Why is it that when there is a drought situation that no one ever digs the reservoirs deeper?

Question

While the reservoir is almost dry, it would be an excellent opportunity to increase the dept so that when it does rain, it will hold more thus preventing flooding and also have more to use in drought conditions.

Answer 1

As the first 2 answers here show, most people are not capable of rational thought. Digging out the sediment that has built up in the upstream parts of a reservoir would be a great way to increase capacity, and would not require making the dam higher. During droughts a back hoe and a dump truck would do the job, and although the digging would not make the reservoir fill up faster, there would be more capacity for more water when it rained.
The sad truth is most people are not capable of such logic, and in a democratic republic like the US those who cannot understand what you ask about vote and they drive policy decisions. There is also the tendency to put off finding solutions until it is too late, and it takes a long time to get the government to appropriate money, and by the time the arguing was over it would be raining and the work could not be done.

Answer 2

Most reservoirs are not just holes in the ground but are lakes contained behind dams. So to enlarge them you do not just dig them out, you have to raise the height of the dam. The heights of the dams were engineered to be as high as practical taking in consideration the geology, need, and economics.

Answer 3

I think it is because it would be too expensive and a hugely unpopular political move.

The Reservoirs are usually miles wide and digging them deeper doesn't make them fill up any faster.

mainly people would complain that their money was being wasted on something that doesn't produce more water.