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California Interagency Watershed Mapping Committee (IWMC)

CalWater – The Committee and the Data

In California, the IWMC works on watershed mapping and dataset creation. For many years this committee has been commonly known as the CalWater Committee. However, the word CalWater can refer to either the Committee or the Dataset. The California IWMC is responsible for all interagency watershed maping and dataset creation in the state, which includes CalWater 2.2.1 and the California section of the Watershed Boundary Dataset (WBD).

CalWater: the Committee is the Interagency Watershed Mapping Committee that traditionally has been known as CalWater. An MOU of nine state and federal agencies forms the basis of this committee, and their commitment is to develop and continue to support updated versions of California Watershed maps and data.

CalWater: the Dataset is the official California State hierarchical Watershed maps, and GIS dataset. There have been several versions leading to the one currently available: CalWater Version 2.2.1.

To avoid any confusion, please note that the California Bay Delta Authority uses the word calwater in its website URL: http://calwater.ca.gov.

CalWater The Data – CalWater 2.2

In California, the current state watershed map and dataset is officially known as the California Interagency Watershed Map of 1999 (CalWater Version 2.2.1), and usually referred to simply as CalWater 2.2.1. It is the current official digital (and paper) watershed map for use by State and Federal agencies in California. The commonly used 8-digit HUCs from the USGS Hydrologic Unit Maps can be dissolved from this dataset.

CalWater can be downloaded from the California Spatial Information Library: http://gis.ca.gov/meta.epl?oid=22175

Click on the image to the left to view a full size map of California Watersheds.

The CalWater Committee has also been working on the California portion of the National Watershed Boundary Dataset (WBD): http://www.ncgc.nrcs.usda.gov/branch/gdb/products/watershed/. The linework developed for the WBD follows the FGDC (Federal Geographic Data Committee) guidelines and standards for watershed delineation. The CalWater committee has agreed to use the linework and attributes from the WBD watersheds for California as the basis of future versions of the CalWater dataset (i.e. CalWater 3.x), which will also include the State naming and numbering system used in the current version of CalWater 2.2.1.

CalWater – Interagency Watershed Mapping Committee

CalWater is also the name of an Interagency Watershed Mapping Committee that has worked since the mid-1990’s to delineate California’s watersheds, and provide a digital dataset that has both a California and a Federal naming and numbering attribute system. For many years, the NRCS and other State and Federal agencies, have been worked with this committee to map the watersheds and hydrologic units in the State of California.

Nationally, the United States Geological Survey (USGS) and NRCS are leading the effort to map all the Watersheds in the United States coverage called the Watershed Boundary Dataset (WBD). The WBD will provide a single, seamless, nationally consistent, and accurate geospatial database of hydrologic units based on scientific hydrologic and mapping principles. This effort builds upon and updates the 1978 USGS Watershed and Hydrologic Unit Code maps that contained the commonly used 8-digit hydrologic units. The CalWater Committee leads the effort in California to map the State’s portion of the WBD. Information on the Committee, upcoming meetings, past meeting minutes, and other activities are available at the CalWater website.

A current update on the Status of the CalWater Committee and its current year activities is available for download:

The following document requires Microsoft PowerPoint.

CalWater 2004 Status Update (2.12 MB)

Features

California Interagency Watershed Mapping Committee (IWMC)

CalWater – The Committee and the Data

CalWater The Data – CalWater 2.2

CalWater – Interagency Watershed Mapping Committee

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