A New Tool for Mapping Water Yield in Cold Alpine Regions

Abstract

Watershed management requires reliable information about hydrologic ecosystem services (HESs) to support decision-making. In cold alpine regions, the hydrology regime is largely affected by frozen ground and snow cover. However, existing special models of ecosystem services usually ignore cryosphere elements (such as frozen ground and snow cover) when mapping water yield, which limits their application and promotion in cold alpine regions. By considering the effects of frozen ground and snow cover on water yield, a new version of the Seasonal Water Yield model (SWY) in the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) was presented and applied in the Three-River Headwaters Region (TRHR) in southeastern Qinghai-Tibetan Plateau (QTP). Our study found that incorporating the effects of frozen ground and snow cover improved model performance. Frozen ground acts as a low permeable layer, reducing water infiltration, while snow cover affects water yield through processes of melting and sublimation. Both of these factors can significantly impact the distribution of spatial and temporal quickflow and baseflow. The annual average baseflow and water yield of the TRHR would be overestimated by 13 mm (47.58 × 108 m3/yr) and 14 mm (51.24 × 108 m3/yr), respectively, if the effect of snow cover on them is not considered. Furthermore, if the effect of frozen ground on water yield were not accounted for, there would be an average of 6 mm of quickflow misestimated as baseflow each year. Our study emphasizes that the effects of frozen ground and snow cover on water yield cannot be ignored, particularly over extended temporal horizons and in the context of climate change. It is crucial to consider their impacts on water resources in cold alpine regions when making water-related decisions. Our study widens the application of the SWY and contributes to water-related decision-making in cold alpine regions.

Spatiotemporal Changes in Water Storage and Its Driving Factors in the Three-River Headwaters Region, Qinghai–Tibet Plateau

“…Plowland and urban constitute smaller portions of the overall landscape, which are less than 1% (Figure 1b). Encompassing a wide range of elevations, from 2062 m to 6788 m, the study area encompasses extensive expanses of FG [34].…”

“…The TRHR is the headwater region of the Yangtze River, the Yellow River, and the Lantsang-Mekong River [34]. The water resources of the TRHR are pivotal to water and food security, economy, and society in the downstream areas, affecting 700 million people downstream [11].…”

“…Although some studies have activated the snowmelt module when applying the SWAT model to the study of WS in CAR, these studies ignored the effect of FG and did not quantify and analyze the effect of SC on WS [32,33]. Zhao et al took the TRHR as an example and incorporated the effects of FG and SC on water amount into SWY by using the temperature (Tem) threshold method and degree-day model and revising the K sat of FG, respectively [34]. The obtained results were subsequently validated, revealing that accounting for the effects of FG and SC could enhance the accuracy of the model [34].…”

“…Zhao et al took the TRHR as an example and incorporated the effects of FG and SC on water amount into SWY by using the temperature (Tem) threshold method and degree-day model and revising the K sat of FG, respectively [34]. The obtained results were subsequently validated, revealing that accounting for the effects of FG and SC could enhance the accuracy of the model [34].…”

“…In this research, using the revised SWY [34], we aim to (1) understand the spatiotemporal distribution and changes in WS in the TRHR from 1981 to 2020; (2) analyze the impact of individual factors and identify the dominant driving factor behind WSC at the grid scale; and (3) classify the importance of WS in the TRHR. It should be noted that the process and ability of ecosystems to store Pre has different names in different studies, such as water storage, water conservation, water retention, and water holding.…”