Jemison, Roy; U.S. Forest Service, Southwestern Region, Albuquerque, NM (Arizona-Nevada Academy of Science, 2015-04-18)
      The USDA Forest Service Southwestern Region (FS) manages over 20.5 million acres of forests and grasslands in Arizona, New Mexico and the Texas and Oklahoma panhandles. Water is one of the most beneficial natural resources used on and off these lands by humans, animals and plants. Water on forest and grasslands generally comes from precipitation which arrives in the form of snow or rain, depending on the location and season. On the ground, water infiltrates, ponds, runs off or evaporates, depending on the surface and climatic conditions. In general, precipitation that falls on these lands is free of pollutants. As water moves across and through soils, rocks and other materials it can become polluted by the surfaces it comes in contact with and by materials added to it. Materials added to flowing water in small amounts over time may have little to no harmful effects on the quality of the water. In large amounts and or concentrated, it can be extremely harmful to the quality of the water and users of the water. Common impacts to water quality include increases in temperature, turbidity, nutrient levels and hazardous chemicals. Sources of pollutants on forests and grasslands can be natural and human introduced. Natural sources and causes of pollution can include soil erosion, wildlife waste, concentrations of naturally occurring materials, drought, and flooding. Human sources and causes of pollution can include runoff from roads, trails, tree harvest areas, recreation sites, sewage facilities, livestock, pesticide applications and fuel and chemical spills (USDA Forest Service 2000). A plethora of methods exist to minimize harmful impacts to water quality on forests and grasslands. In 1990, the FS Southwestern Region developed a core set of practices and procedures, that when properly implemented, can be effective at minimizing and mitigating harmful impacts to water quality. The practices and procedures are both administrative and physical, and are collectively referred to as Soil and Water Conservation Practices, also known as Best Management Practices (BMPs) (USDA Forest Service 1990). Even though these BMPs were designed by FS and state resource specialists in the Southwest, they often require adjustments to make them fit site-specific conditions. The BMPs used by the FS Southwestern Region are acknowledged as being effective control measures by the environment departments of the states (Arizona and New Mexico) in which they were developed, as documented in Memorandum of Understandings (MOUs) that exist between the FS and the states.