Links to things I’ve written before:

Waterlogged? BMJ

the mad colour chart (zillions of versions online, how much money have the NHS spent creating these? ffs)

BMJ on this

and some links to the primary science:

First report I can find of using colour charts of some type to assess urine colour

studies in 1990s of deliberately dehydrating athletes (ie exercising them and forbidding fluids ) eg this and this and there is this and this – very different from people who have free access to, and can access fluids for themselves

IT IS WORTH SAYING HOWEVER

that in one trial of pre menopausal women with recurrent symptoms, drinking more water did reduce the amount of urine infections . this is the only RCT I know that found a benefit .