Reducing Power Costs, Conserving Water, and Increasing Crop through On-Farm Irrigation Efficiency

Thanks to bountiful hydropower electricity, residents of North Central Washington benefit from some of the lowest power rates and live in one of the best fruit-growing regions in the United States. Successful fruit growers in the region are constantly pushing the envelope to reinvest in their crops and rediscover ways to economically maximize yield. Because regional power rates are so low, an often-overlooked opportunity for growers is optimizing pumping-related power costs. 

Power use can be a key tool to uncover significant cost savings and opportunities to gain water, and thus potentially expand fruit operations. Discussed in detail below, performing a power use analysis and implementing infrastructure efficiency improvements could potentially save a grower tens of thousands of dollars in energy costs and reduce water use by hundreds of acre-feet. In some cases, water saved can be used to expand orchard operations or be sold for profit. 

As this hypothetical apple farm scenario shows, a power and water audit has the potential for growers to identify opportunities to reduce power costs and save water at the same time

What Drives Pumping Energy Use?

Pressure and flow are the two primary factors that go into pump power costs, but there are other factors to consider. For example, the age and quality of pumps and motors influences their operating efficiency. A premium-efficiency motor may operate above 90 percent efficiency, whereas an older motor that hasn’t been rewound in a while may be only be 80 percent efficient (or even lower). Pumps have a range of efficiency also. A new properly sized pump operating at its best efficiency point could provide 80% efficiency. An older pump with worn impellers might provide efficiencies of 70 percent or less. 

Pumps operate most efficiently within a narrow range of flows, and efficiencies decrease rapidly when asked to operate outside that range. For example, a pump that was sized to deliver 500 gallons per minute (gpm) at 80 percent efficiency may only perform at 70 percent efficiency when operating at 400 gpm. 

Water Savings in Piping and Sprinkler Upgrades

Piped conveyance systems also contribute to overall system efficiency. Not only can hydraulic problems result in wasted energy, but losses and leakage can result in wasted flow. While 10 percent leakage in pipes is common (and acceptable), improving to a 5 percent leakage rate is achievable—and tremendously valuable. 

Finally, watering application efficiency (i.e., emitter type) can contribute dramatically to the total power bill. For example, a traditional impact sprinkler may be 75 percent efficient, while low-volume sprinklers may be 85 to 90 percent efficient. 

Impact Sprinkler (75 percent efficient)

Impact Sprinkler (75 percent efficient)

Low-volume Emitter Sprinkler (90 percent efficient)

Low-volume Emitter Sprinkler (90 percent efficient)

How to Save a Tree Fruit Grower $20,000 and 440 acre-feet of Water

Clearly, there are many opportunities to tighten up the “wire-to-water”, or in this case “wire-to-fruit,” efficiency. To help illustrate potential savings, consider a ranch with 500 acres of apples in North Central Washington. Hypothetically, the crops alone could take as much as 3.5 acre-feet of water per year. In this case, let’s assume that the irrigation method is with solid set over-tree impact sprinklers fed off an older series pump with an overall lift of 450 feet and an annual energy cost of approximately $57,000 (Current System; Table 1). Compare this to an optimized system with a premium-efficiency motor, properly-sized pump, limited leakage, and efficient emitters (Optimized System; Table 1).

We find that the estimated pump-related power costs could be reduced by one third—about $20,000 in savings! This is due both to a lower water volume being pumped and better efficiencies of the pumps and motors. While there are certainly valuable applications for running over-tree watering applications (e.g., cooling), innovative practices such as installing shade cloth can help mitigate burning effects on fruit in lieu of sprinklers.  The cost of making that conversion could be justifiable if the benefit includes significant power or water savings.

What to do with the Surplus Water? 

In this example, not only has the grower now saved considerable expense related to power costs, but has also managed to save 440-acre feet of water. In water markets, the consumptive use savings have the highest value; and in this instance, approximately 170-acre feet of the water saved is considered consumptive use. Assuming this water is associated with a perfected (certificated) water right, there are a number of ways this grower could benefit:

  • Market the water and transfer through a transaction (note: current value of water is in the $2,500 per acre-foot range). 
  • Spread the water and plant additional acreage.
  • Protect the water for future use through temporary trust donation (relinquishment protection).
  • Seed a water bank for use in other locations. 

Optimizing Your System Makes Sense from Many Perspectives

There is considerable value in looking at ways to better optimize your power and water use. Financial savings can come in the form of lower energy bills simply by modernizing and properly maintaining your system. However, the rewards of conserving water are not limited to lower power bills. In many cases, it is important to consider the market potential of water savings also. The first step to any of this is a power and water use analysis in consultation with a water resources professional.