Like so many other eco-systems, rivers are feeling the pinch from human induced changes. Agricultural run-off, sprawling sub-urbs and other land-use changes, and under-treated municipal water. These four areas are the primary drivers of the declining health not only in the river itself, but in downstream estuaries fed by these watersheds.
Agricultural run-off is perhaps the most damaging to downstream habitat. The heavy load of nitrogen, phosphorous, and organics from fertilizers and manure make a nutrient rich matrix which proliferates the microbial community. When this reaches the ocean, and warm nutrient rich waters mix with the cooler ocean waters, algal blooms explode and quickly consume the nutrients. When they die-off and sink to the bottom, the aerobic decomposers consume nearly all of the oxygen, and creates the "dead-zones", characterized by the hypoxic condition. Since this also happens to be in the inshore and near estuaries, this is highly disruptive to juvenile marine organisms who use these areas for their protection and to grow quickly. Dead zones are now found on the West, East, and South coasts of the United States.
The National Corn Growers Association disputes the link between industrial fertilizers and these dead zones. See their white paper here. Suffice it to say, their findings are in error. A marine scientist has debunked that bunk, here.
This problem can be mitigated. The Black sea was once the world's largest dead zone. Following the rise in fertilizer prices and the fall of the Soviet Union with it's centrally planned economy, the agriculture industry around the Black Sea collapsed. This unwitting change eliminated the dead zone, and now a thriving fishing industry exists there, with some of it's own problems.
This is not an option that is entertaining here in North America. Other serious policy shifts which could meet this challenge is to increase the green belts along water courses. If these buffer zones are widened, and planted with dense rooting plants, the run-off can be reduced. This could be pursued in consort with smarter fertilization schemes, to eliminate this problem.
Untreated municipal waste is the emerging threat, and related to agricultural waste. Manures and waste effluent are inputting endocrine disruptors into the rivers. The Potomac, now shows that >80% of male small mouth bass and >20% for large mouth bass are carrying eggs in their testes. These are both significant popualtion changes, and are not limited to just one river, or one family of fish. Rivers along the west coast have been monitoring similar shifts in salmonids, and smaller fishes like minnows.
The endocrine disruptors have as of yet been unidentified. The current working hypothesis is that the hormones in animal feeds, human medications, and the synthetic oestrogens in plastics. This problem is harder to mitigate than fertilizer run-off. The hormones in human waste cannot be removed from the waste stream. The volume of water is too high through a municipal waste treatment plant.
The sprawling suburbs contribute to the problem through disrupting the filtration of surface run-off. Sprawl contributes to de-forestation which is replaced by impermeable concretes and pavements, and grasses which cannot filter as much water. Storm waters routinely overwhelm waste treatment facilities, with water polluted with grease, garbage and silt. When this happens, the run-off mixes with sewage and is dumped back into the same watershed, downstream. The water is usually warmer, and increases bacterial loading. The result is the same as the excess fertilizer: deteriorated eco-systems, and down stream dead zones.
This problem also has some smart policy changes which can help to tackle the issue. New developments should be low impact. This means preserving the natural systems which deal with drainage. If development builds right up to the watershed, this will reduce it's offsetting potential. Augmentation can be achieved by keeping large buffer zones with water absorbing plants, buildings with green rooftops, and porous pavements/surfaces. Other regulation could include updates to clean water legislation which includes limits to storm water, which would force municipalities to enforce run-off limits by using some of the policy changes listed above.
There are a number of smarter options out there. This short essay only scratches the surface.
Agricultural run-off is perhaps the most damaging to downstream habitat. The heavy load of nitrogen, phosphorous, and organics from fertilizers and manure make a nutrient rich matrix which proliferates the microbial community. When this reaches the ocean, and warm nutrient rich waters mix with the cooler ocean waters, algal blooms explode and quickly consume the nutrients. When they die-off and sink to the bottom, the aerobic decomposers consume nearly all of the oxygen, and creates the "dead-zones", characterized by the hypoxic condition. Since this also happens to be in the inshore and near estuaries, this is highly disruptive to juvenile marine organisms who use these areas for their protection and to grow quickly. Dead zones are now found on the West, East, and South coasts of the United States.
The National Corn Growers Association disputes the link between industrial fertilizers and these dead zones. See their white paper here. Suffice it to say, their findings are in error. A marine scientist has debunked that bunk, here.
This problem can be mitigated. The Black sea was once the world's largest dead zone. Following the rise in fertilizer prices and the fall of the Soviet Union with it's centrally planned economy, the agriculture industry around the Black Sea collapsed. This unwitting change eliminated the dead zone, and now a thriving fishing industry exists there, with some of it's own problems.
This is not an option that is entertaining here in North America. Other serious policy shifts which could meet this challenge is to increase the green belts along water courses. If these buffer zones are widened, and planted with dense rooting plants, the run-off can be reduced. This could be pursued in consort with smarter fertilization schemes, to eliminate this problem.
Untreated municipal waste is the emerging threat, and related to agricultural waste. Manures and waste effluent are inputting endocrine disruptors into the rivers. The Potomac, now shows that >80% of male small mouth bass and >20% for large mouth bass are carrying eggs in their testes. These are both significant popualtion changes, and are not limited to just one river, or one family of fish. Rivers along the west coast have been monitoring similar shifts in salmonids, and smaller fishes like minnows.
The endocrine disruptors have as of yet been unidentified. The current working hypothesis is that the hormones in animal feeds, human medications, and the synthetic oestrogens in plastics. This problem is harder to mitigate than fertilizer run-off. The hormones in human waste cannot be removed from the waste stream. The volume of water is too high through a municipal waste treatment plant.
The sprawling suburbs contribute to the problem through disrupting the filtration of surface run-off. Sprawl contributes to de-forestation which is replaced by impermeable concretes and pavements, and grasses which cannot filter as much water. Storm waters routinely overwhelm waste treatment facilities, with water polluted with grease, garbage and silt. When this happens, the run-off mixes with sewage and is dumped back into the same watershed, downstream. The water is usually warmer, and increases bacterial loading. The result is the same as the excess fertilizer: deteriorated eco-systems, and down stream dead zones.
This problem also has some smart policy changes which can help to tackle the issue. New developments should be low impact. This means preserving the natural systems which deal with drainage. If development builds right up to the watershed, this will reduce it's offsetting potential. Augmentation can be achieved by keeping large buffer zones with water absorbing plants, buildings with green rooftops, and porous pavements/surfaces. Other regulation could include updates to clean water legislation which includes limits to storm water, which would force municipalities to enforce run-off limits by using some of the policy changes listed above.
There are a number of smarter options out there. This short essay only scratches the surface.
