Rainfall And Runoff Characteristics Of Donggou Catchment In Shandong Yaoxiang Small Watershed

The small watershed was the basic unit of soil erosion, the main of soil erosion came from runoff erosion. But runoff process in field measurement, not only included surface runoff,underground runoff in this rainfall, but also a part of runoff in last rainfall. So need to base on flow separation and discharge hydrograph separation for runoff calculation. To master the dynamic law of soil erosion in mountain and hilly areas of Shandong, taken the small watershed of Yaoxiang Taian as the research object. The runoff calculation and the flood segmentation based on the data of runoff by the V-notch Weirs of control station. Also used base flow index and digital filter to base flow separation and comparison of the difference of this three methods to find which was better. The result showed that:(1)Rainfall of rural Donggou catchment in Yaoxiang small watershed had significant seasonal variation, 83.9% of the rainfall concentrated in the rainy season(June to September),and rarely in other months,year distribution is extremely uneven.A total of 17 times of erosive rainfall made up the rainfall of 773.2mm.The heavy rain was subject to the rainfall of the year and accounting for 52.5% of the rainfall; although the number of light rain is the most, accounting for 80% of total rainfall, but the rainfall is small,only 11.9% of the annual rainfall.(2)The runoff of the catchments in 2013 was 103556.31 m3, and was mainly concentrated in June to August, and had cyclical changes. The more the rainfall, the more the runoff, and the peak flow was greater. The greater runoff was in July, and the daily max runoff of a day was 16686.92m3 which was appeared in July 23.The time was consistent with the time of max rainfall appeared.(3)The basic flow of Donggou watershed by base flow index was 2928.03m3, the digital filter method was 3429.88 m3. The result of the base flow index was close to the line segmentation(2668.15 m3), so the base flow index was suitable for this regional.(4) The flood lasted long to rise as well as lasted long to fall by 5 flood segmentation from7.11 to 8.5 and floods were generally lagging behind rainfall. The greater the rainfall intensity of antecedent precipitation, the shorter the lag time,the higher the flood peak. The beginning of the next flood was the turning point of this flood and the last of the flood, and thelast time of the flood was from this point to the end.