| The hydrologic cycle system was driven by multiple systems,such as meteorological systems,environmental systems,and human intervention.The hydrologic cycle and elements have changed significantly under the changed condition of climate and human intervention.These changes further lead to the non-stationary changes in the observed hydrological and meteorological series(such as precipitation,evaporation,runoff),with a significant trend.So that,the stationary assumptions of water resources planning and management,hydrological analysis and calculation was destroyed.The water resources planning and management,and water conservancy projects was not reliable due to the destruction of the stationary of hydrological series.Water conservancy projects,flood and drought control engineering which designed based on the historical hydrological data and stationary assumptions will have certain risks,leading to human property losses and even threatening the safety of life.Therefore,it is extremely important to recognize and identify the definition and connotation of non-stationary.The definition of non-stationary of hydrological series and hydrological process should be distinguished at first.The non-stationary of measured runoff series is regarded as the non-stationary of hydrological series.And the non-stationary of seminatural runoff was drove by the multiple factors(such as underlying surface change caused by the human intervention,climate change).The study of non-stationary of hydrological series and hydrological process in Wuding River basin is carried out based on the definition of nonstationary of hydrological process.The specific research contents and conclusions are as follows:(1)Distinguished the concept of nonstationary of hydrological series/ hydrological process.The non-stationary identification of hydrological process was tested with the semi-natural series.The semi-natural runoff series refers to runoff series which has not the significant runoff consumption by human.But the semi-natural runoff was production and concentration on the current underlying surface and climate conditions.And the semi-natural runoff can reflect the laws of the runoff production and concentration with the current underlying surface and climate conditions.The significant human consumption above the control section of hydrological gauges was obtained through the method of itemized investigation.And the semi-natural runoff series can be obtained by plus the human consumption runoff to the measured runoff data.(2)The preliminary diagnosis of non-stationary.The sliding window Kolmogorov–Smirnov(K-S)test was carried out to diagnosis the non-stationary of measured runoff series and semi-natural runoff series.The 30 scale was set as the window length,and the step was 1.The results show that the measured runoff series of the hydrological gauges in Wuding River Basin all have non-stationary character during the statistical period.Compared the measured runoff series,the year of non-stationary change of semi-natural runoff series was relatively late.And the semi-natural runoff series in Suide gauge has a stationary character.(3)Quantitative identification of non-stationary changes.A quantitative identification system for non-stationary change in Wuding River Basin is constructed,which includes monotonic change,regression change,step change and periodic change.The Mann-Kendall trend test and the Theil-Sen slope value of were used to identify the monotone change qualitatively and quantitatively in Wuding River Basin.The trend of measured runoff series and semi-natural series in first 30 years is stronger than the last 30 years.The absolute statistic value of MK trend test in last 30 years is smaller than the first 30 years,except the Baijiachuan hydrological gauge.For the semi-natural series,the last 30 years series have significant trend in Zhaoshiyao and Baijiachuan gauges.The semi-natural series in rest hydrological gauges have not significant trend.The piecewise linear fitting technique was used to quantitatively identify the regression changes.The results showed that the regression changes of measured runoff and semi-natural runoff series in Wuding River Basin were concentrated in two periods,namely around 1975 and 1995.The MOW-BS-Pettitt method was used to identify the multi-step points of mean and calculate the step amount for the measured runoff and semi-natural runoff series of each hydrological gauge in Wuding River Basin.The results show that there are step change points in mean in semi-natural and measured runoff series at all hydrological gauges in Wuding River Basin.And the step change points in mean in semi-natural runoff are reduced than measured runoff series.The locations of step change points are relatively concentrated compared with measured runoff.Th e Morlet wavelet analysis method was used to analyze the periodic changes of measured runoff and semi-natural runoff series in Wuding River Basin.The main period of semi-natural runoff series in each hydrological gauge was more concentrated than that of measured runoff series.(4)Analysis of environmental parameters with non-stationary changes.The environmental variables(precipitation,evaporation,land-use and runoff consumption by human)that have great influence on production and concentration of runoff in Wuding River Basin were analyzed.The precipitation series of Wuding River Basin has a non-significant decreasing trend,and the annual change of precipitation is gradually decreasing.It can be seen from the analysis of evaporation series that the evaporation series in Wuding River Basin has a certain downward trend,and with the slide of time scale,its variation coefficient tends to be stable and the change of inter-annual decreases.The Soil Conservation Service(SCS)was used to analyze the impact of land-use change on runoff in Wuding River Basin.The results showed that,in terms of landuse alone,the runoff coefficient was the highest in 1990 under the condition of land-use,which was 0.427 and more favorable to runoff production.Under the condition of land-use in 2005,the runoff coefficient was the lowest,which was 0.277.In addition,the Detrended CrossCorrelation Analysis(DCCA)method was used to calculate the correlation coefficients between environmental parameters and semi-natural/ measured runoff in Wuding River Basin.The correlation coefficients between precipitation,measured runoff and measured natural runoff were 0.558 and 0.663,respectively.The correlation coefficients between evaporation and measured/ semi-natural runoff were-0.163/-0.132.The correlation coefficients between NDVI and measured/ semi-natural runoff were-0.766/-0.658.The correlation coefficients between water consumption by human and measured/ semi-natural runoff were-0.372/-0.278.(5)Non-stationary change scene grouping and frequency calculation.According to the results of quantitative identification system for non-stationary changes of runoff in Wuding River Basin,the characteristics of non-stationary changes of runoff in each hydrological gauge were sorted out.The non-stationary changes of runoff in each hydrological gauge in Wuding River Basin were divided into three groups.Semi-natural runoff series of each hydrological gauge in Wuding River Basin for hydrological frequency analysis were obtained based on the quantitative identification system of non-stationary changes.P-III curve fitting was used to obtain the runoff values at different frequencies of the hydrological gauge in Wuding River Basin. |
PDF Full Text Request