Analysis On Runoff Variation Characteristics And Forecast In Ningxia-Inner Mongolia Reach Of The Upper Yellow River

As the main link of water circulation,river runoff is the key factor to maintain water balance,and its change rule directly reflects the natural geographical features of a region.River runoff as a major part of water resources,its variation trend can not only bring immense effect to not only the power generation,irrigation and urban water supply,but also the safety of human life and property.Based on the comprehensive study on the change of river runoff,forecasting its future change accurately can not only strengthen the rational development and utilization of water resources,furthermore,it also has a positive impact on the harmonious development of regional economy.Ningxia-Inner Mongolia reach is rich in mineral resources,and also is minority inhabit district.As one of the China's biggest commodity grain bases,it is of great significance in the development of the national economy.Ningxia-Inner Mongolia reach has been the biggest user of water and most concentrated area since the establishment of the two irrigated areas,including Ningxia irrigation district and Hetao irrigation district,which has been the most heavily affected region by runoff change.Ningxia-Inner Mongolia reach is located in the northwest inland with the rare rainfall,strong evaporation,serious water shortages and severe soil and water loss,these issues brought about serious challenges in the development and utilization of water resources in Ningxia-Inner Mongolia reach of the upper Yellow River.Based on the Ningxia-Inner Mongolia reach of the upper Yellow River,this paper analyzes the variation law of runoff and its future development trend.Combining the datas of the observed runoff for many years,the characteristics,annual and interannual variation trend of runoff were studied by means of mathematical statistics.S everal research methods are used to analyse the change trend,period,mutation of runoff,the accuracy of the analysis results are validated,it will provide valuable references for comprehensive arrangement of the Ningxia-Inner Mongolia reach,rational use of water resource and ecological environment protection.The main research results are as follows:(1)Taking the Ningxia-Inner Mongolia reach as the object of study,th is paper analyzes the basic statistical characteristics,annual and interannual variation features,and then draws the conclusions that the annual runoff presents a normal distribution,the distribution of runoff is concentrated,the runoff in a year shows an uneven distribution and the nonuniformity decreases with time increasing,the interannual change is significant.(2)The annual runoff series in Ningxia-Inner Mongolia reach shows a declining trend,but it is not significant.The future variation trend of the annual runoff is the same as that of the past,that is to say,the annual runoff w ould keep decreasing for some time.(3)Through the period analysis,we can know that there exists 18 years period of the annual runoff in Ningxia-Inner Mongolia reach.The result of period analysis can provide reference for trend analysis and forecast of runoff in Ningxia-Inner Mongolia reach.Mutation analysis shows that the annual runoff in Ningxia-Inner Mongolia reach changed obviously in 1968 and 1986.The operation of Liujiaxia reservoir and Longyangxia reservoir is the main factor of mutation.Because of The combined operation of Liujiaxia reservoir and Longyangxia reservoir,the downward trend of annual runoff in Ningxia-Inner Mongolia reach will continue after 1988,(4)Mann-Kendall mutation detection method and Pettitt mutation point test method are more applicable in mutation analysis of hydrological factors.In addition,Mann-Kendall rank correlation analysis and R /S analysis can be applied to different aspects of the law of hydrological factors,incluing trend analysis,mutation analysis and period analysis,which make them more practical.(5)According to the verification of the predicted result,the forecasting result of the runoff variation in Ningxia-Inner Mongolia reach is accordant with the actual state,the accuracy of the analysis result and the reliability of the analysis methods in this paper are verified.(6)In view of the continued decline of runoff in Ningxia-Inner Mongolia reach,effective measures must be taken to increase the efficiency of the water resources utilization and realize a sustainable development of economic society.