| Reservoirs play an important role in the reasonable use of water resources, reservoir operation is closely linked to sustainable development of society, economy and ecological environment in the local drainage basin. Although reservoir demonstrates its huge economic benefits, some ecological environment problems arise like downstream ecological water shortage and low-temperature discharge, making the living environment of aquatic organisms, especially the fish suffered from varying degree ofdamage. In all cases examining the comprehensive benefits of reservoir and carrying out the ecological operation, present to be the orientation of reservoir management.As one of Yangtze River's eight tributaries, Ganjiang River possess abundant water resources and hydropower potential. Along the river the Wanan water conservancy, Shihutang hydro-junction and Xiajiang hydro-project have been built. In 2012, authorized by the agriculture ministry, the Xiajiang reach of Ganjiang River was selected to be the national aquatic resources reserve for the Four Major Chinese Carps. Aiming to alleviate the negative effects to fish that caused by water conservancy and make an achievement to win-win situation of social economy development and aquatic ecological protection, the method of ecological operationof cascade reservoirs considering the suitable habitat for fish has been extensively studied in the article. The material study and achievement of this paperis presented as follows.(1) We studied the influence on natural hydro logical regimes by large-scale hydraulic engineeringin this paper. Dongbei, Jian and Xiajiang hydrologic station were selected as the representative sites. The variation characteristics and trends of hydrological regime in Ganjiang River were analyzed through the method of M-K trend test, M-K mutation test, frequency analysis and IHA. The computed results illustrated that during the period of 1957 to 2013, the annual flow rate showed increasing trend but the average flow rate during the spawning period decreased. In the 1980s, the fluctuation of variation was rapidly relieved, which had weakened the hydraulic factors that stimulate fish to spawn, this phenomenon showed that hydraulic project constructions have effects on fish resource to a certain extent. The overall varying degree of IHA index was calculated as 27.6%, which showed human activity made hydrologic situation deviated from natural conditions, and may result in the damage of riverine ecosystem.(2) On the basis of full investigation on fish habits,we establishedthe quantitative relationship between hydraulic indexessystem and ecological indicatorsby the mathematical statistical methods,and use the hydraulic indexesto control the flow rate, frequency, timing of occurrence, duration and rate of change, in order to restore suitable habitat for fishes. The study showed that the flow rate in the overwintering season poses a negative impact on fish production, the water level in the spawning season has a positive impact on fish production and wetted perimeter in the fattening season has a positive impact. These indicators were used to mimick the natural flow regimesand calculate ecological flow. The computed results showed that in the overwintering season we should maintain the flow rate of336m3/s; in May and June of the spawning seasonrespectively, we need the continuous processesof rising water level with 10 daysfor more than once,and the flow rate should be kept above 1070m3/s to keep the eggs floating; ecological flowin the fattening seasonis625m3/s.(3) For the reservoir with intakes in the bottom, low-temperature dischargehas negative impacts on the ecology of downstream reaches. To solve this problem, the concept of ecologically suitable reservoir water level was carried out.We improve the disturbance of soloar energy and windby lowering thewater level, in order to make the water temperature in the downstream reach close to the natural condition. To determine the ecological water level of Xiajiang Reservoir, we calculated the water distribution in five conditions with different pool levels from 46.0-44m. According to the model results, when the pool level was 44.5m, the temperature of discharged water was less harmful to the fish habitat in the downstream, so 44.5m was chosen as the ecological water level.(4) In the original artificial beecolony algorithm, the employed bees explore new food sources using a neighborhood dithering method. Every solution is only changed in one dimension, which causes poor performance when it is applied to high-dimensional optimization problems. And the scout bee discovers a new food source randomly without considering the information of the present food source, which also causes poor exploratory performance and causes the algorithm to yield a local optimal value. Therefore, we introduce the DE algorithm and the PSO algorithm into the exploration of the employed bees and exploratory strategy of the scout bee, respectively. An optimal reservoir operation model, which has comprehensively considered the fish habitat, is established using the improved ABC algorithm. Furthermore, the concept of'breakpoint'in the wetted perimeter method is introduced to qualify the relationship between ecological constraint conditions and the generating electricity benefit. |
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