In
2001, I chaired the National Academy of Sciences review of the USEPA TMDL
program (Assessing the TMDL Approach to Water Quality Management, NRC 2001). At
that time, I was an enthusiastic supporter of TMDLs based on watershed analysis
and improvement of surface water quality based on pollutant load reduction. Two
issues have caused me to reconsider my perspective:
·
My colleagues’
endorsement of in-lake management strategies, such as artificial aeration and
biomanipulation
·
My view that current
water quality criteria may not be good indicators of designated use, resulting
in unnecessary and exorbitant costs of compliance
In the past few years my
colleagues, Dick Osgood and Ken Wagner, have made a compelling case for the ineffectiveness
of watershed pollutant load reductions to achieve compliance with surface water
quality standards in many water bodies; instead they have proposed that in-lake
treatment is often a better management alternative. Their examples are hard to
argue against. So what does this mean for the TMDL Program? Should we
acknowledge the limitations of watershed pollutant load reduction and embrace
in-waterbody treatment processes?
The 1972 Clean Water Act (CWA) was
monumental in its positive effect on our Nation’s water quality. At the same
time, the environmental euphoria of the CWA has sometimes resulted in well-meaning
but non-attainable water quality standards in a number of situations. The
result, in the Chesapeake Bay and in my home state of North Carolina, is water
quality criteria that are not really reflective of underlying designated use.
This is an important point because designated use (e.g., swimmable,
recreational fishery) is what we protect with our water quality standards;
water quality criteria, such as chlorophyll a and dissolved oxygen, are just easily-measurable
(and inexact) surrogates for designated use.
I believe that many surface
water quality criteria that have been established by the States are not adequately
representative of designated use. Further, I believe that in many situations we
have set water quality criteria that have resulted in TMDLs that have associated
costs of compliance that are way beyond expected water quality benefits. At the
same time, I am not a proponent of in-lake treatment processes as an
alternative to watershed pollutant load reduction except in small waterbodies
where studies have demonstrated the effectiveness of in-lake techniques. My
bottom-line perspective on the two issues that I raise – we should revisit the
TMDL program and the underlying surface water quality standards, yet we should not
be taken in by the low-cost, but ineffective in-lake treatment technologies (as
recently employed in North Carolina at a waste of $2 million) unless there is compelling
scientific evidence of their effectiveness.
