Reached Indexing Using the NHD Hydrologic Event Management (HEM) Tool IDEM – Joanna Wood

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Indiana uses reach indexing to track our water bodies for assessment and reporting purposes as we evaluate water quality. Early reach indexing was done using the lower resolution data of the early Reach File 3. However, with the higher resolution NHD, we are working with our current assessment data to incorporate the many new headwater streams found in this resource. Reach Indexing Using the NHD HEM Tool

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Reach Indexing Using the NHD HEM Tool To date, we have approximately 70% of the state’s water bodies completed. The left oval is an area yet to be indexed.

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Reach Indexing Using the NHD HEM Tool Getting started, we first set up a project with the relevant spatial data to help us with decisions on assigning assessment units. Next, we set up the geodatabase and workspace for the events and data creation; then it was time to start editing using the HEM tools.

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Reach Indexing Using the NHD HEM Tool

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Reach Indexing Using the NHD HEM Tool We use land use, hydrology, point and nonpoint sources of potential impact. Shown here are permit facility points. This headwater is similar throughout the north eastern part of this watershed. The 3 tributaries share several commonalities with its main stem and will be assessed as one unit.

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships NHD Hydro Net functions provided the Z values for determining upstream/downstream end points. Below shows the options given upon selecting the two points at the right. Reach Indexing Using the NHD HEM Tool

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Reach Indexing Using the NHD HEM Tool At this part of the process, each tributary has been assigned the metadata and source information that was derived from the hydrography layers and saved into the events table. These high res reaches are associated with the 2008 reach indexed layer and the data associated with the main stem at each confluence.

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Reach Indexing Using the NHD HEM Tool Another example of adding new tributaries is shown here with the data from each table used. The Entity_ID is taken from the 2008 Streams and added to the NHD data in the event table.

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships Reach Indexing Using the NHD HEM Tool Event Table

Coordination of Indiana GIS through dissemination of data and data products, education and outreach, adoption of standards, and building partnerships For more information on the IN List Impaired Waters and the Integrated Report Both of which use the reach indexing results for the assignment of assessments units, please check out our website at Additionally, contact information is also available under Contact should you have and questions. Reach Indexing Using the NHD HEM Tool