Characteristic Of Runoff And Its Response On Climate And Land Use Change In Weihe River Basin

Based on the measured data, this paper analyzes the characteristic of runoff in Weihe River Basin in different time scales in order to understand its feature and its response to climate-driven factors and land use change. The climate change characteristics are analyzed using the data of monthly temperature, precipitation and potential evapotranspiration which were estimated by using FAO Penman-Monteith method.In order to analyze the impact of climate and land use change on runoff quantitatively, the SWAT (Soil and Water Assessment Tool (Version2012))is applied to the Weihe River Basin by which we simulate monthly hydrological processes at Wushan, Beidao and Huaxian hydrological Station. The results show that:1. Annual runoff of Weihe river had obvious linear downword trend as a whole time, especially the downword tendency in the1990s, but is had shifted to increase in the early21st century. The interannual fluctuation was severe and hydrological dry year with high probability of occurrence and strong sustainability can last8years. Runoff was concentrated in flood season and it had different distribution forms in different decades. Multi-peak type occurred in high frequency in recent40years, especially in recent10years. Runoff could lag up to nine months and the winter half year was in higher stability.2. Temperature had significant linear upword trend and its mutation point happened in1992. Precipitation was abundant in1970s and1980s then decreased in1990s, but it had weak upword trend in recent10years. Potential evapotranspiration continued to increase and its mutation point happened in1993.The runoff was affected by climate change, when climate was warming, precipitation was decreasing, potential evapotranspiration was increasing and water consumption was increasing too, resulting in decreasing runoff. But the appearce of warming and wetting phenomenon in northwest China was advantageous to the water recovery in the early21st century.3. The response of the runoff to climates-driven factors were not stable, that changed over time. Significant change of response relationship all began in the late1980s when the temperature increased most, suggested that climate warming caused a certain influence on it. Potential evapotranspiration effected on the runoff changes tended to dominate in Weihe River Basin and the runoff at Wushan hydrological station was more sensitive to it.4. Using ARCGIS, the SWAT model which include land use database, soil database and weather database was established. Selecting actual measurement runoff data and using PSO from SWAT CUP, the established SWAT model is corrected to achieve the best simulation result and the result prove that SWAT model is applicable in Weihe River basin.The change of runoff in the different climate and land use scenario is quantificationally analyzed in order to calculation the contribution of climate and land use change. Climate change played the dominant role in variation of the runoff and it effected on the annual runoff gradually from upstream to downstream, but the contribution rates were greater than60%in all hydrological stations. Annual runoff in downstream station was more sensitive to the change of land use due to the impact of human activities in the downstream was more significant. The influence of land use in flood season enhanced gradually from upstream to downstream and was greatest at Beidao hydrological station in drought season.In a word, climate change was still the dominant factor of runoff no matter in seasonal or annual time scale in recent40years, and the influence of land use in flood season was greater than drought season.