Modeling the Effect of Cistern Size, Soil Type, and Irrigation Scheduling on Rainwater Harvesting as a Stormwater Control Measure

• Published in: Water resources management 2014-09, Vol.28 (12), p.4219-4235
• Main Authors: Shannak, Sa’d A, Jaber, Fouad H, Lesikar, Bruce J
• Format: Article
• Language: English
• Subjects: Atmospheric Sciences; Cisterns; Civil Engineering; Clay; Clay (material); Cost control; Drinking water; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Environment; equations; Evapotranspiration; Exact sciences and technology; Geotechnical Engineering & Applied Earth Sciences; harvesting; Hydrogeology; Hydrology; Hydrology. Hydrogeology; Hydrology/Water Resources; Irrigation; Irrigation scheduling; Irrigation systems; Irrigation water; Loam soils; Mathematical models; Methods; Rain; rhizosphere; Root zone; Runoff; Sand; Sandy loam; sandy loam soils; Sandy soils; Scheduling; silty clay soils; Soil moisture; Soil types; Storm runoff; Stormwater; Stormwater management; Urban runoff; Water balance; Water conservation; Water content; Water harvesting; Water quality; Water resources; Water shortages; Water supply
• ISSN: 0920-4741; 1573-1650
• DOI: 10.1007/s11269-014-0740-x

Urban stormwater runoff could have negative impacts on water resources and the environment. Rainwater Harvesting (RWH) can serve both as a stormwater control and water conservation measure. Cistern size and irrigation scheduling are two of the factors that directly impact the total runoff from a residential unit with a RWH system and the amount of potable water used for irrigation. The effectiveness of RWH was evaluated for four soil types; Sand, Sandy Loam, Loamy Sand, and Silty Clay, with a root zone of 15.2 cm using three irrigation scheduling methods (Evapotranspiration (ET)-based, soil moisture-based, and time-based), and five cistern sizes. Total runoff volumes and total supplemental potable water used were compared among the three irrigation scheduling systems and a control treatment without RWH. A model was developed to simulate the daily water balance for the treatments. Irrigation and runoff volumes were compared for the various scenarios. Silty clay soil resulted with 83 % more runoff than Sandy soil, while Sandy soil required on average 58 % more supplemental water than Silty Clay soil. On average, the 833 L cistern resulted with 41 % savings in water supply and 45 % reduction in total runoff. Results showed that the greatest volumes of runoff predicted were for the silty clay soil Control Treatment using a time-based irrigation scheduling method, while the least volumes calculated were for the sandy loam soil time-based irrigation scheduling treatment with 833 L cistern size. The greatest volumes of total supplemental water predicted were for sandy loam soil Control Treatment, while the least volumes were for silty clay soil ET-based irrigation scheduling treatment with 833 L cistern size. Regression equations were developed to allow for users to select a RWH cistern size based on the amount of water they want to save or runoff to reduce.