Gravel is mined from Northern California rivers for such purposes as concrete, asphalt, road base and sub-base, and drain rock. Gravel mining is done by extracting gravel beds in the river with tractors and other large industrial machinery and equipment. Gravel mining is a highly destructive practice. It destroys habitat for endangered salmonids and other aquatic life by destroying the cobble beds used for migratory fish to lay their eggs. Resulting activities from gravel mining include excessive sedimentation, which further degrades fish habitat and impedes a river’s ability to purify its water. A technique called skimming is often used to remove 75% of the vegetation needed for aquatic life’s food sources. Gravel mining creates a wide, shallow, flat and exposed streambed which can destroy the refuge from predators for which migratory fish depend.
Gravel mining is of particular concern to water quality and drinking water. By removing large volumes of filtering gravel from a riverbed, the natural ability of a river to purify drinking water is expended. At risk of contamination are underground aquifers as well as public and private wells located within areas where excessive gravel mining takes place.
Below are informative articles and links providing details of the destruction from gravel mining.
Independent Experts Warn of Hazards of In-Stream Gravel Mining
By Scott Vouri / North Bay Progressive / April 4-17, 2002
Gravel Mining in Rivers
By G. Mathias Kondolf, PhD, Associate Chair of Environmental Planning and Geography
Sand and Gravel Operations
From the Pacific States Marine Fisheries Commission
According to the EPA agriculture is the biggest polluter of America’s rivers and streams, accounting for 70% of water pollution. More than 173,000 miles of waterways have been polluted with chemicals, erosion, and animal waste run-off from agriculture.
Industrial agriculture in Northern California has serious effects on water quality and quantity. Industrial agriculture uses toxic pesticides and consumes more water than any other activity.
In Northern California one of the biggest agricultural polluters are vineyards. Most vineyards are planted on former forest lands. Converting forests to vineyards has serious environmental impacts. When forestland is clear-cut to create a vineyard there is complete and permanent removal of vegetation, which results in the fragmentation of the forest ecosystem and its inhabitants. Excessive runoff leads to increases in the amount of sediment delivered to nearby rivers and streams.
Large amounts of pesticides, herbicides, fungicides, fumigants and chemical fertilizers used by vineyards to kill pests expose all species that depend on rivers for water to dangerous poisons. Commonly used chemicals such as Roundup are particularly dangerous because of their ability to bind to soil particles. These particles, when washed into streams can disrupt the biological processes of fish and other riparian organisms.
Retention dams are used to collect rainwater to be used in the vineyards but they decrease the amount of fresh water to go into the river and decrease river flow. These reservoirs then have to be refilled by over-pumping of wells, which leads to depletion of aquifers and impairs nearby wells.
There are alternative methods of agriculture that could improve the quality and the quantity of water. Small-scale, organic methods of agriculture are emerging rapidly, utilizing sustainable alternatives to the industrial models of the past and incorporating environmental best management practices.
Clean Farms, Clean Water – California Sport Fishing Protection Alliance
Californians for Pesticide Reform