不同土地利用/覆盖情景下东北沟流域植被生态需水量及其对产流影响

Ecological Water Requirement under Different Land Use/Cover Scenarios in Dongbeigou Watershed

针对京津水源区上游生态环境建设需水与向下游多输水的矛盾现实,基于气象、土壤、土地利用/覆盖(1990年和2009年)数据,应用Penman-Monteith公式估算潜在蒸散量,再用土壤和植被信息对其进行修正,计算了水源区东北沟流域1990年、2009年及其他5种不同土地利用/覆盖情景下的最小生态需水量和适宜生态需水量。结果表明:2005—2009年4—10月潜在蒸散量是715.04 mm;2009年流域植被适宜生态需水量是399.42 mm,最小生态需水量是339.68 mm,比1990年的适宜和最小量分别多122.5 mm、144.5 mm;平水年的降雨均可满足各种情景生态需水要求,其中需水量较大的是情景Ⅲ(草地转化为林地),其适宜需水量达784.69×104m3,情景Ⅱ(林地转化为草地)的需水量最小,适宜需水量是687.27×104m3,该情景较适合向下游输水为目的的生态建设,但该情景实施的前提是建立下游向上游的生态补偿机制。

In water source of Beijing and Tianjin,there are some conflicts between ecological rehabilitation water requirement and transferring more water to Beijing and Tianjin.On the basis of meteorology,soil and land use /cover（in 1990 and 2009） data,Penman-Monteith formula was applied to calculate reference evapotranspiration which would be revised through soil and vegetation data to obtain ecological water requirement of different land uses.Taking Dongbeigou Watershed as a study area,the minimum and suitable ecological water requirements were calculated based on land use/cover in 1990 and 2009 and other five land use/cover scenarios.The results showed the accumulative reference evapotranspiration is 715.04 mm from 2005 to 2009;the watershed suitable and minimum ecological water requirements were 399.42 mm and 339.68 mm in 2009 respectively,compared with 254.92 mm and 214.76 mm in 1990.The precipitation in average flow year meets needs of vegetation development of five scenarios.The watershed ecological water requirement under scenario Ⅲ converting grassland to forest is the highest,reaching 784.69×10^4 m^3,while that under scenarioⅡ converting forest to grassland is the lowest,being 687.27×10^4 m^3.The scenario Ⅱ is most suitable for the ecological restoration scheme to transfer more runoff to downstream and enhance water availability in Beijing and Tianjin.The establishment of payments for environmental services from downstream to upstream is the prerequisite to put this scenario into practice.