APPLICATION OF THE MODIFIED GAUSSIAN DISTRIBUTION METHOD TO REPRODUCE WATER TEMPERATURES OF THE OGOUCHI RESERVOIR

Abstract

 Hydrodynamic modeling in reservoirs usually implements the Uniform Distribution Method (UDM) for outflows. While this may work well in single-point portals like for deep penstock withdrawal (DPW), the case may be different for selective withdrawal (SW). Using actual observations of velocity fields through the SW facility of the Ogouchi Reservoir, a new outflow method called the Modified Gaussian Distribution Method (MGDM) was applied to simulate the in-reservoir and outflow temperatures. Results showed that MGDM can reproduce the two thermal properties more reasonably than UDM. Using these techniques, the three conceptual cases were formulated namely, Case A (DPW), B (SW) and C [SW and vertical curtains (VC)]. Case A has wider thermal dispersion and exhibits cold water pollution while Cases B and C develop stronger thermoclines and can mitigate the thermal pollution. Case C has wider epilimnion than B due to the VC yet simulation shows similar trends for outflow temperatures for B and C due to similar release operations. In modeling reservoirs with SW, it is highly recommended to measure the actual velocity field of the outflow and apply these measured velocity distributions in the simulation. MGDM is promising for modeling with better accuracy not only for the reservoir temperatures but also for the sediment and other water quality distributions.