The light blue areas depict waters at the head of Lake Pepin which have fallen below a depth of 3 feet since measured in 1890. The darker blue areas show stretches of the river still greater than 3 feet deep - primarily the navigation channel, which the corps of engineers dredges to maintain a depth of 9 feet for barge transportation - though another 26 years of sediment should be factored in.
Over the past 150 years, the rate of that sediment supply has increase ten-fold, from 79,000 t/yr. before c. 1830 to 876,000 t/yr. during the 1990s (Engstrom et al., 2009b; Gran et al., 2009; Mulla and Sekely, 2009; Schottler et al., 2010; Belmont et. al., 2011).
Drawing conclusions from current sediment accumulation rates, the remaining volume of Lake Pepin (553 x 106 m3 in 1990) is anticipated to be filled completely in roughly 340 years (Engstrom et al., 2009b). With the increased accumulation rates of approximately 3-4 cm / yr, the shallow upper third of Lake Pepin will lack recreational or commercial value within a century (Kelley and Nater, 2000a; Engstrom et al., 2009b). Without the increased accumulation of sediment loading, today, Lake Pepin would be on average 1 m deeper, and could continue to provide recreational and commercial value for another 4,000 years (Kelley and Nater, 2000a; Engstrom et al., 2009b).