Hypolimnetic oxygenation 6. Improvement in fisheries, hydropower, and drought management with costs of installation and operation in Camanche Reservoir, California, United States

Abstract Horne AJ, Faisst WK. 2022. Hypolimnetic oxygenation 6. Improvement in fisheries, hydropower, and drought management with costs of installation and operation in Camanche Reservoir, California, United States. Lake Reserv Manage. 38:268–285. A hypolimnetic oxygenation system (HOS) was installed in Camanche Reservoir, California, in 1993 to eliminate hatchery fish kills caused by hydrogen sulfide in dam tailwaters. It operates from about June through October each year. Algae, nutrients, heavy metals, and turbidity also declined. Fall run Chinook salmon (Oncorhynchus tshawytscha) increased by 3550/yr or 265%. Threatened steelhead trout (O. mykiss), which spend more time in the river than Chinook, benefited more (625%). A 3 yr delay in elevated adult returns indicated that the HOS’s main effect was improved in-river water quality for juvenile fish, rather than better adult attraction flows. Using the California State economist’s value of $1172 for an adult Chinook to freshwater anglers, the increase due to HOS added $6.5 million/yr to California’s recreation. The in-reservoir coldwater fishery improved because dissolved oxygen in the hypolimnion increased from <1 mg/L to ∼5 mg/L. Oxygenation allowed summer operation of a 10.7 MW hydropower plant, making HOS carbon neutral. During droughts, improved water quality at lower reservoir levels reduced dependence on alternative supplies and supported full hatchery operation and in-river spawning. Oxygen addition ($0.64/kg) was much cheaper than nitrate addition ($104/kg). Averaged over 20 yr, HOS reduced phosphorus ($19.3/kg vs. alum addition at $16/kg) and ammonia/nitrate ($2/kg). Iron ($0.0005/kg) and manganese were reduced at lower cost than for conventional methods ($9/kg). Copper ($4441/kg) and zinc ($2169/kg) fell below chronic toxicity levels. Capital cost for HOS was $1.87 million in 1993 or $30,390/km2 ($1248/acre). Operation and management averaged $191,288/yr (1993–2000).