RESEARCH ON THE ECOLOGICAL OPERATION OF A RESERVOIR BASED ON THE PROTECTION OF BENTHIC DIATOMS IN A NATURAL STREAM

摘要

While hydropower exploitation provides great benefits in terms of flood control, power generation, irrigation and water supply, it has a continuous and far-reaching impacts on the ecosystem. The improvement to traditional reservoir dispatching can not only meet the requirements of flood control and impounding but also consider the basic demands of river ecosystems for various hydrological situations. Benthic algae are a food source for fish in the Yangtze River, and these algae have a very important function in river ecosystems. At present, most scholars have paid attention to the protection and restoration of fish spawning grounds and habitats via ecological regulation; however, few studies on the protection of bait in fish bait farms have been conducted. The determination of the hydrodynamic conditions suitable for the growth of benthic diatoms is important for studying the protection of benthic diatoms via ecological regulation. Therefore, this study obtained a habitat suitability curve for benthic diatoms in rivers through field and laboratory experiments and numerical simulations using MIKE 21 software. The weighted usable area (WUA) of benthic diatoms was calculated using instream flow incremental methodology (IFIM) and River2D software under different flows in the Jinsha River. The flow restriction suitable for the growth of benthic diatoms downstream of the Changbo dam was proposed. The results show that the biomass of benthic diatoms is high when the flow rate is within and near the range of 0.86 to 1.2 m/s and the water depth is within and near the range of 0.3 to 0.56 m. In the Jinsha River, when the discharge from the Changbo dam is 8% of the natural average annual flow (77 m~3/s), the WUA for benthic diatoms in the river is the largest (38693 m~2). Based on research results and theory, a set of complete hydraulic habitat restoration measures for river benthic diatoms was established to guarantee the feeding requirements of higher organisms after the completion of power stations, such as maintaining the biodiversity of downstream rivers. The system can provide a reference index for the planning scheme for the Changbo dam and a theoretical basis for the formulation of a hydraulic habitat restoration scheme, the implementation of a restoration project and the protection of the downstream ecological environment.