Understanding Suspended Sediment Concentration

• SSC stands for Suspended Sediment Concentration
• It refers to the concentration of solid particles within a liquid
• The particles are kept in suspension by the turbulence of stream flow or the ambient fluid, which is often water
• SSC is typically gauged in milligrams per liter (mg/L) or parts per million (ppm)
• It is a pivotal indicator of both water quality and environmental health

Sources of Suspended Sediment

• Natural erosion occurs via the weathering of rocks and soil by wind and water
• Deforestation, or the removal of trees, exposes soil and leads to erosion
• Agricultural practices like tillage and overgrazing disturb soil, thus increasing erosion
• Construction activities and land development expose soil
• Urban runoff occurs as stormwater carries sediment from streets and construction sites
• Industrial discharge occurs when some industries release wastewater laden with sediment

Factors Affecting SSC

• Rainfall intensity impacts erosion and runoff, where heavier rainfall usually increases erosion
• Slope of land impacts erosion, as steeper slopes can facilitate it
• Soil type impacts erosion, where some soils are more susceptible to erosion than others
• Vegetation cover reduces erosion, as denser vegetation is able to limit it
• Streamflow velocity impacts sediment, as higher velocities are able to suspend more of it
• Land use practices like agriculture, forestry, and urbanization all impact sediment load

Effects of High SSC

• Reduced water clarity: Turbidity increases, which ultimately negatively impacts aquatic life and recreational possibilities
• Habitat degradation: Sediment smothers spawning beds and benthic habitats
• Reduced reservoir capacity: Sediment accumulates in reservoirs, which ultimately reduces storage
• Increased water treatment costs: Dealing with more sediment necessitates increased treatment for drinking water
• Impact on navigation: Sedimentation can obstruct waterways
• Transport of pollutants: Sediment can carry pollutants like nutrients, pesticides, and heavy metals

Measurement of SSC

• Grab samples: Water samples collected manually before being analyzed in a lab
• Automatic samplers: Collect samples at regular intervals or during particular events
• Turbidity sensors: Measure water clarity, which has a close relationship with SSC
• Acoustic Doppler Current Profilers (ADCP): Measure flow velocity to estimate SSC
• Satellite remote sensing: Estimates SSC over large areas using spectral data

Relationship Between SSC and Turbidity

• Turbidity measures water clarity, while SSC measures the concentration of solids suspended in water
• Turbidity and SSC, while related, are not the exact same because particle size and composition have an influence on turbidity
• Turbidity is often utilized as a substitute for SSC because it can be measured both continuously and in situ
• An accurate estimation requires that a site-specific relationship between turbidity and SSC be established

Sediment Transport

• Suspended load: Fine particles carried within the water column
• Bed load: Larger particles that roll, slide, or bounce along the streambed
• Wash load: Very fine particles that are always suspended and not found in the streambed
• Total sediment load: The sum of both suspended load and bed load

Modeling SSC

• Empirical models: Based on statistical relationships between SSC and other variables
• Physically-based models: Simulate erosion, transport, and deposition processes
• Models help predict SSC under different scenarios and inform management decisions

Management Strategies for Reducing SSC

• Erosion control: Enact practices to reduce soil erosion right at the source
• Sediment control: Trap sediment before it can get to water bodies
• Riparian buffers: Keep vegetation along stream banks to filter runoff
• Stormwater management: Employ detention basins and other practices to reduce runoff
• Best Management Practices (BMPs): Apply agricultural, forestry, and construction practices that minimize sediment pollution
• Streambank stabilization: Protect stream banks from erosion with vegetation or structural measures

SSC and Water Quality Standards

• Many jurisdictions have water quality standards for turbidity or SSC
• These standards seek to protect aquatic life, recreation, and drinking water sources
• Violations of these standards can result in regulatory action

Importance of Monitoring SSC

• Track trends in water quality over time
• Assess the effectiveness of management practices
• Identify sources of sediment pollution
• Support research on aquatic ecosystems
• Ensure compliance with water quality standards
• Provide data for modeling and prediction

Technological Advancements in SSC Measurement

• Development of more accurate and reliable turbidity sensors
• Use of remote sensing to monitor SSC over large areas
• Improved data processing and analysis techniques
• Development of real-time SSC monitoring systems

The Role of SSC in Ecosystems

• SSC impacts light penetration, which has an effect on primary productivity
• Sediment can provide habitat for some organisms
• Excessive SSC can harm aquatic life by clogging gills, reducing feeding efficiency, and burying habitat
• Sediment can transport nutrients and pollutants, which affects both water quality and the overall health of the ecosystem