旱区植被生态需水量间接法计算参数的研究

Study on indirect calculation method parameters for ecological water requirement of vegetation in arid area

植被生态需水问题是水资源优化配置和生态环境研究的热点,间接计算法是量化干旱地区天然植被生态需水量的主要方法。为了使计算结果更加准确,结合0. 618法与去极值法对间接法计算公式中潜水蒸发量E的计算做出改进,建立植被系数K的二阶Gaussian模型,最后运用灰色模型GM(1,1)对植被面积S的发展趋势进行预测。结果表明:优化所得潜水蒸发量——埋深曲线对实测数据拟合度更好,植被系数取值更加精确,以甘肃省民勤县为例,计算出该地2015年各类植被面积与资料记载差异较小,所得生态需水量结果与FOA推荐使用的Penman-Monteith模型相比无显著差异。在此基础上预测出2020年民勤县天然植被生态需水总量为4060. 8×10~4m^3,其中天然林地生态需水量预测为3100. 1×10~4m^3,天然草地生态需水量为960. 7×10~4m^3。研究使间接计算法对植被生态需水量的量化更加准确,为干旱地区水资源的分配及生态恢复政策的制定奠定了一定的研究基础。

The ecological water requirement of vegetation is a hotspot in the research of optimal allocation and ecological environment,and the indirect calculation method is the main method to quantify the ecological water requirement of natural vegetation in arid area. In order to calculate more accurate,by combining the 0. 618 method and the Extremum method to improve the calculation of the submersible evaporation of the indirect method,we established the second order Gaussian model of vegetation coefficient K and forecasted the development trend of the vegetation area S with the grey model GM( 1,1). The results showed that the optimized phreatic water evaporation-buried depth curve fitted the measured data better,and the vegetation coefficient were more accurate. Taking the Minqin County of Gansu Province as an example,the difference of area between recorded and calculated data in 2015 was small,and the results of ecological water requirement were not significantly different from those of FOA recommended Penman-monteith model. Based on which,the total ecological water requirement of Minqin County natural vegetation in the 2020 was predicted to be 40. 608 million m^3,of which the ecological water requirement of natural forest was 31. 001 million m^3,and the ecological water requirement was 9. 607 million m^3. The indirect calculation method is more accurate for the quantification of ecological water requirement of vegetation,which lays a foundation for the allocation and policy of ecological restoration in arid areas.