Last summer we were documenting the impacts of a series of deluges that caused such extensive sewage overflows and runoff that beaches were closed, and much of the Hudson River suffered from poor water quality. This summer, drought coupled with persistent high temperatures is revealing new impacts. Both last summer’s deluge and this year’s drought are examples of the climate extremes we need to prepare for, given the warming already baked in due to greenhouse gas emissions from burning fossil fuels. Around the country and world, these extremes — drought from the southwest U.S. to the Horn of Africa, flooding from Mississippi to Pakistan — are arriving with greater frequency and ferocity.

Drought has affected much of the Hudson River Watershed in New York, as well as large swaths of the U.S. Near-record low flows are being recorded in the two big arms of the Hudson River Estuary, the Upper Hudson River and Mohawk River, as well as in several Hudson River Estuary tributaries, including the Wappinger Creek, Rondout Creek and Wallkill River. Here are some of the impacts:

Harmful Algal Blooms. The most visible and immediately concerning impacts of the drought is in the Wallkill River and Rondout Creek, where a Harmful Algal Bloom (HAB) has appeared at times since August 11 along 15 miles of water from New Paltz to Kingston. Slow-moving water behind dams heats up and – when coupled with an overload of nutrients – allows for cyanobacteria to proliferate. These HABs can form toxins that put swimmers, dogs and others at risk. Riverkeeper and a team of partners that includes the Hudson River Watershed Alliance, the Wallkill River Watershed Alliance, Cary Institute and Bard College have documented the Harmful Algal Bloom, including a first-ever appearance in the tidal Rondout Creek, an arm of the Hudson River estuary. Until this year, we had never documented a harmful algal bloom of this significance in the estuary, where tidal mixing and turbidity have provided a buffer against algal blooms. In both the Wallkill, where this HAB originated, and in the Hudson, sewage, erosion, agricultural runoff and other sources deliver an excess of nutrients that can fuel algal blooms under conditions such as we are experiencing. Riverkeeper is advocating for action to reduce the underlying pollution burdens facing our waterways, to build resilience in the face of climate extremes. [Update 9/30: No observations of HABs have been reported on the Wallkill or Rondout since early September.]

Harmful Algal Blooms have also been identified in several lakes in the region, including drinking water sources: New York City’s New Croton Reservoir, which also serves Ossining and contributes to Croton-on-Hudson’s water supply; Albany’s Basic Creek Reservoir, the city’s backup water supply; and in two lakes in the Peekskill Hollow Brook watershed, which is the water supply for Peekskill. Riverkeeper is seeking more information about how these blooms are being managed to protect the quality of tap water.

Hudson River salt front: As less freshwater enters the estuary, salinity from the Atlantic pushes farther north, presenting a water quality challenge to the Hudson 7 communities that draw drinking water from the estuary. Those on low-sodium diets need to be mindful that their drinking water could include higher-than-usual levels, and the salinity can also increase corrosion of pipes and cause other treatment challenges. Riverkeeper has been supporting the Hudson 7 in requesting a state study of how sea-level rise will impact management of drinking water as the salt front responds to our altered climate.

Water Restrictions: In addition to these water quality concerns in drinking water, communities including are facing low reservoir or groundwater levels affecting their water sources. The City of Kingston is among the cities to declare a drought emergency, and enact water use restrictions. Groundwater levels are near historic lows in the Great Flats Aquifer, which is intimately tied to the Mohawk River, and the drinking water source for the City of Schenectady and several neighboring communities. New York City’s reservoirs, which supply half the population in New York State, are managed to ensure ongoing water supply needs are met. Current reservoir levels range from a low of 29% in the Schoharie Reservoir, to near-full conditions in the Croton system.

Ecosystem stress: In addition to the HABs, which are often an indication of ecosystem stress, low water levels, warm water and low dissolved oxygen levels can contribute to significant stress on aquatic life in our streams and rivers. Native brook trout and other cold-water species like blacknose dace and creek chubs, are particularly vulnerable.

Unmasking pollution sources: Since 2008, Riverkeeper and Columbia University’s Lamont-Doherty Earth Observatory have collaborated to monitor water quality in the Hudson River Estuary at dozens of locations to assess whether water is meeting the “swimmable” goal of the Clean Water Act. We have seen the profound impact of rain on water quality, as our aging and antiquated sewers are designed to spill raw sewage from hundreds of locations in many of our river cities. Often in the absence of rain, we see excellent water quality. Identifying locations that fail to achieve beach quality frequently in dry weather helps pinpoint areas that could be affected by sewage leaks that should be investigated by local communities. These include the mouth of the Mohawk River and just downstream in the Capital District around Troy, Newtown Creek, parts of Rondout Creek, as well as Hudson River access points in Newburgh, Piermont and Tarrytown.

Conditions this summer show that we must reduce underlying pollution burdens facing our rivers, protect and restore forests along stream corridors to shade and cool the water, conserve and protect drinking water at its source, and adapt to unavoidable impacts to our waterways from climate change.

You can help by asking Governor Hochul to sign legislation to protect streams, vote for the Clean Water Clean Air Green Jobs Bond Act at the ballot box in November, and support the passage by the U.S. Senate of the landmark NY NJ Watershed Protection Act.