Irrigation Overview

Water – The Lifeblood of Almonds

One of the continuing challenges to almond production is the availability of water to optimize tree health and crop production. California's Central Valley, where California Almonds are grown, is characterized by a Mediterranean climate — cool, wet winters and warm, dry summers — which is ideal for almond growth as long as the almond trees have access to adequate water.

Limited water supplies — with or without drought — are a reality in California. The Almond Board of California has invested heavily in the area of irrigation strategies and technologies that conserve water while optimizing production and tree health, as well as in ways to protect ground-and surface-water from potential runoff or leaching of grower inputs.

Irrigation Management

Optimum Use of a Limited Resource

The Almond Board of California has supported University of California research on irrigation scheduling and management for over 25 years to determine the optimal use of irrigation water to enhance yields and quality, extend orchard longevity, suppress diseases and insects, reduce energy consumption, and increase the overall sustainability of the California Almond industry.

Ensuring that almond trees are neither over- nor under-watered requires constant monitoring of a number of variables. The timing, frequency and amount of irrigation will depend on several factors, including weather conditions, the amount of water stored in the soil from winter rains, fruit development stage, orchard maturity, orchard-specific soil type(s), water quality, and the irrigation system type and efficiency.

Comprehensive scheduling should be keyed to three factors: 1) weather conditions driving evapotranspiration (ET) and use of a water budget approach with data provided by the California Department of Water Resources’ CIMIS program, 2) soil-based monitoring, which can use a variety of techniques and equipment, and 3) monitoring tree water status using a pressure chamber (pressure bomb).

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Irrigation and Drought Strategies

Almond growers can now go to a UC Division of Agriculture and Natural Resources website to access an extensive compilation of drought-related water management and irrigation strategies developed by UC researchers, farm advisors and Extension specialists.

Good overall summaries of strategies under different water availability scenarios can be found at the UC Drought Management website. The Irrigation Management module of the California Almond Sustainability Program (CASP) contains a broad array of information on setting up and managing an irrigation system in almond orchards. More information can be found in the following California Almond Outlook and Western Farm Press articles available here.

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Managed Deficit Irrigation

Trees can tolerate moderate drought stress during hullsplit, a two-week period prior to harvest, without risk of crop loss or long-term yield effects. Moderate water stress at this time provides three additional benefits: 1) lower potential for hull rot; 2) a more uniform hullsplit, leading to an earlier harvest, when crop damage from rainfall is less likely; and 3) an earlier harvest, all of which can help minimize crop exposure to late-season navel orangeworm flights and potential aflatoxin contamination.

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Water Supply

Water Sources and Infrastructure

California’s Mediterranean climate is conducive to producing high-yielding, high-quality almond crops year-in and year-out. While these ideal growing conditions form the backdrop for the state’s almond-growing productivity, it is our ability to store and distribute water for irrigation during the dry growing season that is the key to this success.

With rain and snow falling almost exclusively in the winter and early spring and mostly in the northern part of the state, Californians rely on an intricate system of dams that create reservoirs for storage, and canals to distribute stored water as needed to irrigate crops, as well as support health and human services, industry, recreation and environmental concerns. The snowpack in the Sierra Nevada mountains acts as an additional water storage device, recharging rivers, reservoirs and groundwater supplies as it slowly melts during the dry months. Underground aquifers, sustained by that same Sierra snowpack, provide an additional source of water that is tapped by wells for irrigation and other uses.

Several issues affect the state’s water supplies:

  • Sustained population growth throughout California
  • Lower-than-average rainfall and a thin snowpack in recent years that have reduced the amount of water in storage, both aboveground and underground
  • An aging and inadequate storage and delivery system that cannot meet the state’s multiuse water needs
  • The failing of the infrastructure of the Sacramento–San Joaquin River Delta, the “crossroads” of the state’s water delivery system
  • Legal and environmental issues, such as the protection of endangered species, that require Delta pumps to be shut down during critical periods of water delivery.

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Water Quality

Almond growers rely on good water quality to ensure both a healthy tree and a healthful crop. Growers also need to protect surface- and groundwater from runoff, spray drift and/or leaching by following good management practices.

Salinity

Almonds have a relatively low tolerance for saline conditions; however, the nature of irrigated agriculture is that salts carried in the irrigation water are added to the soils and accumulate there. Different water sources carry different levels of salts. For example, groundwater on the West Side of the San Joaquin Valley is generally naturally high in salts, while surface water from snowmelt is very low in salts. Depending on the sources of water available to the grower, a part of irrigation management is to ensure enough good-quality water is applied to leach salts below the root zone. Minimizing the addition of salt to the soil and removing salts by leaching are critical for continued almond production.

There is an inherent conflict between the goals of maintaining groundwater quality while maintaining a productive irrigated agriculture. These issues are being addressed by the Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS). CV-SALTS members include entities involved with water management, irrigation districts and some growers, as well as the Central Valley Regional Water Quality Control Board.

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Groundwater Protection

Growers in California have recently been tasked with protecting groundwater quality under the Irrigated Lands Regulatory Program.

Groundwater quality issues include nitrates that primarily come from agriculture, salinity that is often naturally occurring, a few pesticide issues (primarily legacy issues) and issues such as arsenic, which is primarily from natural sources.

Monitoring of groundwater in the Central Valley has detected a number of sites with elevated nitrate levels. Nitrates affect the ability to use the water for drinking. Nitrate is a form of nitrogen that plants can take up as one of their nutrients; however, it also moves easily in water and therefore leaches easily into groundwater. The Central Valley Regional Water Quality Control Board, under the Irrigated Lands Regulatory Program, has developed a Groundwater Quality Protection Strategy that addresses the issue of nitrates and other contaminants in groundwater. With some care, growers can minimize — but not necessarily eliminate — nitrate leaching from their fertilization practices.

The nitrogen budget calculator at the California Almond Sustainability Program website is a tool that growers can use to more precisely apply nitrogen to orchards in the amounts that the crop demands, resulting in less potential nitrogen leaching into groundwater.

In some instances, pesticides have shown up in groundwater. Currently, California’s Department of Pesticide Regulation (CDPR) limits the use of pesticides that have the potential to leach in areas where the groundwater is more vulnerable; these are called Ground Water Protection Areas (GWPA). In addition, CDPR monitors for pesticides that could possibly leach, based on their chemical characteristics.


Preventing Irrigation and Storm Water Runoff

A comprehensive surface water–quality regulation for agriculture in the Central Valley of California was passed in 2003 by the Central Valley Regional Water Quality Control Board. Through participation in the Irrigated Lands Regulatory Program watershed coalitions throughout the San Joaquin Valley, almond growers are meeting their legal requirements under the Clean Water Act to protect water quality. The coalitions also help almond growers take steps to reduce potential levels of farm waste in irrigation drainage or rainwater runoff.

Monitoring and ultimately reducing discharges of pesticides, nutrients and sediments into waterways and groundwater is the goal of almond growers in California’s Central Valley. To help them meet that goal, the Almond Board of California funds research on ways to control runoff from orchards and prevent it from contaminating surface and groundwater.

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Water Glossary

Confused by the terminology used in water management issues?

Click here, this Water Glossary will help.