Yellow River Annual Runoff Analysis And Its Forecast

Water resources system and hydro-environment are vast, variant and nonlinear energy-system. The variance of runoff, which is main factor in the system and dominants the variance of the whole system, has important effects on social economy and environment of water resources of the district. Because of the synthetic influence of weather, geography and human-made development actions, runoff of the Yellow River basin is complicated, multi-time-scale dependent, random, discontinuous, and non-linear etc. Traditional methods of runoff analysis and prediction are difficult to get satisfactory results and facing challenges. For the integrated management and sustainable development of the Yellow River basin, many effects have been made to analyze its runoff characteristic and carry out its runoff forecast, including many domestic and international research programs. Yellow River research is becoming one of the typical study basins in water science.This thesis, under the support of Chinese National Nature Science Fund (NO.50239050), (NO.50249024) and (NO.40271024), and the program of subsidizing (NO.HSY03013), applies modern new theories (such as stochastic theory, wavelet transformation, artificial nerve network theory) and traditional methods, to systematically study the variant characteristic of runoffs for the Yellow River and some of its primary branches (such as the Weihe River, the Fenhe River, and the Bei Lou-he River) by using the latest hydrological records. Based on such analyses, this studyforecasts the future 50-year (2000-2050) annual runoff change trend for the Yellow River. Principal findings are concluded as follows.Firstly, based on the natural annual runoff time series of hundreds years for the Yellow River basin, variance in multi-time scales of the series are probed with Morlet wavelet transform. The major periods of the runoff of the Yellow River are about 128 years and 64 years, respectively. These major periods are dominant change trends of Yellow River runoff.Meanwhile, the research also displays that the periods of the runoff of the Yellow River have about 32 years, 22 years and 8 years. There are 11 -year period in the Bei Luo-he River, 5.6-year period in Fen-he River, 8-year period in Weihe River and annual runoff period of this basin is 3 years. But these periods is discontinuous,Secondly, the correlation of annual runoff time series at different station in the basin is related to the variant periods of annual runoffs. When the variant periods of annual runoff are the same between different stations, the correlation is strengthened between different series, and it is weak or contradicted when the periods are different.Thirdly, the static characteristic of state-transfer is that the state of runoff mean is in dominant position to natural annual runoff of Yellow River (about 2-year), the auto-transfer probability of the runoff mean and low runoff is high, and the state-transfer probability of low runoff is higher than the probability of high runoff, so that the states of runoff mean and low runoff are frequently apparent and persistent. It has been demonstrated that one pattern of state-transfer is in the runoff series, which is adjacent state-transfer around runoff mean, and variant characteristics of annual runoff of Yellow River are influenced by it.Fourthly, the statistical analysis of minus-run showed that the re-appear period of continuous 11-year low annual runoff is about 300-year in the upper Yellow River and 225-year in the lower part. The study also indicated that average time of continuant low annual runoff of the Yellow River is about 3 years, and that persisting time of low runoff in the lower reaches is longer than the upper reaches when the situation of low runoff is happened.Fifthly, the wavelet transform and Lipschitz-exponent analyses demonstrated thatthe annual runoff of the Yellow River had a sudden-change for each 20-30 years, but during the 50 years from 1950 to the end of the 20th century, there were 4 sudden-changes (averagely every 10-year one time), implying the sadden-change frequency is more serious than ever before.At the same time, the research also shows that the sudden-changes are different to the three branches of Yellow River in time and duration, and the sudden-change time of the three branches is about identical to Yellow River during 1960s, 1970s, 1980s and 1990s.Sixthly, as for the main period of 11 years and period of convertible magnetic-pole to the macula movement, the appeared frequency of high or low runoff is more than other time in extremum-year of macula, and that sudden changes of the natural annual runoff of the Yellow River have good relations with macula. It is that variance of the low or high runoff is extremely in connection with macula for long time.Seventhly, using improved BP algorithm, a rainfall-runoff model was developed. In addition, a new AR(P) hybrid model for runoff series prediction was proposed with the Mallat's algorithms and Daubechies's wavelet. Both new models were applied to the Yellow River and their applicability were demonstrated.Eighthly, as the variant trend of the future 50-year (2000-2050) annual runoff in the Yellow River, this study has shown that high runoff would be in the majority, and the trend could be separated into three different stages: â‘ variance of annual runoff is in runoff mean (2001-2013), â‘¡variance of annual runoff is in high runoff (2014-2037), â‘¢variance of annual runoff is in low runoff (2038-2050).Finally, in this study, modern new theories and methods were applied to the Yellow River to analyze and forecast the long-term variant characteristic of its annual runoff.