Changes in land use/land cover, the intensity of agricultural lands management, and other activities within a basin area often result in water quality problems. Most of the time the pollutants are from nonpoint sources (NPS), which by their nature are diffuse. Centralized water treatment systems are often not economically feasible to mitigate such problems, nor are they environmentally desirable. In these situations, the role of forested stream buffers in NPS pollution assimilation becomes important. The main objectives of this paper are to present a method for assessing the extent of potential water quality improvements available through land management options and to identify the potential costs of reaching defined water quality objectives.
In this study, water quality and basin characteristics data from different basins of the Fish River basin, Baldwin County, Alabama, were used to develop a valuation model. This valuation model is based on the effectiveness of "contributing zones" identified and delineated using methods described by Basnyat and others (Environmental Management [1999] 23(4):539-549). The "contributing zone" delineation model suggests that depending on soil permeability, soil moisture, depth to water table, slope, and vegetation, buffer widths varying from 16 m to 104 m must be maintained to assimilate or detain more than 90% of the nitrate passing through the buffers. The economic model suggests the value of retiring lands (to create the buffers) varies from $0 to $3067 per ha, depending on the types of crops currently grown. The total value of retiring all areas identified by the contributing zone model is $1,125,639 for the study area. This land value will then form the basis for estimates of the costs of land management options for improving (or maintaining) water quality throughout the study area.