Conservation Minnesota

What About Lakes?

Dick-Osgood-bioThe Clean Water Land and Legacy Amendment, adopted five years ago, dedicates about $100 million per year for 25 years toward cleaning up our waters – lakes, rivers, streams and wetlands.  Of these waters, what about lakes?

The motivation for clean up Minnesota’s lakes arises from the requirements of the Clean Water Act (CWA).  Accordingly, Minnesota must list its impaired waters – lakes, streams, wetlands – and then prepare plans to reverse the impairments.

There are 1,781 lakes listed in the Minnesota’s impaired waters list for 2014.  The majority of impairments are for mercury in fish (65%) and excess phosphorus (32%), totaling 97% of all lake impairments.

Unfortunately, most of these will not be cleaned up soon.  We will be living with contaminated walleye (Minnesota’s state fish) and toxic algae.

State studies show that 99.5% of the mercury sources are supplied by atmospheric deposition, meaning from the sky.  Of this, 90% originates from outside Minnesota.  Minnesota has a goal of reducing its share by 93%, so at best, we could (if and when the goal is accomplished) reduce the overall mercury sources by 9.3%.  Until outside sources are substantially mitigated, the fish in Minnesota lakes will contain unacceptable levels of mercury.

Much of the mercury is a byproduct of burning coal for energy.  Very low levels of mercury in our lakes accumulate up the food chain resulting in contaminated fish.  This phenomenon is so widespread that practically every lake in Minnesota carries a fish consumption warning.

Minnesota’s “State-Wide Safe Eating Guidelines” recommend no more than one meal per week of walleye and northern pike, but there are no restrictions on sunfish or bullhead.  For children and pregnant women, the recommendation is more restrictive – “do not eat” walleye 20-inches or larger.

I am not aware of any solution other than to reduce the source, so we will live with mercury-contaminated fish in our lakes for a long time.

Excess phosphorus in lakes causes nuisance algae blooms and we are also seeing a greater frequency of toxic blue-green algae blooms in our lakes.

In a report to the legislature (2004), the state identified the sources of phosphorus in major drainage basins throughout the state.  They found that 31% is from “point sources” (from regulated discharges such as sewage plants) and 69% is from “nonpoint sources” (runoff).  Point sources of phosphorus to lakes either do not occur or are already highly controlled, nonpoint sources therefore are the main source of phosphorus impairments.

Over three quarters of nonpoint phosphorus sources in Minnesota is unregulated (agriculture which is exempt from the CWA, 42%), uncontrollable (atmospheric, 19%) or not applicable to lakes (streambank erosion, 16%).  On the other hand, urban runoff represents less than 10% of phosphorus loading in every Minnesota drainage basin, except Lake Superior (which is not impaired).  So while there are many phosphorus-impaired lakes, mitigating the source remains practically out of reach.

Thus, like mercury pollution, it is reasonable to conclude we will not significantly or seriously address phosphorus impairments through source control.

There are effective and inexpensive ways to manage and mitigate phosphorus impairments other than source controls.  The North American Lake Management Society (NALMS) recently adopted a position statement, “Changes in US EPA Policy Implementing the Clean Water Act Are Required to Restore Water Quality in the Nation’s Lakes and Reservoirs,” that concludes watershed-based management (source control) “have yet to be shown to improve water quality in lakes or reservoirs in a cost-effective and timely manner.”  Ironically, EPA policy and funding supports watershed-based management, which does not lead to cleaner lakes.

The changes NALMS supports include increasing the use of within-lake treatments that provide immediate improvements, are safe and affordable.

Source control of phosphorus should not be ignored.  However, there are real and substantial impediments to making this happen in a reasonable timeframe (less than scores to hundreds of years).  Until then, we can clean our lakes.  Our public policy and funding should encourage and support within-lake treatments.

I (and others) have claimed our lake management institutions are broken.  We should expect positive, timely outcomes for the hundreds of millions of dollars we are investing.  We must re-evaluate our management philosophies and priorities if we want clean lakes.

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