Rivers within the basin have a low gradient, slow flow rate and a naturally turbid water quality. Several of the major Lake Eyre Basin river systems are well-known. Because the Lake Eyre Basin is almost flat, rivers flow slowly and frequently split up into floodplains or multiple braided channels. Water is lost to evaporation, to seepage, and in the many ephemeral wetland systems, with the result that downstream flows are typically smaller than upstream flows. Only in exceptional years is there sufficient upstream rain to provide a flow into Lake Eyre itself.