p. 3], monitoring the salt line [26, p. 5], and recycling and re-
use of water [4, p. 3]. Other methods being considered for use
in increasing the water supply are back pumping structures to
reduce runoff losses [26 p. 7] and deep level underground stor-
age [27, p. 11]. Economic approaches and tools can also be use-
ful in water management, but have often been ignored [3, pp.
622-623].
 Fundamental to all economic approaches is information on
 the demand for water. Demand functions provide quantitative
 information on the marginal value of water in all its uses. These
 estimates of marginal value must be known before the economic
 impact of alternative water allocation strategies can be evaluated.
 Demand information has been developed for residential users
 in Dade county [1, 17]. Agricultural demand has also been
 studied in Dade county [31]. Information regarding water use
 for the retail and service business sector in Dade county was the
 subject of the study described here.3 Water demand information
 for commercial uses will be especially useful to water manage-
 ment districts as well as to individual public and private water
 supply utilities.

 Area of Study
 Dade county is the largest county in Southeast Florida, con-
 taining half the population [30, pp. 7-8] and over half of the
 commercial businesses in the Gold Coast Area.' There are four
 major water consuming sectors in the county-domestic, com-
 mercial, agricultural, and industrial. The domestic sector (home
 use) is the largest consumer with a daily use of 185.7 million
 gallons in 1970 [24, p. 7], followed by the agricultural sector,
 which utilizes 44.8 million gallons a day. Commerce withdraws
 an average of 21.2 million gallons, while self-supplied industrial
 use amounts to 10.4 million gallons a day. The Florida Keys
 (Monroe county) also pumps about 6.0 million gallons per day
 from Dade county." Water use in the Keys was also considered
 in this study.

 information from all three of these studies on water demand is used
 to illustrate the importance of elasticity estimates even when water is
not sold in a market in Lynne [16].
 4Information on commercial businesses was derived from the 1972 Census
[28, pp. 10-17; 29, pp. 10-16].
 5The water is pumped from well fields near Florida City and piped to
the Florida Keys. Additional water used on the Keys is from desalination-
plants.