Task 1: Watershed Orientation

Review the forecast data and familiarize yourself with the watershed. Understand where to find important information to help inform release decisions. Consider how watershed characteristics will impact your decisions due to travel times to shared control points.

1. Open the CAVI in Local mode and load the Workshop_HEC_Marsh_of_the_Swans watershed.  
2. Switch to the Modeling tab and open the HEC-ResSim_OSI_Workshop forecast.
3. Compute the Workshop - W0 forecast. The Workshop w OSI forecast will be used later in the workshop.
4. Select the HEC-ResSim alternative in the Forecasts window.
5. Review HEC-ResSim plots for each Reservoir and Control Point.
   1. Right-click on each location and select Plot for reservoirs and Junction-Plot for each control point.
      
      If we get the forecasted rainfall how close will we get to activating the uncontrolled spillway on Reservoir A and Reservoir B?
      
      Answer

      Reservoir A gets within a tenth of a foot of the spillway crest, and Reservoir B has already crested and is within 1.5 feet.

      Which reservoir would you give priority to for releases?
      
      Answer

      Reservoir A should get priority, but the forecasted rain and travel times will impact how much should be released from each Reservoir.

      How did the rules in HEC-ResSim perform? Would you schedule releases this way?
      
      Answer

      The rules in HEC-ResSim performed ok, except most of the capacity at J070 was taken by Reservoir B. You might consider shifting part of the release to Reservoir A, but still keep a higher percentage of flow with Reservoir B since it is closer to the control point. This will allow the water management office to react to rain in the forecast more quickly.

      Did we go over criteria anywhere? Why?
      
      Answer

      J070 exceeds Phase III criteria by almost 700 cfs, if the forecast is correct. J110 goes over Phase II criteria by 350 cfs. A combination of local flows downstream of the projects and releases from the reservoirs take us over criteria.

6. Review the Release Decision Report and Control Point J070 HEC-ResSim plot.
   
   1. There are several ways to access the Release Decision Report. You can go to the Reports tab and select the Release Decision Report button, right click on a reservoir in the Modeling window, or right click on the HEC-ResSim alternative in the forecast tree.

7. Select Options and Edit Options to select the reservoir you are interested in. For this workshop, that is Reservoir A.
   
   Why were releases reduced to minimum flow on June 4^th for Reservoir A?
   

   
   

   Answer

   Releases from Reservoir A were reduced to minimum on June 4th in order to meet maximum flow limits of 7000 cfs at J070. 

   
   

8. Right click on junction J070 in the modeling window and select the HEC-ResSim plot.
   
   What is the difference between the solid green hydrograph and the thin green line with green triangles at J070?

   Answer

   The thin green line with green triangles is local uncontrolled flows downstream of the reservoirs. The solid green hydrograph is the total flow at the junction. Releases from the reservoirs create the difference between the two lines. This can help you determine the timing for shutting off releases from the projects to have the greatest impact on flooding. 

   

   Where did all the additional water come from on June 5^th, the projects or uncontrolled areas downstream?
   Answer

   A large part of the flow is from uncontrolled areas downstream of the reservoirs.

   Look at source junction CP2.5 - that is where the 5,000 cfs hydrograph is entering the system. A majority of the remaining water was released by Reservoir B.

   

9. Review the HEC-ResSim plot for J110.
   
   

   Will the 12,000 cfs target be exceeded if the forecast is correct? How long will the target be exceeded?

   Answer

   Yes, by approximately 350 cfs. The 12,000 cfs target will be exceeded for approximately 12 hours.

   What would you do to prevent exceeding the target at this location?

   Answer

   The Water Manager could reduce releases from Reservoir C approximately 24 hours ahead of time using Release Overrides or the OSI.

   If travel times take 4 days from Reservoir A, three days from Reservoir B, and one day from Reservoir C, how will this impact your decision? 

   Answer

   It would take too long for changes in releases from Reservoir A or B to have any impact at J110.