From [scifiwatcher's answer](https://scifi.stackexchange.com/a/151633):

> The only idea which comes close to, um 'holding water' is that the owners of the mining operations are deliberately creating shortages in order to control their work force. -Except that isn't indicated in the show, (unless you use more strained fan-boy semantics)...

Actually it's quite clear on the show why there are shortages on Ceres.

06:00, during the gaunt Belter's speech:

> Gaunt Belter: Every time we demand to be heard, they hold back our water, owkwa beltalowda, ration our air, ereluf beltalowda, until we crawl back into our holes, imbobo beltalowda, and do as we are told!
>
> Anderson Dawes: We do not want to live under anyone's boot, Fred Johnson, asilik towchu! Even a friendly one, afraid that if we disobey, we will have our air cut off, our water rationed, be spaced, or be herded into chambers to be used like animals.