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<br /> <br />irrigated; the topography of the land; and the crop to <br />be grown. In the flat Central Valley. farmers produc- <br />ing row crops grown in slow-draining soils tradition- <br />ally have used flood or furrow irrigation. Sprinklers <br />or drip irrigation systems typically are chosen for hilly <br />coastal areas where soils tend to be more porous. <br /> <br />Most farmers in California use non-pressurized sur- <br />face irrigation techniques such as border or furrow <br />irrigation. A common furrow irrigation practice diverts <br />water from a head ditch running across the upper <br />end of the field into furrows running the length of the <br />field. Furrow irrigation systems are inexpensive. well <br />understood by farmers and can be efficient, but critics <br />say they are prone to overwatering if not properly <br />designed and managed. Laser field leveling can <br />improve the efficiency of furrow systems, which are <br />commonly used in the flat Central Valley. <br /> <br />Pressurized systems such as surface drip irrigation <br />or sprinklers, though more costly to install and oper- <br />ate than furrow techniques, apply water more slowly <br />and accurately, giving growers more flexibility to <br />apply the amount of water needed tor optimal plant <br />growth. Properly managed, sprinkler and drip sys- <br />tems also result in less surface runoff on fields with <br />compacted soils where water permeates more slowly <br />than in porous soils. Surface drip irrigation systems <br />have become increasingly popular, especially for <br />perennial commodities such as grapes, but are not <br />suitable for some annual field crops such as grains. <br /> <br />Sub-surface drip irrigation systems deliver water di- <br />rectly to the root zone with almost no surface evapo- <br />ration loss. However, these systems are expensive <br />to install and may not be suitable for all crops. <br /> <br />Regardless which irrigation system is used, experts <br />sayan irrigation management program is the single <br />most effective step to ensure that water is used <br /> <br />!!!i' <br /> <br />efficiently. The best irrigation hardware is <br />only as efficient as the management <br />program that runs it. Installing and using a <br />drip irrigation system or sprinklers may <br />seem like a water efficient step, but it can <br />be less efficient than the furrow irrigation <br />system it replaces if the farmer does not <br />know how to manage the new system <br />effectively. By matching irrigation rates and timing <br />to plant needs, farmers can maximize efficient use <br />of water by their crops and prevent overwatering. <br />Evapotranspiration data from CIMIS or other sources <br />in tandem with soil-moisture monitoring are critical <br />to any irrigation management program. <br /> <br />Ihere are Three common <br />irrigatiolll1/l'Thods used in <br />Ca/(lon/ia: furrmr orjlood <br />(fop). sprinklers. and drip <br />(!J01l011l). <br /> <br />Irrigation management can be frustrated by irregu- <br />lar water delivery schedules, excessive heat and <br />even rainfall. Unlike their urban counterparts, farm- <br />ers dependent on surface water do not always <br />receive water on demand from suppliers. In times <br />of peak water demand or reduced allocations, <br />disruptions in water deliveries can upset farmers' <br />irrigation management schedules and induce them <br />to overwater in attempts to compensate for reduced <br />or missed deliveries. For this reason the AS 3616 <br />MOU and CVPIA criteria include increasing system <br />flexibility as an EWMP Farmers with access to <br />groundwater can better endure these kinds of dis- <br />ruptions, but those without groundwater may change <br />their irrigation management programs to preserve <br />their crop investments. <br /> <br />Where farmers use groundwater for irrigation, as <br />they do in Monterey County, efficient irrigation prac- <br />tices can have payoffs. The Monterey County Water <br />Resources Agency. for instance, requires farmers in <br />the Salinas Valley to file annual water conservation <br />plans with the agency, and recommends practices <br />such as reduced sprinkler spacing and oft-wind <br />irrigation to improve water distribution uniformity. <br /> <br />11 <br />