INTRODUCTION

The New Croton Reservoir in southeastern New York is directly north of New York City and provides about 10 percent of the city’s water supply. The 374-mi² Croton River basin above the reservoir (fig. 1) is predominantly (69 percent) forested; about 14 percent is developed, and 17 percent is forest, wetland or water. The forested land in the watersheds of several streams that feed the reservoir is undergoing rapid development; therefore, concern has arisen as to whether pesticides used in these areas are entering these streams (Phillips and Bode, 2002).

Past research on pesticides in surface waters of New York State has generally focused on streams that drain agricultural lands (Phillips and others, 1998; 1999; 2000; Eckhardt and Burke, 1999), but pesticides are also are used in a variety of settings in developed areas, such as on turfgrass, lawns and gardens, and golf courses; in buildings and parking lots; along roads, power-transmission right of ways, and railways; and in areas with ponded water for mosquito control.

The types, rates, and timing (season) of application of pesticides used in developed areas differ from those used in agricultural areas, as do the pathways of pesticide migration to streams. For example, the chlorophenoxy herbicide compounds, including 2,4-D, which are used for weed control, are likely to be used more heavily in developed areas than in agricultural areas (Templeton and others, 1998). Although quantitative estimates of pesticide use in urban areas are generally unavailable, greater amounts are probably used (per acre) by homeowners than on the most commonly grown agricultural crops (Templeton and others, 1998). Pesticide applications in agricultural areas generally occur only in the spring, whereas those in developed areas occur throughout the growing season; some pesticides used in developed areas such as imazaquin, which is used for weed control on turfgrass, can also be applied after the first frost. Pesticide migration to streams in urban areas is generally more rapid and direct than in undeveloped and agricultural areas. The extensive impervious surfaces route pesticides washed by stormwater from lawns, ornamental plantings, and golf courses directly to storm drains and streams, whereas stormwater in undeveloped and agricultural areas generally infiltrates the soil, where its movement downwards to the water table or overland is retarded.