How can I identify which reaches in a file have a SEG number from the EPA reach files?
EPA SEG numbers are less than 500. By reselecting for SEG lt 500 you can seperate these out. Hydrologic Units • What is a Hydrologic Unit? In 1974, a new set of maps depicting approved boundaries and codes of river basins of the United States was produced by the USGS and the U.S. Water Resources Council. These maps present information on drainage, culture, hydrography and hydrologic boundaries. There were four levels of classification: • Region • Subregion • Accounting Units • Catalog Units For a better understanding of what constitutes a hydrologic unit, please refer to USGS Circular 878-A. These fourth level subdivisions are ‘hydrologic units’ and have been identified by a unique code consisting of from 2 to eight digits. For example: 17040101 is comprised of – 17 Region – (Columbia Basin) 04 Subregion – (Upper Snake River Basin) 01 Accounting Unit – (Headwaters of the Snake River) 01 Cataloging Unit – (Snake Headwaters, Wyoming) CU is generally considered to be the descriptive name
