Eutrophication: treat the causes, THEN the left-over symptoms

18 November 2012

I think many would agree that it would be pretty pointless trying to dry out your carpets while rain in pouring in through a hole in your roof.  The logical sequence would be: hole first, carpets second.  The same argument applies to the nutrient enrichment (eutrophication) of lakes and rivers:  if you have tons of nutrients pouring in, day in, day out, from wastewater treatment works, its unlikely you are going to make ANY difference by fiddling around with cosmetic actions in the lake.  At best you will be “seen to be doing something” which, unfortunately, is about all many authorities try for in an attempt to assuage public criticism.  A lot of money gets wasted this way and will continue to happen until Civil Society wises-up!

This argument is currently being considered in Citrus County, Florida, where debate has ensued in Kings Bay regarding a proposal to buy a weedharvester to augment manual removal of aquatic plants that choke waterways.  While realizing that they may well always need to keep “mowing” their river, informed locals are calling for attention to the other end of the problem, i.e. the CAUSE:

They would like to see a broader plan that includes:

…solutions for septic pollution and stormwater runoff. The problem [they] see with focusing on only one facet of water quality is [that] the root cause of the pollutants in the water feeding the [problem plants] [is] not being addressed. Once the King’s Bay project runs its five-year course, a plan needs to be in place to stop stormwater runoff and septic pollution from feeding a whole new generation of aggressive algae growth in King’s Bay.

Perfectly correct – otherwise its just a ‘fiddling while Rome burns’ scenario.  Its unlikely there will ever be a ‘single solution’ to eutrophication, success is going to be built on the aggregate benefit of logically-aligned and implemented “small gains”.

However, effectively addressing the problem at source is not at all easy – at least not in many of the ‘older’ situations where pollution has been continuing pretty much unabated for decades.  Part of the problem is that the population keeps growing and more and more wastewater effluents get discharged into surface waters.

This has been the experience of residents of Vero Beach, Florida, where an expensive re-engineering of the St John’s River has not yet shown any improvements.

The biggest problem is with nitrogen and phosphorus, key ingredients of life, and thus chemical fertilizers. They foster green, fluffy lawns, but in excess, fish-killing algae blooms as well. Their levels in most local St. Johns lakes remain high enough to make the water prone to algae and weed explosions that can clog water plant intakes or leave behind potentially unhealthy byproducts in drinking water, state data shows.

Biologists say ongoing farming and development may have tempered the expected ecological gains from the so-called upper basin project. Cattle waste and fertilizer continue to add phosphorus to soils already rich with the nutrient, as do leaky septic tanks. But regional water managers say the landmark project fended off what could have been much worse.

In most cases it is unlikely that a single solution will solve the problem.  The strategy for winning this battle is going to come from many, smaller tactical successes – the aggregate benefit of which will reduce the pollutant load to ‘manageable’ levels.  The interventions applied have to be verifiable (measurable), as reflected by this case study from Pennsylvania:

In one case, Total Maximum Daily Load (TMDL – the limit of a pollutant a water body can receive and still meet water quality standards) study evaluated dairy and poultry projects and demonstrated verified reductions of nutrients that reach and affect Pennsylvania’s local fresh water sources, including its aquifers, reservoirs and lakes, and rivers and streams.   According to the study, these projects will result in the annual reduction of millions of pounds of nitrogen and phosphorus loading to these local-area fresh water resources, leading to a substantial decrease in nitrates that reach local aquifers. Excess nitrates in drinking water can create serious health concerns in both humans and animals and would be very expensive to treat if future levels exceed safe limits.

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