Study On Evolution Characteristics Of Hydrological Factors In Water Source Area Of The Middle Route South To North Water Transfer Project

The South-to-North Water Transfer Project is a great ecological project and livelihood project.The water source area is the source of the middle route of the South-to-North Water Project.It directly affects the long-term operation of the middle route of the South-to-North Water Project and utilization and sustainable development of water resources in the downstream areas of the water source area.Therefore,grasping the evolution characteristics of hydrological factors is the prerequisite for ensuring the sustainable utilization of water resources and the sustainable development of the water source area.The prediction of hydrological factors directly affects the scientific development,management and operation of the South-to-North Water Transfer Project.Studying the evolution of the hydrological elements in the water source area can effectively and reasonably exploit the water resources,avoid various problems caused by over-exploitation and water transfer,and at the same time avoid too little water transfer to solve the problem of water shortage in northern cities.This study can provide the basis for further revealing the hydrological process-driven mechanism of ecological environmental vulnerability change,a theoretical basis for ecological environment vulnerability assessment,ecological engineering construction,and sustainable use of water resources in the water source area,and serve as scientific explanations for the succession of ecological and environmental systems and the hydrological cycle and their interrelationships.A trend analysis of the hydrological factors in the water source area of the Middle Route of the South-to-North Water Transfer Project was carried out using the trend coefficient method,the Mann-Kendall rank correlation method and the Spearman rank correlation method.The results showed that the hydrological factors all showed a decreasing trend.A simple and effective mutation method of mean accumulation was proposed and compared using the Mann-Kendall mutation test.The results were consistent.The cluster analysis was used to study the jump of hydrological factors.The sediment concentration jumped in 1982.The rainfall jumped in 1982.The runoff jumped in 1983,and the sediment load jumped in 1983.Evaporation jumped in 1981.The wavelet analysis was used to analyze the hydrological factors in the whole year,the flood season and the non-flood period.The results show that the cycle of sediment concentration are about 56,21,8 years,42,12,5 years’ cycles for the sediment concentration in the flood season,and 42,13,5 years’ cycles for the non-flood sediment concentration.There are 55,33 and 7 years’ cycles of rainfall,56,30,20 and 8 years’ cycles of rainfall in the flood season and 54,39 and 22 years’ cycles of rainfall in the non-flood season.There are 29,43,55,6,10 and 16 years’ cycles of runoff,29,43,55,6,9 and 15 years’ cycles of runoff in the flood season and 36,16,10 and 6 years’ cycles in the non-flood season.There are 43,10,5 years’ cycles of sediment load,43,10 and 5 years’ cycles of sediment load in the flood season and 42 years,18 years and 8 years’ cycles of sediment load in the non-flood season.There are 54 and 20 years’ cycles of evaporation,55,27,and 17 years’ cycles of evaporation in the flood season and 55,45,and 21years’ cycles evaporation in the non-flood season.Using the chaotic neural network model to predict the annual,flood season and non-flood season of hydrological factors in 2011.The result is that the sum of the absolute relative error of the sediment concentration is 48.84%,the sum of the absolute relative error of the runoff is 96.12%,the sum of the absolute relative error of the rainfall is 88.39%,the sum of the absolute relative error of sediment load is 48.37%,and the sum of absolute relative error of evaporation is 103.07%.The sum of absolute relative error of the sediment concentration in the flood and non-flood season is 41.84%,and the sum of absolute relative error of the runoff is 85.39%.The sum of the absolute relative error of rainfall is 79.73%,the sum of absolute relative error of sediment load is 55.17%,and the sum of absolute relative error of evaporation is 100.97%.It can be seen that except the prediction of sediment load in the flood and non-flood season,the prediction of sediment concentration,runoff,rainfall,and evaporation are slightly lower than annual’s.Thus,the forecast value of the hydrological factors in the flood and non-flood season is more accurate than annual’s.