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Quality of a River - Water Quality
Dissolved oxygen: Consequences (pg 3 of 4)

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Many human activities can cause a harmful decline in dissolved oxygen levels. Manure spills from feedlots or routine runoff from farmland can vastly increase the biological oxygen demand (BOD) of a stream. This can result in "suffocation" of aquatic organisms and cause fish kills that may occur over a long stretch of a stream. Runoff from city streets and residential lawns, effluent of partially treated human sewage, and discharge of oxidizing industrial chemicals can also increase BOD in rivers and streams.

Human activities that add nutrients to the stream can greatly increase algal abundance. At night, algae no longer produce but only consume oxygen. Dissolved oxygen levels can dip during the night below life-sustaining thresholds.


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Introduction
Flow
Shape
Connections
Quality
Description
Temperature
Oxygen
Alkalinity
Nutrients
Sediment
Contaminants
Status
Life
Summary
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