Eastern Snake Plain Aquifer: Tributary Basins

This dataset contains portions of the HUC8 watersheds, and in some cases the HUC10 watersheds, that are coincident with the Snake Headwaters (HUC6-170401) and the Upper Snake (HUC6-170402) watersheds, excepting the Salmon Falls (HUC8-1704213) and a portion of the Upper Snake-Rock (HUC8-17040212) watersheds. The Watershed Boundary Dataset (WBD) was accessed on December 20, 2023. https://hydrowfs.nationalmap.gov/arcgis/rest/services/wbd/MapServer The Upper Henrys (HUC8-17040202) and Lower Henrys (HUC8-17040203) watersheds were merged into one tributary basin and named Henry’s Fork. The Big Cottonwood Creek (HUC10-1704021202) watershed was included. Portions of watersheds that are coincident with the Eastern Snake Plain Aquifer Model (ESPAM) 2.1 active model domain were replaced with the ESPAM2_ModelGrid_boundary shapefile using the Erase and Append GP tools. (ESPAM2_ModelGrid_boundary.shp represents the ESPAM2.1, and according to the Hydrology Section Technical Engineer 2, the model boundary is the same for ESPAM2.2 and ESPAM2.1.) This process created slivers in several HUC8 watersheds along the outer edge of the ESPA Model Boundary, and these slivers (area < 40 sq km) were merged into a nearby HUC8 as follows: One portion of the Beaver-Camas (HUC8-17040214) into the Henry’s Fork tributary basin. Two portions of the Teton (HUC8-17040204) into the Henry’s Fork tributary basin. One portion of the Little Wood (HUC8-17040221) into the Big Wood (HUC8-17040219). One portion of the Big Lost (HUC8-17040218) into the Little Lost (HUC8-17040217). Two portions of the Idaho Falls (HUC8-17040201) into Palisades (HUC8-17040104). One portion of the Idaho Falls (HUC8-17040201) into Willow (HUC8-17040205). Two portions of the Idaho Falls (HUC8-17040201) into Teton (HUC8-17040204). The following tributary basins were broken out from Lake Walcott (HUC8-17040209): Wagon Butte was re-named from HUC10-1704020910. Marsh was re-named from the largest of the three HUC10 watersheds that intersect (HUC10-1704020906). The other HUC10 watersheds are Brigham Point-Snake River (HUC10-1704020904) and Milner Dam-Snake River (HUC10-1704020913). Rock was re-named from the largest of the three HUC10 watersheds that intersect (HUC10-1704020901). The other HUC10 watersheds are Massacre Rocks-Snake River (HUC10-1704020903) and a small portion of Brigham Point-Snake River (HUC10-1704020904). The following tributary basin was broken out from the Upper Snake-Rock (HUC8-17040212): Clover was re-named from HUC10-1704021212. The following tributary basins were not broken out from HUC8 watersheds: Ross Fork (HUC10-1704020806) was not broken out from the Portneuf (HUC8-17040208). Thorn Creek (HUC10-1704021908) was not broken out from the Big Wood (HUC8-17040219). This dataset was created using the following steps: 1. Select the HUC8 watersheds that are coincident with the Snake Headwaters (HUC6-170401) and the Upper Snake (HUC6-170402) watersheds. Export the selection to a new feature class (25 records). 2. Select the Big Cottonwood Creek (HUC10-1704021202) watershed. Export the selection to a new feature class (1 record). 3. Use the Append GP tool to append the Big Cottonwood Creek feature class created in Step 2 to the HUC8 watersheds selection feature class created in Step 1. 4. Use the Erase GP tool to cut out the ESPA model boundary from the HUC8 watersheds selection feature class. 5. Use the Multipart to Singlepart GP tool on the feature class created in Step 4. 6. Use the Append GP tool to append the ESPA model boundary to the feature class created in Step 5. This feature class will be modified with Steps 7-9. 7. Delete those portions of the Salmon Falls (HUC8-1704213) and Upper Snake-Rock (HUC8-17040212) watersheds that fall outside of the ESPA model boundary. 8. Use the Modify Features: Merge Features editing tool to merge certain features as documented above. 9. Re-name certain features based on HUC10 watersheds as documented above. 10. Modify the attribute table by adding and populating the following fields: Ref_HUC8 Ref_HUC10 Ref_Name LabelName 11. Modify the attribute table by removing the following fields: TNMID METASOURCEID SOURCEDATADESC SOURCEORIGINATOR SOURCEFEATUREID LOADDATE GNIS_ID AREAACRES AREASQKM STATES HUC8 ORIG_FID 12. Use the Project GP Tool to project the feature class to NAD 1983 Idaho TM (Meters). 13. Export as a shapefile.