At Beaver Lake, a problem exists: Low water and its impacts on recreation.
The lake area is about 75 percent of what it would be if the lake was full. The emergence of “islands” is quite common, with future islands hidden just below the surface being most hazardous to boaters.
Docks are aground or often have ramp extensions that are very hard to move. Launching from a lift becomes increasingly diffIcult as the lift can run aground before the boat fl oats. Commercial and private docks, boats, and boat lifts have been damaged. Commercial dock owners are reluctant to rent boats. Access to the lake via boat ramps has become limited and access for the elderly and handicapped is nearly impossible in some places.
Water is removed or lost from the lake five ways: flood control releases, power generation releases, water supply removals, evaporation and seepage losses.
By far the most important is water passing through the dam for power generation during flood control and power generation. Since water supply removals are so important to Northwest Arkansas and flood control releases occur when there is plenty of water in the lake, only a change in power generation releases has potential for solving the low water problem.
That change is to increase the lake level below which no power is generated to prevent what we see today. To be cost-effective, power generation would need to increase at higher lake levels to prevent any decline. And, these shifts need to have minimal impact on flood control.
Today, Beaver Lake is 22 feet below what it would be if full. The last time this happened was in 2005-06 when the lake level fell 25 feet. Using average evaporation, water supply withdrawals and seepage data from the past fi ve years, the 25-foot mark should be reached sometime before June of this year, assuming no power generation and continued drought. If power is generated, it could be reached in April. Much of this is because of a drought that has persisted for months, severely limiting inflow or water additions to the lake.
Not only is drought hard to anticipate, it is also difficult to predict when a drought will be over. This can lead to substantial uncertainty when making management decisions regarding power generation. Yet, some efforts already have been made. After the 2005-06 low water levels,the U.S. Army Corps of Engineers increased the base of the flood control pool by one foot from May to October, effectively increasing lake level without reducing flood control. The Southwestern Power Administration appears to have done something similar as very little power has been generated below 1,110 ft-MSL (feet about mean sea level) over the last 24 years even though it is authorized by law to 1,077 ft-MSL.
But, what would happen if power generation ceased at some higher lake level such as 1,115 ft-MSL? Corps data and a computer model based on those data were used to find out. When power generation ceased at 1,115 ft-MSL rather than the current base of about 1,110 ft-MSL, the lake was predicted to increase 2 feet over the 24-year average.
The 2005-06 lowest lake level was predicted to increase 6.5 feet and our current lake level was predicted to be 5.5 feet higher than we now see.
So, earlier cessation of power generation was predicted to greatly reduce the possibility of low lake levels.
As always, there are some concerns with stopping power generation at 1,115 ft-MSL. The number of months when Beaver Lake would be completely full, requiring spillway releases was predicted to increase from 8 to 14 and power generation was predicted to decline by 3.3 percent. It is likely that power generation could be maintained or increased if the increased spillway losses could be shifted to power generation releases.
Only, those who manage Beaver Lake releases are qualified to tell us whether this is a possibility. If they say “yes,” perhaps what we see today will be a thing of the past.
JOHN GILMOUR IS AN EMERITUS PROFESSOR IN THE DEPARTMENT OF CROP, SOIL AND ENVIRONMENTAL SCIENCES AT THE UNIVERSITY OF ARKANSAS.
Opinion, Pages 5 on 01/30/2013