Upstream Reservoir Operation Research Articles

Comparison of channel geometry changes in Inner Mongolian reach of the Yellow River before and after joint operation of large upstream reservoirs

The impact of reservoirs on downstream river channel change has been a scientific issue in fluvial geomorphology during the last few decades. However, it is still a difficult issue as to how to express quantitatively the channel adjustment in the Inner Mongolian reach of the Yellow River induced by the joint operation of upstream reservoirs. Based on the shape parameters of channel cross-sections at four gauging stations in this river reach over a flooding season in two periods, 1978–1982 and 2008–2012, the present work investigated the channel changes in terms of shape parameter change rate under the same controlling water level in each flooding season at the channel cross-sections. Results showed that most of the change rates of the parameters evidently increased over a flooding season in both periods. However, the change rate of each parameter at the cross-sections decreased evidently in the latter period, compared with the former period. At the same time, the distribution pattern of the change rate of the shape parameters along the cross-sections thus changed from a convex curve in the former period to an S-shaped curve in the latter period. The obvious decrease of the change rates is related to the joint operation of the Liujiaxia and Longyangxia reservoirs. The reservoirs stored a large volume of water and decreased the peak discharge and maximum velocity in the flooding season; as a result, the erosion ability of the flood decreased accordingly. With the joint operation of the large reservoirs, the Inner Mongolian channel shrunk markedly. Therefore, the channel will present the possibility of an extreme flood in the future. Consequently, it is reasonable to adjust the function of the reservoirs in future. The total water and sediment discharges and the peak discharge in flooding seasons should be effectively controlled. Continuous shrinkage of the channel can thus be avoided and it can be ready for a potential extreme flood.

Effects of upstream reservoir regulation on the hydrological regime and fish habitats of the Lijiang River, China

Dam construction may alter the hydrological regime of rivers, and thus may cause profound and accumulative impacts on a river ecosystem. Therefore, research on hydrological and ecological response to river regulation has received increasing interest. This research, takes the middle reach of the Lijiang River as a case and an indigenous cyprinid fish Spinibarbus hollandi (S. hollandi) as a target species for the development of an integrated hydro-environmental-habitat model. In contrast to previous studies focusing only on habitat suitability, this research takes into account habitat quality such as habitat fragmentation. The model analyses the effects of flow regime changes due to upstream reservoir operation on habitats for juvenile fish. Unregulated flow (UF) and regulated flow (RF) were simulated, and the corresponding effects on habitat of S. hollandi were analysed and discussed. Using the developed model, an ecologically-based flow regime was derived ensuring several conservation levels for S. hollandi habitats. Based on the recommended ecological flow regime, rules for reservoir operation are suggested.

Channel change at Toudaoguai Station and its responses to the operation of upstream reservoirs in the upper Yellow River

The application of dams built upstream will change the input conditions, including water and sediment, of downstream fluvial system, and destroy previous dynamic quasi-equilibrium reached by channel streamflow, so indispensable adjustments are necessary for downstream channel to adapt to the new water and sediment supply, leading the fluvial system to restore its previous equilibrium or reach a new equilibrium. Using about 50-year-long hydrological, sedimentary and cross-sectional data, temporal response processes of Toudaoguai cross-section located in the upper Yellow River to the operation of reservoirs built upstream are analyzed. The results show that the Toudaoguai cross-section change was influenced strongly by upstream reservoir operation and downstream channel bed armoring thereafter occurred gradually and extended to the reach below Sanhuhekou gauging station. Besides, median diameter of suspended sediment load experienced a three-stage change that is characterized by an increase at first, then a decrease and an increase again finally, which reflects the process of channel bed armoring that began at Qingtongxia reservoir and then gradually developed downstream to the reach below Sanhuhekou cross-section. Since the joint operation strategy of Longyangxia, Liujiaxia and Qingtongxia reservoirs was introduced in 1986, the three-stage change trend has become less evident than that in the time period between 1969 and 1986 when only Qingtongxia and Liujiaxia reservoirs were put into operation alone. In addition, since 1987, the extent of lateral migration and thalweg elevation change at Toudaoguai cross-section has reduced dramatically, cross-sectional profile and location tended to be stable, which is beneficial to the normal living for local people.

A STOCHASTIC DYNAMIC PROGRAMMING BASED APPROACH TO THE OPERATION OF A MULTI‐RESERVOIR SYSTEM1

ABSTRACT: An heuristic iterative technique based upon stochastic dynamic programming is presented for the analysis of the operation of a three reservoir ‘Y’ shaped hydroelectric system. The technique is initiated using historical inflow data for the downstream reservoir. At each iteration the optimal policies for the downstream hydroelectric generating unit are used to provide relative weightings or targets for operation of upstream reservoirs. New input inflows to the downstream reservoir are then obtained by running the historical streamflow record through the optimal policies for the upstream reservoirs. These flows are then used to develop a new operating policy for the downstream reservoir and hence new targets for the upstream reservoirs. The process is continued until the operating policies for each reservoir provide the same overall system benefit for two successive iterations. Results obtained from the procedure are compared to the results obtained by historical operation of the system. The procedure is shown to develop operating policies which give benefits which are as close to the historical benefits as can be expected given the choice of the number of storage state variables.

Assessing upland reservoirs using a daily flow model

A procedure is given for analyzing multisite upland reservoir storage for water supply at a downstream point. Synthetic monthly streamflow for six sites replicates mean, standard deviation, and lag correlation coefficient of historic data; a matrix of spatial correlations interrelates the sites. Factors translate flow to seven reservoirs operated in two modes and one use point. The Thomas-Fiering formula, using lag-one correlation and coefficient of variation of historic daily flows and a random gamma variable, converts monthly flow to daily supply at the use point. Results comprise probabilistic analyses of deficiencies and reservoir performances. Results of a study of the Washington, D. C., requirements for 1985 indicate that six upland reservoirs reduce the duration of a deficiency occurring once in a hundred years and that a smaller volume of nearby storage is an alternative or can be used for standby. Results indicate that sophisticated operation of upstream reservoirs should enhance recreational values while concurrently satisfying supply requirements at Washington.

A basis for unified flood‐control operation of reservoir systems

Reservoir operations for passage of flood waters customarily depend upon water levels in the reservoir or upon flows entering the reservoir. Both of these factors are influenced materially by the manner of operation of other reservoirs in the watershed, and by the construction and operation of any dam, levee, or channel improvement in the upstream flood plain. The purpose of this paper is to present a criterion of effective operation which would independent of upstream reservoir operation and which would also be equitably alterable as upstream developments increase or decrease the flood‐control capability of the reservoir system. Advance drawdown of pool levels for flood storage and the control of a tributary to keep its flow off the flood peak of a main stream are illustrated. The method is presented as being most useful in reservoir developments principally for power generation, irrigation, and navigation, and secondarily for flood control; and most needed in developments in which only a small amount of reservoir storage capacity is reserved for flood‐time use.