Altman Specialty Plants (Altman) built an irrigation runoff water capturing and recycling system to address concerns about interruption in the supply of and the increasing cost of municipal water that they relied on for irrigation. One container nursery site is 400 acres and located in the “Inland Empire” of Southern California, where a favorable plant production climate allowed the citrus industry to flourish during the last century. However, water is scarce in this area, with about 12 inches of rain per year and as low as 6 inches per year during the 2012-2016 drought. Furthermore, almost all of precipitation occurs in the winter months with the majority of the 50 inches of yearly evapotranspiration occurring in summer. 

Supply and demand

The nursery’s water supply is untreated municipal water provided by the Western Municipal Water District (Western) via the Metropolitan Water Board of Southern California (Metropolitan). The water provided by Western is predominantly from the terminus of the Colorado River Aqueduct with a smaller portion from groundwater. The nursery has no alternative water source (i.e., wells), and an interruption in Western water could cause serious production problems.

In 2013 and 2014, the nursery used 1,007 acre feet (ac-ft) per year, equal to 3.7% of the total volume of water provided to Western customers. During 2013-2014, water cost between $706 to $825 per ac-ft with fixed monthly charges between $122 to $175. Altman’s total water bill for this location in 2013-2014 combined was $1.6 million. 

In 2011, Altman began looking into a water recycling system to both save money and prevent delays or reduced production if the water supply was interrupted for a short period of time (less than 1 week). Initially, they looked at the overall design of the nursery to ensure that existing and future development would facilitate capturing and recycling runoff. 

In 2012, Altman began discussions with the National Resource Conservation Service (NRCS) about designing and engineering a runoff channel and two recycling ponds at the nursery and potential grant funding. The original estimated costs of the recycled water system totaled $750,000, and Altman turned to the water providers for rebates to help offset the cost. Metropolitan and Western authorized a maximum of $358,000 and $100,000, respectively, to be paid out over several years through Metropolitan’s Water Savings Incentive Program. Altman anticipated reusing 230 ac-ft in the first year. The NRCS Environmental Quality Incentives Program provided $195,000 in grants for infrastructure costs (see Table 1).

How it’s structured

Two lined ponds were installed at the nursery: A 10 ac-ft lower pond (see Figure 1) captured irrigation runoff, and a 27 ac-ft upper pond served as the major reservoir. Water from the lower pond is pumped to the upper pond via two 40-hp pumps. Water is pumped from the upper pond for irrigation via two 125-hp variable frequency drive pumps. A remnant pond, into which growing areas originally drained, was saved to slow water flow and increase sedimentation. A half-mile-long channel designed by the NRCS to handle a 25-year flood event was built to connect the remnant pond to the lower pond. This trapezoidal runoff channel was built with a 1-in-3 slope on the sides to eliminate the need for fencing along its length.

The drainage channels are lined with polyethylene sheeting to prevent infiltration water losses and covered with polypropylene weed barrier to delay UV degradation and physical protection of the polyethylene. All growing areas are covered in weed barrier, and half of those areas have polyethylene sheet below to maximize irrigation runoff capture. 
 

 

 

 

Costs — and savings

The final cost for the whole project totaled $930,000 (see Table 1). Construction costs exceeded the estimated $750,000 because design improvements were made and some very large boulders that obstructed the runoff channel and ponds needed to be moved. To control plant pathogens in recycled water, the nursery leases a chlorine dioxide injection system costing $82,800 per year including chemical costs.

Table 1. Costs and rebates for recycled irrigation runoff water system at Altman Specialty Plants.
 

The system came online in September 2014, four months before water prices increased to $944 per ac-ft and fixed charges of $210 per month. In the first year, the nursery reused almost twice the amount of water anticipated, about 429 ac-ft, accounting for 37 percent of total nursery water use. Reusing 429 ac-ft of irrigation runoff resulted in direct savings of $330,500, as this was water that did not need to be purchased from Western. In 2016, the nursery reused 593 ac-ft resulting in savings of $478,700. 

After a couple of years, Altman received the entire available rebate from both Metropolitan and Western. With rebates from the water providers, the NRCS grant, and the savings from reduced water usage, the return on investment was less than one year and continues to pay dividends. Another benefit of pond construction is that the nursery now has a backup water supply of approximately one week or longer, in the event infrastructure problems were to occur and water could not be delivered. 

As water becomes scarcer and more expensive, using recycled irrigation runoff water is a good option to reduce costs and ensure production is not impacted. Although your nursery or greenhouse operation may not realize as great of savings on water costs as Altman Specialty Plants, this example highlights the benefits of recycling water for plant production, especially in locations with expensive water. Visit this link greater detail: https://link.springer.com/article/10.1007/s00271-018-0578-8.

Bruno J.L. Pitton is an Environmental Horticulture Advisor with UC Cooperative Extension in Placer and Nevada Counties. He can be reached at bjpitton@ucanr.edu.