Using Irrigation to Increase Stormwater Mitigation Potential of Rainwater Harvesting Systems

Abstract

Rainwater harvesting (RWH) systems used for irrigation often provide fewer stormwater management benefits than systems used for year-round, nondiscretionary purposes because there is diminished demand for harvested rainwater during the nongrowing season or rainy periods. Thus, identifying demands during these periods would improve the stormwater mitigation potential of RWH systems. This study evaluated how irrigating bermudagrass year-round at rates exceeding those for minimum water conservation affected the stormwater benefits provided by an RWH system. Results indicated significant increases in runoff volume retention when turf was irrigated at 25 and 50 mm/week, compared to an evapotranspiration/effective precipitation (or agronomic)–based regime. While overall soil moisture content increased with irrigation rate, there were no concomitant increases in pest occurrences or runoff generation. Turf quality did not differ from the control irrigation regime for either application rate, and there were no indications of soil nitrate leaching. Irrigating at rates up to 50 mm/week resulted in stormwater volume reductions up to 65% without causing a decline in turf quality.