Opinion ID: 411109
Heading Depth: 3
Heading Rank: 2

Heading: Dissolved Minerals and Nutrients

Text: 8 If dissolved oxygen is totally depleted from the hypolimnion, a further problem develops. A number of minerals and plant nutrients, insoluble under normal aerobic conditions, are soluble in zero-oxygen anaerobic water. These compounds--including iron, manganese, and phosphates--therefore tend to be leached from bottom muds into the reservoir. High concentrations of these minerals and nutrients, released into the downstream river, can harm fish, make the water unpalatable for drinking, and foster undesirable plant growth. 10 9 As for low-dissolved oxygen problems generally, whether mineral leaching will occur depends on a number of factors, including reservoir size, water temperature, and the quality of upstream water. In addition, mineral leaching depends on the amount of leachable matter in the reservoir bottom, which in turn depends partly on how old the reservoir is (for an older reservoir, most leachable minerals may have already been leached). 11 10 Control of mineral leaching primarily involves destratifying or mechanically aerating the reservoir to prevent the hypolimnion from becoming totally depleted, or else discharging water from the epilimnion. When building a new dam, site preparation (e.g., removing organic soils) can reduce future leaching. Once again, the record reveals neither the number of dams for which mineral leaching is a significant problem nor the cost of cure.