Effectiveness of electrical fish barriers associated with the Central Arizona Project

The Central Arizona Project (CAP) canal delivers Colorado River water into the Gila River basin. During its planning and construction, issues arose regarding the unwanted entrainment and transport of nonindigenous fishes and other aquatic biota into, through, and out of the canal. One control strategy was the emplacement of electrical fish barriers on two CAP distributary canals to prevent fishes from moving upstream into the Gila River drainage. The operation, maintenance, and effectiveness of these barriers are described for the period 1988-2000. Documented outages totaled more than 100 h, representing less than 0.001% downtime since installation. It is nearly certain that outages allowed immigration by undesired fish(es). Immigrations that occurred when the barriers were operating according to design criteria indicate that the barriers do not totally block the passage of upstream-migrating fish. The proximate sources of electrical barrier outage included component damage from lightning strikes, component breakdowns, failure to adhere to component maintenance and replacement schedules, failure to incorporate adequate protection and redundancies to certain system components, inadequate training of personnel, and unknown causes. Known outages of remote monitoring systems (which are necessary to document outages and understand the potential for undocumented barrier outages) totaled more than 400 d, representing about 3% of the period of barrier operations. The complexity of electrical barrier systems and the problems such intricacy creates for operation and monitoring may always preclude absolute effectiveness. Additional refinements to system components, personnel training, and operation procedures may reduce barrier failures but add further to that complexity. Management agencies will have to determine the cost-effectiveness of such refinements.