5.3. Impact of Resuspension on Water Quality

Resuspension is when surface sediment gets taken away due to the turbulent action of water. This process increases total suspended solids (TSS) in the water, leading to potential contamination.

Resuspension occurs when sediment, which usually settles at the bottom of water bodies, is dislodged by turbulence. This turbulence can be caused by factors such as increased water flow or disturbances like boat activity. When sediment is resuspended, it turns into suspended solids, increasing the concentration of particulates in the water column, which can carry contaminants with them.

Think of a glass of muddy water. If you let it settle, the mud rests at the bottom. However, if you shake the glass, the mud becomes suspended in the water and makes it cloudy. This shaking mimics turbidity in rivers caused by heavy rain or human actions like dredging.

Resuspension typically occurs during heavy rainfall, flooding, or increases in water velocity, which can lead to sediment being carried into floodplains.

When rivers experience heavy rainfall, the flow rate of water increases, creating turbulence. This turbulence is powerful enough to lift sediment from the riverbed and transport it downstream. These events can create floodplains where sediment is deposited, often leading to ecological changes due to the displacement of sediments.

Imagine a playground after a heavy rain. Just as the rain creates puddles and washes dirt around, affecting the playground's surface, river flooding stirs up and carries sediment into new areas, changing the landscape.

During resuspension, harmful chemicals adhered to sediment particles can enter the water, increasing the effective chemical concentration and posing risks to aquatic life.

When sediment is resuspended, any contaminants that are bound to the sediment particles are also released into the water column. This process raises the concentration of these contaminants, making the water potentially hazardous to aquatic organisms, which may ingest these particles or the chemicals may be desorbed into the water, increasing toxicity.

Consider a sponge soaked in dye. When you wring it out, the dye gets released into the water around the sponge. Similarly, when resuspended sediment is disturbed, chemicals absorbed onto the particles are released into the water, raising contamination levels.

The size of particles in the reservoir affects how contaminants disperse in water. Smaller, colloidal particles tend to remain suspended longer and have a higher tendency to carry contaminants.

In sediment, different particle sizes exist, from larger sand grains to submicron colloids. Smaller particles typically have a larger surface area relative to their volume, allowing them to adsorb more contaminants. When resuspended, these small particles can remain suspended in the water for an extended period, potentially spreading contaminants further as water moves.

Think of a dust cloud in the air. Fine dust particles float longer and travel farther compared to larger particles, just as smaller sediment particles move more freely in water and carry more contaminants with them.

Resuspension can lead to significant water quality issues, affecting not just aquatic life but also human health and ecosystem stability due to the spreading of contaminants.

When contaminants are resuspended into water bodies, this can cause detrimental effects on local fish populations, aquatic plants, and overall ecosystem health. These contaminants can lead to bioaccumulation in fish, which can eventually affect wildlife and humans who rely on these water bodies for sustenance.

Consider a contaminated pond where a storm stirs up the sediment, releasing toxic materials into the water. Fish feeding in this water might get sick or die, and people who fish in this pond risk health issues by consuming those fish, thus connecting the quality of the water to human health.

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