Drought Comparison 2011 to 2023

Drought Comparison – 2011 to 2023

By Jeff Lindner, Harris County Flood Control District’s Director Hydrologic Operations Division/Meteorologist, with a few minor edits for a non-technical audience.

There have been many comparisons of this summer to that of 2011 with respect to the heat and drought. Below, see the comparison of drought, water supply storage, and heat between 2011 and 2023.

Rainfall (Jan 1 to Aug 23)

 2023 Rainfall2023 Departure2011 Rainfall2011 Departure
BUSH IAH29.97-2.2910.93-21.33
College Station21.47-3.7910.57-14.12
As the table above shows, the rainfall departures in 2011 were significantly greater at all sites. That indicates a much more significant drought in 2011 than in 2023.

Rainfall departures in 2023 were tempered by a wet April and May over much of the area, while in 2011 drought conditions in the spring were some of the worst ever recorded with many areas recording their driest spring ever. 2011 was also preceded by dryness in late 2010 that helped to worsen the 2011 drought conditions and water supply concerns. 
Rainfall at Hobby Airport in 2011 (Feb-May) was only 1.31 inches compared to 2023 of 11.85 inches.
While it is clear that 2011 was worse with respect to lack of rainfall, the abrupt change in rainfall from late spring into the summer of 2023 has “shocked” vegetation across the region.

Additionally, it has been hotter to some degree (especially overnight) in 2023 and the flash drought has been severe with nearly the entire area drought free in early June to all of the area in severe to extreme drought as of August 15th.

The very warm maximum temperatures and record “high” low temperatures over the region have resulted in rapid degradation of vegetation health. Tree losses were staggering in 2011 and the area is starting to see losses mounting in 2023, but far below what was experienced at this point in 2011.

Comparison of Drought Conditions, Extents

In 2011, exceptional drought covered most of the state.

In 2023, exceptional drought is minuscule by comparison.

Reservoir Storage

2011 also featured significant drawdown on area lakes and water supply reservoirs as the longer duration “hydrological” drought resulted in record or near record low inflows to several lakes.

As of this afternoon, statewide reservoir storage is at 69.8% of capacity compared to 65.4% on this date in 2011. A low of 58.5% was recorded on 11-18-2011.

The table below summarizes storage capacities for the first 2 weeks of August 2023 compared to 2011:

 2023 Capacity2023 Departure2011 Capacity2011 Departure

Lake Conroe and Houston are much better off than in 2011 with Lake Livingston being nearly the same and both Somerville and Texanna significantly better off in 2023 versus 2011. This matches well with the rainfall trends experienced in late Spring over the area which for the most part filled Houston, Conroe, Somerville, and Texanna to near capacity, allowing the recent dryness to be well handled.

This was not the case in 2011 when a very dry spring and dryness from late 2010 was already depleting capacities prior to the summer increased demand and evaporation losses.

Central Texas Lake Levels Lower in 2023

However, across central Texas at Travis and Buchanan, conditions are worse at this point than in 2011.  Travis is 3.46 ft lower in 2023 than in 2011 and Buchanan is 0.45 ft lower.

Central Texas and the highland lakes chain have been in drought conditions since the summer of 2022 and rainfall this spring was not as significant in this area compared to coastal areas of the state and SE TX, so lake inflows have been very low and evaporation and demand maximized.

Heat Comparison

In addition to the drought conditions, it has been brutally hot. But how does 2023 compare to 2011 with respect to 100 degree or hotter afternoons? This is only part of the story of the heat of 2023, as overnight low temperatures have also been warm.  

College Station has recorded 42 days with a morning low at or above 80 degrees,  BUSH IAH 41, and Hobby 44. However, Galveston has recorded 64 days this summer at or above 80 degrees for a morning low.

The above average Gulf of Mexico waters are resulting in exceptional overnight heat along the coast.

Jeff Lindner, Harris County Meteorologist
 Days At or Above 100Days At or Above 105
BUSH IAH333432
College Station5251229

With the exception of Hobby Airport, 2011 and 2023 are nearly tied for the number of 100 degrees days up to 8-23. Hobby Airport has surpassed 2011 by 14 days.

More significant is the number of days at or above 105 with College Station crushing 2011 by 13 days. All sites have recorded more 105+ degree days in 2023 compared to 2011. The afternoon high temperatures have been higher in 2023 than in 2011 especially at Conroe and College Station.

Most of this has occurred in the last 3-4 weeks as the ground has dried and the influence of high dewpoints from the Gulf has become less. That has let afternoon temperatures spike higher compared to June and July.  

By Jeff Lindner, Director Hydrologic Operations Division/Meteorologist, Harris County Flood Control District, on 8/23/2023

2185 Days since Hurricane Harvey