Thursday, May 2, 2013

New Winter Water Level Plan

Most of you are aware of the District's new policy regarding lowering of Reservoir water levels during the winter.  Below is the official press release on this subject.PRESS RELEASE


Pearl River Valley Water Supply District
EFFECTIVE IMMEDIATELY
April 18, 2013
Barnett Reservoir Board of Directors adopts new lake level plan


Pearl River Valley Water Supply District’s Board of Directors on Thursday approved a
plan to change the lake level operation of Barnett Reservoir near Jackson.

District General Manager John Sigman said the proposal directs an increase of one foot
in winter pool elevation, from 296 feet above sea level to 297 feet, from December 1
through April 10 each year.

The summer or recreational pool will remain 297.5 on the 33,000-acre lake for the rest
of the year.

“Under the previous plan, this month we began raising the lake level April 10 from
winter pool of 296 with a goal of reaching summer pool,” Sigman said. “Historically, there
have been years when we were unable to achieve summer pool. A winter pool of 297 gives
us a greater chance of reaching our target summer pool.

“We are confident that we can do this without increasing flood risk downstream, and maintaining our ability to mitigate the peak of flood events just as we have in the past.Technological advances in areas like river gauging and computer modeling give us quicker,better data to help manage high-water events. For example, we had four river gauges to use in the 1979 and ’83 floods. There are now eight gauges and they provide updatedinformation every 15 minutes.”

Sigman said Barnett Reservoir’s final design was not a flood control reservoir. Original
concept planning hoped to achieve flood control, but it was soon realized that would not be
possible. The reservoir was instead designed to provide a water supply for the City of
Jackson, and provide the area a source of recreation. He said the change in lake level would
enhance both roles, while not reducing the dam’s ability to reduce flood impact.

“Even back in 1979 and 1983, we were able, with the information resources available
then, to take between 25 and 30 percent off the peak of those catastrophic flood events,”
Sigman said. “We underwent a long process with this plan to ensure we could maintain that
ability. We are confident that we can provide the same flood reduction whether we are at
296 or 297 feet above sea level.”

Sigman said the new plan underwent thorough hydrological research by Blake Mendrop
at Mendrop Engineering in Ridgeland and subsequent examination by many groups,
including the U.S. Army Corps of Engineers, the U.S. Geological Survey, and the National
Oceanic and Atmospheric Administration’s National Weather Service and its Lower
Mississippi River Forecast Center.

“We had several of the brightest minds in this field look at this plan and they agreed the
research was sound; they could not poke holes in it,” Sigman said.

Reservoir officials initiated conversation with several counties and municipalities
downstream and met with officials to give them an opportunity to hear the plan.

“We heard their concerns, which range from river bank sloughing, local flash-flooding
and even low water flow in the summer and fall,” Sigman said. “While the reservoir has
little or no impact on some of those, I do feel very strongly that we can better address those
that we can impact, such as the sloughing of banks, by having more water.”

Thursday’s action adopts the engineering report and initiates the new operational rule
— April 10 to Oct 15, a level of 297.5; Oct 15 to April 10, a level of 297, with a half foot
bandwidth on either side of the operational target.

2 comments:

Anonymous said...

That's some good news right there...for everyone that uses the lake from Oct-April and those with waterfront property.

Anonymous said...

Sigman's view of reservoir design history and claims of event mitigation in '79 are open to substantial debate.