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To: jpal

The source of the water for the green spot is obviously a critical issue. What happens this summer may shed some light on that.

IMHO opinion, however, the CRITICAL issue is the trend. If it is worsening we have a major problem that must be addressed as soon as possible.

The green spot provides a very crude measure of this. If it is worse this year than 2011, especially since the average lake elevation is likely to be less, then we may be looking at a worsening trend.

Worsening water flow will NOT be linear even if it appears to be in the early stages. Once it starts to worsen it will accelerate slowly at first, but the rate of acceleration will increase over time.

The head of water (only that above the leak) pushing water through the dam is variable, hence the volume of water is almost certainly variable as well. The volume of water and rate of flow of that water will impact the time it takes for some of that water to reach the green spot. Put those factors together and you have a very hard to estimate, but nevertheless non-linear, curve.

The acceleration will not follow an easily extrapolated exponential curve, but that is basically what it will be.


3,655 posted on 05/13/2017 8:40:01 AM PDT by EternalHope (Something wicked this way comes. Be ready.)
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To: EternalHope; jpal

In my many years on the Earth I have learned one lesson that has served me well.

Government management and intervention in complex issues only insures that the event will reach epic disaster scale before it gets better or turns around.

In a sane world DWR would be, at this point, slowly barbequed by the Kalifornia Legislature. The misfeasance is breathtaking.


3,657 posted on 05/13/2017 9:03:04 AM PDT by mad_as_he$$
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To: EternalHope

I think it is the objective, or at least the hope, of most on this forum that further elucidation of these issues will help lead to their effective remediation. We’ve already found that many of the issues identified in past months have made their way into the press, and thereby into the Legislature, and now DWR is being held accountable. Ideally DWR would be proactive, but it appears that the collective experience on this forum is that the only way DWR will react is via increased public scrutiny.

The key questions regarding the green spot are:
1) Where does the water come from?
2) Is the problem getting worse?
3) How can this be fixed?

The first 2 questions are correlated. If the water is coming from the lake, then the source is essentially unlimited. Once it starts to flow, there could be no mechanism to stop it other than lowering the lake in time.

If the source is rain induced groundwater, that will dry up every year. However, the flow channels could eventually merge with lake water, again yielding catastrophic results.

Right now, we (the public) have no quantitative knowledge on the green spot other than what is reported biannually via DSOD, and what time dated photos have sufficient resolution to make out the green spot. Quantitative data is needed.

IMHO, the quickest, cheapest, and easiest way to acquire this would be to place an array of wireless moisture sensors within the green spot area. If that moisture level (compensated for temperature, wind speed, humidity, and solar radiance) is correlated with lake level (assuming plausibly nonlinear delays), then the water is coming from the lake. Additionally, examining the mineral content can help determine if it is groundwater or from the lake.

Stepping up a notch on the cost/time/expertise needed, the dam could be thermally imaged with FLIR cameras, as ER333 has recommended. A high res 3D profile of the dam should be generated from terrestrial Lidar and/or satellite data, and this should be tied into the existing survey benchmarks to assess the long term settlement of different parts of the dam. Experts such as ER333, Scott Cahill, and Professor Bia would and have suggested additional nonintrusive diagnostics.

Based on this data, a new plan could be developed on where to install new piezos and other in-dam instrumentation. Being intrusive to the dam’s integrity, this would involve considerably more time, money, engineering expertise, equipment, and institutional approval.

Once a valid water migration map is developed for the dam, grouting or other remediation efforts can be initiated. This would be a long term effort, as it would take a year or more to determine if the remediation had been effective.

The best I think we can do here is to help bring this issue out in the open and hope that DWR sees fit, or gets told to see fit, to take action on it. If the green spot dries up over the next month or two, then it may be another year before these diagnostics can be effectively initiated.


3,659 posted on 05/13/2017 1:19:00 PM PDT by jpal
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