Roaring Fork Stream Flow Survey (2)

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NHDinGe~~ undergoes a process called centerlining to make a direct connection through waterbodi~~s and double-banked streams. The NHI~ provides a comprehensive set of digital spatial data that contains information about surface w<<ter features such as lakes, ponds, streams, rivers, springs and wells. Wit:fbin the NHD, surface water features are combined to form "reaches," which provide the framework for linking water-related data to the NHD surface water drainage network. These linkages enable the analysis and display of these water-related data and any associated information about them in upstream and downstream order. These data are developed nationally with the intention of identifying; a local steward to verify and update the hydrology. The CRWCD is working with the USGS to set up a workshop to outline thisprocess. To aid this process, we obtained stream layers frorn the four counties ~~Ga~e1d, Gunnison, Eagle, and Pitkin counties) in o+ar watershed as well as the USFS. These will be compared to the NI-~ layer to identify and corz~ect potential errors or omissions. All of Pitkin County and parts of Eagle County's stream layers were developed using aerial photography which may represent different positions of the channel especially in meandering and braided systems. The other counties were developed using 1:2,000 fJSGS DLG hydrography data, which is the basis for the NHD. The USFS hydrology network contains all "blue line" streams from topographic maps and channels determined from following contour crenulations, most likely ephemeral channels. Our objective is to ensure that all perennial streams, transbasin diversions, reservoirs and major ditches are represented, connected, and flow direction is correct. W'e will retain intermittent channels that are represented in NI~3 and will not add ephemeral channels or move the channel to reflect the aerial photograp:ls. Though this process we can correct obvious errors and flag areas of concern. Initially, counties and USFS will be contacted to determine what is correct in these, areas. A fevv cases may require a site visit t:o determine what is happening. This may be the case in raring to determine if a ditch flows over a stream or is connected to a strew. All edits will be made to the NI-~inGe~~ personal geodatabase and returned to the USGS to redo the hydrologic connectivity and incorporate into the national database. The workshop vvith USGS will be used to outline this process and make sure that the changes can be made in a timely manner. Tools Ar~GIS A geographic information sys~em (GIS) is a system for management, analysis, and display of geographer, knowledge, which is represented using a series of information sets such as maps and geographic; data sets, and data models. We will be using ArcGIS to produce information that will be used to address the stream flow survey c-bjectives and allow us to share that information with others. By visualizing relationships, connections, and patterns in data, we can mak+; informed decisions and increase efficiency. Using the ;VHD data model, events can be attached using linear referencing. This means that stream events such as distribution of a certain species of fish, minimum instream Ilow, and riparian habitat quality can be given an address on the river. Navigation tools can b~e used to identify sections of river upstream or downstream or between two poems of interest, such as between a diversion and its associated retw-n flow. These navigation results can also be turned into events. Once data is referenced in this way it is easy to study the relationships such as intersectio :~ or union between these data within the stream network. GIS can be usc;d to combine