How NYC Water will Change if Climate Trends Continue
New York City has always thought long into the future while expanding, upgrading and protecting its water supply. In fact, our planning horizon has been longer than most units of government across the country. Parts of the water supply were routinely planned 50–100 years in advance!
As the City stressed the capacity of its Croton System in the 1890s, it started plans for reservoirs in the Catskills that were not built until the 1950s. When the Delaware Aqueduct was built during World War II, engineers included the basic infrastructure for a future interconnect with the Catskill Aqueduct that was completed in 2015. Droughts in the 1960s and 1980s compelled City leaders to project population and water demand deep into the 2000s.
That type of long-term planning continues today. And while we remain focused on infrastructure, treatment, and watershed protection, much of our planning is also informed by the changing climate.
We are fortunate to have a team of scientists and post-doctorate fellows who study the effects a changing climate will have on the future state of our water supply. Their ongoing, multi-phase analysis comprises one of the largest and most complex efforts by any water utility to understand the effects our warming planet will have on drinking water.
Preliminary results show a wide variety of potential impacts on our waters, lands, and the plants and animals that inhabit them. Our current study looks out to the years 2081–2100. Here are a few changes we are likely to see if climate trends continue:
- Our watershed could receive only about one-third the amount of snow we currently get in a typical winter. The snow we receive will also melt earlier — a trend we are already beginning to see. The change from frozen to liquid precipitation would cause reservoirs to refill earlier. This would also shift the timing of drawdown season, when the demand for water in New York City is higher than the amount of water coming into our reservoirs.
- The average monthly streamflow will be higher during winter because more precipitation will come as rain instead of slow-melting snow.
- We expect to see additional sediment mobilized into the streams, creeks and rivers that feed our reservoirs. Turbidity, a measure of the cloudiness of water, could increase by as much as three times. That is because more rain will fall during winter when the trees and ground are bare, leaving little protection for soil along stream banks and hillsides.
Warmer air temperatures will also create warmer surface-water temperatures, allowing more algae to grow. Many species of algae can change the taste or smell of drinking water. Our forests are also likely to change as numerous invasive species come into the region. Deep, cold winters used to kill many of these pests, but not anymore. One such invader, the hemlock woolly adelgid, could kill every hemlock tree in the watershed. The hemlocks, which comprise 12 percent of our forest, are historically important for water quality because they grow close to the streams, prevent erosion, and shade the streams in the summer to keep them cool.
Climate change will bring many challenges, and sound science must guide us toward solutions. Advanced modeling has already helped us change our operation of the reservoir system to capture more snow melt and rainfall in the late winter. Our scientists and engineers are also researching new methods to fight algae, modernize our dams and spillways for stronger storms, and improve our protection efforts against turbidity and bacteria.
We are the stewards of this great water supply for only a short time, but we must continue the tradition of looking far into the future. That is especially true when it comes to proactively confronting climate change.
