  Sourcebook of Alternative Technologies for Freshwater Augmentation in some Asian Countries (UNEP-IETC, 1998)  Part D - Annexes  Annex 1 - Additional references Annex 2 - Table of conversion factors for metric and U.S. customary units

### Annex 2 - Table of conversion factors for metric and U.S. customary units

This water quantity equivalents and conversion factor lists is for those interested in converting units. The right-hand column includes units expressed in two systems - US Customary and International System (metric). Units, which are written in abbreviated form below, are spelled out in parentheses the first time they appear. To convert from the unit in the left-hand column to that in the right, multiply by the number in the right-hand column. Most of the quantities listed were rounded to five significant figures. However, for many purposes, the first two or three significant figures are adequate for determining many water-quantity relations, such as general comparisons of water availability with water use or calculations in which the accuracy of the original data itself does not justify more than three significant figures. Quantities shown in italics are exact equivalents - no rounding was necessary. Regarding length of time, each calendar year is assumed (for this list) to consist of 365 days.

 US Customary US Customary or Metric Length 1 in (inch) = 25.4 mm (millimetres) 1 ft (foot) = 0.3048 m (metre) 1 mi (mile, statute) = 5280. ft = 1,609.344 m = 1.609344 km (kilometres) Area 1 ft2 (square foot) 0.09290304 m2 (square metre) 1 acre = 43,560. ft2 = 0.0015625 mi2 = 0.40469 ha (hectare) 1 mi2 = 640. acres = 259.00 ha = 2.5900 km2 (square kilometres) Volume or Capacity (liquid measure) 1 qt (quart, US) = 0.94635 l(litre) 1 gal (gallon, US) = 231. in3 (cubic inches) = 0.13368 ft3 (cubic foot) = 3.78541 = 0.0037854 m3 (cubic metre) 1 Mgal (million gallon) = 0.13368 Mft3 (million cubic feet) 1 Mgal = 3.0689 acre-ft (acre-feet) = 3,785.4m3 1ft3 = 1,728. in3 = 7.4805 gal = 28.317 1 = 0.028317 m3 1 Mft3 = 28,317. M3 1 acre-ft (volume of water, 1 ft deep, covering an area of 1 acre) = 43.560.ft3 = 0.32585 Mgal = 1,233.5 m3 1 mi3 (cubic mile) = 1,101.1 billion gal = 147.20 billion ft3 = 3.3792 million acre-ft = 4.1682 km3 (cubic kilometres) Speed (or, when used in a vector sense, velocity) 1 ft/s (foot per second) = 0.3048 m/s (metre per second) = 0.68182 mi/hour (mile per hour) 1 mi/hr = 1.4667 ft/s = 0.44704 m/s Volume per Unit of Time (discharge, water supply, water use, and so forth) 1 gpm (gallon per minute) = 0.00144 mgd (million gallons per day) = 0.0022280 ft3/s (cubic foot per second) = 0.0044192 acre-ft/d (acre-foot per day) = 3.7854 l/min (litres per minute) = 0.063090 l/s (litres per second) 1 mgd = 694.44 gal/min = 1.5472 ft3/s = 3.0689 acre-ft/d = 1,120.0 acre-ft/d (acre-feet per year) = 0.043813 m3/s (cubic metre per second) = 3,785.4 m3/d (cubic metres per day) 1 billion gal/yr (billion gallons per year) = 0.0013817 km3/yr (cubic kilometre per year) 1 ft3/s = 2.7397 mgd = 448.83 gal/min = 0.64632 mgd = 1.9835 acre-ft/d = 723.97 acre-ft/yr = 28.317 l/s = 0.028317 m3/d = 2,446.6 m3/d = 0.00089300 km3/yr 1 acre-ft/yr = 892.74 gal/d (gallons per day) = 0.61996 gal/min = 0.0013813ft3/s = 3.3794 m3/d 1 acre-ft/d = 0.50417 ft3/s Volume, Discharge or use per Unit of Area 1 in of rain or runoff = 17.379 Mgal/mi2 = 27,154. gal/acre (gallons per acre) = 25,400. m3/km2 (cubic metres per square kilometre) 1 in/yr = 0.047613 (Mgal/d)/mi2 = 0.073668 (ft/s)/mi2 1 (Mgal/d)/mi2 = 21.003 in/yr (inches-of rain or runoff - per year) 1 (ft3/s)/mi2 = 13.574 in/yr = 0.010933 (m3/km2 (cubic metre per second per square kilometre) Mass (pure water in dry air) 1 gal at 15° Celsius (59° Fahrenheit) = 8.3290 lb (pounds avoirdupois) 1 gal at 4° Celsius (39.2° Fahrenheit) = 8.3359 lb 1 lb = 0.45359 kg (kilogram) 1 ton, short (2,000 lb) = 0.90718 Mg (megagram) or ton, metric

Prepared by John -C. Krammer, US Geological Survey (National Water Summary 1990-1991)