Studies of suspended sediment in the 170-km 2 River Ystwyth catchment (mid-Wales) for 1973–1975 suggest two complementary methods of identifying their sources. The colour of yielded sediments, and the details of sediment-discharge relationships with respect to time, allow a separation into “channel” and “non-channel” sources. In two successive years, yields of 43,439 and 12,233 t are estimates, with “channel” sediments contributing 40.5 and 53.3%, respectively. Explanations for such yields and the more general applicability of the methods used, are discussed.