Brief, heavy rains accompanied by high winds and thunder rolled across the area late Tuesday into the early morning hours Wednesday, dumping as much as 2.19″ at Mullin (southeast of Brownwood) which recorded the highest rainfall amount in the San Angelo monitoring area of the National Weather Service.
Officially San Angelo recorded .66″ at Mathis Field, most areas in the city averaged in the .75” range with a high of .96” reported seven miles northwest of the city and a low of .11” measured at O.C. Fisher Reservoir.
The Twin Buttes reservoir jumped over a tenth of an inch in elevation due to the rain and runoff, gaining 702 acre feet (228.7 million gallons) in just 24 hours. The reservoir had been averaging an inflow of 165 acre feet (53.7 million gallons) per day of runoff from the heavy rains which saturated the area in September and October of 2018.
The reservoir now holds a total of 122,019 acre feet (39.7 billion gallons), which translates to 65.44% full. The reservoir has not held that much water since the 1990s and is the first stress test of the cutoff wall, completed in 1999, that was installed to keep the dam from leaking. All current monitoring shows that the dam is working as intended, and the safety modifications installed are performing to all design specifications. (For a complete report on the history of the dam and its leaking problems, PLEASE CLICK HERE).
O.H. Ivie now impounds an even 301,000 acre feet of water (98 billion gallons) after the night’s rainfall and subsequent runoff.
E.V. Spence gained 700 acre feet (228 million gallons) matching the inflow of Twin Buttes.
Oak Creek’s gain rose to put the reservoir over 102% full. Water has been running over its street/spillway since September.
Lake Nasworthy and the O.C. Fisher reservoir reported modest gains as well.
Overall, San Angelo stands at over 68 months (5 years, 8 months) of surface water supply. That time estimate assumes a worst-case scenario of no more rain or any other input to the water supply.