Applications of Monthly and Annual Water Balance Models for Estimating Inflows of the Shihmen and Feittsui Reservoirs

• Main Authors: Guo-rong Cheng, 程國榮
• Other Authors: Ming-hsu Li
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/41801264052156714202

碩士 === 國立中央大學 === 水文與海洋科學研究所 === 100 === Both the Shihmen and Feitsui Reservoirs are the most important reservoirs in northern Taiwan providing water resources for domestic, industrial and agricultural usages. Booming social and economic developments in recent years requires increasing demands of water resources. On the other hand, climate variability brought challenges on reservoir managements. Predicting long-term variability and characteristics of reservoir inflows are essential to water resources planning and managements, which are not necessary to be estimated by distributed hydrological models. Monthly and Annual hydrological models provide alternative approach with simplicity to understand long-term inflow variations of watershed to support water resources planning and management. In this study, we applied monthly and annual water balance model to estimate inflows of the Shihmen and Feitsui Reservoirs. For annual scales, the water balance equation was given based on the Budyko assumptions by neglecting changes of subsurface storages. For monthly scales, the Thornthwaite - Mather Water Balance (TMWB) model was employed to estimate reservoir inflows. In this study, we collect the Shihmen and Feitsui Reservoir inflow and meteorological data for model calibrations. Result showed that the combination of Hamon equation (for estimating potential evapotranspiration) and Fu equation (for estimating evapotranspiration) provided the best skill on estimating annual reservoir inflows. The TWMB has skills on estimating monthly reservoir inflows. However, both monthly and annual water balance approaches underestimated inflows of extreme events. Overestimations of potential evapotranspiration were suggested to be the cause of less skill on extreme events. A reduction coefficient was proposed to modify the amount of potential evapotranspiration estimated in both monthly and annual water balance models. For the TMWB model, a layer of subsurface storage was added with a base flow coefficient. Results showed modifications proposed slightly improve the skills of both approaches on estimating reservoir inflows. In order to ease complicated calibration processes, a Graphical User Interface of models employed in this study was developed via the Microsoft Visual Basic 2012 RC to provide a user friendly interface with simultaneous and instantaneous graph drawing capability.