ET的遥感监测与流域尺度水资源管理

Monitoring ET with Remote Sensing and the Management of Water Resources on a Basin Scale

在水资源短缺、水环境质量恶化的形势下,为实现流域的真实节水,需要以卫星遥感监测的ET(蒸发蒸腾量)为依据,进行流域水资源的有效管理。这是一个新的理念和方法。文中综述了当前国际上几种较先进的遥感监测ET的方法。其中“陆面能量平衡算法(SEBAL)”,由于物理基础较好,近十多年来在许多国家有成功的业务化的应用,已被“GEF海河流域水资源和水环境综合管理”项目采用,以计算从日到季和年,从每个县每种土地利用到全流域的ET分布。以2002年的预分析为例介绍了有关结果。讨论了SEBAL的不足之处及改善意见。

The shortage of water resources is a serious problem particularly in China. Managing water resources on the basis of evapotranspiration(ET), retrieved mainly from satellite remote sensing, is a new concept introduced in the GEF Hai Project on comprehensive management of water resources and environment. The most popular remote sensing algorithms in the retrieval of ET are reviewed. Among them the SEBAL (Surface Energy Balance Algorithm for Land) has better physical background and been used operationally in many countries in last 10 years. Data from the MODerate resolution Imaging Spectroradiometer (MODIS) and Landsat TM/ ETM+ have been used to evaluate daily, seasonal and annual ET per county and per land use category. A preliminary analysis for the Hai Basin, for 2002, is presented. Further studies will be continued for the Hai River Basin over next five years, which will provide a reference for the application of basin scale water use technologies, in particular, the real saving of water resources by the reduction of ET. In the understanding of the limits of SEBAL, an independent validation program, including precise in situ flux observations, is to be operated in the Hai Basin Project. For demonstration periods, we have tried to use mesoscale atmospheric models, such as MM5, to get the meteorological fields near surface, and help SEBAL in its calculation of surface fluxes. The major task is the establishment of a real water saving program through an ET reduction strategy, with more water resources remaining in the basin for production and environmental use, including more freshwater discharges into the Bohai Sea. ET reduction is land use and crop type dependent. Other management factors also need to be included.