California Interagency Watershed Mapping
Committee
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California Watershed Boundary DelineationNational Watershed Boundary Delineation (WBD) StandardsThe National Watershed Boundary Delineation Standards are available online from the Natural Resources Conservation Service (NRCS). The New National Watershed Boundary DatasetThe US Geological Survey (USGS) and the NRCS are sponsoring a National update of watershed maps for the United States. NRCS is the lead agency on updating and certifying the watershed boundaries to 5th and 6th level (10 and 12 digit numbers). NRCS has agreed to change the numbering system to match the FIPS sequence, so that what were the 11 and 14 digit watershed codes, will now be 10 and 12 digit watershed codes. The NRCS guidelines (NI 170-304) were updated into new FGDC standards which replaced NI-170-304. New names and numbers:
The goal is to finish all 5th and 6th level, Nationwide, by December 2003. For local planning and mapping purposes, California plans to extend the watershed hierarchy down two more levels, to include Levels 7 and 8. Please take a look at the full hierarchy and the new WBD codes, related to CalWater 2.2 codes. USGS HUC HistoryThese new maps will update and replace the old HUC maps In the mid 1970's the US Geological Survey (USGS) Office of Water Data Coordination (OWDC), under the sponsorship of the Water Resources Council (WRC), developed a nationally uniform hydrologic unit (HU) system. The Hydrologic Unit Maps series were published in 1978 at the 1:500,000 for each state, and described in USGS Water-Supply Paper 2294 (Seaber, P.R., Kapinos, F.P., and Knapp, G.L., reissued 1987, Hydrologic Unit Maps: U.S. Geological Survey Water-Supply Paper 2294, 63 p.) The report provides a complete list of all the hydrologic units, along with their drainage areas, their names and the names of the States or outlying area in which they reside. This system divides the country into 21 Regions, 222 Subregions, 352 Accounting Units, and 2,149 Cataloging units based on surface hydrologic features. A hierarchical hydrologic unit code (HUC) consisting of 2 digits for each level in the hydrologic unit system is used to identify any hydrologic area of interest. You may still order a print copy of both the maps and Paper 2294 report from the USGS. Digital versions of the maps, and metadata, are available for download from the USGS (scroll down to online linkage). Watershed Boundary Mapping StandardsUntil we are otherwise notified, the official guidelines are still National Instruction 170-304. But word is that they will be officially replaced by the new interagency Federal Geographic Data Committee (FGDC) guidelines. The new DRAFT Interagency Guidelines on Delineation of Watershed and Subwatershed Hydrologic Unit Boundaries are being developed by the USGS Water Information Coordination Program, and the FGDC's Subcommittee on Spatial Water Data (also called the Advisory Committee on Water Information). What About CalWater?CalWater is still the official California Watershed map. (For more
information go to our CalWater
Data page.) It is the best available data for most uses. In its present form
it does not meet the NRCS, or the new proposed FGDC Watershed Boundary Dataset
mapping standards. But we are hoping that it will. The CalWater committee is
working on a "Draft Work Plan" to try and bring the CalWater linework into
compliance with these standards, and then label these watersheds with both the
existing State system, and the Federal system. Ideally, sometime in the future,
you will be able to click on a watershed in CalWater and read the name and
number of that watershed in both the State and Federal systems. |