After a long, dry summer, substantial rain finally fell across the Brazos River basin.
Enough rain, in fact, to fill all three Brazos River Authority reservoirs.
The filling of Possum Kingdom Lake, Lake Granbury and Lake Limestone prompted releases from the dams. And with those releases came a not-so-pleasant occurrence.
The smell of sulfur near the dam is normal during a release.
During large volume releases, one may occasionally notice an odor similar to “rotten eggs.” This odor is hydrogen sulfide gas, a naturally occurring by-product of decaying organic material found in the sediment, or stuff on the bottom, of lakes and riverbeds. Though the strength of the odor may suggest otherwise, hydrogen sulfide gas is considered harmless in low-level concentrations similar to all dam releases.
Once the release is reduced, the smell will pass as well. While no one is fond of the smell, we are thankful for the recent rains that filled BRA reservoirs and increased the water supply across the Brazos River basin water supply system.
The water supply system saw additional rainfall, associated runoff and increased storage in water supply this week. The BRA water supply system includes 11 reservoirs scattered across the 42,000-square-mile river basin. In addition to storing water in the three reservoirs owned and operated by the BRA, the system includes water supply stored in eight federally-owned flood control lakes Proctor, Whitney, Aquilla, Belton, Stillhouse Hollow, Georgetown, Granger, and Somerville. The BRA contracts with the US Army Corps of Engineers for maintenance and operations of these reservoirs.
The heaviest recent rainfall occurred upstream of Possum Kingdom Lake along the Clear Fork of the Brazos River, just north of the Abilene area. In that area, there were 5 to 7 inches of rain over a period of a few days, said BRA Water Services Manager Aaron Able. Areas just south of Seymour, upstream of Possum Kingdom Lake along the mainstem of the Brazos River, also received 6 or more inches of rain over a three-day period, Able said.
Between 1 and 3 inches of rain fell last week in the watershed between Possum Kingdom Lake and Lake Granbury, he said. The upper portions of the Navasota River watershed above Lake Limestone also received between about 1- and 2-inches last week.
The rain came at just the right time, too.
The BRA entered the first stage of our Drought Contingency Plan at Lake Proctor late last month when the lake level dropped below the Stage 1 Drought Watch trigger elevation. Due to the improvements in the water supply, the BRA was able to terminate the Stage 1 Drought Watch for Lake Proctor last week, Abel said.
The total BRA water supply system storage is now about 96 percent full, up from 91 percent just a few weeks ago, Able said.
So while the smell is unpleasant, it’s a sign the reservoirs, and our water supply, are full -- which is, of course, a good thing.