Using Geographic Information System (GIS) to Model Total Phosphorous (TP) and Total Nitrogen (TN) Levels in Andover Lake, Connecticut, Based on Land-use Patterns. abstract by Walter Tokarz.
This study models watershed-derived nutrient loads for Andover Lake using estimates of the area of distinct land-use categories within the watershed. This approach is used to estimate expected total phosphorous (eTP) and expected total nitrogen (eTN) for the lake. Because these nutrients are associated with eutrophication, land-use changes in the watershed potentially affect the trophic status of the lake and resulting water quality. By modeling land-use, it is possible to predict the affects of future development on the water quality in Andover Lake. This study uses a Geographic Information Systems (GIS) to define the Andover Lake drainage basin area, to isolate sub-basins areas, and to identify land-use proportions within each sub-basin. Following the approach of Field et al. (1996), this study estimates springtime eTP and eTN values for current land-use conditions of 15.3 ppb and 380.6 ppb respectively. The eTP value is similar to measured springtime TP in the water column, however, eTN is higher than most measured sources entering the lake. Modeled eTP and eTN values are calculated for 3 growth scenarios, which capture possible future land-use changes within the Andover Lake watershed. Results of these analyses suggest that land-use changes may be less important to the immediate health of the lake than are other nutrient sources, such as faulty septic systems or remobilized nutrients from lake bottom sediments. An important area of future study is the consideration of wave mixing as a contributing factor in lake nutrient loading.