Urban Water Harvesting System, Tucson, Arizona

Abstract

A urban water harvesting system in Tucson, Arizona is described. The system consists of a 100,000 gallon reservoir fed through a 6-inch pipe by a 4-acre urban watershed. In addition a 3-acre watershed is connected to the pond with both a earth lined and fibreglass reinforced asphalt channel. The 3-acre watershed includes the acre lot on which the reservoir is located. A gutter collects the runoff from the house on this lot and directs it into the pond. The front driveway is paved and directly connected to the pond so that a high percentage of its rainfall is harvested. The reservoir is multipurpose providing irrigation for a large (4000 sq. ft.) garden and orchard area in addition to landscape irrigation. Also in the future the reservoir will provide sufficient water to take care of the flushing of toilets for a family of 8. The reservoir also is used for the raising of fish thus providing both food and recreation. Trout is raised in the winter and tilapia in the summer. The pond also provides swimming, rafting and aesthetic enjoyment in an arid environment. The cost effectiveness of the reservoir is high primarily because of the high watershed area to capacity ratio. With a relatively high demand the reservoir refills several times each year. Only a small percentage of the rainfall on the watershed is utilized because of the relatively small storage capacity of the reservoir. This percentage of utilization is estimated to be about 15 percent.