, from 1960 to 2016. The analysis was conducted using the interannual characteristics of droughts, which were studied by the standardized precipitation evapotranspiration index (SPEI) at different timescales. Additionally, the correlation, mutability, and periodicity of two series in both the time and frequency domains in multi-time scales were scientifically analyzed using the wavelet analysis method. The results showed that the occurrence of drought had increased at different timescales (i.e., SPEI1, SPEI3, and SPEI12) during the past 57 years. The autumn drought had the largest share; spring is the high-occurrence season of extreme drought and the overall drought intensity increases towards the north. The periodical change of droughts was described with the wavelet coefficient real part value, wavelet power spectrum, and wavelet variance. The results showed that the 13- and 8-year time scales had the strongest oscillation and energy, and they were the first and the second major periods of drought. Moreover, the drought mutational fluctuations are in better agreement with that characterized by the SPEI12 and actual conditions. The results help to understand the occurrence and evolution of droughts in Ningxia, and to provide a scientific basis to reduce and prevent the drought disaster.

Groundwater is an important source of drinking water, particularly in arid regions. In this study, a total of 66 groundwater samples were collected from the phreatic aquifer in the Shizuishan area, a traditional irrigation region of Ningxia. The results showed that the TDS values were above the drinking water standards for nearly 50% of the groundwater samples. The ions followed the order of Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and SO₄²⁻ > Cl⁻ > HCO₃⁻ in the groundwater. There were four dominant factors in controlling groundwater chemistry based on principal component analysis: the salinity factor, alkalinity factor, carbonate factor, and pollution factor. The high concentration of NH₄-N in groundwater was attributed to agricultural activities, but the high NO₃-N levels were mainly due to sewage or wastewater. F and As were derived from geogenic sources. Based on the result of the WQI assessment, about 40% of the samples in the central part of the study region showed unacceptable water quality for drinking, which was mainly associated with high NH₄-N, TDS, and As concentrations. The total non-carcinogenic risks of drinking the groundwater were 0.05–10.62 for adults and 0.09–20.65 for children, respectively. The order of pollutants in the groundwater in terms of their hazard to residents was: As > F⁻ > NO₃-N > NH₄-N. The carcinogenic risk values of As through oral ingestion for children and adults were 0–7.37 × 10⁻⁴ and 0–1.89 × 10⁻⁴, respectively. Chronic exposure by oral ingestion presented as the main source of susceptibility to exposure to groundwater contaminants for children.