Impacts Of Climate Variability And Land Use Change On Streamflow In Tangwang River Basin

With the increasingly enhancement of global warming and human activities, the spatial-temporal distribution of water resource has obviously changed. The research for climate variability, land use change and hydrological responses related have important meaning to reveal the reasonable use of water resource, regional sustainability, as well as the interactive mechanism between climate, hydrology and human society system. In this study data from 6 streamflow gauges and 6 climate stations in the Tangwang River basin locates at northeast China were analyzed using linear and non-parametric methods (Mann-Kendall), to investigate changes in climatic variables, hydrologic variables and their relationships with human activities. The results demonstrated that,(1)Annual and seasonal mean air temperature increased significantly during 1964-2006, but the spatial distribution of temperature variation showed different trends. Conversely, the regional precipitation showed a decrease trend in this basin, and the trend was not significant. Specially, summer and autumn precipitation exhibited decrease trends while spring and winter precipitation enhanced.(2) Generally, the vegetation dynamics and quality weakened in the upper and middle basin during the past 43 years. Forests and wetlands in Tangwang River Basin reduced by 1326 km2 and 64.59 km2,correspondingly, grasslands, farmlands and urban land increased. Perhaps it showed that the main land use change patterns in this basin are the conversions from forests and wetlands to farmlands, grassland and urban lands, changes of forest area and quality are the primary human activities which bring about the changes of water resource in this basin.(3) The annual mean streamflow and peak flow decreased, but the low flow showed ascending tendency during 1964-2006. The interannual variations of streamflow in January to April are dramatically. Spring and winter streamflow increased while summer and autumn streamflow decreased, especially, the low flow in spring exhibited significant augmented. The results of future trends prediction in streamflow showed that the streamflow in near future will persistently reduced, and seasonal distribution of streamflow will more uneven, it maybe result in continuing drought in the future.(4) The annual mean streamflow significantly positive correlated with precipitation (p<0.05), and the low flow in spring enhanced with the increased snowfall and temperature in winter, this maybe have a positive effect to mitigate the drought in spring. The sensitivity of streamflow will rise according to the enhanced of temperature and precipitation. Land use change, especially the forest harvesting, had a significant effect on the streamflow from 1977 to 1992. In recent years, the forest area and quality recovered in some measure with the implement of "Natural Forest Protection Project", the effect of human activities weakened more or less. Further, the effect of human activities on streamflow account for 46.5%, while the climatic effect account for 53.5%. On the whole, though the influences of human weakened now, but with the increasingly population and mini water conservancy, the intervention of human will strengthen in the future. Therefore, it needs more scientific researches to regulate, develop and exploit the water resource reasonably, and to sustain the sustainability of water resource.