Agricultural Effects on Streams and Rivers: A Western USA Focus

Globally, croplands and rangelands are major land uses and they have altered lands and waters for millennia. This continues to be the case throughout the USA, despite substantial improvements in treating wastewaters from point sources-versus non-point (diffuse) sources. Poor macroinvertebrate assemblage condition occurs in 30% of conterminous USA streams and rivers; poor fish assemblage condition occurs in 26%. The risk of poor fish assemblage condition was most strongly associated with excess nutrients, salinity and sedimentation and impaired riparian woody vegetation. Although the Clean Water Act was passed to restore and maintain the integrity of USA waters, that will be impossible without controlling agricultural pollution. Likewise, the Federal Land Policy and Management Act was enacted to protect the natural condition of public lands and waters, including fish habitat, but it has failed to curtail the sacred cows of livestock grazing. Although progress has been slow and spotty, promising results have been obtained from basin and watershed planning and riparian zone protections.

Automated summary

Croplands and rangelands have altered lands and waters for millennia globally, with 30% of USA streams and rivers showing poor macroinvertebrate condition and 26% showing poor fish condition. Excess nutrients, salinity, sedimentation, and impaired riparian vegetation are the main causes. Despite efforts under the Clean Water Act and Federal Land Policy, controlling agricultural pollution and livestock grazing is essential for restoring and maintaining water quality and natural conditions. Promising results have been seen from basin and watershed planning as well as riparian zone protections.