The Ohio River is a naturally shallow river that was artificially deepened by a series of dams. The natural depth of the river varied from about . The dams raise the water level and have turned the river largely into a series of reservoirs, eliminating shallow stretches and allowing for commercial navigation. From its origin to Cincinnati, the average depth is approximately . The largest immediate drop in water level is below the McAlpine Locks and Dam at the Falls of the Ohio at Louisville, Kentucky, where flood stage is reached when the water reaches on the lower gauge. However, the river's deepest point is on the western side of Louisville, Kentucky. From Louisville, the river loses depth very gradually until its confluence with the Mississippi at Cairo, Illinois, where it has an approximate depth of .