Hydro is a spectacularly poor example. But I'll pay the underlying idea as a possible winner if we substitute something that (unlike hydro) is (a) environmentally friendly, (b) effectively unlimited, and (c) unable to be used directly for baseload power without some very fancy load-balancing and/or storage techniques.
Hydro is none of those things: it is a very serious problem for river health and species preservation (big dams do all sorts of horrible things to streamflow pattens, nutrient loads, siltation profiles, precious landscapes (you are very often flooding prime farming land and the very best soils you have), in-stream biodiversity, and so on). It seldom plays nice with other water storage objectives (for flood control you want to keep the dams empty; for irrigation and town water you want to keep them full; either way, you can only benefit from hydro in an opportunistic fashion, when you are letting water go anyway). Hydro is very, very limited. Only places with massive water resources and tiny populations can get a great deal of benefit from hydro as a mainstream power supply (Norway, Tasmania - and even in the case of that last-mentioned example, their hydro came at a crippling environmental cost and is in any case so inadequate that Tasmania has to buy power from the mainland.) In any country with even a moderate population density, hydro cannot provide anything more than a minor supplement to the overall power system. Lastly, hydro is a poor choice for time-flexible power supply. Other than constraints which apply to multi-purpose storages (i.e., to primary storage and flood control dams), hydro has one great advantage: you can use it any time you like. It is a crime to waste hydro power on non-time-critical generation (such as for daytime baseload power or for turning CO2 into rock) when you can use a less flexible alternative for those things (solar if the sun is shining, wind if it is blowing, thermal if you have no other choice). Hydro is your wildcard. You hold it in your hand as long as possible and only put it on the table when you can't do the job some other way. You keep that dam full 'cause a full dam is ready to get you out of trouble any time you need it. Once you let that water run down the hill, you have to wait for it to rain again.
But, of course, your mention of hydro was a casual thought and I'm even further off-topic than usual by replying to it at such length. Hey - what did you expect?
We can substitute in something like solar or wind power - both things that provide lots of cheap, sustainable power but at inconvenient times sometimes - and, if the CO2 to rock process works as advertised, get a real benefit. I like it.