| The water conservation function is an important part of the service function of the watershed ecosy stem.Quantitatively evaluating the water conservation capacity of a watershed or a region and analyzing its evolution law are of great significance for realizing the.rational development,utilization and scientific management of water resources,as well as the protection and restoration of the ecosystem.At present,the connotation of water conservation is different at home and abroad,and the evaluation methods are not comprehensive enough to meet the research needs of the rapid evolution of water conservation functions under the background of global climate change.Therefore,further analysis of the connotation of the watershed or regional water conservation function,quantitative evaluation of its water conservation capability,and analysis of its evolution law will help to understand and expand the mechanism research of water conservation,and provide theoretical basis and technical support for regional ecosystem protection.Based on the analysis of the connotation of regional water conservation and water conservation capacity,two methods for evaluating water conservation are proposed:the lumped formula based on the regional overall water balance and the distributed water conservation based on the HRU(hydrological response unit in SWAT)water balance.Taking Maqu County,Gansu Province,the Source Region of the Yellow River as an example,the annual water conservation amount and water conservation capacity of the 1980-2018 series were analyzed and studied.The main conclusions are as follows:(1)The water conservation capacity is the amount of water stored or excreted in a certain watershed or region within a certain period of time,while the water conservation capacity represents the influence of the watershed or region on the water quantity,which can be expressed by the maximum water conservation capacity.The lumped water balance method takes the basin or region as a whole,and uses the overall water balance to calculate the annual water conservation of the region;the distributed water balance method divides the watershed or region into different hydrological response units(HRU),and analyzes each The water balance relationship of the hydrological response unit can comprehensively obtain the water conservation amount of the entire basin or region.(2)The annual average water conservation capacity of Maqu County calculated by the lumped and distributed water balance methods is 934 million m3 and 925 million m3 respectively,and the difference between the two is not large;however,the results of the two calculation methods are more obvious in different years.The inter-annual fluctuation of the water conservation amount calculated by the lumped water balance method is large.In terms of the(hydrological)annual maximum water conservation capacity,the water conservation capacity of Maqu County calculated by the two methods is 1.861 billion m3(centralized)and 1.125 billion m3(distributed),the former being 1.65 times that of the latter.(3)The most important factor affecting the water conservation capacity of Maqu County is the underlying surface conditions.There are obvious differences in the water conservation capacity of different land use types.The water conservation capacity per unit area of the four main land types of wetland,grassland,woodland and glacial permafrost is 1.36 million m3/km2,0.78 million m3/km2,0.38 million m3/km2 and-0.29 million m3/km2 respectively.The research results can provide a scientific basis for regional water resources evolution prediction,water resources utilization and allocation decisions,etc.It is also of great significance in the trade-off and optimization of ecosystem service functions and the establishment of ecological compensation mechanisms. |
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