Estimating the sensitivity of annual runoff to changes in climate and land use in the Loess Plateau, China

As a result of the combined impacts of climate change and the long history of human activities, the Loess Plateau region in, north-central China has experienced severe water shortage and soil erosion, which have significantly influenced efforts for sustainable social development. It is critical to understand the impact of changes in climate and land use on water yield to provide a scientific basis for future soil and water conservation planning.The Luoyugou Watershed, located within the third subtegion of the Loess Plateau, was selected for the evaluation of its hydrological sensitivity to changes in climate and land use. Statistical analytical methods were employed to detect runoff trends and climatic variables from 1986 to 2004. Sensitivity analysis, based on the Zhang model and an improved principle of elasticity, was applied to examine the quantitative hydrological sensitivity to climatic variability and land use change, respectively. The results indicate that precipitation and actual evaporation were not significantly different (p > 0.05), whereas the annual runoff decreased significantly (p < 0.05) with a breakpoint identified in 1994. Sensitivity analysis indicated that a 1% increase in precipitation (P) resulted in a 0.35% increase in annual runoff, whereas a 1% decrease in potential evaporation (PET) caused a 0.11% increase in annual runoff.The sensitivity of the annual runoff response to variations of P and PET decreased with the increase in watershed dryness (PET/P). Moreover, the annual runoff variation was positively correlated with slope land, grassland, and settlement but was negatively correlated with terrace, forest, and shrub land. This study indicates that land use changes caused by the implementation of soil and water conservation are responsible for the reduction in annual runoff during the study period. These findings may be useful for future land use and water resource planning and management.