River discharge is of great significance in the development of water resources and ecological protection. There are several large ungauged catchments around the word still lacking sufficient hydrological data. Obtaining accurate hydrological information from these areas is an important scientific issue. New data and methods must be used to address this issue. In this study, a new method that couples unmanned aerial vehicle (UAV) data with the classical slope–area method is developed to calculate river discharges in typical ungauged catchments. UAV data is used to obtain topographic information of the river channels. In situ experiments are carried out to validate the river data. Based on slope–area method, namely the Manning–Strickler formula (M–S), Saint-Venant system of equivalence (which has two definitions, S-V-1 and S-V-2), and the Darcy–Weisbach equivalence (D–W) are used to estimate river discharge in ten sections of the Tibet Plateau and Dzungaria Basin. Results show that the overall qualification rate of the calculated discharge is 70% and the average Nash–Sutcliffe efficiency coefficient is 0.97, indicating strong practical application in the study area. When the discharge is less than 10 m³⁄s, D–W is the most appropriate method; M–S and S-V-1 are better than other methods when the discharge is between 10 m³⁄s and 50 m³⁄s. However, if the discharge is greater than 50 m³⁄s, S-V-2 provides the most accurate results. Furthermore, we found that hydraulic radius is an important parameter in the slope–area method. This study offers a quick and convenient solution to extract hydrological information in ungauged catchments.

The arid desert ecosystem is very fragile, and the change of its river discharge has a direct impact on irrigation and natural environment. River discharge attenuation coefficients is a key index to reveal the stability of desert river ecosystem. However, due to the harsh conditions in desert areas, it is difficult to establish a hydrological station to obtain data and calculate the attenuation coefficients, so it is urgent to develop new methods to master the attenuation coefficients of rivers. In this study, Taklamakan desert river was selected as the research area, and the river discharge of the desert river were estimated by combining low-altitude UAV and satellite remote sensing technology, so as to calculate the attenuation status of the river in its natural state. Combined with satellite remote sensing, the surface runoff in the desert reaches of the Hotan River from 1993 to 2017 were estimated. The results showed that the base of runoff attenuation in the lower reaches of the Hotan River is 40%. Coupled UAV and satellite remote sensing technology can provide technical support for the study of surface runoff in desert rivers within ungauged basins. Using UAV and satellite remote sensing can monitor surface runoff effectively providing important reference for river discharge monitoring in ungauged catchments.

To understand the relationship between spatial water quality patterns and changes in land-use/cover types in the Jinghe Oasis, 47 water sampling sites measured in May and October 2015 were divided into six cluster layers using the self-organizing map method, which is based on non-hierarchical k-means classification. The water quality indices included the chemical oxygen demand (COD), biological oxygen demand (BOD), suspended solids (SS), total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH₃-N), chromaticity (SD), and turbidity (NUT). Data was also collected on the changes in the farmland, forest–grassland, water body, salinized land, and other land types during the wet and dry seasons. Then, we combined these data with the classification results of the GF-1 remote sensing satellite data obtained in May and October 2015 and analyzed the influences of land-use/cover type on water quality for different layers and seasons. The results indicate that Clusters 1 to 3 included monitoring samples from the wet season (May 2015), whereas Clusters 4 to 6 included monitoring samples from the dry season (October 2015). In general, the COD, SS, NUT, TN, and NH₃-N values were high around the Ganjia Lake Haloxylon natural conservation area in the southern Ebinur Lake region, east of Ebinur Lake, and around the Kuitun River during the wet season. The SD values around these areas were high. Moreover, high BOD and TP values were mainly concentrated around the Ganjia Lake Haloxylon natural conservation area, as well as the Kuitun River, during the dry season. In the discussion on the relationship between the different water quality parameters and land-use/cover type changes, we determined that farmland, forest–grassland, and salinized land significantly influenced the water quality parameters in the Jinghe Oasis. In addition, the influences of various land-use/cover types on the water quality parameters in the research zone during the different seasons exhibited the following descending order of magnitude: farmland → forest–grassland → salinized land → water body → others. Moreover, their influences were lower during the wet season than the dry season. In conclusion, developing research on the relationship between the spatial framework of the water quality in the Jinghe Oasis and land-use/cover type changes is significant for the time sequence distribution of water quality in arid regions from both theoretical and practical perspectives.

Ebinur Lake Watershed, with its oases and deserts, is a typically arid and mountainous region on the northern slope of Tianshan Mountains. Along with ever increasing human activities, agricultural and domestic wastes have been directly discharged into river systems around the Watershed, which consequently poses a grave threat to the sustainable development of Xinjiang. Through statistical and spatial analysis, we have determined the relationships between land use/cover (LULC) and hydro-chemical characteristics during rainy and dry seasons in 2014. Spatial patterns of hydro-chemical characteristics as demonstrated by mineralization, pH, electrical conductivity (EC), and SO₄²⁻, HCO₃⁻, Cl⁻, Mg²⁺, Na⁺, Ca²⁺ and K⁺ concentrations were examined in 113 sites. Since hydro-chemical characteristics were affected by LULC patterns, this study delineated six zones to analyze the distribution characteristics of hydro-chemical parameters and its relationship with LULC patterns. The results showed that, except for the pH, all variables demonstrated significant spatial differences during dry and rainy seasons. In addition, the relationships between water quality and LULC patterns indicated that the farmland, forest–grassland, water body and salinized land all affected hydro-chemical characteristics during both rainy and dry seasons. Especially, decreased rainfall, irrigation, surface runoff, the area of lake, etc. largely led to the increase in ion content, which had great influence on hydro-chemical characteristics parameters in dry season. Furthermore, we established several stepwise linear multiple regressions models. The results showed that pH, mineralization and Ca²⁺ were defined by forest-grassland, while the Cl⁻ and Mg²⁺ were defined by salinized land during the rainy season. The pH and Na⁺ were estimated based on farmland, whereas Cl⁻ and Ca²⁺ were estimated based on forest-grassland during the dry season. In conclusion, this research on the relationships between the spatial distribution of hydro-chemical characteristics in Ebinur Lake Watershed and LULC patterns will be significant for the sustainable management of the arid regions in northwest China.