Getting to Know Your Orchard’s Water Supply and Quality

Knowing Where Your Water Comes From

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 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

• Aging and inadequate storage and delivery system that cannot meet the state’s multi use 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.

Manage Your Water’s Salinity Levels

Almonds have a relatively low tolerance for saline conditions, so it is valuable to test for levels in your irrigation water; 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 is critical for continued almond production.

Long-term irrigation in arid climates often leads to build up of salts in the soil. The Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) is a coalition formed to manage salinity and nitrates that threaten farmland and water quality. 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

Growers in California are required to protect groundwater quality under the Irrigated Lands Regulatory Program.

Groundwater quality issues include nitrates, that primarily come from agriculture, salinity, which may be naturally occurring, pesticide leaching (primarily legacy issues) and issues such as arsenic and boron, which is primarily from natural sources.

Protect the Groundwater

The monitoring of groundwater in the Central Valley has detected a number of sites with elevated nitrate levels. Nitrate is a form of nitrogen that plants can take up; however, it also moves easily in water and therefore leeches into groundwater. Nitrates affect the ability to use groundwater for drinking, upon which may rural households and communities depend. 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 in the amounts that the crop demands, resulting in cost savings and 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.

Prevent Runoff From Irrigation or Rainwater

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.