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Annex 4 Table of conversion factors for metric and english units

This water-quantity equivalents and conversion factor list is for those interested in converting units. The right-hand column includes units expressed in two systems - U.S. 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.

U.S. Customary

U.S. Customary or Metric


1 in (inch)

= 25.4 mm (millimeters)

1 ft (foot)

0.3048 m (meter)

1 mi (mile, statute)

= 5 280 ft

= 1609.344 m

= 1.609344 km (kilometers)


1 ft2 (square foot)

= 0.09290304 m2 (square meter)

1 acre

= 43 560 ft2

= 0.0015625 mi2

= 0.40469 ha (hectare)

1 mi2

= 640 acres

= 259 ha

= 2.59 km2 (square kilometers)

Volume or Capacity (liquid measure)

1 qt (quart, U.S.)

0.94635 l (liter)

1 gal (gallon, U.S.)

= 231 in3 (cubic inches)

= 0.13368 ft3 (cubic foot)

= 3.78541

= 0.0037854 m3 (cubic meter)

1 Mgal (million gallon)

= 0.13368 Mft3 (million cubic feet)

1 Mgal

= 3.0689 acre-ft (acre-feet)

= 3.785.4 m3

1 ft3


= 1.728 in3

= 7.4805 gal

= 28.317 l

= 0.028317 m3

1 Mft2

= 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 kilometers)

Speed (or, when used In a vector sense, velocity)

1 ft/s (foot per second)

= 0.3048 m/s (meter 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-fool per day)

= 3.7854 l/min (liters per minute)

= 0.063090 l/s (liters 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 meter per second)

= 3.785.4 m3/d (cubic meters per day)

1 billion gal/yr (billion gallons per year)

= 0.0013817 km3/yr (cubic kilometer per year)

1 ft3/s


= 2.73 97 mgd

= 448.83 gal/min

= 0.6463 2 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

= 0.0013813 ft3/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 meters per square kilometer)

1 in/yr

= 047613 (Mgal/d)/mi2

= 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 (m'/s)/km2 (cubic meter per second per square kilometer)

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, U.S. Geological Survey (National Water Summary 1990-1991).


The Organization of American States (OAS) is the world's oldest regional organization, dating back to the First International Conference of American States, held in Washington, D.C., on April 14, 1890, This meeting approved the establishment of the International Union of American Republics. The Charter of the OAS was signed in Bogota in 1948 and entered into force on December 13, 1951. The Charter was subsequently amended by the Protocol of Buenos Aires signed in 1967, which entered into force on February 27, 1970, and by the Protocol of Cartagena de Indias, signed in 1985, which entered into force on November 16, 1988. The OAS currently has 35 Member States, In addition, the Organization has granted Permanent Observer status to 25 States in Europe, Africa and Asia, as well as to the Holy See and the European Economic Community.

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The General Assembly holds regular sessions once a year. Under special circumstances it meets in special session. The Meeting of Consultation is convened to consider urgent matters of common interest and to serve as Organ of Consultation under the Inter-American Treaty of Reciprocal Assistance (Rio Treaty), the main instrument for joint action in the event of aggression. The Permanent Council takes cognizance of such matters as are entrusted by the General Assembly or the Meeting of Consultation and implements the decisions of both organs when their implementation has not been assigned to any other body, it monitors the maintenance of friendly relations among the Member States and the observance of the standards governing General Secretariat operations and also acts provisionally as Organ of Consultation under the Rio Treaty. The purpose of the other two Councils is to promote cooperation among the Member States in their respective areas of competence, These Councils hold one annual meeting and meet in special sessions when convoked in accordance with the procedures provided for in the Charter. The General Secretariat is the central and permanent organ of the OAS. The headquarters of both the Permanent Council and the General Secretariat is in Washington, D.C.

MEMBER STATES: Antigua and Barbuda, Argentina, The Bahamas (Commonwealth of), Barbados, Belize, Bolivia, Brazil, Canada, Chile, Colombia, Costa Rica, Cuba, Dominica (Commonwealth of), Dominican Republic, Ecuador, El Salvador, Grenada, Guatemala, Guyana, Haiti, Honduras, Jamaica, Mexico, Nicaragua, Panama, Paraguay, Peru, St. Kitts and Nevis, Saint Lucia. Saint Vincent and the Grenadines, Suriname, Trinidad and Tobago, United States, Uruguay and Venezuela.

ISBN# 0-8270-3725-2

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