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Flow Routing

Flow Routing. Learning Objectives Calculate outflow hydrographs for reservoirs using the storage indication method Calculate outflow hydrographs for stream reaches using the Muskingum method Reading: 8.5 and 8.6 in text 9-3 in EM 1110-2-1417. Flow Routing.

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Flow Routing

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  1. Flow Routing • Learning Objectives • Calculate outflow hydrographs for reservoirs using the storage indication method • Calculate outflow hydrographs for stream reaches using the Muskingum method • Reading: • 8.5 and 8.6 in text • 9-3 in EM 1110-2-1417

  2. Flow Routing • Flow, or flood, routing – process of determining the outflow hydrograph from a reservoir or stream reach for a particular inflow hydrograph • Streamflow Routing – technique to compute the effect of channel storage on the shape and movement of a flood wave

  3. Inflow and outflow from a reservoir Inflow exceeds outflow and the reservoir is filling Outflow exceeds inflow and the reservoir empties Inflow and outflow are equal and maximum storage is reached

  4. Reservoir Routing – process of determining the outflow rate from a reservoir for a particular inflow hydrograph Level Pool Routing – process for calculating outflow from a reservoir assuming horizontal water surface when given inflow and storage-outflow characteristicsBased on the Continuity Equation:

  5. Values for I1 and I2 are specified by the inflow hydrograph. Equation 1 contains two unknowns, O2 and S2. • Get a relationship between water surface elevation and reservoir storage by topographic maps or field surveys. • Get a elevation-discharge relation from hydraulic equations relating head and discharge for the type of outlet. • Dt is the time interval of the inflow hydrograph

  6. Central Branch Webb Branch 1000 ft. 1002 ft. 1006 ft. 1004 ft. Step 1 – Develop a stage-storage relationship for the pond

  7. Step 2 – Develop a stage-discharge relationship for the outflow structure

  8. Step 3 – Plot outflow (O) as a function of S/t+O/2 = Storage-indication curve

  9. Step 4 – Route flow through structure, assuming initial outflow equals initial inflow Inflows for the storm are given. Assume inflow = outflow for the first time step. Using the assumed outflow, find S1/Dt - O1 /2 for the first time step ONLY from the storage-indication graph and solve for the initial storage volume. For the second and remaining time steps, calculate Si/Dt - Oi/2 and add it to the average inflow (Ii + Ii+1)/2 to determine Si+1/Dt+ Oi+1/2. Use chart to get Oi+1 and then calculate Si+1. Start again at next time step.

  10. Step 5 – Plot inflow and outflow hydrographs

  11. Flow Routing • Learning Objectives • Calculate outflow hydrographs for reservoirs using the storage indication method • Calculate outflow hydrographs for stream reaches using the Muskingum method • Reading: • 8.5 and 8.6 in text • 9-3 in EM 1110-2-1417

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