frequently asked questions
about the data
I downloaded data from the old TWDB reservoir website and the numbers don't match! Why is this?
We've updated our methods for calculating these numbers. This website uses more accurate and up-to-date elevation-area-capcity rating curves, pool elevations and volume calculation techniques. In addition, we are excluding flood control reservoirs in the totals as they don't really contribute to the available water supply. Hence, small differences are expected between the previous numbers and the data we are publishing now.
Why don't the numbers on this website for lake X match those found on USGS/LCRA/IBWC/etc website?
Current water level (or water surface elevations) on this website should match what can be found on the original source websites. If they don't, you may have found a bug in our website so please let us know. In certain cases historical water levels may not match, since we have adjusted all the historical data to be at the same vertical datum. Historical water level data from the original source website may be shown in a different vertical datum.
Storage and surface area estimates are likely not to match exactly in several cases. The most likely reason is that we may not be using the same Elevation-Area-Capacity curve (or rating curve) as other entities. Through the TWDB hydrographic survey program we often have updated rating curves for many of reservoirs. We share these with partners like the USGS, but their databases may not be completely in sync with ours. In addition, we are using best available information for things like dead pool and conservation pool elevations. It is possible that these may not match between entities.