Beaver Lake is considered a primary watershed of concern in the state of Arkansas (fig. 1). As such, information is needed to assess water quality, especially nutrient enrichment, nutrient-algal relations, nutrient assimilation capacity, turbidity, and sediment issues within the system. A previously calibrated, two-dimensional, laterally averaged model of hydrodynamics and water quality (Galloway and Green, 2006) was used for the evaluation of changes in input nutrient and sediment concentrations on the water quality of the reservoir from April 2001 to April 2003. Nitrogen and phosphorus concentrations were increased and decreased and tested independently and simultaneously to examine the nutrient concentrations and algal response in the reservoir. Suspended-solids concentrations were increased and decreased to identify how solids, which can contribute to decreased water clarity, are distributed in the reservoir. These results can be used in the development of nutrient and turbidity criteria and standards for Beaver Lake, and the methods can be used as a prototype for the assessment of water-quality criteria in other reservoirs. The Beaver Lake model also was evaluated using a conservative tracer. A conservative tracer was applied at various locations in the reservoir model to observe the fate and transport and how the reservoir would react to the introduction of a conservative substance, or a worst-case spill scenario. In particular, tracer concentrations were evaluated at the locations of the four public water-supply intakes in Beaver Lake.