PO to PO: Great Expectations for Lake Heritage
John Doerr and Matt Verdirame
Community residents are generally very excited about the prospects for really great water quality in Lake Heritage. We all watch eagerly the myriad of bubble patterns (23, to be exact) now erupting from the water’s surface and know in our heart of hearts that when Spring returns next year we’ll be able to see all the way to the bottom of the lake center, no more algae will ever discolor our boat hulls, we’ll need to carry heavy duty landing nets because the fish will be so large, etc. etc. Oh, oh. Maybe a little bit of realism is needed here!
Yes, we’ve begun a project to reclaim some long overdue water quality back into our lake. Here’s the stats for when we started this venture:
algal blooms: almost constant
kind of algae: green (true algae), but significant blue-green (cyanobacter, a potentially toxic bacterium) in coves, around docks
water clarity: 1-2 feet max
dissolved oxygen at 10ft or above: ~9.58 mg/l
dissolved oxygen below 10ft: ~2.0 mg/l
Total phosphorus (mg/l)
Top = 1.12
Middle = 2.52
Bottom = 2.45
Sediment phosphorus (mg/l): 1.59
The oxygen diffuser system was installed and turned on September 17, 2015. Changes? 24 hours after system was operational,
dissolved oxygen at 10ft or above: still above 9.5 mg/l
dissolved oxygen below 10ft: around 6 mg/l – WOW!
7-10 days after system was operational the surface temperatures had dropped from 83-84F to 74F, representing the mixing of formerly static cold bottom water with the rest of the lake volume. Some of you may have noticed shortly after the system was turned on that the ‘aroma’ was not too awfully pleasant! If you boated out to a bubbler and got down wind, you discovered that the muck rising from the bottom is less than pleasant. If you repeated that process 4 weeks later, you were delighted to discover that condition has changed and the smell is becoming only barely perceptible.
So, what’s in the forecast? What should we property owners (PO’s) be watching for and expecting?
2016, beginning of season
algal blooms: YES – these will continue
kind of algae: Hopefully mostly green
water clarity: likely still only 1-2 feet
dissolved oxygen at 10ft or above: little change here
dissolved oxygen below 10ft: possibly a slight increase above the ~6 determined in September, 2015.
2016, end of season
Cross finger and hope the sum of all algae blooms is reduced from the 2015 season!
December, 2017 (those marked with a * are performance goals required to be met by LakeSavers under current contract terms)
algal blooms: Less frequent (?) Less intense
kind of algae: virtually all green algae
water clarity: * 4ft average
dissolved oxygen at 10ft or above: little change
dissolved oxygen below 10ft: * 3 mg/l minimum at bottom. Presumably dissolved O2 in the middle ranges will have improved further.
Total phosphorus: (overall 30% improvement)
Top * 0.78
Sediment phosphorus: * 1.27 avg = 20% improvement at all test sites
That’s just a little slower paced than we POs might like, but there’s a good reason for that. Think of it this way:
Know a few folks (maybe check that mirror) who could stand to shed a few pounds? We who have way more experience (‘seniors’) know that age makes keeping those pounds off harder and harder. So we try a quick diet, drop a couple, and very soon have those pounds and more right back on around our middle. For some time now we’ve been trying the quickie diet for the lake….Some tries to reduce inputs (phosphorus and nitrogen) but more focus on going aggressively after algae and weeds with chemicals. We got some temporary success but over time (age!) we’ve just gained back all that and more!
Now we’re going for the real intervention. Diet AND exercise. The aeration system converts the anaerobic digestion that’s been happening in the silt on the bottom for years into an aerobic digestion that over time will consume nitrogen and phosphorus. Add to that some different microbes and we begin to develop a biological system that will help reduce the ‘bad’ nutrients in our water. That shift and the change in ‘metabolism’ is the diet part of our program.
But the aeration system also gets the stagnant water moving and mixing. This expands the volume of water in which fish can operate and grow. Better for them…they should get larger faster…and better for us in that they increase and become better consumers of things that nature puts into that water. The mixing action, itself, contributes to a rise in total dissolved oxygen which also improves water quality. That’s our exercise.
Like any good diet regimen, objective is to lose the excess slowly but ‘permanently’. We are modifying our lake’s environment and lifestyle for a more permanent approach to gaining control of water quality.
So, when you walk out on your dock or visit a recreation area at lakeside next season, don’t fall into the trap of saying “OMG! It didn’t work.” It really already has. We just are unlikely to get some staggeringly awe-inspiring reversal of long years of accumulating problems. It will take time.
Comment? Why not drop a note to Matt at firstname.lastname@example.org or to our community manager, Mike, at email@example.com
And keep watching here. Periodically we will update the reports on water quality so you can help follow our progress with the core asset of this community.