Withdrawn: A novel step function approach for reservoir operation to balance water storage and flood control during extreme rainfall events

Abstract

Reservoir operation is crucial during extreme rainfall events which impact flooding and water supply. Simple models with upgraded operating rules can accurately simulate reservoir operations and used as a tool to investigate operations during extreme rainfall events. In this study, a step function for reservoir operation, that can be upgraded based on historical flood events, was developed and embedded with a simple box model. This model simplifies the simulation of controlled reservoir operation and can be integrated with hydrologic and hydraulic models for the assessment of the impacts of controlled reservoir operation. Chembarambakkam, a large water supply reservoir in Chennai city, India, was used to assess the performance of the developed model. The parameters of the box model were calibrated and validated with an error estimation of 11 and 13 % for inflow, 21 and 22% for outflow, and 15 and 16% for water level, respectively. Furthermore, a massive flood event that occurred in Chennai in 2015 was evaluated with various combinations of reservoir operations using the developed approach. The sensitivity analysis of the parameters shows that the initial water level in the Chembarambakkam reservoir plays a substantial role in balancing water supply and flood mitigation. Restraining initial water levels from 50 to 75 % of storage helps to reduce the flood peaks from 14 to 38 % and inundation extents by 3.19 to 5.18 km2 besides the reliable storage of 81.50 % for water supply. Thus, the proposed box model was proven to be useful in controlled reservoir operation during extreme rainfall events.