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High accuracy forecasting of medium and long-term hydrological runoff is beneficial to reservoir operation and management. A hybrid model is proposed for medium and long-term hydrological forecasting in this paper. The hybrid model consists of two methods, Singular Spectrum Analysis (SSA) and Auto Regressive Integrated Moving Average (ARIMA). In this model, the time series of annual runoff are first decomposed into several sub-series corresponding to some tendentious and periodic motions by using SSA and then each sub-series is predicted, respectively, through an appropriate ARIMA model, and lastly a correction procedure is conducted for the sum of the prediction results to ensure the superposed residual to be a pure random series. The annual runoff data of two reservoirs in China are analyzed as case studies. The results have been compared with the predictions made by ARIMA and Singular Spectrum Analysis-Linear Recurrent Formulae (SSA-LRF). It is shown that hybrid model has the best performance.

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Risk analysis of reservoir flood control operation mode with forecast information (FCOMFI) is an important basis for the design and implementation of FCOMFI. Most of current researches on this issue are incomplete as they only consider flood forecast errors, but not many other uncertainties in reservoir routing. In order to obtain an integrated risk rate of FCOMFI, this paper analyzes four uncertainties, i.e. hydrological, hydraulic, stage-storage uncertainty and time-delay uncertainty, as well as their probability distributions. On the basis of this analysis, an integrated risk analysis model of FCOMFI for reservoirs and its lower reach is established involving the above-mentioned four uncertainties, and this model is solved by Monte Carlo simulation based on Latin hypercube sampling. The simulation results, with Baiguishan reservoir as the example, show that the integrated risk rates of FCOMFI are less than those of the flood control operation mode without forecast information. This article presents the highest limited water level that satisfies flood control safety requirements of the lower reach. flood control operation mode with forecast information, risk analysis, Monte Carlo simulation Citation: Diao Y F, Wang B D. Risk analysis of flood control operation mode with forecast information based on a combination of risk sources.With the development of society and economy, reservoirs are playing an increasingly important role in flood control and water utilization. This sets a higher request for the reservoir flood control operation. In order to relieve the growing contradiction between supply and demand of water resources and to gain a greater amount of available flood water resources, domestic hydro researchers are doing their best in the design and implementation of flood control operation mode with forecast information (FCOMFI). They are technically supported by remarkable improvement in flood and precipitation predictions. As FCOMFI is based on prediction information as a judgment index of flood volume, it helps prolong lead time and thus achieves the purposes of enhancing the flood control storage in advance and uniform releasing. Therefore this mode can improve the flood control standard of the reservoir and its upper and lower reaches, or the utilization efficiency of the flood water resources by rising the limited water level. The implementation of FCOMFI has become an effective way to approach contradictions between flood control and water utilization in China [1]. But, due to inaccuracy in prediction information and many other uncertainties, risks to reservoir and its upper and lower reaches still exist. So analysis of risks is a key factor in the design and implementation of FCOMFI.In the design and implementation of FCOMFI, such risk sources as observation errors of rainfall, stability in telemetry system and decision-making communication system, and decision-making level, are taken as restrictions. Uncertainties affecting decisions of the reservoir flood control operation also include flood, selec...

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This paper develops a new inter-basin water transfer-supply and risk assessment model with consideration of rainfall forecast information. Firstly, based on the current state of reservoir and rainfall forecast information from the global forecast system (GFS), the actual diversion amount can be determined according to the inter-basin water transfer rules with the decision tree method; secondly, the reservoir supply operation system is used to distribute water resource of the inter-basin water transfer reservoir; finally, the integrated risk assessment model is built by selecting the reliability of water transfer, the reliability (water shortage risk), the resiliency and the vulnerability of water supply as risk analysis indexes. The case study shows that the inter-basin water transfer-supply model with rainfall forecast information considered can reduce the comprehensive risk and improve the utilization efficiency of water resource, as compared with conventional and optimal water distribution models.inter-basin water transfer, GFS rainfall forecast, water distribution, risk assessment Citation:Xi S F, Wang B D, Liang G H, et al. Inter-basin water transfer-supply model and risk analysis with consideration of rainfall forecast information. Sci

Since the Three Gorges Reservoir (TGR) was constructed and taken into operation, a series of hydrological consequences between the Yangtze River and Dongting Lake (river-lake) have emerged and received worldwide attention, particularly the changes in flow regime, which are essential for proper understanding this large river-lake system. To assess the impacts of TGR on flow variation, the three outlets on the south bank of Jingjiang River, i.e., Songci, Taiping, and Ouchi, have been selected as case studies, the whole study period was divided into two sub-periods according to the year when the TGR started to store water, i.e., the pre-and post-TGR storage stages. Based on the water level-, flow volume-, and sediment data obtained from the major hydrological stations in the reach, the alterations in flow regime were investigated and the main influence factor were explored for the different periods through comparative analysis of the three major driving forces, i.e., the decline in inflows to the TGR (DWF), the operation function of TGR (TGRO) and the TGR-induced variation in the river-lake relationship (RRL). As a result, we found the river flow of the three outlets has reduced gradually after the impoundment of TGR and quantified that: the DWF accounts for 68.9 % of total decline in mean annual runoff, the TGRO and RRL account for only 13.9 % and 17.2 %, respectively. Evidence suggests that the riverflow reduction at the three outlets in the post-TGR period was mainly governed by the DWF closely related to precipitation changes and large reservoirs in the upper basin, while the impacts of TGR (i.e., TGRO and RRL) indeed made a contribution to aggravation of this river flow variations. These results can provide a reference for future studies on changes in the complicated RRL, and for the management of river networks on the south bank of Jingjiang River.