九龙江流域生态需水量时空变化趋势分析

Analysis of Temporal and Spatial Variations of Ecological Water Demand of Jiulong River Basin

为了维持和保护流域生态系统健康,避免流域生态环境退化,进行流域生态需水量的确定和研究是有必要的。根据九龙江2000—2018年2个水文站实测数据,结合Tennant法确定河道内生态基流,选择面积定额法,利用流域内土壤质地分布状况,以及基于遥感开发的MCD12Q1土地利用产品和MOD16A2蒸散发产品估算植被生态需水量,并对区域生态环境需水量进行时间变化趋势分析和空间分布分析。结果表明:(1)在2000—2018年,九龙江流域有林地、草地面积整体呈现增加趋势,农田、疏林地面积呈现下降趋势;(2)九龙江流域内北溪、西溪河道内多年平均生态需水量分别为22.68亿m3,10.67亿m3,植被多年平均生态需水量为105.27亿m3;(3)有林地、草地的生态需水量呈显著上升趋势,疏林地、农田生态需水量呈下降趋势,前者显著,后者不显著。受人类活动影响,九龙江流域土地覆盖/利用类型年际变化剧烈,因此在区域生态需水量变化中其作用不可忽略,随着遥感/GIS技术的发展,对土地覆盖/利用类型以及植被蒸发量的高时空分辨率观测变得可能,有助于准确预测区域生态需水量。

In order to maintain and protect the ecosystem of a certain region healthy and reverse the degradation, studying and calculating its ecological water demand is necessary. During 2000—2018, based on the data of two hydrological stations, the ecological base flow was determined with the Tennant method, while the area quota method was selected to estimate the ecological water demand of vegetation. The distribution map of soil texture, as well as the remote-sensing based MCD12 Q1 land use types product and MOD16 A2 evapotranspiration product were selected as inputs of the area quota method. The temporal changing trend and spatial distribution of ecological water demands over the whole watershed were analyzed. The results showed that:(1) during 2000—2018, the areas of forestland, grassland in overall increased, while the area of cropland and sparse woods decreased;(2) the instream ecological water requirements of North River and West River were 2.268 billion m~3, 1.067 billion m~3, respectively, and ecological water requirement of vegetated area was total 10.527 billion m~3;(3) the ecological water requirements of forestland and grassland increased significantly, while those of open woodland and cropland decreased significantly and insignificantly, respectively. Affected by human activities, the interannual change of land cover/land use in Jiulong River Basin was obvious, hence it could not be ignored in reckoning regional ecological water demand, and with the development of RS/GIS technology, it could be convenient to obtain land cover/land use data and evapotranspiration data in high space-time resolution, which is useful for predicting the regional ecological water demand.