The ResSim Blog

This blog was created by Kevin Fagot, a water resources engineer for the modeling of reservoir systems in HEC-ResSim. Programming examples in Python and Jython (scripting language used in HEC-ResSim) are also shown. Since data development and analysis plays an important part in the development and use of this model, you will also find examples of this using Python, Microsoft Excel, and HEC-DSSVue. The posts are labeled by topic so you can use the menu on the right or search by topic.

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Maximum Release based on Time of Year and Pool Elevation

on September 30, 2015

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How to Develop a Working Model

The previous blog posts showed specific applications using the HEC-ResSim software. This post will show the creation of an HEC-ResSim model taking the reader through the Watershed Setup module, the Reservoir Network module, and the Simulation module. Note: I have developed a video showing the development of an HEC-ResSim model that can be viewed here: The initial model development will be that of a flow through model. It is recommended that the initial model setup be a flow through model to test the connectivity of the stream network and the overall behavior of the initial model setup. A flow through model consists of the following model characteristics: 1.) No rules of operation are entered into the model 2.) A constant inflow is applied at the upstream ends of the main stem and all tributaries 3.) The reservoirs are set to the top of the conservation pool and are releasing inflow in the lookback period. 4.) The routing is set to null routing. Once the re

Computing Kendall's Tau parameter for time series data

Introduction. In this post, the Kendall's Tau parameter will be computed for the annual peak flow data for Dog Branch at St. Paul, Arkansas. This data was derived from the USGS website. The computation of the Kendall's Tau parameter was performed in Microsoft Excel for this analysis. Examining the Kendall's Tau parameter on time series data will help to indicate if a trend exists and how strong it is. If the Kendall's Tau parameter is close to 1, a strong rising trends exists. If the Kendall's Tau parameter is close to -1, a strong falling trend exists. If the parameter is close to zero, then neither a falling or rising trend exists. First Step - Visualize the Data. A good first step in determining a trend is to visually examine the time series data. This is shown below. From the chart above, it appears that a trend is not apparent. In the next steps, the Kendall's Tau parameter will be computed to see if that assumption holds. Next Step - How is the

Additional error fixing in HEC-ResSim

This post will cover two additional error messages that can occur in the development of an HEC-ResSim model. Special thanks to Logan Osgood-Jacobs of the Seattle District of the Corps of Engineers for supplying these screenshots. Error 1: Ghost Nodes Ghost nodes, or nodes that you did not intend to include in the model, seem to periodically occur in the development of ResSim models. I have gotten these when I have had to edit the watershed configuration and then perform an update to the reservoir network. However, I believe that others have gotten ghost nodes in the initial development of the model. So, how do you tell if you have a ghost node? The most direct way is getting an error message similar to the one below when you compute your simulation. This error message is indicating an issue with Node 81. In the Reservoir Network Module, go to Reports > Advanced > Node List. The report is shown below. There is a node named, "Node 81". Not havi

Python Intermediate #3 - Random Multiplication Practice using randint

In our previous example, we used a list with a for loop in Python to print out multiplication tables. This example allows the user to practice multiplication of two random values. For this post, we will use an if statement along with the randint function from the random module. Additionally we will be using a while loop to ask the user if they want to keep playing. The coding of the randint function can be found at this site: https://docs.python.org/2/library/random.html Scrolling down to randint shows the following: This tells us that this function will produce an random integer from a to b. If we code the following: x = randint(0,9) print("The random integer is ",x) We would expect to get a message giving us a random number between 0 and 9. Instead, we get this: This is because we need to import randint from the random method. We do this as follows: from random import randint x = randint(0,9) print("The random integer is ",x) Now, we

How do I fix my errors?

The error messages that HEC-ResSim produces are not always very clear. So, I thought it may be useful to take a working model and break it in various ways to look at the error messages. The model is shown below. It contains a main stem and a tributary. There are two reservoirs on the main stem. Here is the plot for the upstream reservoir to show that it is a working model. Error #1 . I will remove the inflow from the upstream end of the tributary. Remember that ResSim needs inflow at the upstream end of all tributaries and at the upstream end of the main stem. Here is your error message: Error #2: ResSim requires that the dss files are complete without missing data. So, I am going to remove a value from my dss file during the simulation period. Here is the error message: Error #3: It is easy to forget to specify lookback elevations and releases. These can be either a constant value or a time series. For this error, I specify tha

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