The SRB is geographically located on the northern edge of the Qinghai–Tibet Plateau, in northwestern China. It is bordered by longitude 92°11^′ to 98°30^′ E and latitude 38°00^′ to 42°48^′ N. The mainstream of the Shule River is more than 620 km, covering a drainage area exceeding 40 000 km². Its mainstream origin can be traced back to a network of 347 glaciers nestled in the western section of the Qilian Mountains. Flowing in a northwest direction, the mainstream of the Shule River meanders through many gorges in the Qilian Mountains (Fig. 1), before flowing into the Changma basin. After the Shule River flows out of the Qilian Mountains at the Changma Reservoir, it flows from east to west along the edge of the alluvial fan through Yumen, then enters the Shuangta Reservoir, continues to flow west through Guazhou, and finally disappears in the Kumtag Desert. Therefore, it can be divided into three distinct segments, each characterized by its unique geographical features. The upper reaches, stretching from the river's source to the outlet of the Changma Reservoir (Fig. 1), lie at elevations ranging from 2080 to 5808 m. This region is primarily dominated by towering and precipitous mountain formations, interspersed with relatively gentle valleys, particularly in the vicinity of Changma. Progressing further downstream, the middle reaches encompass the vast expanse of the Yumen Alluvial Fan Plain (Fig. 1). With elevations fluctuating between 1310 and 2050 m, this segment of the river exhibits a notable decrease in altitude from south to north. Finally, the lower reaches of the Shule River encompass the extensive Guazhou Plain, abutting the northern mountainous region of the arid Gobi Desert, with elevations varying from 1020 to 1650 m. Therefore, the upstream region is primarily located in the high-altitude Qilian Mountains, while the midstream and downstream regions are situated in the relatively flat terrain of the Hexi Corridor (Fig. 1).

As for the sources of recharge for the Shule River's flow, they encompass various crucial elements, such as the meltwater from glaciers, groundwater reserves, and localized precipitation. However, the average annual runoff of the mainstream, which amounts to 10.31 × 10⁸ m³, undergoes a gradual decline as the river enters the Hexi Corridor. This decline is largely attributed to the heightened exploitation and utilization of water resources due to agricultural irrigation and industrial production, leading to a higher rate of evaporation and seepage losses.

The study area is situated in the heartland of the Eurasian continent, far from the influence of oceans, resulting in an extremely dry climate. The region is characterized by scarce precipitation and intense evaporation. The SRB, on average, receives a meager annual precipitation of 78.5 mm, while the evaporation rate is remarkably high at 3042 mm. The annual average temperature ranges from 6.9 to 8.8 °C. The southern part of the study area, which encompasses the Qilian Mountain range, belongs to a high-altitude semi-arid climate zone, with precipitation levels ranging from 100 to 200 mm and occasionally reaching up to 400 mm. The temperatures in this area remain cold, hovering between 0 and 4 °C, with an annual evaporation of about 1700 mm. Conversely, the middle and lower reaches of the basin fall within a temperate arid zone, receiving an even more limited annual precipitation ranging from 36 to 63 mm. Precipitation in the study area shows pronounced intra-annual variability. More than 75 % of the annual rainfall occurs between May and September, and these events can even generate temporary floods and intermittent streams (Guo et al., 2015). The average temperatures here range from 6 to 8 °C, and the evaporation rates vary between 1500 and 2500 mm annually.

The study area is situated within a highly tectonically active region in the northern part of the Qinghai–Tibet Plateau. It is characterized by intense geological processes, including thrust faults and structural uplift. Qilian Mountains, which has experienced significant uplift since the late Paleozoic, is subjected to a prominent NNE-directed compressional tectonic force (Lin et al., 2022; Yang et al., 2020). This force has led to the formation of a series of NNE-trending faults (Fig. 2), which play a crucial role in shaping the development of the Shule River system.

The upstream region of the Shule River is extensively covered with various rock types (metamorphic, sedimentary rocks) spanning multiple geological periods (Fang et al., 2005). This includes Precambrian metamorphic rocks such as gneiss, schist, dolomite, and quartzite, as well as early Paleozoic metamorphic rocks like slate, sandstone, conglomerate, and carbonate rocks. Additionally, sedimentary rocks and granitic formations from different geological stages are also present. Furthermore, in the upstream area, sedimentary rocks dating back to the Mesozoic and Late Paleozoic periods, including sandstones, mudstones, and limestones, can be observed. Throughout the Mesozoic era, the Hexi Corridor gradually took shape and experienced significant subsidence (Meng et al., 2020). As it entered the Cenozoic era, the Qilian Mountains region underwent extensive erosion. Rivers transported substantial quantities of debris into the Hexi Corridor, leading to the deposition of thick Quaternary sediments. Over time, this process gave rise to various-sized alluvial fans. Quaternary sediments constitute a significant component of the stratigraphy in the foreland alluvial fans and basins of the study area. These unconsolidated fluvial deposits, which include loess, gravel, and sand, can reach a thickness of 500 to 600 m in the middle to upper reaches of the Shule River. Examples of such deposits can be observed in the Changma alluvial fan and the Yumen alluvial fan in the upper and middle reaches, respectively (Wang et al., 2017; Guo et al., 2015).

Groundwater with water supply significance in the study area is distributed in the alluvial fan plain area or on both sides of the river valley. These groundwaters exist in the pore of the Quaternary loose sediments. Previous studies have indicated that the primary source of recharge for groundwater is atmospheric precipitation, and its flow direction is intimately tied to the local topography (Fig. 2; Guo et al., 2015). Because river water and groundwater have undergone many mutual transformations from upstream to downstream, it is believed that there is a close hydraulic connection between the two (Wang et al., 2016; Xie et al., 2022). In the upper reaches, because it is mostly mountains and canyons, the terrain changes very drastically, so scattered springs are found. In the alluvial–diluvial fan edge area, groundwater flow is impeded, giving rise to the emergence of artesian springs. This phenomenon is frequently observed in the peripheries of the Changma and Yumen alluvial fan plains. Similar to other foreland alluvial fans, the sediments are coarse-grained at the mouths of the Changma and Yumen fans but become relatively fine-grained at the edges. This depositional pattern significantly influences the spatial distribution of groundwater within these alluvial fans. In particular, in both Changma and Yumen, the aquifer systems transition from a single unconfined layer in the southern regions to multiple, interlayered confined layers towards the northern regions. Therefore, the thickness of the aquifers also varies significantly in space, ranging from tens to hundreds of meters. Correspondingly, the groundwater depth also varies, ranging from several meters to several hundred meters (Fig. 3; Wang et al., 2016, 2015).

Given the SRB's vast spatial extent, exhaustive sampling of groundwater and high-resolution river water at every location is neither feasible nor necessary. Accordingly, we first compiled and critically reviewed all available hydrochemical and isotopic data for precipitation, glacier meltwater, surface water, and groundwater within the SRB (Table S1 in the Supplement). Building on this comprehensive dataset and carefully evaluating the spatial representativeness and hydrochemical–isotopic variability of existing samples, we designed our own field campaign to fill key gaps and target the most informative locations. In July 2022, a total of 31 new water sample sets were collected within the study area, whose sites were selected to capture the full range of hydrological settings (Fig. 1). These samples consisted of 23 river water samples and 8 groundwater samples (including both spring and well water). To elucidate GW–SW interactions, groundwater samples were deliberately positioned 500–1000 m from the mainstem of the Shule River, ensuring that our sampling network robustly represents both regional flow paths and local exchange processes.

For river water sample collection, efforts were made to select locations situated away from the riverbed, and samples were collected from a depth of 10 cm below the water surface at flowing sections of the river. When conducting groundwater sampling, spring-water samples are typically collected directly from the spring source, capturing fresh groundwater immediately upon its emergence. Well-water samples are obtained from agricultural irrigation wells within the study area. To ensure the representativeness of these samples, the wells were generally pumped for three times the well volume before sample collection. According to field investigations conducted during sampling, the depths of these agricultural irrigation wells range from 80 to 200 m. To enhance the water supply capacity of the wells, intake screens are installed along their entire lengths, so the samples represent a mixture of shallow and deep groundwater. All sample collection was conducted in a single round.

All samples underwent on-site filtration using 0.45 µm cellulose acetate filter membranes. They were then carefully stored in pre-cleaned polyethylene bottles, which had been rinsed three times with water from the respective sampling site. Three bottles were collected for each sample: one was acidified to a pH below 2 for cation testing, while the other two were designated for anion and stable isotope analysis. Throughout transportation to the laboratory, the water samples were stored at a constant temperature of 4 °C.

On-site measurements included pH, temperature, total dissolved solids (TDS; HANNA HI 9811-5), latitude and longitude coordinates of the sampling locations, and as elevation. HCO3- was determined using a titration method, while all other cations, anions, and stable isotopes were comprehensively analyzed by the Weathering and Hydro-geochemistry Laboratory at the Institute of Geology and Geophysics, Chinese Academy of Sciences. The stable isotopes (D, ²H, and ¹⁸O) in the water samples were analyzed using an L1102-I (Picarro, USA) and the results were expressed as delta values, defined as the per mil deviation from Vienna Standard Mean Ocean Water, as shown in Eq. (1). For precision, each sample is tested six times, with the first two measurements discarded, and the average of the remaining four used as the final value. 1δ=Rsample-RstandardRstandard×1000, where R represents the isotope ratios (2H/1H or 18O/16O) of the sample and standard, respectively. The deuterium excess value can be calculated according to (Dansgaard, 1964) 2d-excess=δD-8×δ18O,

The study area is a major agricultural irrigation region in the northwest of China, known as part of the Hexi Corridor. Both surface water and groundwater play a crucial role in agricultural irrigation and drinking water. In order to assess the quality of irrigation water versus drinking water, sodium adsorption ratio (SAR), sodium percentage (Na %), and the total hardness (TH) were calculated. The calculation methods can be found in Wang et al. (2024a).

The physicochemical data of river water and groundwater in the study area are reported in Table 1. The river water exhibits weak alkalinity throughout its entire course, with an average of 8.36. The TDS in the river gradually increases as it flows downstream, with the headwater area recording the lowest TDS at 209 mg L⁻¹ and the downstream area peaking at 1672 mg L⁻¹ (Fig. 4). It significantly exceeds the global average TDS for rivers (115 mg L⁻¹). Based on the definition of water hardness, the upper reaches of the river (above the Changma Reservoir, Fig. 1) fall within the categories of slightly hard (150 mg L⁻¹ < TH < 300 mg L⁻¹) and hard water (300 mg L⁻¹ < TH < 450 mg L⁻¹), while the middle reaches (from Changma Reservoir to Shuangta Reservoir, Fig. 1) qualify as hard water. The lower reaches of the river (below Shuangta Reservoir, Fig. 1) are classified as very hard water (TH > 450 mg L⁻¹).

In the upstream river water within the study area, the average mass concentration of major cations follows the order Ca²⁺, Mg²⁺, Na⁺, and K⁺, from highest to lowest. Conversely, in the middle and downstream areas, the average mass concentration of major cations exhibits a different sequence, with Ca²⁺, Na⁺, Mg²⁺, and K⁺. Concerning anions, in both the upstream and middle areas, the predominant ion mass concentration is arranged in the order HCO3-, SO42-, and Cl⁻. However, in the downstream area, the sequence changes to SO42-, Cl⁻, and HCO3-. As a result, the hydrochemical composition of the river water in the upstream area is categorized as Ca²⁺–HCO3- type, while in the middle area, it falls into the Ca²⁺–Mg²⁺–HCO3-–SO42- category. In the downstream region, the river water assumes a Ca²⁺–Na⁺–SO42-–Cl type (Fig. 5).

The Gibbs diagram depicted in Fig. 6 is constructed based on the correlation between the primary ion ratios and TDS in the Shule River water. All river water samples fall within the Gibbs model, indicating that the solutes in the Shule River water are largely impacted by rock weathering and evaporation. Furthermore, the TDS values of river water mainly range from 100 to 1000 mg L⁻¹, and the mean Na⁺ / (Na⁺ + Ca²⁺) ratio is 0.19 in the upstream river water, 0.26 in the middle stream river water, and 0.41 in the downstream river water. Additionally, the mean Cl⁻ / (Cl⁻ + HCO3-) ratio is 0.23 in the upstream river water, 0.34 in the middle stream river water, and 0.58 in the downstream river water. This indicates that the primary sources of ions in river water are predominantly controlled by rock weathering processes.

To further clarify the potential impact of various mineral weathering processes on river water ions within the study area, a sodium-normalized mixing diagram was made in Fig. 7. The results reveal that river water samples predominantly cluster between silicate and carbonate rocks, with a closer alignment to silicate rock types. This suggests that the ions in river water primarily originate from the weathering of silicate rocks, but the contribution from the weathering products of carbonate rocks should not be underestimated. It is noteworthy that the Ca²⁺ / Na⁺, Mg²⁺ / Na⁺, and HCO3- / Na⁺ ratios in the upstream river water of the study area exceed those in the middle and downstream river water. This signifies that carbonate rock weathering in the upstream region exerts a more pronounced impact on the major ions in the river water. This phenomenon is not only linked to the extensive exposure of carbonate rock formations in the upstream region, but also to the fact that, under similar natural conditions, carbonates exhibit significantly higher solubilities (12–40 times) than silicates, making them more susceptible to weathering (Meybeck, 1987).

We have calculated the correlation coefficients among ions in the Shule River water and present them in Table 2. Values closer to 1 in this table indicate a stronger positive correlation between the respective ion pairs.

It is evident that the correlation coefficients between Ca²⁺, K⁺, Na⁺, Cl⁻, SO42-, and TDS in the river water are highly significant, all exceeding 0.8. This suggests their substantial contribution to the salinity of the river water. Furthermore, the correlation coefficients between Ca²⁺, Mg²⁺, and SO42- surpass 0.85, which indicates that these three ions may originate from the dissolution of CaSO₄ and MgSO₄. Notably, the correlation coefficient between Na⁺ and Cl⁻ is 0.987, very close to 1, and their respective correlation coefficients with TDS are also greater than 0.9. This implies that Na⁺ and Cl⁻ share a common source and make a pronounced contribution to the salinity of the river water. It is likely that the Na⁺ and Cl⁻ sources may mainly be the inputs of the sea salt brought by the atmospheric circulation and the salt particles of the air in the study area. In addition, the correlation coefficients between NO3- and the other ions are all less than 0.4, indicating a potentially closer association with human activities rather than natural processes (Huang et al., 2014).

Considering the differences in sampling locations and previous studies (see Table S1), groundwater samples from the SRB have been grouped into four categories: Suli and Changma groundwater from the upstream Qilian Mountains, Yumen groundwater from the midstream Hexi Corridor, and Guazhou groundwater from the downstream plain (Fig. 5). Suli groundwater (n = 12, including samples reported by Xie et al., 2024) exhibits a pH range of 7.10 to 8.20 (mean 7.87) and TDS between 304 and 977.9 mg L⁻¹. The dominant controlling cation is Ca²⁺, while HCO3- is the principal anion (Fig. S1 in the Supplement). Changma groundwater (n = 8, incorporating data from Wang et al., 2015, and Xie et al., 2024) shows hydrochemical characteristics closely resembling those of the Suli samples. Measured pH values average 7.81, with TDS spanning 235 to 742 mg L⁻¹. The chemistry type is Ca²⁺-HCO3- type (Fig. S2). Yumen groundwater (n = 37, including He et al., 2015, Wang et al., 2015, Xie et al., 2024) displays a broader pH distribution from 6.84 to 8.29 (mean 7.67) and TDS values ranging from 255 to 1117 mg L⁻¹ (mean 506.85 mg L⁻¹). The hydrochemical content was not dominated by specific cations, whereas HCO3- and SO42- together constitute the main anionic species (Fig. S3). In the downstream Guazhou plain (n = 50, comprising He et al., 2015, Wang et al., 2016, Xie et al., 2024), pH varies between 6.92 and 8.10 (mean 7.69) and TDS ranges widely from 449 to 7142.4 mg L⁻¹ (mean 1499.65 mg L⁻¹). These groundwater samples are of Na⁺-SO42- type (Fig. S4). Overall, groundwater in the SRB is of a weak alkaline nature. Notably, TDS levels are lowest in spring water from the Qilian Mountains region and highest in groundwater from the downstream Guazhou plain. Groundwater chemistry types vary, with the Qilian Mountains region classified as Ca²⁺-HCO3- type, and Guazhou as Na⁺-SO42- type (Fig. 5).

According to the Table 1, in the upper reaches of the Shule River the δD values of river water range from -78.02 ‰ to -58.25 ‰, with an average value of -62.21 ‰, while the δ18O values range from -12.12 ‰ to -8.70 ‰, averaging -9.54 ‰. The d-excess falls within the range of 8.7 ‰ to 18.96 ‰, with an average of 14.10 ‰. For the middle reaches of the river, the average δD and δ18O values are -56.22 ‰ and -8.54 ‰, respectively, with a d-excess average of 12.11 ‰. In the downstream area, the average δD and δ18O isotope values in river water are -50.51 ‰ and -7.05 ‰, respectively, and the d-excess averages at 5.87 ‰.

Concerning groundwater, in the Qilian Mountains region the δD values range from -84.70 ‰ to -67.57 ‰, with an average of -77.19 ‰, while the δ18O values range from -12.46 ‰ to -10.08 ‰, averaging -11.42 ‰. The d-excess falls within the range 8.7 ‰ to 18.96 ‰, with an average of 10.50 ‰. In the Yumen area of the Hexi Corridor, the average δD and δ18O isotope values of groundwater are -63.30 ‰ and -9.22 ‰, respectively, with a d-excess average of 12.11 ‰. Conversely, in the Guazhou area, the average δD and δ18O isotope values of groundwater are -54.23 ‰ and -7.99 ‰, respectively, with a d-excess average of 9.7 ‰.

The potential sources of major ions in the river water include atmospheric transport of sea salt components, weathering products of soluble rocks (comprising evaporites, silicates, carbonates, and sulfides), and pollutants generated by human activities. Human presence is scarce in the upper reaches of the Shule River, while human activities are more frequent in the middle and lower reaches. Consequently, the major ions in the river water may be influenced by both natural processes and human activities. The Gibbs diagrams prove that the sources of ionic components in river water are mainly from the weathering of carbonate and silicate rocks (Fig. 7). In-depth analysis of the correlation between multi-ions can further explain the causes of river water hydrochemistry and the mechanisms controlling its evolution.

To gain insight into the interrelationships among ions in Shule River water, Na⁺ versus Cl⁻ and (Ca²⁺ + Mg²⁺) versus (HCO3- + SO42-) diagrams are presented in Fig. 9. It can be seen that the Na⁺ / Cl⁻ points in upstream river water deviate from the 1:1 line, while points for downstream river water samples closely align with the 1:1 line. Factors affecting Na⁺ in water and the ratio to Cl⁻ include evaporite dissolution, ion-exchange adsorption, and human activities. While human activities are very rare in the very upstream area of the Shule River, we consider that in the very upstream region the dissolution of silicates predominantly influences the source of Na, while downstream, the dissolution of salt rocks becomes the dominant factor. As a result, the Na⁺ versus Cl⁻ ratios show a clear difference between upstream and downstream (Fig. 9a). The average Na⁺ / Cl⁻ ratio in river water is 1.16, which is similar to the world average ratio in seawater (1.15). This shows that the sea salt carried by the atmospheric circulation has a certain influence on the ion composition of Shule River water. Furthermore, the concentration of Na⁺ exceeded the concentration of Cl⁻, which also may indicate that halite dissolution was not the only source for Na⁺. For example, in the case of groundwater recharging a river, the concentration of Na⁺ in the water will increase after cation exchange occurs once the pore water flows through the formation. Moreover, silicate weathering could release Na⁺ into the river water (Guo et al., 2015). In addition, a linear relationship is found between (Ca²⁺ + Mg2+) and (HCO3- + SO42-), with their ratios clustering in the range 0.88 to 1.24, and an average value of 1.06. If the ratio of (Ca²⁺ + Mg²⁺) and (HCO3- + SO42-) is strictly 1:1, then it can be assumed that these four ions in river water are controlled by the dissolution of carbonate rocks. However, it is clear that some points deviate from the 1:1 line, as shown in Fig. 9b. Thus, in addition to carbonate rock dissolution, silicate weathering plays a role in influencing the levels of these four ions in river water, as previously mentioned.

As the SRB is situated in an arid region with scarce rainfall, its water resources predominantly comprise river water and groundwater. Groundwater is known for its superior quality, extensive spatial distribution, and comparatively stable hydrodynamic characteristics within aquifers. Given the limited number of groundwater samples collected in this study, we propose to integrate existing data from the study area for a more robust analysis, aiming to systematically elucidate regional groundwater cycle processes.

The SRB, characterized by a significantly higher annual evaporation rate compared to precipitation, stands as one of the most arid regions in China. Nevertheless, this area accommodates an extensive irrigation network spanning over 1.3 million acres, providing a robust foundation for local socioeconomic development and human livelihood (Ma et al., 2018). Consequently, the water quality of both surface water and groundwater in the SRB directly impacts regional ecological security and sustainable socioeconomic progress. In this context, we evaluate the suitability of river water and groundwater for drinking and irrigation based on parameters such as TH, Na⁺ %, SAR, and NO3- concentration.

In the Shule River's headwaters region, 50 % of the water samples are classified as slightly hard, and the remaining 50 % are categorized as hard water. As we move to the middle reaches, the water is consistently characterized as hard, and in the downstream areas it becomes very hard, demonstrating a gradual deterioration in water quality from upstream to downstream. A similar pattern is observed in the groundwater quality within the study area. However, it is worth noting that in the arid SRB, the water quality remains relatively acceptable despite this progression towards harder water.

In the upper reaches of the Shule River, the Na⁺ % value in river water ranges from 6.05 to 18.69, with an average value of 14.25. This range categorizes the water as excellent, making it suitable for irrigation. In the middle reaches, among the five samples, only one exceeds a Na⁺ % value of 20 (20.48), while the remaining samples also qualify as excellent for irrigation. Downstream, the Na⁺ % value in river water samples varies from 16.3 to 59.17, with an average of 29.18. Of the eight samples in the downstream area, 25 % are considered excellent, 12.5 % fall into the permissible range, and the rest maintain a good quality rating. Conversely, all groundwater samples meet the criteria for excellent quality according to the Na⁺ % value. This implies that both river water and groundwater in the SRB are well suited for irrigation purposes.

The concentration of nitrates in water often serves as a pivotal indicator for assessing the potential influence of human activities on aquatic ecosystems. This is particularly relevant due to the nitrate emissions associated with agricultural practices and livestock husbandry. In the study area, the nitrate concentration exhibited a range from 0.88 to 6.01 mg L⁻¹, with a mean concentration of 3.32 mg L⁻¹. Notably, the nitrate levels in the waters of the Shule River consistently remained below the stipulated standards set by the World Health Organization for nitrate levels in potable water, which is 10 mg L⁻¹.

The SRB, situated in the arid northwest region of China, stands out due to its limited precipitation and heightened evaporation. By integrating the isotopic signatures of various water sources involved in the hydrological cycle, including precipitation, glacial meltwater, river water, and groundwater, the spatial heterogeneity of groundwater and surface water interactions at the basin scale can be clearly characterized.

In the upper reaches of the Shule River, local precipitation represents the most important source of river recharge, while groundwater plays a critical role in maintaining the baseflow throughout the year. In this mountainous upstream region, both precipitation and glacier meltwater serve as important recharge sources for groundwater. Specifically, isotopic evidence indicates that groundwater in the Suli area is predominantly recharged by atmospheric precipitation, whereas groundwater in the Changma area is strongly influenced by glacier meltwater contributions. In contrast, in the middle reaches of the Shule River, under arid climatic conditions, river water experiences progressive evaporation and receives minimal recharge from local precipitation. Instead, groundwater discharges to the surface as springs, contributing significantly to river flow and serving as an additional major source alongside upstream inflow. In the lower reaches, the river water exhibits even more pronounced evaporative signatures. Under the influence of anthropogenic activities, including river water diversion for irrigation and groundwater abstraction, the interactions between groundwater and surface water become particularly close and dynamic. Therefore, a discernible hydraulic connection exists between river water and groundwater in the middle and lower reaches. From a hydrogeological perspective, in the vicinity of the Yumen alluvial fan, numerous springs overflow, ultimately feeding into the river again, constituting a zone where groundwater recharges surface water. Further downstream, in the Guazhou area, river water is extensively employed for agricultural irrigation and subsequently infiltrates, recharging groundwater. Consequently, in the middle and lower reaches of the SRB, there is a close relationship between groundwater and surface water, marked by frequent exchanges (Fig. 11).

Furthermore, combined with the hydrochemical features of river water and groundwater, the factors influencing regional water resource quality can be illustrated. The chemical composition of water in the Shule River is influenced by processes such as rock chemical weathering, including silicates and carbonates. Furthermore, evaporation also plays a non-negligible role in the hydrochemical features of river water. The chemical makeup of groundwater, on the other hand, is primarily controlled by water–rock interactions, involving mechanisms such as mineral dissolution and ion exchange. Both river water and groundwater are suitable for agricultural irrigation; however, in terms of drinking water quality, they are considered to be slightly hard. This not only establishes a scientific foundation for the prudent allocation and sustainable development of local water resources, but also serves as a basis for the effective management of water resources and the enhancement of drinking water quality.