CE 385 D. Water Resources Planning and Management. River Basin Simulation Tutorial. Samuel Sandoval Solis, M.S. and.

Transcription

1 CE 385 D Water Resources Planning and Management River Basin Simulation Tutorial Samuel Sandoval Solis, M.S. and Daene C. McKinney, Ph.D., PE September, 2009 (Revised January, 2011) CENTER FOR RESEARCH IN WATER RESOURCES 1

2 Contents Overview... 1 Introduction... 1 Part I Modeling the River... 2 Construct the Model... 2 Create a New Area... 2 Set General Parameters... 3 Define the Water Resources System... 4 Run the Model Part II Modeling a Reservoir Define Scenarios Add the Reservoir Create Environmental Flow Requirement for Winter Re- run the Model Part III Modeling a Reservoir Operating Policy... Error! Bookmark not defined. Operation Policy for the Reservoir... Error! Bookmark not defined. Declare the Operation Policy in WEAP... Error! Bookmark not defined. Flow Chart... Error! Bookmark not defined. Variables... Error! Bookmark not defined. Variable Schema... Error! Bookmark not defined. Define New Scenario... Error! Bookmark not defined. Enter the Variable Schema in the Model... Error! Bookmark not defined. Incorporating the Operating Policy Into the Model... Error! Bookmark not defined. Re- running the model... Error! Bookmark not defined. References i

3 Overview The aim of this exercise is to provide guidance on the construction of water resources simulation models using the Water Evaluation And Planning System (WEAP 1 ) software. The document is comprised of steps that will help you to build a simple water resources system model, including: one river, two users (the environment, and an irrigation district) and one reservoir. The example for the system is taken from the textbook of Loucks and Van Beek ( ). Introduction The river system with and without the reservoir is shown in the figures below. River inflows - File: Headflows.csv - 21 Years of Inflows Irrigation District - Variable summer demand: MCM/year - File: Demands.csv System without the reservoir Big Reservoir Capacity: 40 MCM Operation policy: Winter: Release only environmental flows Summer: Release water to Irrigation Dist. Env. Flow Requirements - Winter: 5 MCM/year - Summer: 0 MCM/year Heaflow - Headflows.csv - 21 Years of Inflows - 25 Realizations Irrigation District - Variable demand: MCM/year Demands.csv System with the reservoir Loucks, Daniel P. and Eelco van Beek, Water Resources Systems Planning and Management: An Introduction to Methods, Models and Applications, Chapter 7, Section 9.2 River Basin Simulation pages , UNESCO, Paris,

4 The reservoir winter operation policy is to store as much of the winter s inflow as possible. The summer release policy is to meet each year s projected demand if possible. Further details of the operating policy are given later and in Chapter 7, Section 9.3 of Loucks and Van Beek (2005). Part I Modeling the River 1.1 Construct the Model Create a New Area Open the WEAP program. Select Area and then Create Area from the menu. Name the new area Tutorial_Exercise and Select Initially blank Click OK on the following window. Select an area around Texas. Hint: Use the small window on your left to make a zoom in or out on the world map, use the scroll bars in the right window to locate Texas. Drag a rectangle around the central area of Texas. Click OK. Save your model, select Area, Save menu or press Ctrl+S. Name your model Tutorial_Exercise 3. 3 Tip If you want to back up your model and take it with you to another computer, open the Area menu and select Manage Areas, click on Back up to and select the folder where you want to back up your model (this can be on a removable disk). WEAP models are backed up as zip files. When you want to open your backed up model, open the Area menu and select Manage Areas, click on Restore from and browse to your model s zip file and click on open. This way you will be able to save, backup and restore your models. 2

5 Set General Parameters By default, the model stars in 2000 with 12 time steps per year, based on calendar years and starting in January. We will use 2 time steps per year for 20 years. Select the General menu, and select Years and Time Steps.,1100 Let s modify the time horizon. In the time horizon box change the Last Year of Scenarios: to In the Time Steps per Year box, click in the pull- down menu icon and select Other, then set 2 time steps per year. Verify that in Time Step Boundary you have selected the Based on calendar month option. Also verify that you have selected Water Year Start at Time Step 1. We are going to consider time step 1 as Winter and time step 2 as Summer in the example. Notice that the winter period is has 182 days and summer has 183 days. 3

6 Save your model by typing Ctrl+S. Define the Water Resources System Enter the River Inflows Now, lets define our water resource. Let s start with the river. Click on the River symbol in the Element window and hold the click as you drag the symbol over to the map. Release the click when you have positioned the cursor over the upper left starting point of the main section of the river. Move the cursor, and you will notice a line being generated from that starting point. When you double click to finish drawing the river, a dialog box appears asking for the name of the river (see below). Name the river "Main River." Click Finish. 4

7 Let s declare the inflows to the river called headflows in WEAP. These are the upstream inflows to major tributaries for the model. These values are stored in the file Headflows.csv. You will notice that this is a CSV file, or a Comma Separated Value file that stores 25 sets of inflows (in m 3 /sec). First, unzip the compressed archive (*.zip file) and copy the file Headflows.csv to the folder C:\Program Files\WEAP21\Tutorial_Exercise on your computer 4. Let s take a look inside the Headflows.csv file, which is shown below: The first column has the years with one row for each of the two seasons of the year, summer followed by winter; then the season number is shown in column B, and finally the 25 flow values in columns C through AA for the separate simulations; each column is a separate realization of the inflows for the 20 year period. To begin with we will focus on the first realization in column C. Now, let s go back to WEAP and enter the data for the river. To enter and edit data for the Main River, either right- click on the Main River and select Edit data and select Headflows. 4 If you are using the latest version of WEAP (January 2011), then the path should be: C:\Documents and Settings\ your user name \My Documents\WEAP Areas\Tutorial_Exercise 5

8 The "Inflows and Outflows" window should be open - if it isn't, click on the Inflows and Outflows button. Click on the "Headflow" tab. Be sure that the input window Data for has Current Accounts [2000] selected. If it doesn t, then select it from the drop down menu. Click on the area just beneath the bar labeled 2000 in the data input window to view a pull- down menu. Select the Expression Builder from the drop- - down menu. 6

9 In the Expression Builder select the Functions tag; scroll down and find, select and drag down into the text field the ReadFromFile expression from the list of built in expressions. Type the following expression in the parentheses: Headflows.csv,1 ; so, the expression should look like 5 : ReadFromFile(Headflows.csv,1) The 1 in this expression refers to the number in the column above the inflows. If you wanted to read the inflows from the second realization of inflows, you would enter 2. Click on Verify. Then a window will appear that says your expression is verified. If the expression is not verified, please check that you have copied the file Headflows.csv into the folder C:\Program Files\WEAP21\Tutorial_Exercise and that the command you have written is correct. 5 Actually, you can just copy this expression from this document and paste it into Expression Builder. 7

10 WEAP is reading the data from the Headflows.csv file in column 1. WEAP reads the year and time step columns, after this it starts counting the column numbers; this is the reason we are declaring column 1 in the expression. Click on Finish. Note that now there is inflow declared for the river. Save your model. 8

11 Enter the Irrigation Demand Data Creating a demand node is similar to the process you used to create a river. Click on the Schematic view (little map icon in upper left- hand corner) and select and pull a Demand Site node symbol over to the map from the Element window, releasing the mouse when you have positioned the node on the right bank of the river (facing downstream). Enter the name of this demand node as Irrigation District. Declare a Demand Priority of 2. Click on Finish. Copy the water demand for the Irrigation District that is stored in the file Demands.csv to the C:\Program Files\WEAP21\Tutorial_Exercise folder 6. This file is reproduced in the figure below (demands in million m 3 per year) 6 If you are using the latest version of WEAP (January 2011), then the path should be: C:\Documents and Settings\ your user name \My Documents\WEAP Areas\Tutorial_Exercise 9

12 Go back to WEAP, right click on the Irrigation District demand site and select "Edit data" and "Annual Water Use Rate." Once again open the expression builder and let s read the demands from the file Demands.csv using the ReadFromFile() function. The expression should look like: Click on Verify ReadFromFile(Demands.csv,1) The previous expression should be verified OK. If not, double check that the Demands.csv file was copied to the correct directory (see above) and that the expression was written correctly. Click below the Scale label and select Million because the data uploaded has this unit. 10

13 Now, let s declare the distribution of water for Irrigation District in Summer and Winter. Click on the tab of Sub- yearly Variation Click below 2000 and select Sub- yearly Time- Series Wizard Declare a value of 0% for time step 1 (Winter) and a value of 100% for time step 2 (Summer). Click Finish. 11

14 Now, you need to tell WEAP where the water will come from; this is accomplished by connecting a supply resource to the demand site through a transmission link. Return to the Schematic view and create a Transmission Link from the Main River to the Irrigation District. Do this by dragging the Transmission Link first to a position on the river, releasing the mouse, then pulling the link to Irrigation District and double clicking on this demand node. Select a Supply Preference of 1 for the Transmission Link. Run the Model Let see the first result of our model. Click on Results and Yes. 12

15 Select Demand and then Reliability. Notice that more than 60% of the time the demand for Irrigation District is supplied fully. Click on the Table tab and you will see that the reliability for Irrigation District is 64.3%. 13

16 Go back to the Chart view, and select Demand\Supply Delivered. At the bottom of the screen select All Years, in the middle upper pull down menu All Time Steps and check the option Annual Total. Notice how variable the water demand is for the Irrigation district. Select Table and click on the Stat icon that is in the right tool bar of the screen. Drag the displacement bar to the right in order to see the statistics at the end of the Supply Delivered results. Notice that the average supply delivered is 24.7 MCM/year, and the minimum and maximum values are 11.1 and 45 MCM/year respectively. Now let s see when the deficits happened. Click on the Chart tab, and select Unmet Demand. Notice that the deficits happened in several years, 9 to be precise. 14

17 Click on the Table tab. Notice that the total deficit (Unmet demand) for the Irrigation district in this scenario is MCM (under Sum in the table). Also, notice that the mean deficit is 16.0 MCM and the minimum and maximum deficits are 0 and 32.9 MCM, respectively. Save your model. Part II Modeling a Reservoir Define Scenarios One of the purposes of modeling is to answer What if questions. In this case, we are interested in the question, How will the Irrigation District s operation improve if a 40 million m 3 reservoir is constructed on the river? We are going to define 2 scenarios: 1. Without the reservoir; and 15

18 2. With the reservoir. Go to the Schematic view, open the Area menu and select Manage Scenarios. Select the Reference Scenario and then click on Rename. Rename the Reference Scenario as w/o Reservoir. Click OK. We are going to keep this scenario as a reference for what would happen with no reservoir. Now, lets create another scenario that will consider the creation of a reservoir. Select Current Accounts and then click on Add and name the new scenario with Reservoir. Click OK Click on Close. Save your model. 16

19 Add the Reservoir Let s create a Reservoir upstream from the transmission link to the Irrigation District. Return to the Schematic view and pull a Reservoir node symbol onto the schematic from the Element window, releasing the mouse when you have positioned the node upstream of the transmission link. Enter the name of the reservoir node as Big Reservoir. Unselect the option of Active in Current Accounts. Click on Finish. In this way we continue to have no reservoir in the w/o Reservoir scenario. Now, let s declare the reservoir in the with Reservoir scenario. Right click on the Reservoir icon, select Edit Data and Startup Year Select the with Reservoir scenario in the Data for view. 17

20 Declare the Startup Year to be Now, let s declare the characteristics of the Big Reservoir. Click on the Physical button and declare the storage of the reservoir to be 40 Million m 3 in the Storage Capacity tab. Click on the Operation bottom and enter 40 Million m 3 in the Top of Conservation tab (this will be the active capacity of the reservoir). 18

21 Under the Operation button, select the Top of Inactive tab and enter 0 Million m 3. Save your model. Create Environmental Flow Requirement for Winter Go to the Schematic view and select a Flow Requirement and place it on the river downstream of the diversion to the irrigation district. Declare a demand priority of 1. 19

22 Right click on the flow requirement node and select Edit Data Minimum Flow Requirement. Enter the Expression Builder and enter the following command: If( TS=1, , 0 ) This will require the flow to be m3/sec passing the Environmental Flow Node in Time Step 1 of every year. Re- run the Model Click on Results. Say Yes for recalculating the results. 20

23 Look at the results. Select Demand, Supply Delivered and notice that more water was delivered in the with Reservoir scenario than w/o Reservoir. In fact, the mean supply delivered increased from 24.7 to 37.3 Million m 3 /year. Be sure to select All Year at the bottom, and All Scenarios to the right hand side. Select Reliability and note the difference: 64.3% ( w/o reservoir scenario) versus 85.7% ( reservoir scenario). Go to Demand, Unmet Demand and All Years (at the bottom) and notice that for the with Reservoir scenario, the deficits decreased compared to w/o Reservoir scenario. In fact, the mean and the maximum deficit decreased from 16.0 to 3.4 MCM/year and from 32.9 to 15.9 MCM respectively. Save your model, Ctrl+S. 21

24 You can also explore several other interesting aspects of the simulation, such as reservoir storage and flow through the environmental flow requirement node. References Loucks D. P. and E. Van Beek (2005). Water Resources Systems Planning and Management. Page 213. UNESCO 22