Frequency Analysis Of Extreme Rainfall In Shiyang River And Hei River Basin Based On Regional L-Moments Method

China is one of the countries most seriously affected by flood hazard in the world.Extreme rainfall is the main cause of flood in our country.Researches on the frequency of extreme rainfall events can provide basis for emergency response plan and the design standard of water conservancy project,besides,it is also a part of artificial weather modification research.Under the background of global warming,the intensity and frequency of precipitation in most mid-latitude areas show an increasing trend,which will bring enormous challenge for prevention over natural disasters.However,the method we use in hydrologic frequency analysis have not been updated in good time.During the past several decades,the method,regional frequency analysis based on L-Moments,have been successfully used in many places around the world and achieved fruitful results.In this paper the author expatiated on theory about L-Moment and regional frequency analysis and then applicated this method to the frequency analysis of extreme precipitation in Shiyang river-Hei river basin.Finally this research successfully get a series of design value corresponding to different return periods.The main work of this research includes:(1)Specified the trend of observed meteorological elements during 1968-2016 by Mann-Kendall non-parametric test and checked the basic hypotheses of regional frequency analysis.It showed that annual mean temperature sequences of all 20 meteorological stations appeared obviously upward tendency,extreme rainfall series(maximum rainfall of 1 day/3 days)in most sites do not show obviously trend.(2)By choosing reasonable factors as input of cluster analysis and conducting a series of adjustments and measurements,study area was finally divided into three hydro-meteorology homogeneous regions.(3)Based on the method of Regional Frequency Analysis,this paper analyzed the frequency of extreme rainfall of each hydro-meteorology homogeneous regions.After specifying the best-fitted frequency distribution of three regions by goodness-of-fit statistic measure and L-moments ratio diagrams,this paper finally got design extreme rainfall values of each site by an index-flood procedure.Author found that the main risk area of extreme rainfall hazard located in the east of Qilian mountain and the upstream area of Shiyang River.(4)Assessed the accuracy of design values of each site by Monte Carlo simulation and drew 90% error bounds of regional growth curve.