Optimal operation of a multi-reservoir system for environmental water requirements of a river-connected lake

Jingqiao Mao, Peipei Zhang, Lingquan Dai, Huichao Dai

Friday 3 july 2015

9:30 - 9:45h at Europe 1 (level 0)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology

Parallel session: 14G. Environment - Renewable

River-connected lakes play important roles in flood attenuation, drought mitigation, water quality maintenance, and biodiversity conservation of watersheds. In particular, the functioning and stability of their ecosystems are sensitive to the altered flow regimes due to dam construction and flow regulation. Dongting Lake is a large shallow lake directly connected to Yangtze River in the middle region, of which the ecosystem functions have been threatened or disturbed by the upstream water resource development and operations. In the study, an optimization model that considers both the basic human needs and environmental water requirements (EWR) of Dongting Lake is developed for the operations of a multi-reservoir system. The system consists of the world’s largest water resource project (Three Gorges Reservoir built on the Yangtze River) and two reservoirs situated on the tributaries of Dongting Lake. The optimal target in pursuit of the ecological objective is to maximize the EWR of Dongting Lake, which has been estimated from the analysis of long-term hydrological data. We use an artificial neural network based model to examine the response of lacustrine hydrological conditions to reservoir operation and other tributaries’ inflow. The simulation is carried out for different scenarios, and the results show that: (1) the existing operation policy results in significant hydrologic alteration in the natural flow regime; (2) an optimal joint operation policy proposed in the study could increase the general EWR of Dongting Lake from 89.4% to 96.9%; (3) the lake’s EWR level is mainly affected by the operation of Three Gorges Reservoir, and the eastern part (near the junction of Dongting Lake and Yangtze River) is more sensitive to the alterations of Yangtze River discharges.