Two state agencies have agreed to a compromise that will clear the way for construction of the last four of 11 giant water export pumps in the Sacramento-San Joaquin Delta. The agreement between the Departments of Water Resources and Fish and Game calls for agricultural interests in Southern California to pay up to $25 million over the next five years to mitigate the damage the pumps will cause to Delta fish. The money will be used to build fish screens and hatcheries and to increase water flow to aid the striped bass, salmon and steelhead populations. Environmentalists have fought construction because the pumps disrupt fish spawning habits and food supplies. The pumps, which eventually will be used to increase the state's capacity to move water to the south, are to be constructed in Clifton Court Forebay in Contra Costa County during the next five years at a cost of $46 million.