Table 4.4: Major principal sources and impacts of sedimentation

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Table 4.4: Major principal sources and impacts of sedimentation
Pertinence	Sector	Action or mechanism	Impacts
Source: Adapted from Environment Canada (2005a), www.atl.ec.gc.ca/udo/mem.html
Note: Water transforms landscapes and moves large amounts of soil and fine-grained materials in the form of sediment. Sediment is: 1) eroded from the landscape, 2) transported by river systems and eventually 3) deposited in a riverbed, wetland, lake, reservoir or the ocean. Particles or fragments are eroded naturally by water, wind, glaciers, or plant and animal activities with geological (natural) erosion taking place slowly over centuries or millennia. Human activity may accelerate the erosion. Material dislodged is transported when exposed to fluvial erosion in streams and rivers. Deposition occurs as on flood plains, bars and islands in channels and deltas while considerable amounts end up in lakes, reservoirs and deep river beds.
SOURCES
Agriculture areas, downstream catchments	Agriculture	poor farming with excessive soil loss	increase soil erosion add toxic chemicals to the environment sediment and pollutants are added to streams irrigation systems maintenance cost increased
Forest and development access areas, downstream catchments	Forestry, Road Building, Construction, Construction, Mining	extensive tree cutting lack of terrain reforestation lack of runoff control in steep terrain	increase natural water runoff accelerated soil erosion creating more sediment
MAJOR IMPACTS
Major rivers and navigable waterways	Navigation	deposition in rivers or lakes dredging (streams, reservoirs, lakes or harbors)	decreases water depth making navigation difficult or impossible. releases toxic chemicals into the aquatic or land environment.
Aquatic ecosystems	Fisheries / Aquatic habitat	decreased light penetration higher suspended solids concentrations absorbed solar energy increases water temperature carrying toxic agricultural and industrial compounds settling and settled sediment	affects fish feeding and schooling practices; can reduce fish survival irritate gills of fish, can cause death, destroy protective mucous covering n fish eyes and scales dislodge plants, invertebrates, and insects in stream beds affecting fish food sources resulting in smaller and fewer fish, increased infection and disease susceptibility stress to some fish species release to habitat causes fish abnormalities or death buries and suffocates eggs reduces reproduction
Lakes, rivers, reservoirs as water supplies	Water supply	increased pump/turbine wear reduced water supply usability for certain purposes additional treatment for usability required	affects water delivery, increases maintenance costs reduces water resource value and volume increased costs
Hydroelectric facilities	Hydropower	dams trap sediment carried downstream increased pump/turbine wear	diminished reservoir capacity shortened power generation lifecycle higher maintenance, capital costs.
All waterways and their ecosystems	Toxic chemicals	become attached or adsorbed to sediment particles	transported to and deposited in, other areas later release into the environment.

Source: UNESCO The United Nations World Water Development Report 2
Section 2: Changing Natural Systems,
Chapter 4, Part 2. Nature, Variability and Availability, p.134