A mature almond tree in full production uses roughly 1,200 millimeters of water over the growing season, which works out to about 47 inches or just over a meter of water from spring through fall. That figure represents the total crop evapotranspiration, meaning water consumed by the tree itself plus what evaporates from the soil surface around it. But the real answer gets more interesting when you consider that growers rarely apply the full amount, that not all almond varieties respond the same way to cutbacks, and that where and how the water arrives matters as much as the raw volume.
The Baseline Numbers
Research on fully irrigated almond orchards in Mediterranean climates puts seasonal water consumption at around 1,200 mm, with peak transpiration coefficients reaching just above 1.0 during midsummer, the period when trees are filling their kernels and using the most water.1Agricultural Water Management. Water use of irrigated almond trees when subjected to water deficits In southern Spain, where almond acreage has expanded rapidly, irrigation demand has been estimated as high as 7,000 cubic meters per hectare, a figure that aligns broadly with those 1,200 mm when you account for local climate and irrigation efficiency losses.2ISHS Acta Horticulturae. Assessment of canopy transpiration from temperature: application to almond orchards
Those numbers describe a full canopy in warm, dry conditions. A young orchard with small canopies and partial ground shading will use substantially less, sometimes half or less of the mature-tree figure, because much of the incoming solar energy hits bare soil rather than leaf surface. Soil type, wind exposure, humidity, and row spacing all shift the total. The 1,200 mm figure is best understood as a ceiling for a mature, healthy orchard in a hot, interior valley, not as a one-size-fits-all prescription.
When the Water Matters Most
Almond water demand is not spread evenly across the year. It builds through spring as the canopy leafs out, peaks during the hottest months of summer when kernel fill is underway, and drops once the hulls split and harvest approaches. This seasonal curve means growers face a choice about when to be generous with irrigation and when they can safely pull back.
Hull split, which happens in mid to late summer, turns out to be one window where cutting irrigation can save water without devastating yields. Regulated deficit irrigation during hull split reduces the volume applied while still allowing the crop to finish developing.3Agricultural Water Management. Variety specific irrigation of almonds during hull split, effects on yield and quality The rationale is that by this point the kernels are largely formed and the tree can tolerate moderate stress.
Post-harvest is trickier. Cutting water after the nuts are shaken off might seem harmless since the crop is already in, but the tree is simultaneously initiating the flower buds that become next year’s crop. Research tracking yield over multiple seasons found that one year of post-harvest water deprivation did not reduce the proportion of spurs that flowered or set fruit the following spring. But two successive years of cutbacks led to clear yield declines, with losses estimated at roughly 7.7 kilograms per tree for each unit of additional water stress beyond a critical threshold.4Tree Physiology. Effects of irrigation deprivation during the harvest period on yield determinants in mature almond trees The damage was cumulative: stressed trees grew fewer new shoots, and the fruiting wood they depend on gradually died off without being replaced. So skipping post-harvest irrigation one dry year is survivable, but making it a habit erodes the tree’s productive capacity.
What Happens When You Give Them Less
Because almonds are grown overwhelmingly in water-scarce regions, a huge amount of research has gone into figuring out how much water you can withhold before yields really suffer. The short version: almond trees are more responsive to deficit than many other tree crops, and modest cutbacks do not translate one-for-one into yield losses.
In a multi-year trial, trees irrigated at about two-thirds of the full amount still consumed 79 percent of maximum evapotranspiration, totaling roughly 900 mm over the season instead of 1,200 mm. Trees under severe deficit irrigation, receiving only about 40 percent of the control, still used nearly two-thirds of the water that fully irrigated trees did.1Agricultural Water Management. Water use of irrigated almond trees when subjected to water deficits The reason is that almonds partly compensate by pulling harder on whatever soil moisture is available and by slightly adjusting leaf behavior. But there is a clear physiological breakpoint. When internal stem water potential drops below about negative 1.1 megapascals, transpiration falls steeply, dropping to only 55 percent of the fully watered control in one study’s rain-fed treatment.5Scientia Horticulturae. Responses of transpiration and transpiration efficiency of almond trees to moderate water deficits
One finding that surprised researchers is that, unlike some other fruit and nut trees, almonds do not become more water-efficient under mild drought. In many species, a slight water deficit actually increases the ratio of carbon gained to water lost, a trait that would make deficit irrigation a clear win. Almonds, at least the cultivar tested, did not show that benefit.5Scientia Horticulturae. Responses of transpiration and transpiration efficiency of almond trees to moderate water deficits This means every unit of water withheld from an almond tree costs some production, and growers cannot rely on a biological free lunch where stressed trees make up for lost water with improved efficiency.
Variety and Rootstock Make a Real Difference
Not all almond trees respond to drought the same way. A field comparison of four varieties grown in Sardinia found considerable differences in how well each cultivar maintained photosynthesis, managed leaf water loss, and held onto yield under water stress. Two varieties, ‘Arrubia’ and ‘Texas,’ showed substantially greater physiological acclimation to drought and sustained higher yields than the self-fertile ‘Tuono.’ Leaf size, shoot architecture, and the hydraulic properties of the leaves all played a role.6PubMed Central. Almond Tree Adaptation to Water Stress: Differences in Physiological Performance and Yield Responses among Four Cultivar Grown in Mediterranean Environment The practical takeaway is that varietal selection is itself a water-saving strategy: choosing a drought-adapted cultivar can reduce the amount of irrigation needed to maintain a profitable yield.
Rootstocks offer another lever. Because most commercial almond trees are grafted, the root system belongs to a different species or hybrid, and that root system controls how well the tree extracts soil moisture under stress. Evaluation of seven peach-by-almond hybrid rootstocks under drought conditions identified ‘TT’ and the widely used ‘GF677’ as the most tolerant, maintaining photosynthetic function even when soil moisture was cut to 40 percent of capacity. Other rootstocks showed markedly worse performance under the same conditions.7PubMed Central. Assessment of drought tolerance in peach × almond hybrids to identify promising rootstocks In regions where water allocations are shrinking, pairing a drought-tolerant rootstock with a water-efficient scion variety could be the difference between a viable orchard and one that hemorrhages money in dry years.
Measuring Water Stress in the Real World
Knowing how much water an almond tree needs in theory is one thing. Figuring out whether your actual trees are getting enough is another, and growers have historically relied on a tool called a pressure chamber. You clip a leaf or shoot, seal it inside the chamber, and pressurize it until sap appears, which tells you the internal water tension the tree is experiencing at midday. This midday stem water potential reading is considered the single best indicator of crop water status in almonds.8Irrigation Science. Mapping almond stem water potential using machine learning and multispectral imagery The trouble is that it requires a person to walk into the orchard in the heat of the day, clip leaves, operate the chamber, and repeat the process across enough trees to get a representative picture. It is accurate but impractical at scale.
Remote sensing has started to fill that gap. Satellite-based evapotranspiration estimates using Landsat imagery have shown strong agreement with ground-level measurements in California almond orchards, with monthly accuracy within about 10 percent of observed values across multiple growing seasons.9Remote Sensing. Evapotranspiration Estimate over an Almond Orchard Using Landsat Satellite Observations More recently, the OpenET platform has brought this capability into a user-friendly format, offering daily evapotranspiration maps at 30-meter resolution. Evaluation across six almond sites and 148 additional orchards in California’s Central Valley found that the tool produced reasonable, actionable estimates of water use.10Agricultural and Forest Meteorology. A comparative analysis of OpenET for evaluating evapotranspiration in California almond orchards For growers managing hundreds or thousands of acres, the ability to see where individual blocks are over- or under-irrigated without stepping foot in the orchard is a genuine game-changer.
Machine learning is also being applied to predict stem water potential from drone-mounted multispectral cameras, potentially bridging the gap between the precision of a pressure chamber and the scale of satellite imagery.8Irrigation Science. Mapping almond stem water potential using machine learning and multispectral imagery These tools are still being refined, but the trajectory is clear: almond irrigation is moving from schedule-based (“apply X gallons every Y days”) to feedback-based, where the trees themselves signal when and how much water they need.
Water Quality Matters Too
Volume is only half the equation. Almonds are sensitive to salinity, and as growers increasingly turn to recycled or marginal water supplies, salt content becomes a limiting factor. Sodium is the biggest culprit. Controlled experiments with 14 different almond rootstocks showed that sodium-dominant salinity treatments caused the most severe reductions in survival and growth, with trunk diameter increasing by only about a third as much as under fresh water.11Scientific Reports. Linking diverse salinity responses of 14 almond rootstocks with physiological, biochemical, and genetic determinants Chloride added to the stress, though its effect was secondary to sodium.
Desalinated reclaimed water can be used successfully to irrigate almonds, which is encouraging for water-scarce regions looking for alternative supply. But combining reclaimed water with deficit irrigation is a bad idea. When trees were given both less water and saltier water simultaneously, the negative effects of each stress multiplied rather than simply adding up. Trees receiving the combination had the lowest photosynthetic rates, and the damage worsened the longer the exposure continued.12Agricultural Water Management. Physiological responses of almond trees under regulated deficit irrigation using saline and desalinated reclaimed water The practical rule: if you are irrigating with marginal-quality water, do not also try to save water by cutting volumes. Pick one stress or the other, not both.
The Per-Almond Water Footprint
Almonds have become a lightning rod in water-use debates, especially in California, where the industry accounts for a large share of agricultural irrigation. The numbers often quoted to make almonds sound profligate are real. Over the period from 2004 to 2015, the water footprint of California almonds averaged about 10,240 liters per kilogram of kernels, which works out to roughly 12 liters per individual almond.13Ecological Indicators. Water-indexed benefits and impacts of California almonds
Context matters, though. That same analysis found that the water footprint varied twofold across the production area, with orchards in the southern Central Valley producing almonds with the smallest footprint per kilogram. Year-to-year variation was also substantial, driven by differences in rainfall, temperature, and the proportion of young versus mature trees in the state’s total acreage. And while almonds had the largest aggregate water footprint of any California crop, they also had the highest direct economic returns from market sales.13Ecological Indicators. Water-indexed benefits and impacts of California almonds Whether that tradeoff is acceptable is ultimately a policy question, not an agronomic one. But framing almonds as uniquely wasteful overlooks the fact that water intensity per kilogram is a feature of all tree nut and many protein crops, and that the economic return per unit of water invested in almonds is competitive.
Climate Change and Rising Demand
Warmer temperatures mean more evaporation, and almond water needs are projected to creep upward. Modeling for Mediterranean almond-growing regions estimates that under moderate warming scenarios, annual crop evapotranspiration could increase by about 1 percent by mid-century, and by about 3 percent under more aggressive warming. Those are small percentages, but applied across the millions of hectares planted worldwide, they translate to substantial volumes of additional irrigation water, on the order of 260 million cubic meters per year for almonds alone in the modeled regions.14Agricultural Water Management. Water use dynamics of almond and pistachio crops in the Mediterranean region amid climate change
There is a partial offset: rising atmospheric carbon dioxide tends to make plants close their stomata slightly, reducing water loss per leaf. The same modeling suggests this effect could reduce almond irrigation demand by about 35 million cubic meters per year, a meaningful but modest countermeasure against the warming-driven increase.14Agricultural Water Management. Water use dynamics of almond and pistachio crops in the Mediterranean region amid climate change The net direction is still more water needed, not less.
How California Got Here
The enormous scale of almond irrigation in California did not happen overnight. Almonds were introduced to the state by Spanish colonists as low-input plantings around coastal missions, where rainfall alone sustained modest production. The real transformation came with the adoption of peach and plum rootstocks in the early twentieth century, which allowed the trees to thrive in the hotter, drier conditions of the Central Valley, and with the development of dependable irrigation infrastructure through state and federal water projects. Together, these shifts enabled high-input, high-return production, and the cultivar ‘Nonpareil’ came to dominate new plantings because it yielded well under those intensive conditions.15ISHS Acta Horticulturae. History of almond improvement in California: challenges and opportunities In other words, California’s almond industry was built on the assumption of abundant, cheap water. As that assumption erodes, the industry faces pressure to adapt through the tools discussed above: deficit irrigation strategies, drought-tolerant rootstocks, precision monitoring, and, in some cases, rethinking where new orchards get planted in the first place.