Hydrologic analysis indicated that surface runoff from manure accumulated in dairy areas would not occur very frequently in southern California. This was verified by a field test using simulated rainfall. Hydrologic data collected in this experiment were used to establish the runoff-rainfall relationship for the Chino-Corona dairy preserve. Though the amount of runoff may not be large, the high mineral and organic carbon contents of manured runoff is detrimental to the water quality of receiving streams. The high salinity and low nutrient content would make its possible beneficial use on cropland seem doubtful. In wet years, the disposal of salt-laden wastewater could become a problem. Holding ponds and retention structures for surface runoff merely prevent it temporarily from entering the receiving water.