Fixed weir pool simulation delayed due to excessive precipitation

Due to conditions from heavy November and December rainfall we must delay the pool simulation of the recommended fixed crest weir at the New Savannah Bluff Lock and Dam site, originally scheduled to begin Jan. 5.

U.S. Army Corps of Engineers officials in the Savannah District now expect to conduct the simulation in early February if runoff rates return to acceptable levels by the end of January.

During a November public meeting in North Augusta, South Carolina, Corps leadership offered to conduct the simulation for local observation. The simulation, which deviates from normal operations, is part of the district’s effort to maintain transparency with the local community throughout the Fish Passage analysis process.

Congress directed the Fish Passage process through passage of the Water Infrastructure Improvements for the Nation (WIIN) Act in 2016. The simulation will demonstrate how the Savannah River in the Augusta area will appear with the recommended fixed crest weir during the low end of average flows.

The low-end of average flow is approximately 5,000 cubic feet per second (cfs). Just for context, and based on historical flow data, river levels in Augusta are higher than 5,000 cfs 77 percent of the time.

We cannot simulate a low-average flow condition in January because November and December rainfall is approximately 150 percent of normal above Thurmond Dam.

As a result of soil saturation, high water table and winter conditions, Hartwell runoff is at 200 percent of normal and Thurmond runoff is 300 percent of normal. Water levels in both reservoirs have risen into flood storage, requiring discharge rates at Thurmond as high as 28,000 cfs.

This discharge rate is much higher than the necessary low-average flow of 5,000 cfs for the simulation.

Furthermore, Thurmond discharge has remained high for all of December. As a result pool levels in Augusta, Georgia, have likewise been higher than what we typically observe throughout the year, which is roughly between 6,000 and 7,000 cfs.

The plan to conduct the simulation in early February remains tentative depending on January rainfall, runoff conditions and reservoir levels at Hartwell and Thurmond.

The recommended fixed weir with fish passage, which will replace the New Savannah Bluff Lock and Dam, is an environmental mitigation feature of the Savannah Harbor Expansion Project. It is required mitigation in accordance with the Endangered Species Act and is among the final seven proposed alternatives and refinements that the Corps studied under the direction of the WIIN Act.

The intent of the legislation is to provide a means for certain endangered fish to move upstream of the lock and dam to traditional spawning grounds.

~Russell Wicke, Corporate Communications Office

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It’s beginning to look a lot like … 2015

Hartwell Dam during a spillway release Jan. 24, 2016.

If you’ve been following the weather lately (or in practical terms, have begrudgingly just stopped putting away your umbrella), you’ve noticed the uptick in precipitation in the past two months.

While the rainy season for the Savannah River Basin is technically a few months away, as the fall arrives and plunges into winter, the average monthly rainfall steadily increases in its march toward … March, the basin’s wettest month.

Wet weather isn’t generally a problem as our hydroelectric dams were designed to handle massive amounts of water and precipitation. However, when transpiration and evaporation decrease (typical for the cooler seasons) and combine with a deluge or two, the effect is compounded.

October’s rainfall was just a whisper above average, while November’s tallies were much more pronounced. Hartwell gathered 8 inches compared to its 4.6-inch average, while Russell and Thurmond posted similarly elevated amounts of 7.5 and 6.9 inches, respectively (compared to their 3.6- and 3.4-inch averages, respectively).

The most impressive aspect of this statistic is that the overwhelming majority of the rain fell in the first two weeks of November, and the same phenomenon appears to be happening again this month.

As of Dec. 18, Hartwell has collected just under 7 inches (compared to its 5.2-inch average). Russell and Thurmond have 6.2 and 5.7 inches compared to their 4.1- and 4-inch averages, respectively.

Again, while these numbers are not alarming in and of themselves, they do bring to mind the period from October-December 2015 when the sub-basins received 200+% of their averages and we were forced to release from the spillway gates. (Stakeholders might also recall the late 2015 rainfall mitigated the effects of the subsequent drought in 2016, which lasted nearly two years.)

These multiple cascades are a sight to behold, but we try to avoid sending water over the spillway whenever possible. Besides losing the potential to generate electricity, the sheer volume of the discharge can present a risk to life and property for our downstream stakeholders when water is released in this manner.

The current forecast suggests the basin will collect another inch of rain by this weekend, making the rainfall on par with November’s numbers with more than a week left in 2018.

Our water managers are continuing to monitor and if necessary, aggressively manage the pools in accordance with the water manual. In the meantime, we put “moderate amounts of rainfall” on the basin’s Christmas list.

~ Jeremy S. Buddemeier, Corporate Communications Office

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Permission granted: How the Corps governs federal waterways

By Tunis McElwain
Savannah District Regulatory Chief

A dock in a river requires permission from the federal government. Private-, public-, government-owned; all docks – and any other kind of work or construction in federal navigable waterways, must have a Department of Army permit granting permission for construction and existence – in perpetuity. Continue reading

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Fish passage weir with floodplain bench to replace lock and dam

Today we announced at a public meeting in North Augusta, South Carolina, the District’s recommended plan for replacing the New Savannah Bluff Lock and Dam with a fixed weir that can pass fish.

Out of seven possible alternative plans that were revealed in June, the recommended plan is the Higher Fixed Weir with Dry Floodplain Bench, known for short as Alt 2-6d. The construction cost for this plan is estimated at $68.9 million. Continue reading

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Leaning into fall

Despite having two hurricanes slash across the Southeast in as many months, the Savannah River Basin managed to collect only modest amounts of rain in September and October. Continue reading

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Corps of Engineers to reveal recommended fish passage alternative for lock & dam

SAVANNAH, Ga. – Officials with the U.S. Army Corps of Engineers, Savannah District, are scheduled to give a public presentation announcing the recommended fish passage plan Nov. 14 in North Augusta, South Carolina. Continue reading

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When does the federal government get involved in water resources issues?

By Steve Fischer
Chief of Planning Branch

It may strike some as an oddity that the U.S. Army is charged with riverine projects.

National civil works is a primary mission of the Army’s Corps of Engineers, but there are qualifications. Continue reading

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Savannah District Commander: Our system is a magnificent design

By Col. Daniel Hibner, Savannah District Commander

We are always grateful for an opportunity to explain how we operate the dams and reservoirs on the Savannah River. The Augusta Chronicle editorial staff has given us one such opportunity based on their Sept. 13 article in their explanation of why we don’t pre-release water from Thurmond Dam in anticipation of Hurricane Florence.

They are correct to report we do not make pre-releases in response to forecasted weather. Part of the reason for this is the lack of precision in weather forecasts.  So our engineers incorporated the unreliability of forecasts into the design of the Hartwell, Russell and Thurmond dams and reservoirs. Continue reading

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On rainfall and reservoirs re: Hurricane Florence

A photo of the eye of Hurricane Florence taken from space by European Space Agency astronaut Alexander Gerst.

(Editor’s Note: We have received several calls from media and concerned citizens related to our operations and posture as Hurricane Florence makes her way toward the East Coast. Below is a consolidation of our responses to these questions as of Sept. 12.)

The Savannah District remains at normal operations. This includes the District’s three hydropower dams and their associated reservoirs.

We have no plans at this time for any pre-releases of water from the reservoirs. The Corps bases its releases on current conditions, not on predictions that may or may not happen. Continue reading

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Wet summer could make Southeast more vulnerable

The graph shows the hurricane and tropical storm activity by month. September and October are normally the most active times during the year.

Hydrologists from NOAA’s Southeast River Forecast Center released their most recent Water Resources Outlook last week. Continue reading

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