Modeling Project 2 Part 1
Basic Model Formulation
Dr. Nelson
Overview
This assignment will help you review the different models and modeling options studied this semester. It will also help us determine how well the HMS and GSSHA models can be applied to solve the runoff for a watershed for an actual event. It is to be done individually in order to insure that you are all prepared for the final, but it is okay to get help from a team member (or someone else in the class).
You will be provided with the data necessary to develop a model and after you run the simulation we will compare it to observed runoff. After that we will introduce some methods for performing a long term simulation.
The watershed you will be using is in Wisconsin and part of the Eau Galle basin named 8 Mile Creek. You will perform the analysis with Green and Ampt infiltration for both HMS and GSSHA.
Assignment
Get the following data and perform the tasks listed
DEM data Soil Type data Land use data
The land use and soil type data have different classification IDs than those we have used previously, but you can read the accompanying text files to discover how the ID's are interpreted so that you can develop appropriate parameters.
Tasks
Delineate the watershed
This is a small watershed as compared to what you have been working before (less than a square mile) and unless you lower the threshold you will not generate stream arcs when you run TOPAZ. So, in the display options under DEM data change the Minimum Accumulation for Display to a smaller number than the default of 1 sq. mile. Your basin should look somewhat like this (note the approximate location of the outlet).
HMS set up
Your final HMS model should have single Green and Ampt infiltration model that we will define an actual storm (will be provided) for the meteorological model. Use the Clark Method for the transformation. Ultimately you will use this model and optimize (estimate parameters from observed data) for both the Clark and G&A parameters based on peak and volume optimization. For optimization, you will be provided with the observed data set for the real storm and you will compare the outcomes of your model with the real storm.
At the end, you will use the same HMS model and perform long term simulation for real data and compare your results with the observed discharge data.
The following guidelines should be helpful to you
Set up single basin model for HMS. Use following parameters:
Use Green and Ampt Method for infiltration in HMS (use soil type and land use info for the parameters)
Clark Unit Hydrograph method
To make sure things are running define precipitation to be 2.5 inches over 24 hrs with a Type I distribution (we will give you the actual storm later).
Set up a single basin model for HMS using SCS CN method for losses and SCS lag time method for transformation.
You might want to refer to the HMS reference manual (Table 5-2, page 43) for roughness and infiltration (Green and Ampt) parameters. Other references you might need:
Save and Run your HMS model long enough to capture the entire hydrograph.
GSSHA set up
Your final GSSHA model should have 30m grid, Green and Ampt with redistribution infiltration model with a real storm (will be provided). You will have variable roughness and variable infiltration parameters based on land use and soil type data. You will want to create an index map based on both the land use and soil coverages because this is probably more realistic for defining infiltration. Your model should have rivers turned on, redistributed and smoothened.
You already have a lot of experience on GSSHA modeling but it is good to always follow the following sequence of processes for better modeling performance.
Set up a GSSHA grid of 30 m resolution (which is same as the resolution of the DEM you are using).
Set up Job control parameters, have uniform index map for uniform roughness and use uniform precipitation (you may use any logical rainfall intensity - mm/hr) but do not turn on your infiltration yet. Change the display units to CFS in Job control.
Save your project file and run clean dam. Do not forget to replace the old elevation file with the new one.
Run your model and see if there are any puddles or ponding. If so adjust manually either by changing elevation of cells or by changing the stream locations etc.
When you have your basic model set up, now turn the streams on (check Diffusive wave routing option ON), define the shape (Trapezoidal, 0.7 m deep, 2.4m wide, 4.2 side slope) redistribute the vertices and smooth them. You may also toggle on the display of channel depth and channel flow from output control.
Run GSSHA and view your results (summary file to see if there is still ponding on the watershed), if so you may change the river orientation a little bit or adjust the cell elevation around the ponding areas.
Create three index maps for soil type, land use and both of them combined. Each of these index maps are used to determine the roughness and infiltration parameters. Use the combined (landuse and soil type) index map to define the Green and Ampt Redistributed parameters and landuse index map to define roughness. Do not forget to turn the Green and Ampt with soil moisture redistribution in the Job control under infiltration method.
Run your model and make sure that each component you have entered is working well.
Later you will be provided with the actual rainfall data using which you will run your model.
Finally, you will use the G&A parameters optimized in HMS (where ever possible) and compare your results.
State any assumptions made
Useful links and references:
GSSHA reference Manual - Table 10, page 94
Manning's n values are available here and here.
Do not hesitate to refer to previous assignments.
PS: If your GSSHA model (also HMS models) is not working, crashing or not working as you would expect, do not spend endless hours in the lab unproductively trying to figure it out. Get help from a teammate, or contact me or Murari. For this problem we are mostly interested in your "best" effort at getting a result. Don't worry if it is different than another person, what we want is the solution from your best modeling practice. You will see how close to reality you have modeled your watershed later, and it is a good time to judge your/our modeling skills developed throughout this semester. Do not hesitate to ask me/Murari for help.
