USING STATISTICAL ANALYSES TO CHARACTERIZE EFFECTS OF POPULATION GROWTH ON WATER QUALITY

This study evaluates the effects of population growth on water quality in a mountain watershed using multivariate statistical techniques. Extensive development in Turkey Creek Basin (TCB), Jefferson County, Colorado, accommodates the need for residential living in the mountains near the Denver metropolitan area. Two large water quality datasets, collected by the US Geological Survey and the Colorado Geological Survey, are supplemented with irregular water sampling over the last thirty years and continued monitoring by the Colorado School of Mines research team. This collection of water quality data documents water chemistry evolution. The compilation of data into a relational database includes ~450 sampling sites in the 47 mi2 basin with ~15,000 results including field parameters, major ions, nutrients and trace elements. Hierarchical cluster analysis (HCA) using these chemical and physical properties objectively partitions the water-chemistry samples into hydrochemical facies with specific chemical characteristics.

The hydrochemical facies can be related to either natural background or anthropogenic influences based on those chemical characteristics. This technique demonstrates that the spatial and temporal variability in water chemistry occurring as population has increased over the last two decades is related to an anthropogenic hydrochemical facies. Possible anthropogenic sources related to development include transportation infrastructure, runoff from construction activities, commercial activities, agriculture, and individual home sources (i.e. septic tanks and leach fields). The chemical characteristics of the anthropogenic component may help identify the sources of the degradation in water quality.