Discussion on lake-ronkonkoma-silt-causes-high-water-table
jabba
is logical. There has been alot of media attention recently about the
flooding in the bog north of the lake. If the lake level was
controlled would the flooding be alleviated not only in the bog but in
the surrounding areas? Also how would it affect the ecology of the
natural drainage areas if the controlled outfall would go directly
into the Great South Bay?
LIWat...@gmail.com
Thank you.
Gee, you ask tough questions. For this response, I am assuming that
when you talk about controlling the level of the lake you are not
talking about "adding" water to the lake during a drounght, but only
removing water from it when the water table is high.
Your question is excellent, because we should be intelligent enough to
not just follow a solution because some politician or pundit recites
it. As you point out, the solution has to take into consideration
other factors such as the impact on the ecology of the area. This is
the whole point of why we need people qualified to look at this
problem from a much wider perspective. Unfortunately, you would need
a team of experts to answer this having far more knowledge than I
possess, but I will answer the best that I can. I would suggest that
investigation needs to be done to specifically determine what would
actually happen since much of this has to do with the horizontal
hydraulic conductivity of the various ground materials at various
depths in the areas around the lake and the overall impact on the
magothy layer by reducing water the upper glacial aquifer. Models
would need to be created which assume certain flow rates for the
action you are suggesting to determine if removing that much water
will cause future problems during drought conditions or whether it
will increase the potential for salt water intrusion into the
aquifers.
If the lake level were kept down, it should help the water problems in
the bog north of it to also decrease in height. The process would
initially be relatively slow but since the Lake mirrors the water
table, if you control the height of the lake by taking water out, it
should form a huge cone of depression in the water table around the
lake and similarly impact the surrounding areas. How far that impact
goes is an open question (and another reason why modeling needs to be
done to determine the impact). Currently, the lake in some way acts
as a buffer for the water table. As the water table rises, the lake
will take in water from the land around it. As the water table
lowers, the lake will give up water to the ground.
Overall, if the water from the lake is flowing to other areas and
causing problems, reducing the height of the lake would reduce that
flow. If the problems in the surrounding area are not caused by water
from the lake, but by water flowing towards the lake, those problems
would likely continue until something is done about the source of
their problems. Draining sufficient water from the lake would cause
the water table in the area to equalize at the lake's new, lower
level, but if the water is flowing to that area from elsewhere, it
still needs to get there first. In other words, during high water
table years, areas with a high water table "upstream" from the lake
would still have a problem, but those which are "downstream" from the
lake would likely would have their problems reduced. Models would be
needed to confirm precisely where upstream and downstream are in this
respect to determine if the benefit is sufficient to outweigh the
costs.
Remember, the lake is not "causing" the problems, the problems are
caused by groundwater. The lake merely reflects that groundwater
level, and is thus the most visual indicator of the problem for most
of us. The water in the mound north of the lake generally peaks in
the area near Nichols Rd, Route 347, Middle Country Road, Browns Rd
and Moriches Rd. The water in this mound will still need to flow
somewhere. It probably flows south or north at a rate of a few
hundred feet a day or less. Measurements need to be taken to
determine the actual flow and whether that flow is sufficient to be
impacted by reducing the height of the lake. Plus, if other solutions
are also being pursued, such as sanitary sewering or water usage
controls, you may not want or need to then also reduce the level of
the lake.
My crystal ball is not strong enough to see the answer to your second
question about ecology. I will answer it with "that depends."
It depends on how much water is taken from the lake and what the
weather conditions are after the water is removed. Once you remove
the water from the lake there will be no mechanism for replacing it
during a drought. There has been a tendency for the lake to rise and
fall through the years, but if we remove water from it, we will be
tampering with that cycle. There is a likelihood that while we will
minimize the peaks, the valleys will also be affected. In other
words, during the next dry period, the lake will start off much lower
than it has in the past and it could reach record lows. What problems
that could cause, I do not know, but there is a lot of vegetation and
wildlife around the lake that relies on its waters. Further
downstream, there has always been concern about the potential for salt
water intrusion into the island's groundwater if too much of it is
removed. What you are describing is another way of removing
groundwater, so much so that the lake's height is reduced and the
water table around it, so this will add to that concern. If, by
reducing the level of the lake, you reduce the mound to the north,
then you need to also consider the effect on the north shore because
that mound doesn't just flow south. Whether this would have sufficient
impact to endanger our aquifers would take some significant study. I
think they would need to know how much water would be expected to be
removed and then controls would need to be put in place to measure
those amounts and ensure that they are not exceeded without additional
research into the existing impact. Reliable long range climatic
forecasts would need to be considered so that we do don't remove water
right before a drought. The impact of global warming would need to be
considered since the rising height of the oceans may make salt water
intrusion an even greater problem. Whether global warming will cause
greater or lesser rainfall on Long Island is a question that the
experts continue to debate, so that is a big open question, too.
As I indicated, since I do not have the models and knowledge available
to me, the above is my best guess given what I know. The following is
just my opinion.
Personally, my preference would be to try to control the mound north
of the lake rather than the lake itself. I think that was part of the
purpose of the Smithtown pumps on Browns Rd. However, in my perfect
world, I would have pumped it north rather than south. Right now,
they pump the water towards the lake and it then needs to flow south
from there. The mound is about 5 miles from the Long Island Sound,
but less than 2 miles to the lake, so I can understand why they chose
that solution. However, once it reaches the lake, it is now south of
the divide and needs to flow further south towards the Great south
Bay. That trip south is more than 6 miles. So by pumping it a mile,
it is now further from the shore than it was when it started.
Secondly, that mound appears to drain towards both the Nissequogue and
lake areas. Since both of those areas have reported significant
problems, this would seem to be the common denominator that needs to
be focused on. How you would drain such a vast area is a very big
question, a very big question which I can't answer. The impact on the
environment of both the north and south shores would still need to be
carefully evaluated as indicated above.