One inch of draft（吃水） in a single barge is about 17 tons of cargo,and that's almost enough to fill a semitruck（半掛車）.Combine that with carrying about 30 barges instead of the more typical 45,and the drought is decreasing the cargo carried per tow by more than 500 semitrucks worth of goods.
combine為什么用動詞原型?carry about這里是考慮的意思嗎,字典查查沒這個用法.