Jill A. Marshall

Anthropogenic stressors on large rivers have significantly modified riverine sediment transport. However, the impacts of dredging and sand and gravel (S&G) mining are poorly monitored. We quantify these impacts on the lower Arkansas River, USA, where anthropogenic processes are well documented. The construction of dams caused a 98% reduction in suspended sediment discharge ( Q ss ). Since dam construction, fluvially transported suspended sediment (4.4 ± 0.5 Mtyr −1 ) and suspended sand discharge ( Q sand ) (1.1 ± 0.1 Mtyr −1 ) are of the same order as the dredging rate (1.2 ± 0.1 Mtyr −1 ) and S&G mining rate (1.7 ± 0.1 Mtyr −1 ). While the modern sediment deficit on the Arkansas River is smaller than in rivers documented in developing countries, dredging and mining significantly alter the sediment balance in this large river, indicating that extraction management is needed worldwide, especially in developing economies, to improve ecosystem sustainability in large rivers.