| The outstanding contradiction of water use and plenty of uncertain factors in the process of development and utilization of water resources in the lower reaches of the Lancang River,which makes water resources regulation and control face multiple risks.In order to improve the social and economic benefits with taking the eco-environmental benefits into account,it is urgent to deeply explore the risk problems faced by the water resource regulation and control system.In this paper,the hydropower plants of Nuozhadu,Jinghong,Ganlanba in the lower reaches of Lancang River were selected as the study object,firstly,the multi-objective opitimal scheduling model was constructed with the objective of power generation and ecology protection in lower reaches to explore the competition relationship among the multiple objectives.Secondly,to undertake risks identification and assessment of comprehensive water resource systems based on power generation and ecology,and safety thresholds for rational usage of water resources were obtained and divide them into three risk levels.Thirdly,the multi-objective cascade reservoir scheduling model in the lower reaches of the Lancang River was constructed with the constraints of the tolerable risk threshold for sensitive risk indicators,according to the results,the VAR model was constructed to analyze the relationship and values of dynamic transmission for each risk indicator.Fourthly,the Copula joint function and Gibbs method are used to simulate the tochastic inflow runoff for Nuozhadu,and a stochastic optimal scheduling model of cascade reservoirs in lower reaches of Lancang River was constructed to analyze the scheduling rules considering the runoff uncertainty.The reseach results is good to the improvement of water resources management in the Lancang River Basin and the scientific scheduling of reservoirs,promoting the sustainable development of basin.And the main results are as follows:(1)The long-term inflow runoff data of 57 year for Nuozhadu was adopted with monthly time interval,and the multi-objective cascade reservoir scheduling model in lower reaches of Lancang River(Model-?)was constructed with the objectives of maximum power generation and minimum degree of ecological change,at the same time maximum power generation model with considering firm output(Model-?)were constructed,14 case sets were set,the improved GA method was used to solve the two models.The optimal case was determined by the method of entropy weight and grey relational analysis.The results show that there is an obvious competitive relationship between the ecological benefits and power generation benefits of the cascade hydropower plants optimal scheduling on the lower reaches of the Lancang River.The mean power generation of Model-? decreased by 1.145 billion kW·h(accounted for 3.33%of the total)compared with Model-?,while the degree of ecological change has reduced by 10.36%(accounted for 49.95%of the total)(2)From the perspective of actual problems in the lower reaches of the Lancang River,5 kind of risk indicators were identified,the risk threshold was evaluated by Monte Carlo method,and it then was divided into three levels by means of Fisher Optimal Dissection method.The acceptable,tolerable and unacceptable risk thresholds of 4 sensitive risk indicators were obtained(3)Taking the tolerable risk thresholds of 4 sensitive risk indicators as constraints,the multi-objective cascade reservoir scheduling model in lower reaches of Lancang River considering multiple risks was constructed,and the scheduling schemes with the combination constraints of single and multiple risk indicator thresholds were analyzed.The results showed that the risk of degree of ecological change in scenario 1 was the lowest,the risks of power generation and output in scenario 2 were both the lowest,and the risk of abandoned water in scenario 4 was the lowest,but in scenario 3 the 4 risks were higher than the other 3 scenarios.Therefore,the risks of power generation,output and degree of ecological change brought from the multi-objective scheduling with only considering abandoned water constraint were higher than those in other scenarios While in scenario 5,except that output risk(44.49%)was a little higher than that in scenario 2(44.35%)and abandoned water risk(1.04%)was increased by 0.3%compared with scenario 4,other risks were all lower than the scheduling results with considering single-risk constraint.And it is concluded that the multi-objective cascade reservoir scheduling model in the lower reaches of Lancang River with considering multi-risk performed better than that with considering single-risk.(4)The risk transmission model for multi-objective cascade reservoir scheduling in the lower reaches of Lancang River was constructed,and a standard deviation fluctuation was added to each risk indicator to analyze the dynamic transmission relationship among each risk indicator,and the Variance Decomposition method was used to quantitatively estimate its transmission amount.The results showed that except its own risk transmission,power generation risk dominated in the transmission amount of the remaining 3 risk indicators,and the transmission amount of power generation risk to output,degree of ecological change and abandoned water were 7.94%,12.48%and 9.17%,respectively;the output risk only made a significant contribution to the power generation risk and the degree of ecological risk,and transmission amount were 13.87%and 8.40%,having less transmission amount to abandoned water risk(2.34%);the degree of ecological risk had some transmission to the output risk,but the transmission to the power generation risk and the abandoned water risk can be ignored(0.57%and 0.82%),and the transmission amount of abandoned water risk to the other 3 risk indicators is far less(5)The inflow of Nuozhadu was taken as the study subject,a joint distribution model between adjacent monthly runoff was constructed based on the Copula function,and 5000 sets of monthly runoff were simulated by Gibbs method.The measured mean annual runoff plusing or minusing a standard deviation was set as a reasonable interval,and 71.12%of the simulated values were covered by the interval,and the years of simulated values exceeding and being below this interval respectively accounted for 13.98%and 14.9%,which fully reflected the inflow uncertainty.Based on above results,the transmission probability of different inflow intervals at each month was obtained,the cascade reservoir stochastic dynamic optimal scheduling model(Model-IV)in lower reaches of Lancang River was constructed and solved by SDP method to obtain scheduling rule curves for the Nuozhadu with future interval inflow information.And the results can provide as a direct reference for the power generation optimization scheduling work of the Nuozhadu hydropower plant.Taking the runoff process in the normal year as a typical case,the annual power generation results were almost the same based on SDP and DP,305.97 kW·h and 306.91 kW·h,respectively,which verified the reliability of the scheduling rule curves constructed. |
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