Management of Dry Weather Flows in Semi Arid Climates Using Low Impact Development Technology

Urbanized semi-arid regions experience a significant amount of dry-weather flows in the form of return from excessive irrigation on suburban lawns. These dry-weather flows also carry significant amounts of nutrients from household fertilizers, which are discharged to receiving water bodies. These nutrients cause unsightly algal growth sometimes known as "urban slobber," that result in oxygen depletion due to organic matter decay. These flow rates can constitute a large component of dry-weather flow in urban streams. The conditions of semi-arid climates are conducive to turn these flows into a more visible nuisance than in humid regions. This paper explores the application of LID technology to manage dry-weather flows in semi-arid climates. LID's infiltration-based controls can be deployed to intercept and treat nutrient-laden excess irrigation flow. The concept is illustrated in a subdivision in Los Angeles, California area by applying the LIFE^TM model developed by CH2M HILL for simulation of LID hydrology.