2018 ASHS Annual Conference

In the U.S., container plant growers often use expensive, high-quality water sources for irrigation. Irrigating with recycled irrigation runoff water has potential to reduce production costs. The objective of this study was to compare the cost of capturing and recycling irrigation runoff water to the cost of untreated municipal water at a nursery in Southern California during water years (WY) 2010-2016. Water year begins October 1 and ends September 30 of the following year. The untreated municipal water was supplied by Western Municipal Water District (Western), with the majority from Lake Mathews and a lesser portion from groundwater. The total cost of Western water consisted of variable charges based on volume used and fixed charges associated with the water delivery infrastructure. The irrigation runoff water capture and recycling system was installed at the end of water year 2014 and recycling began in water year 2015. The system included polyethylene and weed barrier lined growing beds and runoff channels, a lower capturing pond (10 ac-ft), an upper holding pond (27 ac-ft), pumps, rapid sand filters, and a chlorine dioxide injection system. The total price of recycled irrigation water consisted of consumable and capital costs. Consumable costs included electricity to operate two sets of pumps, one set for transferring water from the lower capturing pond to the upper holding pond and the other set for irrigating from the upper pond. Capital costs included the infrastructure and construction of the capturing and recycling system. Cost for Western supplied water ranged from $2.26 to $2.91 per 1,000 gallons for WY 2010-2016. The cost of recycled water was $0.92 and $1.21 per 1,000 gallons for WY 2015 and 2016, respectively. However, water provider rebates and a Natural Resource Conservation Service (NRCS) grant further reduced per unit volume cost of recycled water to $0.43 and $0.53 per 1,000 gallons for WY 2015 and 2016, respectively. Greater recycled water volume use resulted in lower per unit volume price for both scenarios, with and without rebates and grant. This is because the majority of recycled water cost is attributed to the large capital cost for the recycled water system. Due to its potential cost savings, recycled irrigation runoff water is a viable alternative to many high-cost water sources and public funding can help further reduce the cost of recycled water for growers of containerized plants.