If such a rain event occurred on these two tributaries when Travis were near its 681' pool stage, the water might be lost or spilled into Matagorda Bay. Lake Buchanan, while close to Travis in total volume, is broad and relatively shallow compared to Lake Travis. Water stored in Buchanan, because of its large surface area, is more subject to loss by evaporation than water stored in Travis. Considering these characteristics of the two lakes, and using the criterion of minimizing total water lost to spills and evaporation, the present procedure was developed. The result of the present system is that Travis is typically drawn down for all of the boating season, while Buchanan is drawn down only near the end of the summer boating season.
Weather plays a role in the procedure, of course.
In 2000, both reservoirs were comparatively low at the start of the irrigation season, and the drawdown during the irrigation season only compounded a serious low water situation. In 2001 a completely different situation exists. Because of the frequent rains, both in the hill country and the lower Colorado basin, there has been little stored water released by the rice irrigators, because there was enough water in the river to take care of their needs during the early part of the season. Some recreational users of Lake Travis have criticized the present system because it considers water conservation as the sole criterion, and ignores the impact of water level on the boating economies of the reservoir lakes. The disparity in economic activity between the two lakes has increased substantially since that study was done.