Wednesday, April 11, 2012

Rez Level Being Raised

April 10th marks the day the Pearl River Valley Water Supply District begins to raise the reservoir to it's summer level.

The lake is lowered to around 296 feet above sea level in the winter and raised to 297.5 ft above sea level for the remainder of the year.   When the summer pool is reached is dependent on the amount of rain fall received in the Pearl River Basin north of the reservoir.

Back in 2000 the Corps of Engineers conducted a study of the Barnett Reservoir and produced a report that helped shape the policy used by the PRVWSD to manage water levels.  A copy of that report is available here.

However, the District is reviewing their policies and studying options that would allow them to operate the lake at a consistent level year round.

No decisions have been made regarding lake levels at this time - we will keep you posted on any information released by the PRVWSD.

The U.S. Geological Survey provides a real time tracking system that monitors the lake level - it's available on the web here.   


An excerpt from the Corps of Engineers:

As stated, the primary risk of holding a higher pool level is associated with the loss of storage with which to "knock the peak" off of storm events. However, it should be noted that the storage capacity of the Ross Barnett Reservoir is very small compared with typical flood control reservoirs, which is the most likely reason that it was not designed and authorized for flood control. The risk associated with an earlier transition period is obviously the increased period of time during the rainy season that the pool is at a higher level. But what are the potential results of such a risk?

The storm events of 1979 and 1983 are the 2 largest events since the reservoir was constructed. In order to determine the results of holding a higher pool level during flood events, these 2 events were analyzed for 4 different scenarios - pool stages of296.0, 296.5, 297.0, and 297.5 with minimal warning time and no prereleasing operation. (Pre-releasing operation is when the operators have sufficient warning time of the flood
such that they can begin releasing large volumes of water before the peak arrives such that the reservoir level is lower when the peak inflows reach the reservoir). The results of this analysis showed that for each half-foot of additional reservoir storage between 296 and 297.5, the stage at Jackson could be lowered at most 2- to 3-tenths of a foot. For example, holding a stage of297 versus holding a stage of296 would result in the peak stage at Jackson being about 0.5 ft. higher for large storm events in the worst-case conditions. In reality, these events typically have a lag of several days before the peak inflow reaches the reservoir, and the operators would have time to pre-release and provide additional storage. Under typical conditions, the above example (297 vs. 296) would most likely result in an increase of the peak stage by 0 to 2-tenths of a foot.

Full report here.

The Rez News
Barnett Reservoir

9 comments:

Anonymous said...

DROPPING THE LAKE TO 296 IS STUPID. I GOT STUCK ON A SAND BAR IN THE MIDDLE OF THE REZ ON MY JET SKI. YOU READ IT RIGHT, A JET SKI. I WAS STUCK FOR OVER AN HOUR AND FINALLY ROCKED IT BACK AND FORTH AND PUSHED IT OVER 50 YARDS TO FIND WATER DEEP ENOUGH TO RIDE IT BACK TO THE BAY PARK LAUNCH WHERE I GOT STUCK AGAIN ABOUT 10 FEET FROM THE PIER. NO SENSE HAVING BOAT LAUNCHES WHEN WE CAN'T USE THEM.

Anonymous said...

This would be the greatest news ever if they would leave it at full pool. I have never understood what 1.5' was such a big deal. I live on one of the shallow canals off the bay and cant use my boat at 296 but can at 296.50 (churning mud)

RWX said...

A fraction of a foot sounds like nothing, but for a storm in the range of 1983 or 1979, the impact of another foot of water are:

- 650 additional structures damaged

- $110 million additional damage

(Ref: Table 6-4 of the Corps February 2007 study)

Anonymous said...

Still letting water out. Wow. So much for this article!

The Rez News said...

The gates below the spillway will always be open. The PRVWSD has to maintain a minimum flow of 240 cubic feet per second in order to keep the Pearl River flowing. The lake will rise when the inflow exceeds the minimum discharge. It will take some time, it's all dependent on the amount of rainfall in the areas north of The Rez.

Anonymous said...

I know that they have to maintain a minimum flow for the water plant but it seems like they are starting a pattern of when plenty of water is flowing in they dump it and slow it down after extra water quits coming in. Late last year it had dried up to almost winter pool and we get a tropical storm which fills it up quickly and they dumped it all and it never came back up ruining the fall boating season for those of us who live on the undredged channels around the bay. Here we are again where just a few days ago plenty of water and they dump it, slow the flow and its barely rising.

Anonymous said...

Recently returned from Pickwick Lake State park...gosh at the complete difference between that state run body of water and surrounding facilities and ours.

Jim Burleigh said...

I live in the Beaver Run Subdivision on the Mill Creek canal. At 296 I can't even use my 25 foot Pontoon boat without getting stuck. I witnessed 3 pontoon boats cruising the canal yesterday of which all got stuck to some point. Many of the boat houses in my area are dry with silt from Mill Creek at the 296 stage and the pearl river Res. Board could care less. I may start posting these peoples names as being of no help what so ever with this ever increasing problem. A steady level of 297 will help a little until more sediment is allowed to clog up our canals even worse and therfore lowering our porperty values. Thanks, Jim Burleigh 601-955-3808

Chris Merck said...

That is very disconcerting, Mr. Burleigh. I just don't want things like this to affect waterfront homeowners, whether from a recreational/peace of mind aspect or a resale aspect.
The PRV is on record for their inability to do even rudimentary dredging.
Shame