Research On The Hydropower Water Footprint In Lancang—Mekong River Basin

The large-scale hydropower development in the basin has a long-term and significant impact on regional society,economy,ecology and environment.Unsustainable hydropower development can cause serious negative impacts on river basin ecosystems.Irrational consumption of water resources in the basin may seriously interfere with regional supply and demand relationship.The water footprint as a new research method,it can quantitatively describe the amount of water resources consumed by the unit energy of hydropower stations,and the water footprint evaluates the power generation efficiency of hydropower stations from the point of view of water consumption.It has a good ecological indication.At present,there are few studies on the calculation of water footprint and spatial and temporal differentiation of trans-basin hydropower stations.In order to study the temporal and spatial differentiation of water footprint and its key driving factors,this paper takes 37 major hydropower stations built in Lancangjiang-Mekong River Basin as the research object.Based on the analyswas of the shortcomings of traditional methods,the optimal calculation model of recalculating data and remote sensing image data was constructed.The optimization model makes up the deficiency of the traditional calculation method.According to the optimization model to calculate the monthly and annual average water footprint of hydropower stations in 2015.This paper analyzes the law and characterwastics of the spatial and temporal differentiation of the water footprint of the Lancangjiang-Mekong River Basin,identifies the driving factors of the time variation and spatial difference of the water footprint of the hydropower station,and builds the ecological compensation model of the water loss of the hydropower station based on the water footprint.The main research results are as follows:1)The traditional calculation method was considered to be low accuracy and the calculation result was too large.The water footprint optimization model based on MERRA reanalyswas data and Landsat 8 OLI remote sensing image was proposed.It meets the calculation of monthly and annual mean water footprints of hydropower stations with higher accuracy and large spatial scales.2)The water footprint of 37 major hydropower stations in the Lancang-Mekong River basin was calculated by the optimization model.The results showed that the annual average water footprint of the 37 hydropower stations was 88.56 m3/GJ,or 318.81 L/kw·h.Thailand's Siridhorn hydropower station has the highest average annual water footprint of 878.02 m3/GJ;Thailand's Pak Mun Hydropower Station has the lowest average annual water footprint of 0.43 m3/GJ.The average annual water footprint of the hydropower stations in the four watersheds was:Lancang River Basin<Vietnam Section<Lao Section<Thailand Section.The annual average water footprint of the 9 hydropower stations in the Lancang River Basin was 3.17 m3/GJ,or 11.42 L/kw·h,and the water footprint in the Lancang River was the lowest.3)The peak values of the hydropower water footprint in the Lancang River Basin were mainly in the period from April to June,the variance coefficient of monthly average water footprint was 0.26 and the extreme ratio was 2.53.The hydropower water footprint of the lower Mekong River Basin was low in April-September,while the trend of water footprint was higher at the beginning and end of the year,the variation coefficient of monthly average water footprint was 0.12,and the extreme value ratio was 1.51.The change of water footprint in the Lancang River Basin is significant.4)The annual average water footprint of each hydropower station has a tendency to increase with the decrease of latitude.The water footprint of the hydropower station at 900-1500m higher altitude was lower.The annual average water footprint of the hydropower stations in the four terrain areas was:Alpine Gorge Area<Medium and Low Mountain Wide Valley<Mountainous Hilly Area<Plain Area.From the perspective of water footprint,the Lancang River Basin was more suitable for the construction of hydropower stations than the Mekong River Basin.5)The main driving factors of hydropower water footprint time variation was meteorological factor(the depth of evaporation).The main driving factors of the hydropower water footprint space difference is efficiency factor(Unit installed capacity of the surface area)and topographic factors(surface area and average reservoir water depth ratio).6)The total annual water evaporation of the main 37 hydropower stations built in Lancang-Mekong River Basin is 26.434 billion m3,and the water consumption is huge.This kind of consumption aggravates the water resources carrying capacity in a certain period of time,which affects the water supply and demand relationship and the sustainability of water ecology.Based on the water footprint of the hydropower station,the ecological compensation model of the water loss of the hydropower station was established.The model was based on the water footprint as the main parameter.It was applied to the main 9 hydropower stations in the Yunnan section of the Lancang River Basin.The results show that the average ecological compensation index of the water loss of the 9 hydropower stations is 0.001644 Y/kw·h,and the total annual ecological compensation is 57.252 million yuan,which is about 0.31%of the total annual power generation income.