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The arid endorheic basin of northwest China is characterized by rich land resources, water shortage, and a fragile ecological environment. The establishment of a credible coupling model of groundwater and surface water based on multi-source observation data is an effective means to study the change in basin water cycles and the sustainable utilization of water resources in the past and future. Based on the latest understanding of hydrogeological conditions, hydrology and water resource utilization data in the middle reaches of the Heihe River Basin (HRB), this paper constructs an up-to-date coupling model of surface water and groundwater to study the water balance change of the basin. The water resources data series under historical replay and CMIP5 climate model prediction are constructed to predict future changes in water resources. The study shows that, under the joint influence of natural conditions and human activities, the average annual recharge of groundwater in the study area from 1990 to 2020 is 17.98 × 108 m3/a, the average annual discharge is 18.62 × 108 m3/a, and the difference between recharge and discharge is −0.64 × 108 m3/a. The total groundwater storage is −19.99 × 108 m3, of which the groundwater storage from 1990 to 2001 was −17.52 × 108 m3 and from 2002 to 2020 was −2.47 × 108 m3. Abundant water from 2002 to 2020 in the basin significantly improved the loss of groundwater storage. Under the prediction of historical reappearance and the CMIP5 CNRM-CM5 model RCP4.5 and RCP8.5 pathways, the groundwater level of the Heihe River–Liyuanhe River inclined plain falls first because the HRB has just experienced a wet season and then rises according to future climate change. The groundwater level of the inclined plain east of the Heihe River and Yanchi basin decreases continuously because of the change in water cycle caused by human activities. The erosion accumulation plain is located in the groundwater discharge zone, and the water level is basically stable. Under the conditions of water resource development and utilization, the runoff of Zhengyixia hydrological station cannot meet the requirements of the “97 Water Dividing Plan” of the State Council in most years in the future, and the ecological and production water in the lower reaches of HRB cannot be effectively guaranteed. With the implementation of water-saving irrigation under the RCP4.5 and RCP8.5 scenarios, the runoff of Zhengyixia can meet the “97 Water Diversion Plan”. It is suggested to further improve the level of agricultural water savings in the middle reaches of the HRB and control the reasonable scale of cultivated land in order to reduce water consumption in the middle reaches of the HRB and implement sustainable utilization of water resources in the HRB.

The ecological environment of the northwest inland basin is fragile. The groundwater environment is a crucial influencing factor for the harmonious and sustainable development of the local social economy and the ecological environment. It is significant to investigate the groundwater chemical characteristics, water quality, and the factors that influence groundwater chemistry for groundwater resources development and construction of the ecological environment. In this study, the Jinta Basin (JB), Gansu Province, was the selected study area. Three hundred and fifty groups of shallow groundwater samples in the JB were collected and analyzed, and the characteristics and controlling factors of groundwater were determined by using Piper diagram, Gibbs plot, ion ratio relationship, and factor analysis. Single index evaluation method, comprehensive evaluation method, and entropy-weighted water quality index method were used to evaluate the water quality of the groundwater. The results indicated that the shallow pore water in the JB was alkaline as a whole; the ranges of total dissolved solids (TDS) in the Beidahe River impact area (BIA), the transition area (TA) and the Heihe River impact area (HIA) were 328.4–12,400 mg·L−1, 372.70–3774.0 mg·L−1, and 366.30–75,200.0 mg·L−1, respectively; the major anions and cations of the shallow pore water were SO42−/Cl− and Mg2+/Na+, respectively. The Piper diagram illustrated that the hydrochemical type of groundwater in the JB were mainly HCO3·SO4-Mg type, SO4·HCO3-Mg type, SO4-Mg·Na type, SO4·Cl-Na·Mg type, and Cl-Na type. The overall water quality of the shallow groundwater in the JB was relatively poor, mainly falling into Class IV-V water quality. Sulfate, total hardness (TH), TDS, chloride and sodium were the main influencing factors of water quality. The chemical characteristics of groundwater in the JB were controlled by a variety of natural factors, including rock weathering, evaporative concentration, and cation exchange, among which the main controlling factors of shallow pore water were leaching, evaporative concentration and anthropogenic activities (contribution rate of 73.94%), and sulfate rock and carbonate rock dissolution (contribution rate of 14.91%).

Being a famous hometown of vegetables in China, Shouguang City has a long history of vegetable cultivation and is a comprehensive national commodity base for vegetables and fruits. In recent decades, with the expansion of agricultural production, the use of pesticides is increasing. Although organochlorine pesticides (OCPs) have been banned, there are still some residues in soil, groundwater and other media. The study on the migration of the OCPs in soil and groundwater is of great importance for the maintenance of food security. Using methods of hydrogeological survey, laboratory testing and numerical simulation, the spatial distribution characteristics, sources and pollution degree of OCPs in soil and groundwater were analyzed, and the migration and transformation of OCPs in soil–groundwater was dynamically simulated and predicted. The study showed that there were many kinds of OCPs residual in the soil environment. The hexachlorocyclohexane (HCHs) in the topsoil of the study area were mainly due to the use of lindane, and the main source of dichlorodiphenyltrichloroethane (DDTs) in soil was the use of DDTs in history. The contents of HCHs, DDTs and hexachlorobenzene in the topsoil of the study area were at a low level, while the content of endosulfan metabolite endosulfan sulfate was comparatively higher. In recent years, the content of organochlorine pesticides in soil has generally decreased. The indexes of OCPs in groundwater can meet the Standards for Drinking Water quality of China. It was predicted that the HCH pollutants would mainly be distributed in Gucheng Street, Shangkou Town, and its south area where the concentration exceeds 3 ng/L exceeds that of 240 km2. DDT pollutants would mainly be distributed in the east and north of Shouguang City, where the concentration beyond 0.6 ng/L exceeds that of 200 km2. Endosulfan sulfate pollutants would mainly be distributed in the Gucheng Street Office, Shangkou Town, and its south area where the concentration exceeds 1.5 ng/L will exceed that of 150 km2. Hexachlorobenzene (HCB) pollutants would mainly be distributed in Fengcheng in the west of Shouguang City and Nancha River in the northeast, where the concentration exceeds 0.2 ng/L will exceed that of 200 km2. The study enriched the monitoring data of OCPs in agricultural planting areas and provided reference for source analysis, migration prediction, and pollution prevention of OCPs.

The Jiuquan Basin, with area of 6,800 square kilometers, located in the arid northwest of China, is a vital part of the Hexi Corridor. Investigating its groundwater circulation model is essential for understanding regional hydrogeological processes, sustainable water resource management, and ecological protection. This study, building upon previous research, utilizes hydrogeological surveys, hydrogeochemical analysis, isotope tracing (δD and δ 18 O) with sample size of 439, and radiocarbon dating ( 14 C) with sample size of 45 to evaluate the groundwater flow systems and groundwater age distribution. Results reveal that groundwater primarily originates from meltwater from the Qilian Mountains and atmospheric precipitation, flowing from south to north. The central basin exhibits slower circulation and older groundwater, while the groundwater in the Heihe River mainstream and the Beida River Basin was relatively young due to the favorable conditions for recharge and discharge. The local meteoric water line (LMWL) is defined as δD = 6.02 × δ 18 O- 2.5. Based on isotopic and age data, the basin is divided into several secondary groundwater flow systems (SGFS). This work contributes valuable insight into arid-zone hydrodynamics and supports ecological and water management strategies in the Jiuquan Basin.

The dynamics of the water table is an important control on the connection of groundwater to land surface processes. Agricultural intensification has resulted in a significant decline in the groundwater table in the eastern part of the Sanjiang Plain, China. This decline may have caused significant changes in groundwater recharge and circulation, with implications for natural resources and the environment. In this study, hydrogeological (hydraulic head observations, unsaturated zone lithology), hydrochemical (major ions, redox-sensitive parameters, metasilicic acid) and isotopic (δD and δ18O) data was interpreted through spatial analysis, scatter plots and multivariate statistical methods to construct a conceptual model of shallow groundwater circulation in the Sanjiang Plain following decades of agricultural development. The distribution of the hydraulic head clarified the direction of groundwater flow, and the stable isotope compositions confirmed that shallow groundwaters mainly originated from precipitation and river water. Shallow groundwater levels and enriched groundwater isotopic compositions along the Songhua River and in the upper reaches of the Naoli River indicated some influence by evaporation. The relatively high nitrate concentration and coupling of isotope characteristics showed that sandy unsaturated zones enabled groundwater to be easily influenced by land surface processes. In the Jiansanjiang District and Naolihe Basin, the clayey unsaturated zones inhibited the connection between groundwater and the surface. Redox-sensitive components indicated that the groundwater features a reducing environment and weak groundwater update capability. If the current rate of exploitation continues in the Jiansanjiang District, the groundwater levels will continue to decline.

The Muji spring travertines, located in the Muji Basin in the eastern Pamirs Plateau, represent a typical spring deposit found on plateaus that is characterized by arid and semi-arid climatic conditions. However, its formation mechanisms remain poorly understood. This study aims to explore the recharge processes of the spring, the sedimentary environment, and the genetics of Muji spring travertines through a comparative analysis of conventional hydrochemistry, H-O stable isotope analysis of both spring and river water, and petrographic observation, as well as in situ analysis of major and trace elements present in calcite within travertines. The basin is surrounded by mountains with a topography that facilitates groundwater convergence within it. Carbonate-bearing strata are extensively developed around the basin, which serves as a crucial material foundation for travertine development. It infiltrates underground through fractures and faults, interacting with carbonate rocks to produce significant amounts of HCO3−, Ca2+, and Mg2+. The observed range of isotopic compositions (δ2H, −102.27‰ to −96.43‰; δ18O, −14.90‰ to −14.36‰) in water samples suggests that their primary origin was from glacial and snowmelt sources. The concentration of HCO3− in spring water samples exhibits significant variability, with the highest value being 1646 mg·L−1, which deviates significantly from the typical composition of karst groundwater. During its migration, groundwater undergoes the dissolution of gaseous CO2 derived from deep metamorphic processes, leading to variable degrees of mixing with geothermal groundwater containing elevated concentrations of dissolved components that enhance the dissolution potential of carbonate rocks. Eventually, upwelling occurs along the Southwestern Boundary Fault of Muji, resulting in the formation of linear springs characterized by CO2 escape. The Muji laminated travertines exhibit distinct white and dark laminae, and radial coated grains consisting of micritic and sparry layers. Chemical composition analyses reveal significant differences in the trace and rare-earth element composition, as well as the Mg/Ca ratio, of the two types of travertines. Specifically, the micritic laminae of the pisoid (Mg/Ca = 0.019; Sr = 530 × 10−6; Ba = 64.6 × 10−6) and the dark laminae of the laminated travertine (Mg/Ca = 0.014; Sr = 523 × 10−6; Ba = 48.1 × 10−6) exhibit generally higher Mg/Ca ratios and Sr, Ba contents than the neighboring sparry laminae (Mg/Ca = 0.012; Sr = 517 × 10−6; Ba = 36.6 × 10−6) and white laminae (Mg/Ca = 0.006; Sr = 450 × 10−6; Ba = 35.6 × 10−6). The development of laminated travertines and radial coated grains here is attributed to periodic changes in groundwater recharge induced by seasonal temperature fluctuations, as evidenced by the structural characteristics of the two types of travertines and the trace element analysis of different layers. Algae play a role in forming the dark laminae of laminated travertines and the micritic laminae of pisoids.