June 2009, Vol. 21, No.6
Big City, Big Challenge
It wasn’t raining when Noah built the ark. Likewise, the New York City Department of Environmental Protection isn’t waiting for heat waves and coastal flooding before raising aeration tank walls, moving pumps to higher
ground, and otherwise preparing the city’s water and wastewater infrastructure for climate change.
DEP is one of 38 New York City agencies, public authorities, and private companies that are part of the city’s Climate Change Adaptation Task Force. Together, they have been charged with creating a plan for preparing the city’s critical infrastructure for the impacts of global warming.
Guiding their efforts is a report released by Mayor Michael Bloomberg in February that outlines how climate change is expected to affect this low-lying coastal city during the coming century.
In some cases, the impacts could be substantial. The report paints a picture of rising sea levels and higher temperatures, as well as more frequent and intense heat waves, rainstorms, and coastal flooding.
For example, current projections suggest that New York City’s mean annual temperature will increase by 2.2°C to 4.2°C (4°F to 7.5°F) by the 2080s. The total number of days with temperatures higher than 32°C (90°F) could quadruple between now and then, and droughts that now occur once every century could happen as frequently as once every dozen years. With annual precipitation climbing by 5% to 10%, sea levels also are projected to rise between 300 and 580 mm (12 and 23 in.) by the century’s close.
A Changing Mind Set
None of these changes is good news to DEP, which manages the region’s water supply and stormwater systems and also treats the wastewater for the region’s 9 million residents.
“Climate change has the potential to impact everything from the way we size our sewers to how we mitigate the impact of stormwater,” said Kathryn Garcia, assistant commissioner of DEP’s Office of Strategic Projects.
More-severe storms could translate into additional combined-sewer overflows and increased basement and sewer flooding, among other things. Hotter summers, warmer water temperatures, and intense drought also could increase the strain on the city’s upstate water reservoirs and lead to poorer water quality.
DEP’s biggest concern, however, is the location of the region’s 14 wastewater treatment plants.
“Our plants are located primarily at the water’s edge,” Garcia said. “So a rise in the sea level, increased precipitation, and large coastal storms all make these facilities more vulnerable.” Higher sea levels, for example, could mean more seawater entering wastewater treatment plants and more untreated wastewater spilling out and polluting coastal waterways.
“When sea levels are rising, you don’t want pump motors and circuit breakers located below the floodplain,” said Vincent Sapienza, DEP’s assistant commissioner for waste-
That’s why DEP is making plans to relocate wastewater treatment plants’ electrical equipment, chemical tanks, controls, and other critical equipment to higher elevations.
These concerns were hardly a consideration in the original design and construction of the city’s treatment facilities and pumping stations, many of which date to the 1930s. Back then, plants were located along the coast to minimize pumping requirements, Sapienza said. Decisions about the location of equipment inside those plants also were based primarily on cost.
“Historically, it made more sense to install electrical equipment in the basement because it was cheaper that way,” Sapienza said. Occasional flooding wasn’t a major concern — at least until passage of the Clean Water Act.
“Before the Clean Water Act, if you had a flood and had to shut down a plant temporarily, you just discharged untreated sewage into the ocean,” Sapienza said. “But expectations are different now, and the criteria we use to make decisions are changing as well.”
Consider the issue of flooding. According to the city’s current climate change models, floods that today occur only once every 10 years likely will increase in frequency to once every 1 to 3 years by 2080. By then, today’s 1-in-100 year floods are expected to occur every 15 to 35 years.
While increased flooding will affect the entire DEP system, it could create extra challenges in some locations, such as the city’s Rockaway wastewater treatment plant. With Jamaica Bay on one side and the Atlantic Ocean on the other, the 170,000-m3/d (45-mgd) plant is particularly vulnerable to flooding.
Some of the system’s release points already can be submerged during high tide, Sapienza explained. Tide gates prevent seawater from getting into the sewer system but open up during low tide to release flow. “Our fear is that climate change will result in the gates being closed more frequently, limiting our ability to release flow and creating more sewer backups,” Sapienza explained.
This fear and dozens of others have DEP staff rethinking every component of their system.
“Might we need additional aeration for hot weather days?” Garcia asked. “Should we add more capacity for wet weather events? These are the kinds of questions we’re asking.”
The panel’s work isn’t limited to adapting existing facilities to climate change, Garcia said.
“You don’t need to be located near the ocean to see these changes as a reason to rethink everything about how you use energy and how you measure your impact on the Earth,” Garcia said.
As a result, DEP’s priorities include planning and designing projects that don’t exacerbate climate change further. This includes finding ways to be more energy-efficient.
“Wastewater treatment is a chemical- and energy-dependent process,” Garcia said. “We’re pushing our designers, and lots of ideas are coming from the field on how to be more efficient.”
“There are different ways to treat wastewater,” Sapienza added. “To help minimize energy use, for example, we might in the future focus more on methods that involve gravity, rather than energy-consuming centrifuges.” Likewise, DEP is considering adding solar and wind power to one of its Staten Island facilities and using more of the methane gas it produces to power its engine-driven pumps.
One area where energy efficiency is less of a concern is the city’s water system. “New York City was blessed with a drinking water system that does not require energy,” Garcia said.
The region’s primary water source is the fresh mountain spring water that flows via gravity from the neighboring Catskill Mountains. “Unlike the Southwest, we don’t anticipate that climate change will result in shortages of drinking water here,” Garcia said.
But New York City’s water system still isn’t completely out of the woods. One area that DEP officials are closely monitoring is how climate change might affect the snowpack in the Catskill Mountains. As the snowpack melts each year, it’s not only the quantity of water that DEP is watching but also the quality.
“Increased storm activity could produce more turbidity in the Catskill System, which can create water quality issues for us here,” Garcia said. DEP currently has enough redundancy built into its system so that it can allow turbid water to settle out and achieve clarity without interrupting the city’s water supply. “If storms become more severe and frequent, that could change,” Garcia said. “We may not have what we need.”
Planning Can’t Wait
While some of the worst effects of global warming may not be felt for decades, planning efforts to deal with them must begin now, Garcia said. The region’s 14 wastewater treatment plants only undergo major upgrades every 2 to 4 decades. “We don’t want to miss the cycle,” Garcia said. “It will be long time until we get another chance.”
Planning changes and implementing them, however, are two different things. New York City’s climate change adaptation plans are complicated by the sheer size of its water and wastewater systems.
“Anything we do at a wastewater treatment plant is going to be expensive,” Garcia said. “All of our plants are very, very large and incredibly space-constrained. We don’t expect all of our thinking will be incorporated instantaneously.”
In today’s economic climate, DEP does not have a huge surplus of spare dollars waiting to be spent, Sapienza added. “So we’re trying to make sure we’re really smart about our recommendations,” he said, “especially in cases where we’re working to meet new water quality parameters as well.”
Nonetheless, some changes are already in the works. Motors on the main wastewater pumps at the city’s Hunts Point wastewater treatment plant, for example, already have been moved from the basement to sea level — or at least where sea level is today.
This raises one more question that Garcia, Sapienza, and others at DEP must grapple with continually: Will global warming play out the way the projections suggest?
New York City’s climate change report was developed by a panel of scientists, academics, and private-sector specialists using global climate models and local information. They know as much about the issue as anyone.
But as the report itself acknowledges, it’s difficult to predict what greenhouse gas emissions will be 100 years from now. Likewise, exactly how greenhouse gases and other climate drivers will alter the global energy balance are still far from certain.
“All of our planning is based on models and projections that could potentially be wrong,” Garcia said. “Of course we’d like the models to be more precise. But waiting to see how things turn out is not an option.”
— Mary Bufe, WE&T
Severe Drought in the Golden State
Larger populations and court-ordered pumping restrictions add to the severity of California’s prolonged drought; considerable impacts to the state’s agricultural industry are anticipated
Earlier this year, Gov. Arnold Schwarzenegger declared a state of emergency in California due to extremely low water supplies brought about by a severe drought that has now entered its third consecutive year. Schwarzenegger also called on residents to reduce their current water usage by 20%, and on March 24, the Santa Clara Valley Water District voted unanimously for mandatory rationing in Silicon Valley.
With little to possibly no water available for farming later this year and severe economic impacts being forecasted for California’s agricultural economy, the question remains how the current drought compares to past droughts in California’s history. Is this particular drought unprecedented or only another very dry episode?
According to Elissa Lynn, senior meteorologist at the California Department of Water Resources (DWR), severe droughts are part of the state’s natural hydrologic cycle. “In addition to the current drought, California experienced a number of major droughts over the last 100 years,” she said. “However, these droughts were not nearly as bad as they were in the Middle Ages, from the 900s to the 1100s, when droughts were much more severe and pronounced. Water quantities during those times could be characterized as 45% of what we would consider normal.”
DWR records show major past droughts occurring from 1929 to 1934, 1976 to 1977, and 1987 to 1992. The driest 2-year period on record was from 1976 to 1977, when the average water year runoff for the Sacramento Basin was only 35% of normal. The driest 3-year runoff period for the Sacramento Basin occurred from 1990 to 1992, during the last major drought. Based on precipitation levels at the end of March, if water year runoff for the rest of 2009 is similar to the previous 2 years, then the 3-year period from 2007 to 2009 would rank in the top eight driest on record.
“In terms of runoff, snowpack, and statewide precipitation, this current drought is comparable to the hydrological conditions of past droughts,” Lynn said. “However, in terms of impacts, this current drought is more serious. There are roughly 9 million more people living in California since the last major drought. The socioeconomic impacts of drought today are much more pronounced, especially compared to droughts early last century, because the water demands associated with a significantly higher population are much greater. This includes water storage requirements, as well as the need for distributing and supplying water across the state.”
Another factor contributing to the significant impacts of the current drought is the court-ordered restriction on pumping from the Sacramento–San Joaquin Delta because of endangered fish species. The delta, which is the hub of California’s water distribution system and includes the State Water Project (SWP) and the federal Central Valley Project (CVP), is the water supplier for roughly two-thirds of the state’s population in addition to millions of acres of irrigated farmland.
“The SWP is projecting that it will only be able to deliver 20% of the requested water supply for urban and agricultural users, while the CVP is projecting it will not be able to deliver any of the agricultural requests,” Lynn said. “As of late March, these are the forecasts for what will happen after the spring.”
The economic impacts from the drought have been devastating to California’s agricultural industry. According to the University of California at Davis, this year’s projected farm revenue losses are between $483 million and $647 million. “Communities in the Central Valley that rely on federal water, like the town of Mendota [with 40% unemployment], have been hit very hard, because there is no water available for farming,” Lynn said. “These agricultural districts do not know if they will get more than between zero to 20% of their water requests. This uncertainty makes it very difficult to determine what crops to grow, since their planting cycles are beginning now.”
Uncertain Water Supplies
In January, with California’s agricultural industry already facing continued economic decline, drought conditions across the state reached a critical stage, with water levels in Northern California’s reservoirs having slipped to only 35% capacity. But then, in late February and March, much-needed storms arrived and helped recharge the northern Sierras, where much of California’s water supply originates.
“The drought situation in January was looking very severe,” said Wendy Martin, executive project manager and statewide drought coordinator at DWR. “The February–March storms basically brought us back from the brink of disaster.”
Although the storms were essential in bumping snowpack up to near-normal levels, it remains to be seen whether that precipitation can hold and have a sustainable effect on California’s yearly water supply.
“Last year, around mid-February, California experienced a number of storms which resulted in above-
average snowpack in the Sierras,” Martin said. “But then the storm systems abruptly stopped, and the weather turned unusually warm. This caused sublimation to occur, in which the snowpack evaporated. Losing all that runoff turned a good year into a disastrous one. The storms we got this year were needed to saturate all the soils that had become dried out. This rewetting of the watershed will cause future precipitation to runoff, which is what we need to increase supply.”
Although the state’s immediate water-supply condition looks encouraging, it is still uncertain what will happen throughout the remainder of the year. “If the rest of this season is similar to last year, we could potentially lose all that water content,” Martin said. “But even if the snowpack lasts and this turns out to be an average year precipitation-wise, it will not be enough to end the drought.”
With the prospect of further abnormally dry conditions this year and beyond, DWR has developed several drought-response actions. They include a drought water bank that was established for the purpose of purchasing water shares from potential sellers located mostly upstream from the Sacramento–San Joaquin Delta.
DWR also is implementing conservation programs and drought education and outreach, as well as providing financial support to drought programs and technical assistance to smaller water systems and private well owners.
“It is very important to address the immediate impacts of this drought, but we also need to be prepared for beyond this year,” Martin said. “This is the third year of this drought, but if you look at Australia, the drought in that country has entered its 10th year. That’s why we need to establish much more efficient long-term water-use measures, because we don’t know how long this drought will persist.”
The severe water shortage in Queensland, Australia, prompted the Queensland Water Commission to implement high-level water restrictions and water conservation measures that target residential water usage of 170 L/d (45 gal/d). “That amount represents a quarter of the average water use in California,” Martin said. “We can learn from the example set in Australia, but to get to that level, lifestyles would need to change considerably.”
With the onset of climate change, Martin said unpredictable weather patterns and extreme weather events could become more common. With that, California’s periods of acute dryness have the potential to become much more pronounced. “We need to prepare for the uncertainty of climate change,” Martin said. “Conservation is a very important component, but we also need to be able to transfer and distribute water as quickly as possible. Additionally, we need to establish a high level of flexibility in how water can be used. These measures will help ensure that we get the greatest possible value out of our water.”
— Jeff Gunderson,
©2009 Water Environment Federation. All rights reserved.