Side effect of drinking lot of water.

I have always had high hemoglobin(17.9) and hematocrit(53.5) level. These have been fluctuating up and down a bit but never goes below the upper limit. I consulted a physician and i was told to take plenty of water, 15-16 glasses. I am a little concerned about that recommendation. I have tried drinking it for past few days and i can feel lot of weird things. - mild throbing around crotch. (Not kidneys, more like track leading to crotch) - muscle cramps - today, i woke up with a swollen hand. Now, i don't want to relate coincidence to causality but when i look these things up, its related to over hydration. On top of that, i am in bangalore, the weather isn't hot, surely that much water won't be retained, i have to pee almost every hour or two. Enough story, now question. - will drinking that much water actually help? - any alternative to water like ORS and all? - Any concern for kidneys as these are overused?