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