This study was conducted to ascertain the possibility of applying n ural networks to environmental engineering problems. Eutrophication of Lake TenkilLer (Oklahoma) due to inflow of phosphorus from various point and non-point sources was selected for this case study. The phosphorus sources are distributed across Oklahoma and Arkansas and are transported to the Lake by the Illinois River. This study attempts to determine the contribution of point and non-point sources to the eutrophication of the Lake and reductions in nutrient inflow required for remediation of the Lake. Further, results obtained are compared with results from similar studies carried out using different methodologies.