15 Feb Why is sediment in our water an issue?
Sediment is a natural part of the ecosystem, it is any mineral or organic matter that is deposited by wind, water, or ice. Therefore, the transporting of sediment by rivers is a natural function. However, here in Minnesota, we have more sediment being deposited than we want and it’s polluting our water.
How?
Erosion transports sediment. It can come from stream banks, agricultural land, and urban sources like construction sites. Sediment can be transported from any of these sources into bodies of water. Storms, snowmelt, and other weather phenomena can cause erosion and high sediment deposits. Storms deliver large amounts of water and sediment and after a big storm, water levels rise. The intense rainfall causes water to run through the land picking up small rocks and other debris. Soil permeability and infiltration rate then determine how much water is able to pass through the soil or if runoff will occur. Once in the water, the large deposit of sediment settles to the bottom or in swift-moving water the sediment can be transported further downstream.
Who cares about some rocks in our water anyways?
While sediment is a natural function of moving bodies of water, like anything too much of it can have a negative impact. In fact, the environmental protection agency lists sediment as the most common pollutant in rivers, streams, lakes, and reservoirs.
Fish and other aquatic life can experience difficulties breathing, eating, reproducing. Sediment polluted water can also ruin natural vegetation growth. Decreasing the growth of vegetation can reduce food sources for other animals that depend on it.
Sediment pollution can also be expensive. The Environmental Protection Agency states that sediment pollution causes $16 billion in environmental damage annually. Murky sediment-filled water can be difficult to clean and can have odor and taste problems. Having murky waters can also decrease water aesthetics, which can lead to a decrease in tourism and recreation.
There’s more
Lake Pepin bordered by Minnesota and Wisconsin is an excellent example of the damage’s sediment can cause. In 2002, Lake Pepin was deemed un-swimmable and unfit for fishing. Sediment is filling the lake quickly and with sediment comes high amounts of other unwanted nutrients like phosphates and nitrates. Pesticides and other substances can attach themselves to sediment and be carried into bodies of water, making high sediment deposits even more of an issue.
What can we do?
- Sweep sidewalks and driveways rather than hosing them down.
- Use compost or weed-free mulch on your garden to reduce soil erosion.
- On construction sites, erosion can be minimized by only breaking ground when necessary, implementing sediment traps and ditches, and stabilizing soils.
- Managing soil health is one of the most effective ways for farmers to prevent erosion and increase crop profitability. Soil health management systems include:
Crop Rotation
Cover Crops
Tillage Reduction
Mulching
Nutrient Management
Pest Management
Sources
https://cfpub.epa.gov/npstbx/files/ksmo_sediment.pdf
https://www.pca.state.mn.us/water/sediment-studies-mississippi-river
https://www.pca.state.mn.us/water/tmdl/lake-pepin-excess-nutrients-tmdl-project
http://www.fao.org/3/w2598e/w2598e05.htm
http://blueearthcountymn.gov/DocumentCenter/View/1529/Priority-Concerns-Scoping-Document-2016?bidId=