many of the rivers in this list have uncertain discharges. with the exception of those in russia, streamgauges have seldom (if ever) been placed on the majority of the largest unfragmented river systems, due to the remoteness and/or ruggedness of the terrain in which they are located. apart from the fly which is clearly the largest, all ranks listed here are not perfectly certain, and there also exist a number of rivers in sundaland that might qualify with reliable discharge data, such as the kapuas.