i think huobi volume is ok but take a look at okcoin: the volume and order book depth doesnt fit with its low volatility. prolly there are bots buying and selling the same amounts all day generating huge volumes.
OKCoin's figures have been iffy for a while now. Every time I look at
this page, they're always dwarfing the volume of every other exchange put together. It's incredibly difficult to believe that could possibly be accurate in any way, shape or form.