ABSTRACT:Increasing block‐rate prices for irrigation water were implemented during 1989 in a 10,000‐acre irrigation district in California's San Joaquin Valley. The program motivated improvements in irrigation practices that reduced the volume of water delivered to farm fields and the volume of drain water collected in on‐farm drainage systems. The ratio of net crop water requirements to field deliveries increased from 0.65 in 1988 to 0.73 in 1989. The volume of drain water collected at a subset of 20 drainage systems was reduced by 351.1 acre‐feet (11.5 percent). Estimated loads of salt, boron, and selenium were reduced by 2,407 tons (11.0 percent), 3.33 tons (11.0 percent), and 0.07 tons (9.2 p
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