1960-2010年延河水沙特征及其对退耕工程的潜在响应

河流水沙特征与流域降水量和下垫面变化密切相关.为揭示流域降雨以及退耕还林对延河流域水沙特征的影响,本文以延河甘谷驿站控制区1960-2010年流域降水量、河流径流量和输沙量实测数据为基础,统计分析了延河水沙变化特征及其对流域降水量的响应,并对比分析了退耕前、后(以2002年为界)延河水沙变化.结果表明:在1960-2010年间,延河甘谷驿站控制区年及汛期(6-9月)降水量、径流量和输沙量呈波动递减趋势,汛期降水量、径流量和输沙量值约占年值的64.8％、71.7％和98.1％;年及汛期输沙量与径流量呈极显著正相关关系,径流量变化可分别解释年及汛期87.6％和92.2％的输沙量变化,降水量变化可分别解释年及汛期22.7％和23.6％的输沙量变化;退耕后流域年及汛期平均输沙量、径流量和径流系数显著低于退耕前,剔除退耕前后降水量差异影响,退耕工程对年及汛期累计输沙量变化分别贡献87.5％和86.9％,对年及汛期累计径流量变化分别贡献77.4％和75.4％.研究阐明退耕可显著降低年及汛期平均径流量、径流系数和输沙量.

Characteristics of runoff and sediment transport during 1960-2010 and its response to Grain for Green Project in Yanhe River

[Background] Analysis on the trends of runoff and sediment transport and their driving forces,such as precipitation,human activities and other factors,is the basis for watershed management.Previous studies showed that the dynamics of river runoff and sediment transport were closely related to soil erosion and precipitation.The relationship of rainfall-runoff-sediment delivery is important for evaluating the benefits of erosion control practices.In recent years,the sediment discharge of the Yellow River is decreasing dramatically,which has caused wide public attention.[Methods] In this study,on the basis of runoff and sediment data measured at Ganguyi station,and the precipitation data of 5 meteorological stations in Yanhe River basin,we analyzed the dynamics of precipitation,runoff,sediment discharge,runoff coefficient,and the response of runoff and sediment dynamics to watershed precipitation in Yanhe River during 1960-2010.Meanwhile,in order to explain the effect of Grain for Green Project on runoff and sediment transport,the difference of river runoff and sediment delivery between 1960-2001 and 2002-2010 were also studied.Based on precipitation-runoff curve and precipitation-sediment transport cumulative curve,the relationship between precipitation and runoff and sediment was determined in 1960-2001,and with the determined relationship,the simulated runoff and sediment transport were predicted in the period of 2002-2010,then were compared to the measured data in the same period of 2002-2010,thus,the effect of Grain for Green Project on river runoff and sediment transport was determined.[Results] 1) The annual precipitation,runoff and sediment transport at flood season decreased with fluctuation from 1960-2010.The flood season accounted for 64.8％,71.7％ and 98.1％ of average annual precipitation,runoff and sediment transport,respectively.2) The sediment transport were significantly related to runoff per year and in flood season.The variation of runoff caused 87.6％ and 92.2％ sediment load changes per year and in flood season,respectively.The watershed precipitation also affected sediment transport due to its significant relationship with runoff.3) Compared with the data of 1960-2001 before the Grain for Green Project conducted,and the average yearly and flood season runoff and sediment transport were decreased significantly in the period of 2002-2010 after the Grain for Green Project conducted.Excluding the impact of precipitation difference between 1960-2001 and 2002-2010,the Grain for Green Project contributed 87.5％ and 86.9％ cumulative amount of sediment changes,and 77.4％ and 75.4％ cumulative amount of runoff changes per year and flood season.[Conclusions] These results are beneficial to understand the dramatic changes of runoff and sediment transport in Yellow River in past 10 years,and also conducive to evaluate the effects of Grain for Green Project on soil erosion controlling on the Loess Plateau regions.