黑河中游地区植被生态需水量估算

Ecological water requirements of vegetation in the middle reaches of Heihe River

以水量平衡关系为理论基础,引用195 6～2 0 0 0年黑河中游地区各县的气象资料和2 0 0 2年4月～2 0 0 3年10月不同类型植被区的土壤水分动态监测数据,并采用GIS技术进行生态分区的基础上估算该地区的植被生态需水量,分析生态需水量的时空变化以及缺水量。结果表明:黑河中游地区每年最适生态需水量在9.4 8×10 8～11.5 8×10 8m3之间,除去相应植被区域上的有效降水量4 .74×10 8m3,还需要从径流中补给4 .74×10 8～6 .84×10 8m3。除山丹和民乐县外,其它各县的降水量均不能满足临界生态需水量。若以最适生态需水量为标准,山丹县的缺水量最大,占整个中游地区缺水量的4 0 .9%。另外,在水资源配置方案中,不仅要考虑空间上的差异,而且更要注意生态需水量在时间上的变化。分析表明。

In order to reduce the environmental and ecological problems induced by water resources management and use, this paper proposes a concept of ecological water requirements (EWR). It is defined as three grades for EWR, including critical EWR, optimal EWR and saturation EWR. Critical EWR are the water regimes needed to maintain vegetation growth at a low level of risk. Optimal EWR are the water regimes needed to maintain ecological function of vegetation at a continuable level. Saturation EWR are water regimes needed to maintain maximum throughput of vegetation community. Based on the definition, the method for calculating the amount of ecological water requirements is determined, which is that auording to the theory of relationship water amount balance,using meteorological data of each county from 1956 to 2000, monitoring data of soil moisture in the different vegetation areas from 2002 to 2003,and 3S technique including geographical information system (GIS), global position system (GPS) and remote sensing (RS) to calculate ecological water requirements and analyze ecological water shortage. In this study in the middle reaches of Heihe River, the water requirements is divided into three parts, including arbor forest, shrub forest and herbage community. The results of calculation show that the Critical ecological water requirements in the middle reaches of Heihe River are 5.78×10~8m^3\5a^(-1), optimal ecological water requirement is (9.48×10~8～)11.58×10~8 m^3·a^(-1) and saturation ecological water requirements are 30.33×10~8～37.08×10~8 m^3·a^(-1), available precipitation of corresponding ecological areas is 4.74×10~8 m^3·a^(-1). The arbor forest, shrub forest and herbage community water requirements account for 33%, 35% and 32% of the amount of total ecological water requirements, respectively. Except Shandan and Minle County, the precipitation of other counties could not provide critical ecological water requirements. Furthermore, in the course of water resource adjusting, it is necessary that not only to consider spatial heterogeneity but also pay attention to season variability of ecological water requirements. This paper shows that ecological water shortages of April, May and June are the most serious in the middle reaches of Heihe River.