Meeting Summaries

Date: Wednesday, July 6, 2011, 12 pm -2 pm

Location: Columbia/NASA GISS

Invited attendees: CCRUN Team

DEP: Alan Cohn, Don Pierson, Anandhi Aavudai, Larry Beckhardt, Mark Zion, Adao Matonse, Lorraine Janus

Hazen/Halcrow: Tim Groninger, Adam Hosking

Calling in: Murray Dale, Laura Baird

The second meeting of members from the New York City Department of Environmental Protection (DEP) and the Consortium for Climate Risk in the Urban Northeast (CCRUN) emphasized the importance of climate change discourse from both a scientific and planning perspective. Although members came from diverse backgrounds, their shared concern illustrates how our changing natural landscape impacts the way one creates and lives in the built environment. The main objective of the meeting was to discuss ways of developing new rainfall intensity-duration frequency (IDF) curves and other precipitation models to project future climate conditions. Presentations fell within the confines of water supply, precipitation, and storm water/wastewater.

The DEP’s Climate Change Integrated Modeling Project (CCIMP) analyzes climate impacts on the NYC water supply using reliable climate projections. Its major tasks are to develop watershed erosion, hydrology, sediment transport and phytoplankton production models that account for the changing climate, create downscaling methods, and utilize these models and improved data sets to more accurately project the future state of NYC’s drinking water. Phase 1 of the project focused on describing models the DEP are using to predict the changing patterns of the Winter-Spring stream flow as a consequence of global climate change. Interestingly, the models predict that the DEP will have to deal with both earlier and increased fill of NYC reservoirs with higher levels of turbidity and nutrient flow as a result of greater future precipitation and increased frequency of drought events. The project is now in Phase 2, setting up Soil Water Assessment Tool (SWAT) models in various parts of the upstate watershed and rerunning simulations from Phase 1 using improved methods and data sets.

When assessing the impacts of climate change on the city’s drinking water, it is essential to look at both changes in the water quality as well as its quantity, though the interwoven threads of natural and anthropogenic systems in the reservoirs make these consequences more difficult to predict. A few Weather Researching and Forecasting Model (WRF) projects have begun to evaluate adaptation strategies, to assess risk management and vulnerability in the region, and also to reevaluate the actual management of the watershed under these projected conditions. Assessment requires an integrated modeling system. Watershed, Reservoir and Water Supply models estimate various environmental factors such as growing season, soil freezing, stream water temperature, ice cover, and assess the impacts of changes on the reservoirs. What these models do not incorporate, as pointed out by a member of the DEP, are human-induced changes in land-use.

The meeting provided an effective forum for modelers and operation managers of the New York City water supply system to engage with climate scientists and researchers from the CCRUN team. As climate and weather patterns change in progressively extreme ways, the future remains unknown, yet this collective effort of scientists and policymakers gives hope that the region will adapt to and prepare for the challenges of responding to our changing environment.