Figure I: Bromoler Hill Catchment adjacent to the University of the Virgin Islands Campus Covers 220,000 Square Feet.


various levels of weekly demand. The area of this catchment
is 220,000 square feet and its cistern has a storage capacity of
3,000,000 gallons (see Figure 1). The surface is felt-coated
corrugated galvanize and if it were in perfect condition, its
efficiency as a catchment surface is estimated to be about 85
percent. Twenty one years of Virgin Islands weekly rainfall
data with an annual average of 48 inches was used in the
simulation. A summary of the results are presented in Table
1. Reliability as used in this table is defined to be the prob-
ability of the system being capable of satisfying the particu-
lar demand at any time period used in the simulation.


 Large scale water harvesting using purpose-built catch-
 ments with cisterns can be a water supply alternative in the
 Virgin Islands. Proper evaluation of the costs associated
 with constructing and maintaining these structures must be
 made. The potential yield from these structures as well as
 their reliability must be realistically evaluated. With proper
 management and application of current treatment tech-
 nology, the quality of water derived from hillside catch-
 ments may be readily maintained within acceptable limits.


TABLE 1


 Reliability of Bromoler Hill Catchment for Several Demands

Weekly Demand Reliability Weekly Demand Reliability
 (gallons) (percent) (gallons) (percent)



 100,000 90 160,000 45

 110,000 85 170,000 40

 120,000 80 180,000 40

 130,000 70 190,000 35

 140,000 60 200,000 30

 150,000 55 210,000 30