My recent post on the Bloede Dam removal in Maryland prompted me to dwell a little bit on the nutrient pollution that continues to plague our water resources. Nutrients are the chief polluter of our river systems, lakes and coastal waters. It is such an old problem, but it just never gets resolved. When scientists talk about nutrient pollution, they are referring to phosphorous and nitrogen entering our waterways through surface run-off and groundwater discharge (referred to as “non-point sources”) and through direct discharges from wastewater treatment plants and other end of pipe sources (commonly called “point sources.”) Scientists are alarmed about the ever increasing amount of nutrients in our waters. So much so that a few years ago, the U.S. Environmental Protection Agency (EPA) commissioned a Nutrient Innovation Task Group composed of water managers and scientists from state governments, federal agencies and universities to define the problem. The Task Groups Report was issued in late 2009 and was actually entitled “An Urgent Call to Action.” It is a source of amazing statistics.
Just a refresher in case you don’t remember, but the problem with nutrients in our waterways is the resulting algal blooms. Scientists don’t call phosphorus and nitrogen nutrients for no reason. Both nitrogen and phosphorous are needed by living organisms for cell growth. This is why farmers spread it on their crops as fertilizer. It is why homeowners use it on their lawns. So when you have a lot of nutrients going into the water, it is like fertilizing the algae. Add sunshine and you get a bumper crop. Not really what anyone wants, because when the algae inevitably die off, the decay of their little dead algae corpses uses up the dissolved oxygen in the water through a process called eutrophication. Eutrophication produces “dead zones” or what scientists refer to as hypoxic zones. The quantity of floating algae (called phytoplankton) can increase so much that their mass actually blocks sunshine into deeper waters, depriving beneficial grasses and other vegetation that are to be found in the bottom of water bodies of the light they need for growth.
The Nutrient Innovation Task Group’s report states nutrient pollution along with the consequent overgrowth of algae and other nuisance aquatic plants as well as decreases in dissolved oxygen impairs 31% of assessed rivers and streams in the U.S., 30% of our lakes, and 50% of our bays and estuaries. The word “impairs” simply means that the function of the water resource is diminished. An example of an impaired water body would be an estuary which once supported a vital fishing industry but now has large “dead zones” where there is so little oxygen that fish can’t breathe and they have either died or vacated the area.
All of the excess nutrients entering our water bodies are from just a few sources, but they are large sources. Much of it comes from agricultural production. If there are no runoff controls on agricultural fields, excess fertilizer applied to crops can be washed into local streams. Manure from chicken and cows are also a big source of nitrogen and phosphorous to local waterways if not managed and controlled adequately. Urban storm water is another big source of nutrients as a result of all that lawn fertilizer we apply. Then there’s all the nitrogen and phosphorous coming out of wastewater treatment plants and septic systems. Humans in the U.S. produce about 18 million pounds of poop annually which is treated somewhat inadequately at our wastewater treatment plants. In 2009 when “An Urgent Call to Action” was published only 4% of the 16,500 wastewater treatment plants in the U.S. had limits for nitrogen in their permits and only 10% had limits for phosphorous. Then there are the 20% of homes in the U.S. which are on septic systems and are contributing nutrients to our surface waters via groundwater flow.
Oh wait a minute; I nearly forgot to mention another major source of nitrogen. It is from atmospheric deposition. When fossil fuels are burned in cars and power plants, it results in nitrogen oxides being emitted into the air. As they say, what goes up eventually comes down. And it comes down directly into our water resources or it is washed off our urban centers during storms and eventually makes its way into our waterways as well.
There are two well known, well studied water bodies where nutrients have caused major problems – the Gulf of Mexico and the Chesapeake Bay. The 2009 report cites that hypoxic zones cover 7900 square miles of the Gulf of Mexico and over 40% of the Chesapeake Bay. The report had a very interesting chart which I’m going to share here. It is the estimated sources of phosphorous and nitrogen going into these two water bodies.
As you can see the source of most of the nutrients going into the Gulf of Mexico are from agricultural production, while nutrients going into the Chesapeake Bay are about equally split between agricultural production and urban sources.
Nutrient pollution is not a stagnant problem, because the population continues to grow. In the report by the EPA Nutrient Innovations Task Group, the chief cause cited for the escalation of nutrient pollution in water is the increase in the U.S. population. In addition, the report predicts the U.S. population will grow by 135 more million people by 2050, exacerbating the amount of nutrients flowing into our waters. The report written almost eight years ago now, states that current controls to reduce nutrient pollution of our water resources are totally inadequate. In response, the U.S. EPA and state environmental regulators developed a “Framework for State Nutrient Reductions” in 2011. The framework reflects a partnership effort to reduce nitrogen and phosphorous in U.S. waterways by prioritizing watersheds for reduction efforts and then setting actual goals such as strengthening permits for waste water treatment plants and other point sources, establishing strong programs to promote land stewardship practices for agricultural lands, and improving storm water management in urban areas.
As part of this effort states are being asked to establish numeric goals in priority watersheds for reduction of nutrients. When water scientists talk about the amount of nutrients entering a water body, they call it a load. So these efforts are aimed at reducing nutrient loads into water resources. EPA guidance in the past allowed for narrative or numerical criteria for establishing pollution concentrations below which a water body would be able to achieve its full designated use – such as commercial fishing or swimming. Narrative criteria have been mostly used by state water managers and have been rather useless in achieving improvements. Narrative criteria simply state what condition you want to achieve. Numerical criteria establish what nutrient loads must be imposed for both point sources and non-point sources entering a water body. As you can imagine numerical criteria are much harder to establish than a simple statement of what you’d like to achieve.
With the proposed framework and a call by EPA to provide numeric criteria as opposed to narrative criteria for attaining the water quality goals for a water body, I would expect to see some improvements over the last six years. After all as the old adage says, what gets measured gets done. So as a follow-up to this blog post, I will be examining over the next few months whether improvements have been achieved in the two largest hypoxic water systems in the U.S. – the Chesapeake Bay and the Gulf of Mexico.