Ground-water conditions in the Eureka area, Calif., were evaluated during 1975 to determine whether significant changes had occurred since 1952, when an earlier reconnaissance was made. No major changes in water levels or water quality were noted at 1975 pumping rates. Recharge to the ground-water system compensates for both artificial and natural discharge. The position of the freshwater-saltwater transition zone underlying the alluvial flood plains in the summer of 1975 were unchanged from those in 1952. Ground water continues to be used principally for irrigation on the alluvial flood plains of the Eel and Mad Rivers. In 1975, about 425 irrigation wells supplied an estimated 24,000 acre-feet of ground water to the Eureka area; half of those wells were located on the Eel River flood plain. The estimated total ground-water pumpage for irrigation, industry, public supply, domestic use, and livestock was 27,500 acre-feet. During the irrigation season, there is a higher rate of recharge from the rivers which helps to maintain ground-water storage and stabilize the freshwater-seawater transition zone. (Woodard-USGS)
