Runoff and sediment yield in relation to precipitation, temperature and glaciers on the Tibetan Plateau

Abstract

The riverine sediment is an essential carrier for nutrients and pollutants delivery and is considered as an important indicator of land degradation and environmental changes. With growing interest in environmental changes over the Tibetan Plateau, this study investigated mean annual runoff and sediment yield from eight headwater catchments in relation to annual precipitation, air temperature, and glacier area ratio, etc. Results show that runoff (Q) is positively correlated with both precipitation (P) and temperature (T), i.e., Q = 0.357P+20.3T-6.4, indicating combined water supply from rainfall and meltwater, increase of which may exceed the evapotranspiration water loss caused by temperature raise. Sediment yield (S) shows an inverted parabolic relationship with precipitation and at the same time positive correlation with glacier area ratio (Ag), i.e., S = 0.000609 P2-0.470P+48.5 Ag+202.53, indicating that sediment yield is a minimum at about 500–600 mm of precipitation, increasing sharply on both sides of this minimum in one case owing to decreased vegetation protection and in the other to enhanced erosive power and that erosion rate in the glacierized area is generally higher than non-glacierized area. The variation in sediment yield with precipitation can be explained by the operation of two factors, i.e., rainfall erosive action that increases continuously with increase in precipitation, and vegetation protective action that is unity for zero precipitation and decreases with increases in precipitation. The above results may be useful in visualizing not only variations in rates of erosion among climatic zones on the Tibetan Plateau but also the probable changes of erosion during a climatic change.