Best management practices for dairy farms in the Pacific Northwest have focused on protecting surface water quality, by providing winter manure storage and preventing contaminated runoff

Since the 1940s, the widespread adoption of synthetic fertilizers has reduced the need for manure as a nutrient source in crop production. This has led to separation of crop and animal production, increased use of imported feeds, and a growth in animal numbers relative to land area on dairy and other livestock farms. A net flow of nutrients into areas with a concentration of dairies is now common (Lanyon, 1995).