xigema
Civil/Environmental
- Sep 16, 2010
- 1
Hi, I have a question about the reservoir routing using MHS:
I am developing a HMS model for reservoir routing calculation. There is a tailwater at downstream of reservoir, so I need to put a flapgate at the outlet structures. When water surface elevation within reservoir is higher than the tailwater, the gate will be opened.
Also I was told to set starting water surface at tailwater stage as reservoir initial condition (assuming there is some rainfall stored in reservoir before the 100-year event)
(1) First I used outlet structure to calculate outflow, and the elevation-storage paired data starting from tailwater elevation, the model was crashed because the outlet structure invert is lower then the bottom of reservoir(actual is tailwater stage)
(2) Second I used outlet structure to calculate outflow. But only set the initial condition as elevation = tailwater, the elevation-storage paired data is starting from reservoir bottom. The results showed some inflow is stored in the space below the tailwater which is not what I want.
(3) Now I am using outlet curve to calculate the outflow. The curve is storage-discharge paired data, the zero storage is starting from tailwater elevation, and the discharge is based on the head in reservoir which is water level from inflow plus tailwater stage.
The computed the results show no difference in peak flood stages with the assumption of reservoir storage staring either (1) from reservoir bottom elevation, or (2) from tailwater elevation. There is only peak storage having some different.
Is my calculation correct? Or is there anybody can help me to figure out the reason? Thanks!
I am developing a HMS model for reservoir routing calculation. There is a tailwater at downstream of reservoir, so I need to put a flapgate at the outlet structures. When water surface elevation within reservoir is higher than the tailwater, the gate will be opened.
Also I was told to set starting water surface at tailwater stage as reservoir initial condition (assuming there is some rainfall stored in reservoir before the 100-year event)
(1) First I used outlet structure to calculate outflow, and the elevation-storage paired data starting from tailwater elevation, the model was crashed because the outlet structure invert is lower then the bottom of reservoir(actual is tailwater stage)
(2) Second I used outlet structure to calculate outflow. But only set the initial condition as elevation = tailwater, the elevation-storage paired data is starting from reservoir bottom. The results showed some inflow is stored in the space below the tailwater which is not what I want.
(3) Now I am using outlet curve to calculate the outflow. The curve is storage-discharge paired data, the zero storage is starting from tailwater elevation, and the discharge is based on the head in reservoir which is water level from inflow plus tailwater stage.
The computed the results show no difference in peak flood stages with the assumption of reservoir storage staring either (1) from reservoir bottom elevation, or (2) from tailwater elevation. There is only peak storage having some different.
Is my calculation correct? Or is there anybody can help me to figure out the reason? Thanks!