Preliminary Study On Hydrological Similarity Of Watersheds

In many regions of the world,there is a shortage of hydrological stations.Even if monitoring stations are established in some regions,it is still difficult to meet the requirements for parameter calibration of hydrological forecasting models due to the short construction time and short data sequence.In addition,due to the rapid development of social economy,the underlying surface conditions change dramatically,resulting in the lack of representativeness and consistency of the original hydrological data,which further increases the difficulty of hydrological forecasting in ungauged watersheds.Therefore,how to carry out hydrological forecast on the ungauged watershed is still a difficult problem to be solved.At present,for the hydrological forecast of ungauged watersheds,the International Hydrographic Association(IAHS)PUB plan proposed the use of watershed hydrological similarity and grouping methods to carry out hydrological forecasting of ungauged areas.On the basis of identifying the gauged watersheds similar to the ungauged watersheds,the model parameters of the gauged watersheds are transferred to the ungauged watersheds to carry out their hydrological forecasting studies.In order to help solve the prololem of hydrological prediction in ungauged watersheds through the methods of hydrological similarity of watersheds,this paper selects data-based watersheds to study their hydrological similarity and the effect of parameter transplantation,and explores them for future application to ungauged watersheds.21 closed watersheds in Jiangxi Province were selected,and determined the optimal parameter groups of 21 research watersheds through model parameter calibration.8 kinds of watershed characteristic indexes were selected,and the corresponding similarity indexes of 21 research watersheds were extracted and calculated respectively.The similarity index permutation and combination method was used to construct 255 similarity index combinations.The similar watershed grouping and parameter transfer research were carried out,and the indexes that played a major role in similar watershed grouping were identified.On the basis of previous work,three sets of nested watersheds were selected from 21 research watersheds.Based on the three similarity indexes of watershed area,average topography index,and soil texture,similar watershed grouping and parameter transfer studies were conducted for nested watersheds.And explored the directionality of parameter transfer based on similar watershed grouping.The article conclusion show that:(1)The results of parameter transfer based on grouping of similar watersheds generally perform better.In addition,based on three similarity indexes of watershed area,average terrain index,and soil texture and four similarities of watershed area,average terrain index,soil texture,and vegetation index,the results of parameter transfer perform best.(2)The three similarity indexes of watershed area,average terrain index and soil texture play an important role in similar watershed grouping,while vegetation index has little influence on similar watershed division compared with the three similarity indexes of watershed area,average terrain index and soil texture.Because the selected watersheds are all located in Jiangxi Province,and the vegetation conditions are good,and there is little difference in vegetation between the researched watersheds.(3)The parameter transfer based on the hydrological similarity cannot avoid the directionality problem of parameter transplantation,but it is feasible to conduct the research on the directionality of the parameter transplantation using different similarity index combinations.Based on the combination of three similarity indicators of watershed area,average terrain index,and soil texture or based on the combination of four similarity indicators of watershed area,average terrain index,soil texture,and vegetation index,the effect of parameter transplantation is optimal and the influence of directionality problem can be reduced.(4)The hydrological similarity between nested watersheds is not necessarily high.Therefore,the nesting relationship should be ignored in the process of parameter transfer to nested watersheds,and the hydrological similarity between watersheds should be given priority.