How many IRRMs are being implemented at Beaver Lake Dam?
There are approximately 15 non-operational IRRMs for Beaver Lake Dam and three operational IRRMs (how water is managed at the dam).
What are the non-operational IRRMs for Beaver Lake Dam?
Emergency action plan
Seasonal testing of remote gate operations
Lake release probability frequency analyses
Downstream warning system
Emergency flood barriers (inside dam)
Increased monitoring plan for seepage
Gate equipment waterproofing
Hoist and catwalk door waterproofing
Added sensors for remote operation
What are the three operational IRRMs for Beaver Lake Dam?
Double flood risk management minimum release after floods.
Deeper Drawdown After Surcharge (release to prevent gates from overtopping).
Revised Guide Curves at Newport and Georgetown.
What risk is being decreased by the operational IRRMs for Beaver Lake Dam?
The IRRMs are designed to reduce the risk that the machines that lift and lower the gates are inundated by high water. Reducing the risk of losing the gates also reduces the risk of overtopping the dam or the gates being stuck in a position that allows large releases. See Figure 2 through Figure 4 for pictures of machinery, top of gates, and high pool proximity to the machinery.
Figure 2. Machine Deck is at elevation 1133.5 feet.
Figure 3. 2015 flood event, two days after the flood peak at 1132.04
Figure 4. May 10, 2018, elevation 1128.5', catwalk (middle), top of gates (left), and machine platform (lower left).
Why is USACE implementing operational changes for Beaver Lake Dam and the White River system?
The operational changes reduce:
the population at risk by about 1000 people per day,
the number of days at Beaver Lake Dam the flood pool is full or nearly full,
and the frequency that Beaver Lake reaches the elevations near the machinery.
What temporary operational changes will USACE be making to decrease risk at Beaver Lake?
Three operational changes are being made at Beaver Lake Dam.
How long are the IRRMs expected to last?
The plan is to follow the IRRMs for three years. This time might be shortened if ongoing analyses reveal a better way to reduce risks at Beaver Lake Dam.
I like the operational IRRMs, could they be made permanent?
The IRRMs cannot be made permanent without a careful study of ways to best address the risk. Even if the IRRMs are shown to be the best long-term solution, the IRRMs are subject to National Environmental Policy Act (NEPA) evaluation. Additional study may discover better alternatives than the IRRMs.
What sort of differences might I see at Beaver Lake due to the operational IRRMs?
The lake is expected to spend more time near top of conservation pool instead of top of flood pool.
The lake levels are not expected to change much during the winter but should see a reduction the fraction of time the lake is high during late spring, summer, and fall. The releases will shift, there will be less days with releases near 1,000 cfs (approximately firm power release) and more days with releases near 2000 cfs (approximately double firm power release) because the minimum flood release is doubled.
What sort of differences might I see at Bull Shoals Lake due to the operational IRRMs?
Bull Shoals Lake will not be affected as much as Beaver Lake; however, Bull Shoals Lake may experience fewer days near the top of its flood pool during summer months. Bull Shoals Dam releases are not expected to change much.
What sort of differences might I see at Greers Ferry Lake due to the operational IRRMs?
Greers Ferry Lake is the least impacted lake from the IRRMs. It may see a few more days near top of conservation pool, days of releases at 3,000 cfs should decrease, and the occasional 10,000 cfs release might begin sooner after a large flood event.
How might farming downstream of the lakes (near Newport, AR) be impacted by the operational IRRMs?
The impacts are expected to be mixed depending on where the farming is occurring and what agricultural practices are being used. Holding a stage near 21 to 24 feet is expected to be more likely in late April, but not other times during the growing season.
The time the river is calculated to be near 14 feet is not expected to change much between the current plan and the IRRM during the summer and fall. The time the river is at 12 feet is expected to noticeably decrease for both wet and dry years during the summer and fall.
How might farming downstream of the lakes (near Georgetown, AR) be impacted by the operational IRRMs?
Expecting similar results as Newport.
What sort of differences might I see at Norfork Lake do the operational IRRMs?
Norfork Lake will not be affected as much as Beaver Lake; however, Norfork Lake may experience fewer days near the top of its flood pool in the summer. Norfork Lake releases are not expected to change much.
What sort of differences might I see at Table Rock Lake do the operational IRRMs?
Table Rock Lake will not be affected as much as Beaver Lake; however, Table Rock Lake may experience fewer days near the top of its flood pool in the summer. Table Rock may see a small decrease in the time it makes flood releases.