2013 Dead Zone

The NOAA-funded forecast, for the Chesapeake Bay, calls for a smaller than average dead zone in the nation's largest estuary this summer. Professor Bill Dennis of the University of Maryland Center for Environmental Science attributes this smaller dead zone to the cool and relatively dry spring followed by late arriving rains. The spring load of nutrients into the bay was light and locked in a lighter load of nutrients in the water layers within the Chesapeake Bay for the summer. The forecast is based to a large extent on the quantity and timing of rainfall in the Chesapeake Bay watershed, but the overall health of the Chesapeake Bay is also a contributing factor. So, there is hope that this forecast also reflects that the overall condition of the bay may be improving.

Dead zones have become a yearly occurrence in the Chesapeake Bay and other estuaries. Dead zones form in summers when higher temperatures reduce the oxygen holding capacity of the water, the air is still and especially in years of heavy rains that carry excess nutrient pollution from cities and farms. The excess nutrient pollution combined with mild weather encourages the explosive growth of phytoplankton, which is a single-celled algae. While the phytoplankton produces oxygen during photosynthesis, when there is excessive growth of algae the light is chocked out and the algae die and fall from the warmer fresh water into the colder sea water. The phytoplankton is decomposed by bacteria, which consumes the already depleted oxygen in the lower salt level, leaving dead oysters, clams, fish and crabs in their wake.

In a wedge estuary such as Chesapeake Bay where the layers of fresh and salt water are not well mixed, there are several sources of dissolved oxygen. The most important is the atmosphere. At sea level, air contains about 21% oxygen, while the Bay’s waters contain only a small fraction of a percent. This large difference between the amount of oxygen results in oxygen naturally dissolving into the water. This process is further enhanced by the wind, which mixes the surface of the water. Scientists are still studying the impact of the winds in delivering oxygen to various water layers. The other important sources of oxygen in the water are phytoplankton and aquatic grasses which produce oxygen during photosynthesis, but when they die consume oxygen during decomposition by bacteria. Finally, dissolved oxygen flows into the Bay with the water coming from streams, rivers, and the Atlantic Ocean.

From USGS

Stream flow into the Chesapeake Bay is currently at “normal” levels after a relatively dry early spring. Overall, data from the U.S. Geological Survey, USGS, shows that the dry years of 2000-2004 are behind us and we may be entering a wet period. The Chesapeake Bay Program in partnership with USGS, monitors stream flow, nutrients and sediment in the rivers throughout the Chesapeake Bay watershed. There are 85 sites in the network; currently being monitored; however, only 31 of these sites have enough long-term data to be used to forecast trends. In the mid-1980s, the Chesapeake Bay Program (CBP), a partnership between the Commonwealths of Pennsylvania and Virginia, the State of Maryland, the District of Columbia, the Federal Government, and the Chesapeake Bay Commission, began efforts to reduce nutrients and sediments in the bay. Improvement in water-quality conditions in the bay has been slower than promised; however, and the U.S. Environmental Protection Agency, EPA, stepped in to put the entire region on a pollution diet. The Chesapeake Bay pollution diet, the Total Maximum Daily Load (TMDL) was mandated by the EPA to the six Chesapeake Bay Watershed states and the District of the Columbia. TMDLs for nitrogen, phosphorus and sediment were assigned by the EPA to each segment of the Chesapeake Bay Watershed in all six Chesapeake Bay watershed states.

Dead zones have become common summer events caused by man, human waste, and the waste and excess nutrients from agriculture necessary to feed us and ornamental gardens to please us. It has be predicted by Researchers from Texas A&M University that the Gulf of Mexico dead zone currently estimated at 3,300 square miles will exceed the typical summer average of 5,600 square miles. The scientists are predicting more than 9,400 square miles of dead zone in the coastal waters of the estuary due to the heavy rains in the upper  Mississippi that flooded fields and towns during the spring carrying with the flood waters the excess nutrients from farms, yards, septic systems and sewage treatment plants in its wake. The Gulf of Mexico Dead Zone is not expected to peak until late August.

From IAN UMCES source of nitrogen pollution in Chesapeake

Low Impact Development and Why it Matters

It has been called green infrastructure, conservation design, sustainable storm water design, natural stormwater management, and rain management but Low Impact Development, LID, seems to be the term that has taken hold in the United States for the site level actions and strategies. LID is a strategy of stormwater management emphasizing conservation and natural features combined with small scale stormwater controls to mimic as closely as possible the natural hydraulic properties of a site. The idea is to move water slowly through open conveyance systems and use distributed stormwater retention in open unpaved areas to allow infiltration of rain water into the earth. This reduces the quantity and velocity of stormwater as it leaves a site reducing the damage that uncontrolled stormwater runoff can cause when we change the amount of impervious surfaces a site has by building roads, sidewalks, playgrounds, and structures and compacting soil.

Traditional development practices cover large areas of the ground with impervious surfaces such as roads, driveways, sidewalks and buildings. These paved and impervious surfaces prevent rainwater from infiltrating into the ground, causing it to run off site at velocities and volumes that are much higher than would naturally occur. The collective force of such rainwater scours streams erodes stream banks resulting in large quantities of sediment and other pollutants entering streams, rivers, estuaries and bays every time it rains or snow melts. The US EPA believes that sediment and nutrient pollutions contained in runoff from urban areas is the largest source of water quality impairments to estuaries (areas near the coast where seawater mixes with freshwater) in the United States and has turned its water quality focus on these areas starting with the Chesapeake Bay Watershed and moving forward with the Gulf Coast estuaries.

Groundwater is recharged from rain and sources of surface infiltration. In many areas where development has occurred, we pump the groundwater for drinking water supplies (both public and private) and create barriers to rain infiltration by paving significant portion of the urban and suburban landscape as well as allowing if not encouraging storm water to leave a site as quickly as possible reducing the time that rainwater has to infiltrate the remaining soil and percolate into the subsurface. If we do not allow adequate rain water infiltration we will deplete the groundwater aquifers as we continue to pump water from wells. The U.S. Geological Survey’s (USGS) Groundwater Resources Program has found that the volume of groundwater stored in the earth is decreasing in many regions of the United States, and if this continues we could deplete our groundwater. We are running a groundwater deficit in many parts of our country, though we have adequate rainfall. LID can help by increasing water infiltration and reducing runoff.

In addition to the problems caused by stormwater and non point source runoff, many older cities (including many of the largest cities in the United States), have combined sewage and storm water systems which results in the storm water runoff overflowing the combined sewer system during storm events and diluted, but nonetheless raw sewage being released to rivers and estuaries. This is an ongoing problem in Baltimore and at Blue Planes in Washington DC as well as other cities throughout the nation. In the late 20th century, most cities that attempted to reduce sewer overflows did so by separating combined sewers, expanding treatment capacity, expanding storage within the sewer system, or by replacing broken or decaying pipes. San Francisco and many other cities have taken all of these steps, but still have much more that needs to be done. It is unfortunate that more of the stimulus dollars were not spent to repair expand and improve the waste water treatment facilities in our oldest cities instead of pursuing $54 billion in direct loans and loan guarantees to green energy companies. Repairs and improvements to our waste water treatment systems would have served our nation for several generations rather than been wasted on unproven technology or enriching favored entrepreneurs.

Managing rain water and snow melt is at the heart of LID. Rain water and storm water management under LID is landscape based and not particularly new. At the larger regional or watershed scale, green infrastructure is the interconnected network of preserved or restored natural lands and waters that provide essential environmental functions. Large-scale green infrastructure may include habitat corridors and water resource protection. At the community and neighborhood scale, green infrastructure incorporates planning and design approaches such as compact, mixed-use development, parking reduction strategies and urban forestry that reduces impervious surfaces and creates walkable, attractive communities.

At the site scale, green infrastructure is LID and mimics natural systems by utilizing permeable surfaces to absorb storm water back into the ground (infiltration), using trees and other natural vegetation to convert it to water vapor (evapotranspiration) and using rain barrels or cisterns to capture and reuse storm water. These natural processes manage storm water runoff in a way that maintains or restores the site’s natural hydrology, allowing groundwater to recharge. Site-level green infrastructure is LID, and can include rain gardens, porous pavements, green roofs, infiltration planters, trees and tree boxes and rainwater harvesting for non-potable uses such as toilet flushing and landscape irrigation. LID not only reduces the velocity and quantity of runoff protecting our streams, rivers, lakes and estuaries, it is essential to allow the recharge of groundwater.

The difficulty with LID is compliance and maintenance. Federal Clean Water Act requirements, such as the Combined Sewer Overflow (CSO) Control Policy and National Pollutant Discharge Elimination System (NPDES) permit program, do not allow for deviance from traditional control strategies. EPA guidance which encourages LID and green infrastructure to manage storm water is inconsistent with permit requirements under NPDES that call for more conventional methods of stormwater management.
NPDES regulations require development and implementation of a municipal separate storm sewer system (MS4) program to address post-construction runoff from newly developed and redeveloped areas. Investments in stormwater management and wastewater treatment plants are driven by compliance with regulations, which do not allow local policy makers to implement watershed-based or decentralized LID infrastructure solutions that may not yet have the data necessary to demonstrate performance and receive regulatory credit under a permit. Within the Chesapeake Bay Watershed the Chesapeake Bay Model provides credit under the Watershed Implementation Plans for LID retrofits, but not all practices are credited appropriately (both because of the amount of time needed for these practices to show long-term performance, as well as limitations in historic data collection). LID is by its nature a distributed design involving, rain gardens, porous pavements, green roofs, planters and rainwater harvesting require ongoing maintenance of the plants, replanting after severe winters or prolonged droughts, weeding, and clearing of porous pavements. There does not yet exist a method of ensuring that these features are maintained appropriately to continue functioning over time and that any repairs or replacements are done with LID in mind.

The Dead Zone

For the past few decades dead zones have become a yearly occurrence. Dead zones form in summers when higher temperatures reduce the oxygen holding capacity of the water, the air is still and especially in years of heavy rains that carry excess nutrient pollution from cities and farms. The excess nutrient pollution combined with mild weather encourages the explosive growth of phytoplankton, which is a single-celled algae. While the phytoplankton produces oxygen during photosynthesis, when there is excessive growth of algae the light is chocked out and the algae die and fall below the interface between the warmer fresh water and fall into the colder sea water. The phytoplankton is decomposed by bacteria, which consumes the already depleted oxygen in the lower salt level, leaving dead oysters, clams, fish and crabs in their wake.

In a wedge estuary such as Chesapeake Bay where the layers of fresh and salt water are not well mixed, there are several sources of dissolved oxygen. The most important is the atmosphere. At sea level, air contains about 21% oxygen, while the Bay’s waters contain only a small fraction of a percent. This large difference between the amount of oxygen results in oxygen naturally dissolving into the water. This process is further enhanced by the wind, which mixes the surface of the water. Scientists are just beginning to study the impact of the winds in delivering oxygen to various water layers. The other important sources of oxygen in the water are phytoplankton and aquatic grasses which produce oxygen during photosynthesis, but when they die consume oxygen during decomposition by bacteria. Finally, dissolved oxygen flows into the Bay with the water coming from streams, rivers, and the Atlantic Ocean. http://www.dailypress.com/news/science/dead-rise-blog/dp-scientists-say-wind-reduces-chesapeake-bay-dead-zones-20110725,0,7046457.story?track=rss

Water temperature and total river flow are linked to the size of the summer dead zone. The peak of oxygen depletion typically occurs in July or August. Water temperatures are highest during these months and the days are longest accelerating the growth of phytoplankton that ultimately consumes all the dissolved oxygen. The dead zone is typically gone by November. Cooler air temperatures at this time of year chill the surface waters, while the deeper water remains warm and allows more mixing of the layers during storms. Cooler water also will hold more oxygen. The size and shape of the dead zone is variable from month to month during the summer. Typically, the largest dead zones occur in years with the highest spring snow melts and rains. Though this year may surpass it, 1993 had the largest cumulative spring river flows of the past 22 years and the largest average summer dead zone with an average of 5.2% of the channel.

River flow volume is linked to increased size of the dead zone because the heavy rains and snow melt that create the river flow carry excess nutrients of nitrogen and phosphorus from agriculture, septic systems, overflows from sewage treatment plants and runoff from lawns, gardens and paved surfaces. These nutrients fuel the out of control grow of the phytoplankton that overwhelms the natural system. The decomposing phytoplankton, combined with higher water temperatures, can cause large areas of the deepest parts of the Chesapeake Bay's deep channel which is the ancient Susquehanna riverbed to have little or no oxygen to support marine life.

These excess nutrients are washed from agricultural fields and animal / feed lots as well as from suburban yards. The Chesapeake Bay Foundation has emphasized the importance of agricultural nutrient management plans and the Commonwealth is phasing out the use of phosphorus in ornamental lawns. However, an additional significant contribution to the excess nutrient contamination during storms is from waste water treatment plants and over taxed sewer systems. The sewer system in Baltimore (where the dead zone begins) still overflows with frightening regularity despite a consent order with the EPA signed in 2002. In a single storm in mid March of this year 4.7 million gallons of untreated but diluted sewer water overflowed from city sewer lines. That was just one of many spring storms. The Baltimore public works department is in the 8th year of a $1 billion rehabilitation of the city's aging, leaky sewer system, which won't be finished for several more years. In Washington DC one third of the sewer system is a combined system that is also subject to direct release of sewage during storms and snow melt. Combined sewer systems are sewers that are designed to collect rainwater runoff and domestic sewage, and industrial wastewater in the same pipe. http://cfpub.epa.gov/npdes/home.cfm?program_id=5
http://articles.baltimoresun.com/2011-03-14/features/bs-gr-sewage-overflows-20110314_1_overflows-sewer-lines-jones-falls

The combined efforts of state and local governments with conservation organizations have made much progress since 1978 in improving the health of the Bay, but are still short of the regional goal. According to the indices created by the Chesapeake Bay Foundation, The Chesapeake Bay Program and Chesapeake EcoCheck, there has been little if any progress in the past decade in the health of the estuary. The size of this summer’s dead zone puts a big exclamation point on the work that still needs to be done to restore the health of the Chesapeake Bay estuary. http://stateofthecoast.noaa.gov/hypoxia/dead_zone.html

The Chesapeake Bay is not the only estuary with a dead zone. Dead zones have become common summer events caused by man, human waste, and the waste and excess nutrients from agriculture necessary to feed us and ornamental gardens to please us. It has be predicted by Researchers from Texas A&M University that the Gulf of Mexico dead zone currently estimated at 3,300 square miles will exceed the typical summer average of 5,600 square miles. The scientists are predicting more than 9,400 square miles of dead zone in the coastal waters of the estuary due to the record flooding in the Mississippi valley that flooded fields and towns up and down the river during the spring carrying with the flood waters the excess nutrients from farms, yards, septic systems and sewage treatment plants in its wake. The Gulf of Mexico Dead Zone is not expected to peak until late August.