Suspended sediment load under future climate in headwater basins of the Northern slope of the Tianshan Mountains

It has been reported that fluvial sediment load from High Mountain Asia may increase with increasing temperature and precipitation. However, responses between suspended sediment load on the Northern Slope of the Tianshan Mountains (NSTM) and climate variation and its future projections remain uncertain. In this study, measured water and suspended sediment load at eight hydrology stations during 1961–2011 were collected. The relation between suspended sediment load and climate variation at each river basin was investigated. A climate elasticity model was then applied to assess variation of suspended sediment load from these eight headwater basins in the coming decades (by 2050) under three climate scenarios. The analysis shows that water and suspended sediment load of all these eight headwater basins increased with the increase in precipitation and temperature during 1961–2011, and the mean increase rate in suspended sediment load during 1990–2011 is seven times that of runoff. The area-weighted mean value of sensitive coefficient between suspended sediment load to temperature change is 0.89 ± 1.26 %/°C (mean ± SE, SE is Standard Error) and that to precipitation change is 4.27 ± 2.88 (mean ± SE), suggesting an increase in the runoff and suspended sediment load with warmer and wetter climate. The sensitive parameter between suspended sediment load varies considerably among rivers, with greater sensitivity to temperature variation but less to precipitation variation in glacier-rich basins compared to glacier-poor basins. The estimation shows that annual suspended sediment load of these eight river basins could increase by one to two times the 1990–2011 average under future climate change, threatening reservoir and channel functions and jeopardizing the sustainability of water supplies in the NSTM.