Spatial variability of runoff recharge sources and influence mechanisms in an arid mountain flow‐producing zone

Abstract

In‐depth knowledge of the hydrological conditions of basins in arid regions can help to maintain the long‐term water security. The mechanisms of runoff generation and flow paths in different landscape areas are not fully known due to spatial variability. We have explored the mechanisms by which spatial variability affects the runoff recharge sources in the Xiying River Basin. The results showed that the spatial variability of the sources and generation mechanisms of runoff in the arid mountain flow‐producing zone is the result of the combined effect of different landscape, elevation and meteorological elements. In the upstream area, the short mean transit time (MTT) combined with the high contribution of recharge from the meltwater (29.32%) and the proportion of pre‐event water (between 60% and 90%) means that runoff production processes are strongly controlled by meltwater recharge and precipitation events. The MTT and the proportion of pre‐event water in the midstream area are ranked in the middle of the three landscape areas, but the highest contribution of precipitation (16.57%) indicates the importance of precipitation to runoff production processes. In the downstream area, the MTT is the longest and the proportion of pre‐event water is the smallest, and groundwater remains the basis for long‐term stability of runoff (groundwater contribution rate: 40.62%). By enhancing the spatial resolution for identifying runoff recharge sources can reduce the model uncertainty by 69%. Thus, taking full account of the spatial heterogeneity in arid regions is an important initiative to achieve scientific water resources management.

Mechanisms of isotopic control of precipitation in the Yellow River source region

“…Meanwhile, many studies have focused on the stable isotope variation of precipitation in the eastern region of the Tibetan Plateau (Cui & Li, 2015), studied the stable isotope characteristics of precipitation in the Qinghai Lake region, analysed the water vapour source of precipitation in Qinghai Lake, and calculated the contribution of lake evaporation to local precipitation. However, the stabilization isotope method has been used to study the rainfall control mechanisms in the Yellow River source region in the north-east of the Tibetan Plateau, and rainfall is not only affected by large-scale circular currents, such as western winds, East Asian cyclones, and South Asian typhoons, but also by the terrain, so that the precipitation process is more complex and the corresponding water vapour sources are complex and variable, while the high altitude range of the Yellow River source region is large and sampling is difficult, which makes the long-standing unknown water cycle mechanism and water resource assessment errors (Sang et al, 2022) difficult to eliminate. The purpose of this study is to: (1) systematically analyse the characteristics of time and space changes in precipitation-stable isotopes; (2) explore the main sources of water vapour in the area of study; and (3) investigate the relationship of regional precipitation and stabilization isotopes with major environmental and geographical factors.…”