Increasing Water Supply for Home Irrigation

Abstract

Low rainfall and humidity, and high evapotranspiration, make irrigation necessary for domestic plant growth and commercial crop production in the American Southwest. Irrigation is restricted to dwindling ground-water supplies, and rainfall- or snowmelt- dependent streamflow. Both sources are susceptible to droughts and overdrafts. A large percentage of potable water used in Southwestern homes is used for irrigation of domestic gardens and yards. Another large percentage is returned to sewers. Water fees increase with dwindling supplies, increasing depths to ground water, scarce surface water, and high treatment costs. Sewer-user fees increase because of high construction and treatment costs. Both water and sewer fees increase because of rapid urban expansion and increased water-quality standards. As fees increase, supplemental home irrigation sources become attractive and are sought. Major supplemental water sources are grey water, harvested runoff, and roof runoff. Grey water is all home sewage effluent other than from toilets; it includes effluent from sinks, showers, tubs, dishwashers, clotheswashers, swimming pools, and evaporative coolers. Harvested runoff is all water produced from specially landscaped or prepared surfaces; such as driveways, streets, walks, or treated land. Roof runoff is all water produced by rainfall that drains a roof. The amount of grey water depends on family size and habits. The amount of harvested runoff depends on land size and slope, soil's and material's properties, and rainfall. The amount of roof runoff depends on roof size and geometry, and rainfall. The quality of grey water, harvested runoff, and roof runoff is generally suitable for home irrigation. Engineering systems are required to collect, store, treat, distribute, and apply supplemental home irrigation water. There are many possible combinations of components, but the most preferred systems will have low capital expenditure and low energy requirements. Economic considerations are different for large and small scales. Large-scale analysis indicates that a large and significant reduction in municipal costs and services is possible if supplemental home irrigation water is developed. Small-scale analysis for the 100-unit trailer park, 50-unit two-story apartment complex, double family home of six, and single family home of three, indicates that costs are favorable for supplemental irrigation systems, particularly for future large-scale units. A suggested research program emphasizes field trials and demonstrations, which test design, operation, maintenance, and economics, as well as public and institutional acceptance.