Hydropeaking effects on movement patterns of brown trout (Salmo trutta L.)

Radiotelemetry was used to investigate seasonal movement and home range of brown trout Salmo trutta (size range 188–420 mm fork length, N = 30) in two reaches of the Noguera Pallaresa River (Ebro Basin, north‐east Spain) subjected to different flow regulation schemes. NP‐1 reach is a bypassed section with near natural flow conditions, whereas the downstream reach NP‐2 is subjected to daily pulsed flow discharge (i.e., hydropeaking) from an upstream hydropower station. Significant differences in home range size (95% kernel estimates) and seasonal movement pattern between study reaches were found. Mean home range size was (μ ± SE) 112.1 ± 11.5 m in the bypassed reach NP‐1 and increased significantly in the hydropeaking reach NP‐2 up to 237.9 ± 37.2 m. There was a large individual variability in fish home range size within reaches. Most of the seasonal differences in fish movement among reaches were associated with the spawning season. Pulsed discharge events in NP‐2 during daytime in summer (lasting about 3 hr and increasing water flow from 1 to 20 m³/s) did not cause significant displacements in either upstream or downstream direction during the duration of the event. Our results highlight the importance of habitat connectivity in hydropeaking streams due to the need of brown trout to move large distances among complementary habitats, necessary to complete their life cycle, compared with unregulated or more stable streams.     

基于聚合水库蓄放水模拟的洪水预报研究

大量水利工程建设很大程度上改变了流域的天然水文特性,特别是对洪水产生了更显著的影响,给流域水文预报工作带来很大的难度。本文首先基于聚合水库的思想,将众多水利工程聚合成一个水库,并根据各水利工程的基本调蓄规律制定聚合水库的蓄放水模拟图;然后将聚合水库的蓄放水模拟图与天然期洪水率定得到的TOPMODEL模型相结合,构建考虑水利工程影响的洪水预报模型;最后在丰满水库五道沟以上流域进行实例验证。结果表明,考虑水利工程影响的洪水预报方案优于原预报方案,显著提高了洪水预报合格率,并能有效克服原方案在初汛和久旱后预报产流偏大及主汛大洪水期间预报产流偏小的问题;预报洪水过程与实测洪水过程也更加吻合。对3种类型洪水过程的分析表明,聚合水库蓄放水模拟图能较好地反映水利工程在洪水过程中的蓄放规律和对洪水的综合作用。     

Experimental and numerical simulations of the hydraulic flushing of reservoir sedimentation for planning and design of a hydropower project

Hydropower projects located on rivers transporting heavy sediment loads require design and operation criteria based on sediment management as a means of sustaining the project life. Sediment management is achieved by designing projects as a run‐of‐the‐river scheme, with provision for drawdown flushing, noting hydraulic model simulations are essential for optimizing the design of these projects. Sediment deposition levels are generally predicted with long‐term simulations using 1‐D numerical models, as well as experiments with scaled physical models that simulate drawdown flushing. The present study presents experiments with scaled model and 3‐D numerical model simulations conducted for hydraulic flushing of a reservoir. Experiments were conducted for various durations and discharges to finalize the intake alignment and optimize the flushing. The results of the 3‐D numerical model simulations are in agreement with the results of the experimental study (4%–6% variation). The results also indicate a combination of a 1‐D numerical model for sedimentation and a 3‐D numerical model for flushing can be effectively used to simulate the sedimentation and flushing of reservoirs during the planning and design stages.     

Re‐operating the Three Gorges Reservoir for Environmental Flows: A Preliminary Assessment of Trade‐offs

The Three Gorges Reservoir (TGR), located on the Yangtze River in China, is operated for hydropower, flood control and navigation, with minimal environmental releases. This study explored the potential trade‐offs between better environmental releases from the TGR and hydropower generation using three performance indicators. Spearman's rank correlation coefficient between unimpaired flows and regulated flows was used as an indicator of environmental performance (eco rho). Energy generation as a fraction of capacity (energy fraction) and power reliability were used as hydropower performance indicators. We first assessed TGR performance without and with basic instream flow requirements (IFRs). We then imposed an IFR consisting of a minimum release of fraction k of inflow and maximum release of 1/k of inflow and assessed the sensitivity of reservoir performance to different fixed k values. Finally, we allowed k to vary within the year in a genetic algorithm to estimate the Pareto optimal trade‐offs between performance indicators. In all cases, flood and navigation rules were prioritized over environmental and hydropower. With a fixed k of 1.0, eco rho increased from 0.865 to nearly 1.0 (completely natural). Energy fraction reduced from 43.5 to 39.3%, or about 9.5%, and power reliability decreased from 97.0 to 59.2%. The Pareto optimal trade‐off surface not only showed similar results but also indicated that energy fraction and environmental performance can both be increased together, up to a point, but at a cost of reliability. This study helps understand the potential costs of re‐operating the TGR. Limitations and potential future directions are discussed. Copyright © 2015 John Wiley & Sons, Ltd.