Research On Water And Soil Conservation Of Dam System In Small Watershed Of The Loess Plateau

This paper investigated the construction, engineering safety, sediment deduction reservoir and the increase production of the dam in the loess hilly-gully region during the year from 2006 to 2010, which was located in the Shuerliang Basin of Hequ County in Shanxi Province. The results were significant in the dam construction, the safety operation and the crop increase production etc.The main conclusions were:(1) The remediation area of the basin was 3956.57hm2,with the remediation efficiency was 39.43%. It included the area of tractor ploughing terrace was 274.6hm2, the areas of building the arbor, the shrubwood, the economic forest, the mixed forest of arbor and shrub, the artificial grassland were 163.3hm2,2596.7hm2, 29.9hm2,240.2hm2 and 358hm2, respectively. The area of channel remediation was 285.67hm2, including 15 new dam,24 medium-sized silt dams, and 20 small-sized silt dams.(2) The security risk of the silt dams was evaluated. The results presented that the management of silt dams is very important. Thus, the feasible measures were necessary to insure the safe operation of silt dams.(3) The average rainfall of five years of Shuerliang Basin was 378.96 mm, which was 2.47% higher than the average of many years. The sediment runoff decreased gradually, and there was significant difference for sediment runoff. The rainfall caused the sediment runoff was more than mainly 40 mm and mostly occurred in July and August. The construction of silt dams significantly decreased the sediment runoff under the same precipitation. The silt dams recharged to Shantougou dry dam and Dagou medium-sized dam. The floods in other dams have been evaporated and leaked. The results of sediment distribution presented that the deposition thickness gradually decreased. The character of sediment in the upstream was rough, and in the downstream was fine (clay loam or silt clay). The sediment reduction benefit of water and soil conservation measures of the basin increased under specific precipitation. The heavy rain could increase the sediment reduction benefit, while the light rain could decrease the sediment reduction benefit.(4) The water and fertilizer conditions of dam were better than sloping fields, and soil layers was stabilized. However, the soil nutrient was lower. The spike length, spike thickness, Hundred-grain weight, kernel weight of corn was best for the coverage optimization, and worst for the traditional treatment in dam and terrace. The corn production was highest for coverage optimization of dam and terrace, in which the coverage effect was better for the dam. The production increased 1146.0kg/hm2 and 1944.3kg/hm2 for dam and terrace, when compared with the slope, the corresponding increase efficient were 24.07% and 49.07%, respectively.