Response Of Runoff And Sediment To Land-use Change In Wei River Source Region

In this paper,over the main stream of the Weiyuan hydrological station in the source region of the Weihe River,which area is 114 km~2,was selected as study region. Precipitation,runoff and fiver sediment concentration data from different meteorological stations in the study area were collected,and the impact of land use dynamic changes on runoff efficiency and changes of sand transporting in the Weihe River source region was analyzed.The main research contents include:the wet period and dry season runoff process changes with the development and utilization of terraced fields under the study area;the impact of terraced development of the study area on the peak years of torrential rain,flood and runoff;the impact of land use dynamic changes on the wet period,dry season and flood changes in the sediment concentration.The work is summarized as followings:(1) In the case of annual precipitation remaining stable,greatest rainfall in a slight decline for three wet months and the most rainfall in a three dry months increasing litter, the runoff coefficient tends to decrease during three study periods.In 1970s,there is a good correlation of rainfall and runoff in study area.And,over time,the correlation was decreasing,and after 1990s,the correlation has been very weak.However,the correlation of terrace area and runoff coefficient of study area was gradually increasing as time went on,and after 2000,the correlation has been very good.This showed that the decreasing of runoff coefficient can be attributed to the development of terrace in study region.Terrace development and then increasing retention of rainwater infiltration and evaporation, which may be the most reason that reduced the runoff coefficient of the study area.(2) Since the 1980's,the relationship between decline of runoff coefficient and the terrace development was different during three study stages.The statistical regression analysis of terrace area and precipitation concluded that the correlation of terrace area and runoff coefficient was 0.4495,0.3924 and 0.8304 respectively,about annual,three wet months and three dry months.In other word,the terrace development has largest influence on the runoff during low-flow period,and the least influence during high-flow period.(3) Large scaled terrace development has a noticeable effect on storm flood in the source region of Weihe River.Supposed the quantity of precipitation was a constant,the peak flow,runoff modulus and runoff coefficient were weakened by terrace development in study area. (4) The river sediment concentration during low-flow period has no significant relation with terrace development in the source region of Weihe River.The changes of sediment concentration depended largely on the effective precipitation that formed the runoff.The river sediment concentration for the past many years was close to 0,when there was no any effective precipitation.Conversely,the sediment concentration would be a slight increase.(5) The comparative analysis of runoff processes during high-flow period and storm flood showed that terrace development has some effect on river sediment concentration. There was a negative correlation between terrace development has some effect on river sediment concentration,in other word,the more terrace area,the less river sediment concentration in the source region of Weihe River.