Evaluation Of Basin Water Resources Based On Principles Of Eco-hydrology

Based on the principles of eco-hydrology, the subject of water resourcesevaluation changes from runoff to precipitation gradually. In order to evaluate thewater resources objectively and reasonably, green water should be considered into thecategory of water resources, and both green water and blue water should be evaluatedrespectively. The Ziya River Basin was selected as the research basin, using theremote techniques and the traditional mathematical model, the spatial distribution ofgreen water in the basin was researched. The major research aspects are listed below:The observed precipitation data of Ziya River Basin was used as the basic data toanalyze the characteristics and the regularity of temporal and spatial variation of theprecipitation. The major research aspects are listed as below: The analyticalexpression of the annual average rainfall intensity and rainfall duration were derivedand the related parameters were evaluated using the observed precipitation data; thecalculation of the variation coefficient of the precipitation data using moments methodand compute of the rainfall at different frequencies; the statistical analysis of thevariation of the precipitation data from1957to1990at the typical sites, and analyzethe trend using the normalized anomaly method and the5-point sliding averagemethod; the analysis of the spatial variation law of the precipitation at the current year2008.Combing the remote sensing technology with the Penman-Monteith(P-M) modelis a new proposed method for calculating evaporation in recent years. This paperachieved the effective estimation to daily evapotranspiration in Ziya river watershedby using the P-M model based on MODIS remote sensing leaf area index andrespectively estimated plant transpiration and soil evaporation by using coefficient ofsoil evaporation. This model divided Ziya river watershed into seven differentsub-regions which are tussock, meadow, grasslands, shrub, broad-leaved forest,cultivated vegetation and coniferous forest through thoroughly considering thevegetation diversity on watershed space. Furthermore, optimizing and calibratingparameters based on each sub-region and analyzing spatio-temporal variation rules ofthe model main parameters which are coefficient of soil evaporation f and stomatalconductance gsx. The results indicate that the coefficient of soil evaporation f andstomatal conductance gsxcalibrated by model are basically consistent with measureddata and have obvious spatio-temporal distribution characteristics. And the monthly average evapotranspiration value of simulation is37.96mm/mon in this watershedwhich is close to the measured value with33.66mm/mon and the relative error ofsimulation results in each subregion are within11%, which illustrates that simulatevalues and measured values fit well and the precision of model is high. In addition,plant transpiration and soil evaporation account for about84.64%and15.36%respectively in total evapotranspiration, which means the difference between values ofthem is large in Ziya river basin. What is more, this model can effectively estimate thegreen water resources in basin and provide effective technological support for theestimation of basin water resources.The instrumental reduction method, mathematic model method, empiricalformula method was applied to compute the water surface evaporation in Ziya Riverbasin at the current year2008, and the calculation accuracy of each model wascompared. The results show that the accuracy of the modified Penman model isrelatively high; the calculation of the monthly evaporation using the remote data canmeet the accuracy requirements; the precision of the modified Dalton model isrelatively low; the accuracy of the C coefficient in the general empirical formula isrelatively limited; The above methods were contracted in view of their simulatingperiods and simulating precision, and the results show that Penman model is moresuitable for the calculation of the water surface evaporation in Ziya River Basin.The soil evaporation, plant transpiration and water surface evaporation werecombined to calculate the total evapo-transpiration in Ziya River Basin. Besides, theregularity of the temporal and spatial variation was analyzed, and then water resourcesstatus in the whole basin was assessed according to the relationship betweenprecipitation and evaporation.