The Tibetan Plateau, known as the “Water Tower of Asia”, has made important contributions to global climate regulation and water conservation. With global climate change and water shortages, the yield and reserves of water on the Tibetan Plateau have undergone obvious changes, and its water yield function and water conservation function have gradually attracted widespread attention. The results show that the total water yield in the past 20 years is 128,403.06 billion m3, spatially reduced from southeast to northwest, and the interannual variation is large but increases slowly overall. The water yield capacity is higher in the areas of less than 3000 m and 3500~4500 m, and it is stronger with the increase in slope. The water yield capacity is extremely strong in the middle and north subtropical zone. Ecological zones with high water yield capacity are mostly covered with woodland and alpine meadows. The precipitation (P) is the dominant factor in the water yield function before actual evapotranspiration (AET) = 500 mm, and then the negative force of AET is enhanced. High altitude inhibits the positive effect of the normalized vegetation index (NDVI), and the water yield at altitudes of less than 3000 m shows an almost linear relationship with the leaf area index (LAI). When LAI > 0.2, the slower the slope, the higher the water yield and the lower the growth rate. The spatial distribution of P change and water yield change is consistent and significantly positively correlated; P and NDVI changes positively affected changes in water yield, while AET and LAI changes had the opposite effect. In summary, combined with topographic factors, this study emphasizes the influence of climate and vegetation changes on the spatiotemporal changes in water yield on the Tibetan Plateau, which can provide a theoretical basis for the assessment and prediction of water yield capacity and water conservation capacity in this area.

The ubiquity of soil water erosion in the Yarlung Tsangpo River Basin leads to a series of natural hazards, including landslides, debris flows and floods. In this study, the Revised Universal Soil Loss Equation model (RUSLE) was used to quantify potential soil water erosion, while the Height Above Nearest Drainage model (HAND) was used to delimit potential flood hazard zones. Remote sensing and geographic information system technologies were employed to spatialize the results, which showed that the annual soil loss from water erosion was less than 1239 t ha−1 y−1. The total soil loss was estimated to be over 108 × 106 tons, of which about 13 × 106 tons (12.04% of the total) occurred from the agricultural land in the downstream valley. Soil erosion mapping was performed using six levels of soil erosion intensity and the effects of precipitation, land use/land cover and topography on soil erosion were revealed. Increases in precipitation and slope gradient significantly increased the soil loss rate, while the maximum rate of soil loss occurred from densely vegetated land, reaching 9.41 t ha−1 y−1, which was inconsistent with erosion preconceptions for this land type. This may be due to a combination of the region’s unique climate of high intensity rainfall and steep slopes. Flood hazard mapping showed that all regional cities were located in a flood hazard zone and that, within the total basin area (~258 × 105 ha), 9.84% (2,537,622 ha) was in a high flood occurrence area, with an additional 1.04% in aa vulnerable to moderate flood hazard area. Approximately 1.54% of the area was in a low flood risk area and 4.15% was in a very low flood risk area. The results of this study provide an initial identification of high-risk soil water erosion and flood hazard locations in the basin and provide a foundation upon which decision-makers can develop water and soil conservation and flood prevention policies.

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