Accurate estimation of evapotranspiration(ET),especially at the regional scale,is an extensively investigated topic in the field of water science. The ability to obtain a continuous time series of highly precise ET va...Accurate estimation of evapotranspiration(ET),especially at the regional scale,is an extensively investigated topic in the field of water science. The ability to obtain a continuous time series of highly precise ET values is necessary for improving our knowledge of fundamental hydrological processes and for addressing various problems regarding the use of water. This objective can be achieved by means of ET data assimilation based on hydrological modeling. In this paper,a comprehensive review of ET data assimilation based on hydrological modeling is provided. The difficulties and bottlenecks of using ET,being a non-state variable,to construct data assimilation relationships are elaborated upon,with a discussion and analysis of the feasibility of assimilating ET into various hydrological models. Based on this,a new easy-to-operate ET assimilation scheme that includes a water circulation physical mechanism is proposed. The scheme was developed with an improved data assimilation system that uses a distributed time-variant gain model(DTVGM),and the ET-soil humidity nonlinear time response relationship of this model. Moreover,the ET mechanism in the DTVGM was improved to perfect the ET data assimilation system. The new scheme may provide the best spatial and temporal characteristics for hydrological states,and may be referenced for accurate estimation of regional evapotranspiration.展开更多
Currently,lakes and artificial reservoirs are increasingly threatened by eutrophication,which is the result of the combined action of many natural and anthropogenic factors.In the past,the effect of nutrient load on t...Currently,lakes and artificial reservoirs are increasingly threatened by eutrophication,which is the result of the combined action of many natural and anthropogenic factors.In the past,the effect of nutrient load on the trophic state of water bodies has attracted much attention,while few studies have addressed the effect of hydrological characteristics.Therefore,to reveal the coupling effects of hydrological characteristics and nutrient load in sediments on the trophic state of water bodies,this study collected relevant data from 36 lakes and reservoirs across China.Pearson correlation analysis showed that trophic level index was positively and significantly correlated with nutrient load in sediments and hydraulic retention time,while it was negatively correlated with mean depth and hydraulic load.The principal component analysis showed that the nutrient load was the first major component that influenced the trophic state of water bodies,followed by the mean depth and hydraulic retention time.Eutrophication was prone to occur in water bodies with mean depth less than 7 m and hydraulic retention time greater than 14 d,and the trophic level index regression equation with hydrological characteristics and nutrient load in sediments was derived by multiple regression analysis.This study revealed that the trophic state of water bodies influenced by both nutrient load and hydrological characteristics.It provides a new idea to reduce the occurrence of eutrophication in reservoirs by using the artificial hydrological regulation capacity of reservoirs.展开更多
基金National Key Basic Research Program of China(973 Program),No.2015CB452701National Natural Science Foundation of China,No.41271003+1 种基金No.41371043No.41401042
文摘Accurate estimation of evapotranspiration(ET),especially at the regional scale,is an extensively investigated topic in the field of water science. The ability to obtain a continuous time series of highly precise ET values is necessary for improving our knowledge of fundamental hydrological processes and for addressing various problems regarding the use of water. This objective can be achieved by means of ET data assimilation based on hydrological modeling. In this paper,a comprehensive review of ET data assimilation based on hydrological modeling is provided. The difficulties and bottlenecks of using ET,being a non-state variable,to construct data assimilation relationships are elaborated upon,with a discussion and analysis of the feasibility of assimilating ET into various hydrological models. Based on this,a new easy-to-operate ET assimilation scheme that includes a water circulation physical mechanism is proposed. The scheme was developed with an improved data assimilation system that uses a distributed time-variant gain model(DTVGM),and the ET-soil humidity nonlinear time response relationship of this model. Moreover,the ET mechanism in the DTVGM was improved to perfect the ET data assimilation system. The new scheme may provide the best spatial and temporal characteristics for hydrological states,and may be referenced for accurate estimation of regional evapotranspiration.
基金funded by the Shanghai Science and Technology Development Foundation (19010500100)the National Key Research and Development Program of China (No.2016YFA0601003)。
文摘Currently,lakes and artificial reservoirs are increasingly threatened by eutrophication,which is the result of the combined action of many natural and anthropogenic factors.In the past,the effect of nutrient load on the trophic state of water bodies has attracted much attention,while few studies have addressed the effect of hydrological characteristics.Therefore,to reveal the coupling effects of hydrological characteristics and nutrient load in sediments on the trophic state of water bodies,this study collected relevant data from 36 lakes and reservoirs across China.Pearson correlation analysis showed that trophic level index was positively and significantly correlated with nutrient load in sediments and hydraulic retention time,while it was negatively correlated with mean depth and hydraulic load.The principal component analysis showed that the nutrient load was the first major component that influenced the trophic state of water bodies,followed by the mean depth and hydraulic retention time.Eutrophication was prone to occur in water bodies with mean depth less than 7 m and hydraulic retention time greater than 14 d,and the trophic level index regression equation with hydrological characteristics and nutrient load in sediments was derived by multiple regression analysis.This study revealed that the trophic state of water bodies influenced by both nutrient load and hydrological characteristics.It provides a new idea to reduce the occurrence of eutrophication in reservoirs by using the artificial hydrological regulation capacity of reservoirs.
