Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

Ranching practices have led to increased soil erosion and sediment loads within adjacent
tributaries. The worst of these effects may have occurred in the late 1800s and early
1900s from deliberate burning to increase grass production (NRC 2004). Several
measures are currently in place to reduce the impacts of grazing. Measures include
restricted grazing in degraded areas, reduced grazing allotments, and lowered stocking
rates. Today, the agricultural industry impacts water quality within the basin.
Agriculture is second only to the large-scale influences of hydromodification projects
regarding power generation and irrigation. Water quality impacts from agricultural
activities include alteration of the natural temperature regime, insecticide and herbicide
contamination, and increased suspended sediments.
Roughly 6% of the annual flow from the Columbia River is diverted for the irrigation of
7.3 million acres of croplands within the basin. The vast majority of these agricultural
lands are located along the lower Columbia River, the Willamette, Yakima, Hood, and
Snake rivers, and the Columbia Plateau (Hinck, Schmitt et al. 2004).
Agriculture and ranching increased steadily within the Columbia River basin from the
mid- to late-1800s. By the early 1900s, agricultural opportunities began increasing at a
much more rapid pace with the creation of more irrigation canals and the passage of the
Reclamation Act of 1902 (NRC 2004). Today, agriculture represents the largest water
user within the basin (>90%).
The USGS has a number of fixed water quality sampling sites throughout various
tributaries of the Columbia River. Many of the water quality sampling sites have been in
place for decades. Water volumes, crop rotation patterns, croptype, and basin location
are some of the variables that influence the distribution and frequency of pesticides
within a tributary. Detection frequencies for a particular pesticide can vary widely. One
study conducted by the USGS between May 1999 and January 2000 in the surface waters
of Yakima Basin detected 25 pesticide compounds (Ebbert and Embry 2002). Atrazine
was the most widely detected herbicide and azinphos-methyl was the most widely
detected insecticide. Other detected compounds include simazine, terbacil, trifluralin;
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