The rainwater harvesting BMP compared evapotranspiration based irrigation (ET), homeowner standard irrigation (HO), and soil moisture based irrigation (SM) with rainwater harvesting to a control (C) consisting of a homeowner standard irrigation without rainwater harvesting.
RWH Control Plot (Click to Enlarge Photo)
Table 1. Volumes and reduction rates comparing the 4 treatments in the rainwater harvesting system for the project period.
| Event | Rainfall | Control | ET | ET % reduction | HO | HO % reduction | SM | SM % reduction |
| 12/15/2012 | 0.39 | 0 | 0 | 0.00% | 0 | 0.00% | 0 | 0.00% |
| 12/28/2012 | 1.52 | 94 | 94 | 0.00% | 52.79 | 43.84% | 94 | 0.00% |
| 1/10/2013 | 2.61 | 224.75 | 224.75 | 0.00% | 198.32 | 11.76% | 224.75 | 0.00% |
| 1/30/2013 | 0.39 | 0 | 0 | 0.00% | 0 | 0.00% | 0 | 0.00% |
| 2/11/2013 | 0.9 | 29.1 | 29.1 | 0.00% | 11.28 | 61.24% | 29.1 | 0.00% |
| 2/13/2013 | 0.41 | 1.38 | 1.38 | 0.00% | 1.38 | 0.00% | 1.38 | 0.00% |
| 2/21/2013 | 0.37 | 0 | 0 | 0.00% | 0 | 0.00% | 0 | 0.00% |
| 3/11/2013 | 1.67 | 51.56 | 51.56 | 0.00% | 31.2 | 39.49% | 51.56 | 0.00% |
| 4/1/2013 | 0.84 | 11.64 | 11.64 | 0.00% | 1.03 | 91.15% | 11.64 | 0.00% |
| 4/4/2013 | 0.84 | 14.11 | 11.54 | 18.21% | 5.22 | 63.00% | 9.95 | 29.48% |
| 4/11/2013 | 0.46 | 2.46 | 2.46 | 0.00% | 0 | 100.00% | 2.46 | 0.00% |
| 4/18/2013 | 0.87 | 26.59 | 26.59 | 0.00% | 5.11 | 80.78% | 26.59 | 0.00% |
| 5/10/2013 | 0.25 | 0 | 0 | 0.00% | 0 | 0.00% | 0 | 0.00% |
| 5/16/2013 | 1.96 | 75.56 | 18.83 | 75.08% | 18.83 | 75.08% | 21.6 | 71.41% |
| 5/22/2013 | 0.89 | 70.54 | 37.34 | 47.07% | 40.7 | 42.30% | 70.54 | 0.00% |
| 6/7/2013 | 0.45 | 2.16 | 0 | 100.00% | 0 | 100.00% | 0 | 100.00% |
| 6/10/2013 | 1.08 | 45.51 | 28 | 38.48% | 11.71 | 74.27% | 25.16 | 44.72% |
| 6/17/2013 | 0.67 | 9.9 | 9.9 | 0.00% | 0.69 | 93.03% | 9.9 | 0.00% |
| 7/11/2013 | 0.72 | 15.42 | 1.9 | 87.68% | 1.9 | 87.68% | 1.9 | 87.68% |
| 7/17/2013 | 1.12 | 3.22 | 0 | 100.00% | 0 | 100.00% | 0 | 100.00% |
| 7/19/2013 | 0.36 | 0 | 0 | 0.00% | 0 | 0.00% | 0 | 0.00% |
| Total | 18.77 | 677.9 | 548.99 | 19.02% | 380.16 | 43.92% | 580.53 | 14.36% |
All treatments showed some reduction in runoff volume, but the homeowner treatment with rainwater harvesting showed a significant reduction of 43% compared to 19% and 14% for the ET and SM treatments.
The concentrations of pollutants in the runoff for pH, EC, nitrate nitrogen, orthophosphate, and total suspended solids were also compared. There were no specific trends of concentration reduction in any of the treatments for any of the pollutants since this BMP is mainly a volume reduction BMP.
Peer-Reviewed Publication:
Shannak S. A., Jaber F. H., and Lesikar B. J. 2014. Modeling the Effect of Cistern Size, Soil Type, and Irrigation Scheduling on Rainwater Harvesting as a Stormwater Control Measure. Water Resources Management 28(12): 4219-4235.