Drinking water in New York City -graph

LimnoTech’s decision-support tool shows relative contributions by subwatershed of solids from different sources, helping managers prioritize watershed protection efforts.

Drinking water in New York City


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Success Story

Tool Helps Managers Protect New York City Water

The water supply system managed by the New York City Department of Environmental Protection (NYCDEP) provides drinking water for 9 million consumers in the City and surrounding areas. Up to 30% of this water comes from the 380-square-mile Croton watershed, which adjoins the City and includes 12 reservoirs and three controlled lakes in Putnam and Westchester Counties. LimnoTech implemented a risk-based assessment tool to help prioritize future water quality actions in the watershed.


New development in the Croton watershed may result in degradation of source water quality, shown by increases of parasites, turbidity, and levels of disinfection by-products in finished drinking water. NYCDEP needed to characterize current and future water quality stressors and focus available resources on effective, efficient management strategies to ensure source water protection.


LimnoTech developed a GIS-based decision-support tool that allows managers to evaluate various point and nonpoint source controls and their impact on water quality. The tool implements a risk assessment methodology that addresses nutrient, solids, pathogen, and toxics impairments from land-based, septic, and point sources. The methodology combines numerical scores that reflect risk, proximity, and severity for each source category to generate reports summarizing current risk levels and possible future trends.


With LimnoTech’s decision-support tool, NYCDEP will be able to prioritize its watershed monitoring, modeling, protection and restoration efforts to ensure protection of the City’s drinking water supply.