Weather Station / Lake History
(as of November 19, 2020 HOBOlink inoperable) Since Lake Minterwood was created the lake level has dropped about three feet. Estimates to repair the likely leaks were in six figures, and the Board of Trustees installed a weather station to monitor all the factors, in addition to leaks, affecting the lake level. You can view the real time and historical results of this station.
(Since this 2014 report the Lake Management Committee reports very little fluctuation of the lake level as of April 17, 2021)
MITIGATING LAKE LEAKAGE 11/07/2014 Core sampling, one at the beach and seven at the western side of the beach, showed nothing unusual and no flowing water. Robin Harvey later used a weighted-down plastic sheet on the lake bottom near the dock and found a possible leak where the plastic was sucked down.
A BRIEF HISTORY OF THE WATER LEVEL OF LAKE MINTERWOOD ( from 2014)
In the early days of the Lake Minterwood development the lake was fed by two wells (which are
now owned by Washington Water Service). The Beach Club elected to negotiate a water-rights
agreement with the developer and in 1985 a third well was drilled for LMBC to be dedicated to
maintaining the lake level. The lake level is now about 37 inches below the design level (top of
the spillway). We would like it higher, but our water rights and ability to pump are limited and it
is usually worst in a dry August.
Seepage under the beach area has long been suspected to add to the evaporation problem.
Several repair projects were attempted over the decades, but the lake still leaks. Estimates to
fully plug the leak go well into six figures, if it is indeed under the beach area (and not
elsewhere). We have been seeking a lower cost solution. A leak of this kind would increase
with the water pressure. And as the lake level varies it gives us a handle on how far below the
water level we should look.
Presently we estimate the leak accounts for 60% of the pump flow at the water fall, the rest is
due to effects like evaporation. In order to help locate the depth of the leak the Board of Trustees
authorized retired scientists Robin Harvey and Gary Klauminzer to install a weather station to
monitor the local weather (air temperature, rainfall, relative humidity, barometric pressure, wind
speed and direction) as well as lake level and temperature. The system was installed in 2012 and
has been running continuously since then, with results shown on the web site along with the lake
level. In parallel, Robin developed a complex physical model of the lake level. This model
applies weather conditions for use to test for hypothetical leaks.
Robin has analyzed the data extensively and determined that the mean depth of the seepage
seems in winter to be at about 61 inches below the design level, i.e. relatively shallow and hence
at least half runs somewhere under the shoreline. In recent years the Lake Committee dug some
test holes in the beach area under the supervision of a professional soils engineer. A slow leak
through a sandy gravel “lens” was found near the pavilion area at about the expected depth (not
the main leak however). We think that seepage was reduced by putting the material back in a
different order. The process continues, and more factors come into play. The Lake Committee
is committed to solving this problem, and if you want more details, contact Robin Harvey
THE FOLLOWING POWERPOINT SLIDES WERE PRESENTED AT THE APRIL 15, 2023 ANNUAL MEETING