INFLUENCE OF LAND USE CHANGE ON RESERVOIR SEDIMENTATION: A COMPARATIVE STUDY

Between 1960 and 2004, the population surrounding Beaver Reservoir in northwest Arkansas grew from approximately 92,000 to an estimated 395,000 (sustained average annual growth of approximately 4.0%). Rapid population growth and associated land clearing activities during this interval increased potential sedimentation pressure on Beaver Reservoir (the principal drinking water supply for northwest Arkansas) through hydrologic modification (e.g. increased impervious area runoff, sediment flux from construction sites, water treatment discharges, storm water runoff, etc.). A comparative analysis of lacustrine sedimentation in three arms of Beaver Reservoir draining three sub-watersheds with differing quantities and trajectories of land use change provides insight into the influence of different land use change processes on reservoir sedimentation. A pristine sub-watershed draining the Hobbs Wildlife Management Area within the Ozark National Forest serves as a control site to determine background sedimentation to Beaver Reservoir. Two additional sub-watersheds drain largely suburban residential and industrial/agricultural upland areas adjacent to Beaver Reservoir. Observed sediment volume in each arm of Beaver Reservoir will be compared to sedimentation predicted by two widely accepted erosion models, the Revised Universal Soil Loss Equation (RUSLE) and the Watershed Erosion Potential Project (WEPP) model. The utility of commonly-used erosion models is evaluated against empirical data documenting long-term (40-year) response of each watershed to potential sediment-producing activities within each sub-watershed. Such analyses are useful in developing clearer understanding of influences of land use change on surface water quality.