Particulate Material

Freshwater inflows carry sediments, nutrients, and organic materials into estuaries providing necessary components to maintain productivity and habitats of estuarine ecosystems (Montagna et al. 2002). The estuary is protected from strong tidal action and currents due to offshore peninsula and barrier islands, created by sediments settling out and forming banks. The sediments also support beaches and provision the inter-tidal wetlands. Particulate matter delivered to estuaries by freshwater inflows the primary energy source for organisms living in the estuary (Day et al. 1989). The timing of conveyance of sediments, nutrients, and organic material is affected by changes upstream (Montagna et al. 2013). Upstream diversions of freshwater are decreasing the amount of freshwater inflows that carry water, sediment, nutrients, and organic material to the estuaries.

Dams are a source of upstream diversions, affecting the water quality of freshwater inflows by catching sediment and reducing the downstream delivery of particulate materials (Alber 2002). The catchment of particulate material behind dams can lead to lag times in its release to the estuary disrupting the quality and accessibility of organic material (Vorosmarty and Sahagian 2000).

Other upstream changes affecting the loading of sediment, nutrients, and organic material include both point and non-point sources. Non-point sources are difficult to determine because the pollutants that result from them are wide spread and disperse. Some examples of non-point source discharges include agricultural runoff, gas and pipe leaks, salt from irrigation practices, and sediment from construction projects. The sources of point source discharges are more distinct and identifiable. Some examples of point source discharges include discharges from wastewater treatment facilities, industrial plant’s discharges, and sewer outfalls. Both point and non-point sources affect downstream water quality including nutrient and sediment concentrations and when combined with changes in freshwater inflow delivery times, can greatly alter loading patterns to an estuary. (Alber 2002).