Three-fourths of California's developed surface water is used by agriculture. Because farming is a water- intensive industry, farmers have felt their supplies squeezed in recent years by declining water allocations brought on by drought, growing competition from urban users, concerns about ground water over pumping, and increasing water demands for fish and wildlife.
Rainfall in California rarely occurs during the peak growing season in the areas of heaviest cultivation, so farmers rely almost entirely on artificial "rainfall," or irrigation water. Thus, a farmer's ability to manage water use without reducing crop yield becomes not only a hedge against water-supply fluctuations but also a way to cut overall production costs and ensure long-term economic viability.
As the single largest water-consuming industry, agriculture has become a focal point for efforts to promote water conservation. This became especially true in the late 1980s and early 1990s as the drought reduced surface water supplies and federal laws required more instream flows for the environment. In those few years, water conservation took on added importance for farmers. Indeed, the number of state, federal and local programs devoted to increasing the efficiency of water use in agriculture has multiplied.
One collaborative federal-state- local program is a fleet of mobile laboratories that have provided more than 2,500 on-site irrigation evaluations to California farmers since 1982. Originally supported by funding from the state and about 60 water agencies and resource conservation districts, as well as in-kind services from the U.S. Department of Agriculture, the mobile labs assess individual farmers' irrigation systems and practices and recommend ways to improve efficiency. "As a result of the mobile lab field test, I was able to see that with a little inexpensive maintenance, we could make better use of our water, get it where we need it, and improve the field efficiency of our pumping engine," said one grower after seeing the mobile lab in action.
Discussions about agricultural water use often become polarized. Environmentalists cite practices such as flood or furrow irrigation, in which entire fields or furrows are covered with water that is allowed to soak gradually into the soil, as evidence of inefficient- use. Critics also contend that farmers could use less water if they changed cropping patterns to grow higher-value, less water-intensive crops, retired marginal lands, and adopted "sustainable" farming methods.
One 1995 study released by the Pacific Institute suggested that irrigation water used in California agriculture could be reduced by 3.5 million acre-feet by 2020 if farmers shifted from growing water-intensive- , low-value crops such as alfalfa, cotton and rice, to growing crops that have higher market value, such as almonds, grapes, artichokes and olives, and used water efficient irrigation technologies. The Pacific Institute said its recommendations could raise farm income, cut surface water and ground water use, and reduce agricultural drainage problems.
But farmers counter that the real issue is not the type of irrigation used or crop choices, it is the efficient management of irrigation systems. If managed properly, they say, the flood and furrow irrigation techniques in use in many areas are efficient. As far as crops, farmers say crop choice is - and should continue to be - determined by the market forces of supply and demand, and not be mandated by water use.
Most of the state's soil drains well, so irrigation water that is not used by crops washes harmful salts from the soil and replenishes ground water. Tall water runoff, the water that drains from an irrigated field, typically is reused by farmers on another field or sometimes to preserve wetlands. However, some areas, primarily on the west side of the San Joaquin Valley, have poor drainage, and excess irrigation water contributes salts to shallow ground water.
There has been a protracted debate over
whether this land should continue to be farmed. Critics say much
of the poor-draining crop land should be retired from production,
but farmers are employing sophisticated irrigation management
techniques that reduce the amount of water used, reducing
the volume of salty drainage outflow or contributions to
the shallow ground water table. New irrigation technologies
such as subsurface drip systems and more precise sprinkler
controls for pre-irrigation also have helped growers in areas
with poor drain- age to improve their water management practices. In
areas with porous soils, where water moves too quickly through
the soil, growers are experimenting with synthetic polymers
that help hold moisture in the soil, making it available
longer for absorption by plants.