Colorado Data Sharing Network (CDSN) - Interactive Web Map of water quality, biological, and habitat data
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The NHD is a comprehensive coverage of hydrographic data for the U.S. It was developed by combining EPA Reach File version 3 (RF3) and the USGS Digital Line Graph (DLG) coverages. The NHD is often used by scientists using GIS technology. This takes advantage of a rich set of attributes that can be processed to generate specialized information. These analyses are possible because the NHD contains a flow direction network that traces the water downstream or upstream. It also uses an addressing system to link specific information about the water such as water discharge, water quality, and fish population. Using the basic water features, flow network, linked information, and other characteristics, it is possible to study cause and affect relations, such as how a source of poor water quality upstream might affect a fish population downstream.
The Environmental Data Unit (EDU) of the Colorado Department of Public Health and Environment (CDPHE) gathers, assesses and reports data regarding the chemical, physical and biological integrity and quality of state surface waters for the Federal Clean Water Act (CWA) as the EPA Integrated Report. The Integrated Water Quality Monitoring and Assessment Report (305(b) report) is the primary vehicle for informing Congress and the public about general water quality conditions in the State of Colorado. This document characterizes our water quality, identifies widespread water quality problems of significance, and describes various projects implemented to restore and protect our waters.
The 305(b) is one component of the Integrated Report. The Integrated Report is due to EPA on April 1st of every even-numbered year. Other report components include the 303(d) list of impaired waters, submission of the electronic 305(b) database; the ADB, and a GIS layer.
The United States is divided and sub-divided into successively smaller hydrologic units which are classified into four levels: regions, sub-regions, accounting units, and cataloging units. The hydrologic units are arranged within each other, from the smallest (cataloging units) to the largest (regions). Each hydrologic unit is identified by a unique hydrologic unit code (HUC) consisting of two to eight digits based on the four levels of classification in the hydrologic unit system. HUC basins decrease in size with an increase in levels. Hydrologic Unit Codes (HUC) data describe watersheds as polygons, defined by digital elevation model data. For example, HUC6 watersheds are major river basins while HUC12 watersheds are for 2nd and 3rd order streams.
HUC provides a standardized base for use by water-resources organizations in locating, storing, retrieving, and exchanging hydrologic data, in indexing and inventorying hydrologic data and information, in cataloging water-data acquisition activities, and in a variety of other applications. Because the maps have undergone extensive review by all principal Federal, regional, and State water-resource agencies, they are widely accepted for use in planning and describing water-use and related land-use activities, and in geographically organizing hydrologic data.
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