Integrating Seasonal Climate Forecast to Develope Novel Reservoir Rule Curves – A Case Study of the Shihmen Reservoir
Date Issued
2015
Date
2015
Author(s)
Tseng, Shin-Yi
Abstract
Due to significant seasonal rainfall variations, reservoirs and their flexible operational rules are indispensable to Taiwan. Furthermore, with the intensifying impacts of climate change on extreme climate, the frequency of droughts in Taiwan has been increasing in recent years. Drought is a creeping phenomenon, the slow onset character of drought makes it difficult to detect at an early stage, and causes delays on making the best decision of allocating water. For these reasons, novel reservoir rule curves using projected seasonal climate are proposed in this study, which can potentially reduce the adverse effects of drought. This study dedicated establishing new rule curves which consider both current available reservoir storage and anticipated monthly inflows with leading time of two months to reduce the risk of water shortage. The monthly inflows are projected based on the seasonal climate forecasts from Central Weather Bureau (CWB), which two disaggregation models, weather generator(WGEN) and semiparametric weather generator (SWG), are used to produce daily weather data for the hydrological component of the GWLF. To incorporate future monthly inflow projections into rule curves, this study designs an information flow index which is a linear combination of current available storage and inflow projections with leading time of 2 months. By optimizing linear relationship coefficients of decision flow index, the shape of rule curves and the percent of water supply in each zone, the best rule curves to decrease water shortage risk and impacts can be developed. The Shimen Reservoir in the northern Taiwan is used as a case study to demonstrate the proposed method. Existing rule curves of Shimen Reservoir (M5 curves) are compared with two cases of new rule curves, including hindcast simulations and historic seasonal forecasts. The results show new rule curves can allocate shortage amount to preceding 1 to 3 months to avoid extreme shortage events under perfect forecasts. However, the accuracy and uncertainties in historic forecasts would result unnecessary discounts of water supply, it may cause worse performs than M5 curves during droughts.
Subjects
Seasonal Climate Forecast
Water Resources Management
Reservior Operation
Optimization
Climate Change
Type
thesis
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