Water quality monitoring by the City of Dallas, Texas (US) and the Institute of Applied Science, University of North Texas, has recently shown elevated atrazine concentrations in the watershed of a large drinking water reservoir in the Dallas-Fort Worth metropolitan area serving over 3,000,000 people. Atrazine is under investigation by numerous researchers as an environmental estrogen that may be involved in increasing breast cancer incidence in humans and impacting health and reproductive systems in wildlife. Since treatment technologies for atrazine removal from finished drinking water can be expensive and provide no protection to aquatic ecosystem health, watershed managers are currently seeking proactive methods to reduce the amount of atrazine entering water supply systems.

The most viable approach for reducing atrazine in a drinking water reservoir begins with understanding the distribution and extent of landuse in the watershed where atrazine may be applied. Understanding the spatial distribution of areas potentially contributing atrazine runoff facilitates developing an effective atrazine reduction program of the best management practices that are appropriate to a particular region. Using remotely sensed satellite imagery and geographic information system modeling, an analysis of the spatial distribution of landuse, soil erodibility, and surface slope information in a large watershed in north central Texas was conducted. An ‘atrazine pollution potential’ model was developed and applied to over 224,000 hectares draining into Lake Lewisville which provides drinking water to Dallas and surrounding communities. Model results compared well with in situ water quality measurements of atrazine, and point to areas most in need of best management practice implementation.

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