Deficit Irrigation: Finding the Balance Between Survival and ROI

Every season, California growers are forced to make impossible choices with water. In December 2024, the State Water Project announced just a 5% allocation; by April 2025, after winter storms, that figure jumped to 50%. Meanwhile, the Central Valley Project set allocations at 35% for south-of-Delta ag contractors (Westlands WD).

This volatility is not a blip. Under the Sustainable Groundwater Management Act (SGMA), subbasins like Tulare Lake have already been put on probation, triggering new fees and state oversight. California planners warn that climate change could cut the state’s water supply by 10% by 2040.

Layer in the economics, groundwater pumping now costs about $200 per acre-foot, and power rates are rising. The picture is clear. It is not just drought anymore. Policy, economics, and climate are stacking together to squeeze growers from all sides. The Public Policy Institute of California estimates that up to 900,000 acres could be fallowed in the San Joaquin Valley by 2040.

In this environment, deficit irrigation has become less of a “what if” strategy and more of a necessity. But cutting water is not as simple as turning down the pump. The timing, severity, and targeting of those cuts matter, and the wrong move can cost next year’s crop.

The Agronomic Stakes

Let’s start with almonds. In a UC Davis simulation, two orchards applied the same total water, 16 inches per acre, but one concentrated it early while the other shifted cuts later. The early-season orchard looked fine in the current year, but the following year’s production collapsed by 75 percent, even after returning to full irrigation. The lesson is clear: if cuts are unavoidable, bias them toward the late season, and use imagery to pinpoint zones most at risk.

Pistachios tell a different story. Large deficits during shell expansion and kernel fill damage quality, reducing split percentage, increasing blanks, and worsening alternate bearing. UC guidance is clear: if you must run regulated deficit irrigation in pistachios, keep it moderate and carefully timed.

Citrus offers a quality tradeoff. Research shows that moderate deficit irrigation can improve flavor by raising °Brix and balancing sugars and acids, but applied too early or too severely, it shrinks fruit size.

Wine grapes, on the other hand, are among the crops best suited to strategic deficit irrigation. Pre-veraison to veraison deficits can enhance color and phenolics, directly tied to quality. In Napa, a California Energy Commission field program using imagery and sap-flow sensors reported about 60 percent average water and energy savings, with grape quality actually improving.

Not all deficits are equal. The same irrigation cut in July versus August can mean flavor gains in grapes or yield losses in almonds.

Probes vs. Imagery: It’s Not Either/Or

When it comes to managing deficit irrigation, tools matter.

Soil moisture probes are effective for timing irrigations and verifying infiltration depth. A typical setup runs about $50 to $100 per acre in the first year, then drops to around $10 to $15 per acre annually with subscriptions and maintenance. The catch is that they are point measurements. To cover a 40-acre block properly, you need at least two stations, more if the soils vary.

Imagery-driven optimization, by contrast, offers a whole-block view. For about $4 to $6 per acre, aerial thermal and NDVI imagery can flag stress, variability, and distribution uniformity issues that probes alone will miss.

What imagery shows that probes can miss:
 • Distribution uniformity issues (pressure or plugging) visible as hot and cool patterns
 • Canopy stress pockets from soil or texture breaks that one or two stations will not capture
 • Over- or under-irrigated sets that align with valve groups or slope
The most effective growers are not choosing one over the other. They are combining probes (for when to irrigate) with imagery (for where). That integrated approach turns deficit irrigation from a gamble into a plan.

Beyond Survival: The Sustainability and Compliance Dividend

Done right, deficit irrigation does not just stretch water. It pays off in sustainability and compliance too.

In Napa, imagery-based irrigation optimization saved about 60 percent of water and energy while maintaining or improving grape quality. Less over-irrigation also means less nitrate leaching, keeping nitrogen in the root zone instead of groundwater.

This is increasingly important for regulatory compliance. Under SGMA, spatial evapotranspiration data and imagery help groundwater agencies monitor consumptive use. Under the Irrigated Lands Regulatory Program (ILRP), efficient irrigation supports nutrient management plans and groundwater protection targets. For institutional landowners, investors, and food buyers, these practices are becoming part of the ESG scorecard.

How to Put Deficit Irrigation Into Practice

1) Set goals and guardrails
Decide if the goal is yield protection, quality improvement, or hitting a water budget. Mark “no-go windows” for each crop (for example, early season in almonds, kernel fill in pistachios).

2) Fix uniformity first
Run a distribution uniformity check, repair leaks, and confirm pressures. Deficit irrigation on a poor system magnifies risks.

3) Instrument smartly
Use imagery for where to irrigate and probes or plant tools for when. Budget: probes ≈ $50 to $100 per acre in year one; $10 to $15 per acre ongoing. Imagery ≈ $4 to $6 per acre.

4) Write the in-season plan
Map phenology week by week, note where deficits can be applied, and set thresholds or “tripwires” for pausing deficit irrigation during heat waves or stress.

5) Pilot with an A/B design
Compare deficit irrigation versus business-as-usual blocks. Track water (acre-feet per acre), pump kilowatt-hours per acre, stress area percentage, and yield or quality. Use ROI = (ΔRevenue – ΔCosts) ÷ Program Cost.

6) Operate with safety valves
Pre-irrigate before heat waves, avoid aggressive deficit irrigation in young plantings, and keep regulated deficit irrigation moderate in alternate-bearing crops.

7) Close the loop
Post-harvest, compare results and update next year’s phenology plan.

The Bottom Line

Deficit irrigation is not about doing more with less blindly. It is about using timing, targeting, and technology to make smart tradeoffs.

Almonds demand protection early. Pistachios punish deficits during kernel fill. Citrus can trade size for flavor if you are careful. Grapes, with the right program, can deliver both savings and quality.

Growers who approach deficit irrigation like Agronomic COOs, treating water as a line item to be optimized, not just rationed, are the ones who will stay competitive in the era of volatility.

The water squeeze is here to stay. The question is: will you cut blindly, or will you cut with a plan?

And here is the good news: imagery is no longer just a scouting tool. It is becoming the backbone of how forward-thinking operations are running regulated deficit irrigation. With whole-block visibility, managers can target cuts precisely, protect quality, and turn water scarcity into a strategic advantage.

Meet the Author

Anubhav Sharma - Head of Marketing

Anubhav is a B2B product marketing leader with 10 years of experience building and leading product marketing and GTM teams at fast-growing tech start-ups.