Why shall victims of water deprivation situations require water taken in at gradual stages in most novels?

after water deprivation your total blood volume reduces drastically,by taking in a large volume of water there would not be effective exchange of the wate b/n the blood and the cells of the body hence a large amount of it remains in the blood increases the filtration rate and hence the volume of water u bring out,but sipping water at spaced intervals gives enough time 2 equilibrate and hence does not affect thet urine output that much hence a larger percentage of the water is conserved as compared 2 the former.NB there is more to it than wat is written above.