our body need to conserve its blood volume to almost five litres..bt dere are losses of fluids through various routes in a day..like sweating,breathing,urine and stools if u dont replenish those losses it the amount of urine keep decrease its concentration and color vl increase. its nt kidney disease till nw bt it ds put unneccessary load in kidneys..thicken ur blood make u vulnerable to get brain stroke. all dese catastrophe cn be prevented if u take 3 to 4 litter water a day. its like loss hs replinished. hisaab barabar.