WWHM4 MODELING USING NATIONAL MAP

Transcription

1 WWHM4 MODELING USING NATIONAL MAP Clear Creek Solutions, Inc., 2010 How to create a project that uses national data. WWHM4 is one of the most powerful continuous simulation hydrologic models available. Until now its use has been limited to select locations around the country. With the inclusion of the National Map option this limitation has been removed. Now we can use WWHM4 for any location in the lower 48 states. The National Map has access to meteorological data from all 48 states. In addition, the WWHM4 soils parameter wizard will allow the user to customize the WWHM4 soil parameters to local soil characteristics. This combination of existing data and customizable soil parameters allows the WWHM4 to be used anywhere in the lower 48 states. For the purposes of this example we will create a simple project and size a stormwater facility. If the National Map is not visible in the WWHM4 Map Info window we can select it from the map pulldown menu. 1

2 The National Map shows 48 states (Alaska and Hawaii are not included). Now we can locate our site on the map. We can find our project site on the National Map using one of three different approaches: 1. We can use Internet mapping feature to locate our site. 2. We can use longitude and latitude to locate our site. 3. We can use navigation tools to locate our site. 2

3 Use internet mapping feature to locate our site. We will first use Internet mapping to locate our project site. We select the state in which the project is located by clicking on the appropriate state on the National Map. We click on MD to select the state of Maryland. We get a message box that lets us know that we currently don t have any meteorological data for this state in our WWHM4 folder. NOTE: All of the WWHM4 meteorological data is stored in files by state. The total amount of National Map meteorological data exceeds 10 gigabytes of storage. As a result WWHM4 only downloads the meteorological data for the state in which the modeling project is located. Once downloaded the state meteorological data will reside on our computer and can be used in the future without needing to download it again. When we select Yes in the message box the meteorological data download begins. 3

4 We can observe the progress of the meteorological data download using the above progress bar. 4

5 At the conclusion of the meteorological data download the Soil Parameter Options window automatically appears. The purpose of this window and accompanying soil parameter wizard is to allow us to customize the WWHM4 HSPF pervious land (PERLND) parameter values to our specific soil, vegetation, and topographic conditions. We can select from one of three options: Use Defaults Load Parameter File User Defined If we select the Use Defaults option then WWHM4 will automatically load these default parameter values and we will use them in our model runs. We don t have to do anything else. Note that the default parameter values were developed for Western Washington watersheds and may not be appropriate for other climatic regions of the United States. 5

6 The second option is Load Parameter File. Use of this option requires that we have available a previously created parameter file and will be using it for this project. We click on the Load Parameter File button in the lower right corner of the window. Then we browse to find and load the appropriate parameter file. 6

7 Our third option is User Defined. The User Defined option requires that we answer a series of questions about the soil groups and vegetation types found in our study area. We can have more than one soil group and vegetation type. Based on the information that we provide, the soil parameter wizard will compute the appropriate HSPF parameter values to hydrologically represent the pervious land type that defines each soil-vegetation combination. Soil groups are divided into the typical NRCS A, B, C, and D classifications. We need to select the infiltration rate and soil depth for each of the soil groups. The input infiltration rate should be the maximum infiltration rate based on in-field soil measurements or literature values. The soil depth is the depth of soil from the surface down to a restrictive layer such as clay, till, or bedrock. We can define each soil group to represent any soil type we want. However, it is generally best (and least confusing) if the infiltration rates of the soil groups decline as we progress from the A group to the D group. A group soils generally have good infiltration rates. Infiltration rates decline as we go from A soils to B soils to C soils, with D soils group having the lowest infiltration rates. In most cases the D soil group should be used to represent wetland soils. 7

8 The soil infiltration rates are grouped into three general categories: greater than 10 inches per hour 2 to 10 inches per hour less than 2 inches per hour Note that the D soil group s infiltration rate has been preset to represent wetland soils and cannot be changed. The soil depth (depth of soil from the surface down to a restrictive layer such as clay, till, or bedrock) is also grouped into three general categories: greater than 6 feet 1 to 6 feet less than 1 foot When we select an infiltration rate and soil depth for each soil group WWHM4 determines the appropriate HSPF soil-based parameter values to use. Note that the specific values can be viewed in the UCI file (details below). 8

9 WWHM4 has five standard vegetation categories: Forest Shrub Pasture Grass Lawn Forest is trees; either evergreen or deciduous, depending on the selected growing season. Shrub is large bushes and similar vegetation; either evergreen or deciduous, depending on the selected growing season. Pasture is generally open agricultural land. Grass is native or natural grassland vegetation. Lawn is urban landscape and includes sod and ornamental plants. We can specify the vegetation growing season. We select the starting month and ending month of the growing season. This will adjust HSPF parameters such as interception storage, surface soil absorption, and evapotranspiration from vegetation. 9

10 We also need to tell WWHM4 whether or not the vegetation has access to groundwater and/or base flow. Access to groundwater depends on the vegetation root depth and the depth of groundwater. If the vegetation can access groundwater then evapotranspiration from groundwater occurs. Otherwise there is no depletion of the groundwater storage by vegetation. Access to base flow depends on the vegetation root depth and the location of the vegetation near conveyance systems (stream channels, etc.) that have a base flow. If the vegetation is located along the channel banks and can access the water then the Access to base flow box should be checked. 10

11 When we have completed making our soil and vegetation selections we can save them by clicking on the Save Parameter File button. 11

12 We select a parameter file name that we can remember and save the file. 12

13 We are now finished with the input of soil and vegetation parameter options and can close the window. We can later load this saved parameter file for use in future projects (assuming the soil and vegetation parameter options are the same as those we have entered for this project). Now that we are finished defining our soils and vegetation we can locate our project site in the state (in this case in the state of Maryland). 13

14 We click on the down arrow next to Internet Map to see our options for locating our project site. Our mapping options are: Bing Google Maps MapQuest Yahoo 14

15 For this example we will locate our project in Rockville, Maryland, near the intersection of East Gude Drive and Display Court, as shown above using Google Earth. The latitude and longitude for this project site are 39o N and 77 o W, o o respectively. These convert to N and W. For input to WWHM4 these coordinates become , Other mapping services also can be used for selecting project site coordinates. 15

16 One example is Yahoo! Maps. Using Yahoo! Maps we can determine project site latitude and longitude coordinates based on an address. 16

17 We input an approximate address of East Gude Drive, Rockville, MD and the map makes the appropriate change to a location near the project site. 17

18 We right click on our project site (point B) and select Drive to here and Yahoo! Maps puts the point B latitude and longitude coordinates in the corresponding box. We can now copy these latitude and longitude coordinates directly into WWHM4. Remember: We need only the appropriate longitude and latitude for our project site so that WWHM4 assigns the correct (closest) precipitation station to the project site. The coordinates can be provided by any of the mapping services, although admittedly some are easier to use than others. Use the one that works best for you. 18

19 For input to WWHM4 we will use the longitude and latitude coordinates ( , ) that we obtained from Google Earth. We can enter these longitude and latitude values manually to locate our project site. As can be seen on the map, the Maryland precipitation stations are shown. WWHM4 selects the closest precipitation station for use by the model. In our example this is station MD187705, also known as Rockville 1NE. 19

20 Project Site Precipitation Station The WWHM4 map controls give us the ability to zoom in or out to better locate our project site. Precipitation station MD is just to the southwest of our project site. 20

21 We now use View, Options to set the appropriate flow duration criteria for our project site, based on the regulations of our local jurisdiction. Note: We are currently in a transition period as jurisdictions implement NPDES MS4 requirements. Some, although not all, jurisdictions are adopting flow duration standards to meet hydromodification regulations. Contact your local jurisdiction/permitting agency to determine the appropriate criteria for sizing stormwater facilities. For this theoretical example I am making the assumption that the flow duration criteria for sizing stormwater facilities needs to be adjusted from the default Western Washington flow control criteria range of 50% of the 2-year flow to the 50-year flow to a different criteria range. The new duration criteria range that we will use will be 100% of the 2year flow to the 10-year flow. (This is a made-up criteria and is not necessarily the criteria used by Rockville, MD.) 21

22 The new flow duration criteria are entered and the Update button is clicked to set these criteria for POC 1 (this criteria change needs to be done for each Point of Compliance). 22

23 We select the predevelopment land use as 10 acres of C, Grass, Flat. We can have a mixture of land use types if that is appropriate for our project site. We set the predevelopment POC 1 at the downstream end of land use Basin 1. 23

24 We click on Run Scenario to compute the predevelopment runoff using HSPF. Now we can move on to the Mitigated scenario. 24

25 The proposed development will create 2.5 acres of Roads, Flat; 2 acres of Roofs; 0.5 acres of Sidewalks, Flat; 2.5 acres of Parking, Flat; and 2 acres of C, Grass, Flat. That totals 9.5 acres of our 10-acre development. We will set aside 0.5 acres for the stormwater pond surface area. 25

26 We connect the land use basin to the pond and then connect the pond to POC 1. We check both the Precipitation Applied to Facility and the Evaporation Applied to Facility boxes to rain on and evaporate from the pond surface. Next we will use AutoPond to size the stormwater pond. 26

27 We slide the Automatic Pond Adjuster bar all the way to the right and then click the Create Pond button. 27

28 WWHM4 s AutoPond sizes the stormwater pond to produce the smallest pond possible while still meeting the specified stormwater flow duration criteria. 28

29 The dimensions and outlet structure information are automatically filled in, based on the results produced by AutoPond. We can look at the pond s surface area by clicking on the down arrow to the right of the Show Pond Table. 29

30 We scroll down to the bottom of the table to look at the maximum surface area of the stormwater pond. At the maximum stage of 7.00 feet the surface area is 0.34 acres. We initially set aside 0.50 acres for the pond surface area. We can now go back and add some area to the land use basin and then resize the pond with this new area. I will let you do that exercise if you are interested. 30

31 SUMMARY: 1. Select National Map. 2. Click on state in which the project site is located. 3. Download state meteorological data. 4. Select Soil Parameter Options to set HSPF parameter values. 5. Use Internet or other source to determine project site latitude and longitude. 6. Set flow duration criteria for stormwater pond sizing. 7. Place Predeveloped basin element on schematic grid. 8. Input Predeveloped land use information. 9. Select the Predeveloped point of compliance (POC 1). 10. Click on Mitigated scenario. 11. Place Mitigated (developed) basin element on schematic grid. 12. Input Mitigated land use information. 13. Add a pond to Mitigated schematic grid. 14. Link the basin to the pond. 15. Select the Mitigated point of compliance (POC 1). 16. Use AutoPond to size pond. 17. Use Create Pond and move the Automatic Pond Adjuster to the far right level to optimize pond. 18. Look at the Analysis screen flow duration table results. 19. Check pond maximum surface area. 20. Adjust land use basin areas, if necessary, and rerun AutoPond. 21. Finished. 31