Conversion Factors, Datums, and Abbreviations and Acronyms


All conversion factors have been rounded to four significant digits. To reduce errors resulting from rounded conversion factors, reverse conversions should multiply by the inverse of the conversion factors originally used. For example, to convert feet into meters multiply by 0.3048. To convert meters into feet multiply by 1/0.3048.


Conversion Factors


Inch/Pound to SI


Multiply	By	To obtain
inch (in.)	2.54	centimeter (cm)
inch (in.)	25.4	millimeter (mm)
foot (ft)	0.3048	meter (m)
mile (mi)	1.609	kilometer (km)
square mile (mi2)	259.0	hectare (ha)
square mile (mi2)	2.590	square kilometer (km2)
acre-foot (acre-ft)	1,233	cubic meter (m3)
acre-foot per year (acre-ft/yr)	1,233	cubic meter per year (m3/yr)
foot per day (ft/d)	0.3048	meter per day (m/d)
foot per year (ft/yr)	0.3048	meter per year (m/yr)
inch per year (in/yr)	25.4	millimeter per year (mm/yr)
foot per day (ft/d)	0.3048	meter per day (m/d)

SI to Inch/Pound


Multiply	By	To obtain
meter (m)	3.281	foot (ft)

Datums


Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88). Vertical coordinate information for historical data collected and stored as National Geodetic Vertical Datum of 1929 (NGVD 29) has been converted to NAVD 88 for this publication. Conversion between NAVD 88 and the commonly used NGVD 29 varies spatially; however, over most of the study area the following conversion can be used:


NGVD 29 = NAVD 88 – 3.6 feet.


This conversion generally is accurate within about ± 0.5 feet for 95 percent of the study area. The reader is directed to either the National Geodetic Survey Web site for VERTCON at http://www.ngs.noaa.gov/TOOLS/Vertcon/vertcon.html or the U.S. Army Corps of Engineers Web site for Corpscon at http://www.agc.army.mil/corpscon for more accurate conversions.


Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83). Horizontal coordinate information for historical data collected and stored as North American Datum of 1927 (NAD 27) has been converted to NAD 83 for this publication. Conversion between NAD 83 and the commonly used NAD 27 varies spatially, and the difference in horizontal positions can be greater than 300 feet within the study area. For assistance with conversions, the reader is directed to either the National Geodetic Survey Web site for NADCON at http://www.ngs.noaa.gov/TOOLS/Nadcon/Nadcon.html or the U.S. Army Corps of Engineers Web site for Corpscon at http://www.agc.army.mil/corpscon.


Elevation, as used in this report, refers to distance above the vertical datum.


Abbreviations and Acronyms


Abbreviation or Acronym	Definition
CPRAS	Columbia Plateau Regional Aquifer System
CRBG	Columbia River Basalt Group
eYFB	eastern Yakima Fold Belt
GWMA	Columbia Basin Ground Water Management Area
MAF	million acre-feet
NWIS	National Water Information System
OWRD	Oregon Water Resources Department
SOWAT	SOil WATer balance model
USGS	U.S. Geological Survey
WADOE	Washington State Department of Ecology

First posted February 5, 2013