California Interagency Watershed Mapping Committee

Understanding and Working with CalWater 2.2

CalWater 2.2 is still the official California Watershed map. It is the best available data for most uses, though it does not, in its present form, meet the Federal Geographic Data Committee's (FGDC) Watershed Boundary Dataset mapping standards. The CalWater committee is working hard to update the watersheds, so that the next version will meet the standards and be hydrologically correct.

The California Watershed System

CalWater 2.2 has more watershed detail for many areas on the west and east sides of Northern California than for the Central Valley and Southern California areas. You can read more about the history and development of CalWater from versions 1.2 to 2.2 on our History page.

Click on the image to the left to view a larger image.

The hierarchy of watershed designations consists of six levels of increasing specificity and detail:
 

Watershed Designation level	Acres
Hydrologic Region (HR)	(12,735 sq miles / 8,150,000 acres)
Hydrologic Unit (HU)	(672 sq miles / 430,000 acres)
Hydrologic Area (HA)	(244 sq miles / 156,000 acres)
Hydrologic Sub-Area(HSA)	(195 sq miles / 125,000 acres)
Super Planning Watershed (SPWS)	(78 sq miles / 50,000 acres)
Planning Watershed (PWS)	(5-16 sq miles / 3,000-10,000)

Note: These do not directly correspond to the USGS 8 Digit HUCs, or to the new WBD Watershed Levels. (See the WBD Hierarchy Table). However, they are currently the best available delineated watersheds for California. The next version of CalWater (3.0) will meet the FGDC standards, be hydrologically correct watershed boundaries, and provide attributes for both the Federal System and State System of names and numbers.

CalWater 2.2 Metadata

Projection Information

• Datum: NAD 27
• Projection: Albers
• Units: Meters

Complete CalWater 2.2 Metadata can be found at the California Spatial Information Library (CaSIL).

CalWater 2.2 is not a true hydrologic dataset.  Read more about it on Frequently Asked Questions.

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