1956-2009年延河水沙变化特征及其驱动力研究

分析降雨、人类活动等因子驱动下的流域水沙效应是流域管理的基础。本文采用移动平均法、累计距平法,线性回归统计等,分析了1956-2009年期间延河流域的降雨、径流和输沙量变化及其驱动因素。结果表明:延河流域降雨量与径流量、输沙量变化趋势基本一致,均可分为1956-1969年的基准期和1970年以后的3个时段的治理期等4个阶段。基准期三者均达到最大,治理期以输沙变化的时段性最为显著;且三者基本符合先大幅度下降(1970-1983年),然后明显上升(1984-1993年),再迅速下降(1994-2009年)的时段性。径流泥沙的时段性既是降雨量出现阶段性变化的结果,更是阶段性人类活动的水沙效应结果。整个治理期降雨和人类活动对减少径流的贡献比是60∶40,对减少泥沙的贡献比为30∶70;治理时段引起水沙变化的主要人类活动包括:1970-1983年的淤地坝、水库等水利设施建设大大减少水沙;1984-1993年的农业包产到户政策使得减水减沙幅度逐渐减少;1994年以来延河治理和退耕还林战略等极大地减少了流域径流泥沙。研究结果对延河流域管理实践有指导意义。

Trends of runoff and sediment load of Yanhe River Basin and their related driving forces during 1956 -2009

Analysis of the trends of river flow and sediment load and their related driving forces,such as rainfall,human activities,and other factors,is the basis for watershed management.By using the methods of moving average,comparative analysis of time series,cumulative anomalies and linear regression methods,the trends of precipitation,runoff and sediment load in the Yanhe River Basin during 1956～2009 are comprehensively analyzed.The results show that the precipitation,runoff and sediment load in the basin had the similar trends which could be divided into the reference period(1956-1969) and three management periods after 1970,therefore,four stages totally.They all reached the peaks in the reference period.In the management periods,the sediment load was of the most significantly time-phased.For the runoff and sediment load in the management stage,the trends showed a significant decline in 1970-1983,and a significant increase in 1984-1993,then a rapid decline in 1994-2009.Both the runoff and sediment load trends were somehow the results of periodical change of rainfall.The human activities imposed very strong effects on those time-phases.Throughout the management periods,the contribution ratio of rainfall to human activities for reducing runoff was 60 to 40 and for reducing sediment load was 30 to 70.The human activities include dams,reservoirs and other water conservancy facilities in 1970-1983 which reduced runoff and sediment load greatly;the household responsibility policy imposed in rural areas in 1984-1993,made the water and sediment load reduction gradually reduced;the "returning farmland to forest" management policy has sharply reduced the sediment load and runoff in the Yanhe River Basin since 1994.These results could guide the management practices in related areas.