In 2018, the Highland Lakes watershed saw both serious drought and significant flooding. The year started very dry, but ended with major flooding on the Llano River that caused Lake Travis to rise to its fifth-highest level.
From January through August, the amount of water flowing into the Highland Lakes on the Colorado River was the fourth lowest on record for that eight-month period.
The weather pattern changed in September, as the basin began to see widespread, frequent rain. Inflows to the Highland Lakes in September were more than the previous eight months combined.
In October, back-to-back floods on the Llano River sent 1.3 million acre-feet of inflows into the Highland Lakes – the highest amount of inflows on record for October. During the flooding, LCRA had flood operations underway at every dam along the Highland Lakes simultaneously.
By the end of the year, lakes Travis and Buchanan – the region's water supply reservoirs – were full, at the top of their water supply pools.
With dry conditions for so much of the year, municipal water use from the Highland Lakes increased by 16% from 2017 to 2018. The amount of water released from the Highland Lakes for downstream agriculture also increased from 2017 to 2018 – by 130%.