Almond trees are a high-value, water-intensive crop, and precise water management is necessary for maximum yield and long-term sustainability. The amount of water they require is dynamic, influenced by biological and environmental factors. Determining the correct volume is a complex calculation that balances the tree’s physiological needs against available resources. Effective management ensures the trees receive the right volume of water exactly when needed.
Calculating the Base Water Requirement
The industry standard for measuring the water an almond orchard needs is a metric called Evapotranspiration, or ETc. This measurement accounts for two types of water loss: evaporation from the soil surface and transpiration, which is the water vapor released by the trees through their leaves. Evapotranspiration is calculated by multiplying the reference evapotranspiration (ETo)—the water loss from a standardized reference crop like grass—by a crop coefficient (Kc). The Kc accounts for the specific water needs of almond trees at a given stage.
Mature, high-yielding almond orchards typically require between 40 and 58 inches of water annually to maximize production. This volume is often expressed in acre-feet for large-scale agricultural use. An acre-foot is the volume of water needed to cover one acre of land to a depth of one foot, equivalent to approximately 325,851 gallons.
On average, a mature almond orchard requires about 3 to 4 acre-feet of water per acre per year. This high demand stems from the tree’s physiology, as developing the nut and its shell requires sustained water uptake throughout the long growing season. Consistent water application is necessary because almond trees are cultivated in hot, dry regions, leading to high rates of water loss.
Critical Irrigation Periods by Tree Stage
Water needs fluctuate significantly throughout the almond tree’s annual cycle, making irrigation timing as important as the total volume applied. The tree’s susceptibility to water stress varies dramatically, which dictates application scheduling.
During the winter dormancy period, water requirement is lowest, but a certain level of soil moisture is still necessary. This early-season moisture is important for root health and prepares the tree for upcoming growth stages. Insufficient soil moisture early in the season can hinder growth and reduce the potential crop.
The spring months, from bud break through the early fruit set, are considered highly sensitive to water stress. During this time, the tree is undergoing rapid vegetative growth to develop the canopy and set the fruiting positions for the following season. Water deficits in this period can reduce shoot growth and leaf area, negatively impacting future productivity.
The highest water demand occurs during the nut fill and hull split stages in summer, as the kernels rapidly expand in size and weight. Water stress during this time severely impacts the final quality and size of the nut. However, the two months leading up to the hull split offer a brief window for strategic reduction in irrigation, known as deficit irrigation. This practice encourages hull splitting and reduces hull rot incidence without significantly affecting kernel weight.
Post-harvest irrigation is necessary, especially in orchards using low-volume drip systems. This application helps the tree restore energy reserves and promotes the formation of flower buds for the next season’s crop. Insufficient water immediately after harvest is directly linked to a reduction in blossoms and fruit set the following year.
Factors That Modify Water Consumption
While the base water requirement uses Evapotranspiration, several external factors modify the actual amount of water an orchard consumes. The prevailing climate is a primary variable, as hot and windy weather increases the rate of water loss from the soil and the tree. Areas experiencing high temperatures and low humidity require a greater water allocation than those in more moderate environments.
The type of soil in the orchard significantly impacts how often and how much water must be applied. Sandy soils drain quickly and have a low water-holding capacity, necessitating more frequent, lighter irrigation events. Conversely, clay-rich soils hold moisture for longer periods, allowing for less frequent but deeper watering.
The age and density of the trees also affect the overall consumption rate. Young trees require less water than mature trees, and high-density orchards with a larger canopy area naturally have a higher collective water demand. Furthermore, the efficiency of the irrigation system determines how much water is wasted before reaching the root zone. Drip irrigation is highly efficient, delivering water directly to the roots, which saves significant water compared to traditional flood irrigation methods.