Water + Weather for April 2026

Transcript

Dr. Mark Wentzel - Hydrologist, Texas Water Development Board

Hi everyone, and welcome to the Texas Water Development Board's latest Water and Weather report. I'm Dr. Mark Wentzel, a hydrologist in the Surface Water Division here at the agency. And today, we'll be taking a look at conditions for our state at the end of April and some of the reservoir data available on the Board's Water Data for Texas website.

Let's take a look at some of the big water and weather headlines. Statewide, April was wetter and warmer than normal, a welcome break from the previous eight months, which were all drier and warmer than normal. Near the end of April, 75 percent of the state was in drought, down 14 percentage points since the end of March. At the end of April, storage in our water supply reservoirs was 74.7 percent of capacity, up more than a percentage point from the end of March, but still nearly nine percentage points below normal for this time of year. Modest declines in drought area are expected to continue at least through the end of July.

Let's take a closer look at the reservoir data available on the Board's Water Data for Texas website, and how that data gets rolled up into one number, statewide water supply storage, also called conservation storage as a percentage of total capacity. If you go to the link provided at the top of the screen, you'll land on this web page. Note the tabs across the top. There's a lot of data to explore here. We're only going to touch on reservoir data today. Also at the top of the page is one statewide number.

As I'm recording this episode, the monitored water supply reservoir storage across Texas is at 75 percent of capacity. How did we derive this number? It all begins with data from individual reservoirs. On the map, you can see a representation of data for the 120 individual water supply reservoirs monitored across the state. These 120 reservoirs account for 31.5 million acre-feet of water supply' more than 96 percent of the total water supply storage in the state. Where is the other 4 percent? In small lakes that do not post their data on the web, where it can be quickly retrieved.

At the bottom of the page, there's a table that includes recent conditions from individual reservoirs. They're listed by name in the left-hand column, with the most recent data for each reservoir in the columns to the right. Note the second column from the left, which shows the type of reservoir. Water supply reservoirs like Abilene, at the top of this list, have a dark blue wedge of water to the right of the dam icon. Their data is counted in the statewide water supply percentage. Flood control reservoirs like Addicks, second on the list, have a light blue wedge to the right of the dam icon. Their data is not counted in the statewide water supply percentage. Why not? Flood storage is only temporary. Lake owners do not have a state water right to divert this water for water supply. This water can only be discharged into the channel downstream as the danger of flooding recedes.

Many reservoirs like Amistad, fourth on the list, have both a portion of the reservoir dedicated to water supply, sometimes called the conservation pool, and a portion dedicated to flood control, known as the flood pool. These lakes have both a dark blue and light blue volume of water to the right of the dam icon. For these reservoirs, only data related to the water supply portion of the reservoirs contributes to the statewide water supply percentage. Note also that Lake Amistad, like several other reservoirs, is on the border of Texas. The water supply portion of these lakes are shared with one or more of our neighbors, either Mexico or a neighboring state or states. For these shared lakes, only data related to the Texas share is used in the calculation of statewide supply.

The individual reservoir data can be rolled up into many different groupings, as shown on the tabs on the second from the top row at the top of the page, including statewide or across an individual water planning area, river basin, municipal area, or climate region. All the percentages provided for each of these groupings is based on the total water supply capacity over that entire grouping. So, when you see that statewide water supply storage is 75 percent, that doesn't mean that a large number of lakes in Texas are 75 percent full. It means that the monitored water supply lakes statewide have a combined storage of 75 percent of the statewide monitored capacity, or a volume of about 23.6 million acre feet, out of a capacity of 31.5 million acre feet.

To see the condition of reservoirs in your local area go to the page for your municipal area, river basin, planning area, climate region or individual reservoir. That concludes our report. Until next time, I hope you all stay healthy and safe and receive some beneficial inflows to your local reservoir.