Journal list

BOB MAINDELLE: With abundant rains, why are our lakes low? |

From my house nestled between Salado and Harker Heights, I can physically see Stillhouse Hollow Lake.

During the week of August 14, my rain gauge picked up two inches of rain. The following week another half inch was added. Then, on August 29, the area between Salado and Fort Hood received between three and five inches of rain, causing minor flooding.

With all this rain, many are wondering why our two local reservoirs, Stillhouse Hollow and Belton Lake, have not risen appreciably? Indeed, after Labor Day weekend, Stillhouse stood 8.59 feet down and fell; Belton Lake was 8.92 feet down and also falling.

The answer to this question revolves around the concept of watersheds.

Simply defined, a watershed is all the land on which a drop of rain can fall and, if it flowed unimpeded as runoff, would end up in a given body of water.

The reason our recent heavy rains did not cause our local lakes to rise is that most of the rain that fell over central Texas ended up in the Nolan Creek watershed and fell flowed away from us to the south and east, and not into the watershed of the Leon River, nor into the watershed of the Lampasas River.

For a rain to cause the water to rise in Belton Lake or Stillhouse Hollow, certain things have to happen. First, there must be sufficient rainfall to cause runoff. Runoff can occur in a number of circumstances. One way for runoff to occur is that steady rain seeps into the ground to the point where the ground becomes saturated to the point where it can no longer absorb water. Once the soil is saturated, any additional precipitation will run off. This runs over the ground, goes down and ends up in gutters, ditches, streams, streams, rivers, etc.

Another scenario that leads to runoff is a heavy, sudden, high-volume rainfall event. In this case, the soil is not completely saturated, but the rate at which it can absorb water is exceeded by the amount of rain present to absorb.

Once runoff begins, the potential for our lakes to benefit begins. This runoff must occur within the geographic boundaries of each lake’s watershed. Although the attached maps graphically depict the Leon River watershed for Belton Lake and the Lampasas River watershed for Stillhouse Hollow Lake, generally speaking the Leon River watershed extends northwest of Belton Lake toward Comanche in a band about 30 miles wide.

The Lampasas River catchment also extends to the northwest of our region from Stillhouse Hollow Lake towards Goldthwaite and Evant in a band about 20 miles wide.

Differences in topography, soil types, and land use account for the many differences between the two bodies of water, despite being located so close to each other.

For example, Stillhouse Hollow is much clearer than Belton Lake. This is partly because the waters of Lake Belton are more fertile because the water contains more nutrients that are carried away by the watershed. This greater nutrient load acts as a fertilizer for the algae and allows them to grow more in a cubic foot of water. This greater density of algae makes the water darker and greener than Stillhouse water. There are also many other examples of differences between these two neighboring bodies of water.

So, if we hope to see our reservoirs fill up, we must hope (personally, I prefer prayer!) not only that the rain continues to fall, but that it falls in the right places.

Now that we’ve visited the real reasons our local lakes stay below full pool, let’s dispel some of the misconceptions. I compiled this list based on the rumors I heard from local anglers.

First, there are no ongoing works on the dams requiring the Corps of Engineers to keep the water level low to allow such works.

Second, Stillhouse’s inability to rise with our recent rains is not due to over-pumping of water to Georgetown Lake.

Finally, the waters of Belton and Stillhouse Hollow lakes are not released in order to lower the water level to try and kill zebra mussels and/or hydrilla.

The bottom line is that Belton and Stillhouse Hollow Lakes will only rise significantly when heavy rains cause abundant runoff into the watershed for each body of water.