Conversion Factors, Datums, and Abbreviations

Conversion Factors

Multiply	By	To obtain
Length
inch (in.)	2.54	centimeter (cm)
inch (in.)	25.4	millimeter (mm)
foot (ft)	0.3048	meter (m)
mile (mi)	1.609	kilometer (km)
Area
square mile (mi2)	259.0	hectare (ha)
square mile (mi2)	2.590	square kilometer (km2)
Volume
acre-foot (acre-ft)	1,233	cubic meter (m3)
acre-foot (acre-ft)	0.001233	cubic hectometer (hm3)
Flow rate
million gallons per day (Mgal/d)	0.04381	cubic meter per sec (m3/s)
acre-foot per year (acre-ft/yr)	1,233	cubic meter per year (m3/yr)
acre-foot per year (acre-ft/yr)	0.001233	cubic hectometer per year (hm3/yr)
cubic foot per second (ft3/s)	0.02832	cubic meter per second (m3/s)
cubic foot per second per square mile [(ft3/s)/mi2]	0.01093	cubic meter per second per square kilometer [(m3/s)/km2]
inch per year (in/yr)	25.4	millimeter per year (mm/yr)
Hydraulic gradient
foot per mile (ft/mi)	0.1894	meter per kilometer (m/km)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (µS/cm at 25°C).

Datums

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 1929), or to the North American Vertical Datum of 1988 (NAVD 1988), as indicated in text, plate, figures, and tables.

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 1927), or to the North American Datum of 1983 (NAD 1983), as indicated in text, plate, figures, and tables.

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

Abbreviations

Abbreviation	Meaning
DEM	Digital elevation model
GPS	Global Positioning System
NWIS	National Water Information System
NWS	National Weather Service
OWRD	Oregon Water Resources Department
PRISM	Precipitation Elevation Regressions on Independent Slopes Model
RM	River mile
TMDL	Total Maximum Daily Load
UIC	Underground injection control
USGS	U.S. Geological Survey
UTM	Universal Transverse Mercator
WY	Water year, the 12-month period from October 1 through September 30, and is identified by the calendar year in which it ends