Representing management practices in GLEAM

Agricultural and forestry management practices may adversely affect surface and groundwater quality. The GLEAMS model was developed to assess management effects on edge-of-field and bottom-of-root-zone loadings of water, sediment, and chemicals. Management systems may affect one or more of the four model components : hydrology, erosion, pesticides, and plant nutrients. Each component is briefly described, and parameter sensitivity is discussed. The effects of changing management practices are soil and climate dependent, but generalized effects are presented. Effects of crop rotation, terracing, irrigation, and tillage practices on hydrologic response, and their impact on a erosion, pesticide fate, and plant nutrient losses are summarized in a table. Effects of timing and application methods for pesticides, inorganic fertilizer, and animal waste are also discussed.