At present, the Willamette River is cloudy and murky – something that may help or hinder salmon fishing efforts.
City water plants in Sweet Home and Wilsonville are working around the clock to filter mud washing downstream from reservoir drawdowns carried out under court order to assist migrating salmon.
What is Turbidity?
Willamette River provides Oregonians with their drinking water source, with water quality parameters like temperature, dissolved oxygen levels, pH level, and conductivity all being regularly measured. Turbidity also plays an important role; it estimates how much material in suspension reduces light passing through it – this could include clay particles, silt particles, sand grains, or microbes, among other substances – thus decreasing passage.
Turbidity measures how cloudy the water is. To calculate it, special meters send light beams through to estimate how much is scattered or absorbed into it.
Maintaining a turbidity meter at every spawning area takes considerable work and money since each meter must be transported in a secure case, kept optically clean to protect its glass cells, and volunteers trained on how to use the device correctly. However, doing this is crucial to monitoring water quality in the Willamette River.
Turbidity makes it hard for fish to find suitable breeding areas and photosynthesizing plants to receive enough sunlight, as well as displaces naturally present dissolved oxygen, leading to decreased plant and animal growth and encouraging pathogen growth that can make people sick if they come into contact with it. When this level is reached, fish spawning sites become hard for fish to locate as they struggle to find adequate spawning spots; additionally, displacement of oxygen displacement can displace natural levels that should exist naturally in water bodies, which causes displacement of naturally present dissolved oxygen which results in decreased plant and animal growth due to fallen plant and animal growth due to reduced plant and animal growth due to decreased plant and animal growth – leaving animals struggling when trying to locate suitable spawning areas; displacement of natural oxygen which leads to reduced plant and animal growth due to displacement by displacement or replacement by pathogen growth which potentially can make people sick from coming into contact with it – leading to sickness caused by contact.
How is Turbidity Measured?
The easiest, lowest-cost method of measuring turbidity is with a Secchi disk or turbidity tube, both manual instruments that can be submerged into lakes and streams until their markings become obscured before cross-referencing them against a scale for comparison. However, this approach relies heavily on user eyesight and appropriate lighting conditions.
An accurate and precise way of measuring turbidity is with a nephelometer or turbidity meter. These devices feature a photodetector at an angled position from the light source (usually 90 degrees), which eliminates stray light interference as well as color interference issues. Turbidity measurements are reported using NTU or FTU units.
Water turbidity measures the amount of material suspended in a body of water — including soil particles, plankton, bacteria, and algae — which can impact everything from fish finding their breeding areas to drinking water quality.
Turbidity reduces water’s ability to hold and transport oxygen, leading to decreased levels of dissolved oxygen, which are detrimental to aquatic life and can increase treatment costs and timeframes for groundwater wells in communities such as Sweet Home that depend on South Santiam, Middle Fork, and mainstem Willamette reservoirs for drinking water supplies. As drawdowns have repeatedly occurred at these reservoirs over the years, they have released massive amounts of sediment into Oregon streams, providing this community with drinking water supplies. This poses a real problem as it reduces their capacity as they act as reservoirs act as reservoirs holding large quantities of sediment that have caused multiple drawdowns to release mass amounts downstream into Oregon streams from where these Oregon communities depend on for drinking water supply systems like Sweet Home in Oregon replete.
What is the Threshold for Turbidity?
The Willamette River is an invaluable asset to Oregonians. It provides drinking water to residents and serves as a recreational playground. Furthermore, its ecosystem services – flood control and pollination, among others – make it an essential asset.
Unfortunately, the Willamette River is experiencing many threats to its health and sustainability, such as habitat loss, pollution from industrial activities, dam operations, non-native species invasion, and non-native species infestation. All these issues have contributed to a decrease in biodiversity along the river as well as negatively affecting its water quality.
As part of their effort to maintain high water quality standards, Portland has established a Total Maximum Daily Load (TMDL) for Willamette River that includes limits for bacteria, dissolved oxygen, and turbidity. They have also found a treatment plan designed to safeguard its waters.
Turbidity in the Willamette River can be affected by several factors, including rainfall and soil conditions. However, erosion from urban development and agricultural activities is perhaps its single most significant influence, carrying sediment, phosphorus, and other pollutants into the river and significantly increasing turbidity levels.
How Long Does Turbidity Last?
Persistent turbulent water conditions can reduce dissolved oxygen levels and hinder aquatic plant growth, potentially leading to fish kills. Furthermore, high turbidity limits light penetration to lakes, rivers, and streams in ways that diminish marine habitat value and recreational enjoyment.
Turbidity measures the amount of suspended matter in water and correlates with, but does not equal, total suspended solids (TSS), which are measured by weighing a sample of water. As turbidity rises, more suspended solids appear.
Particulates enter natural bodies of water through various sources, leading to increased turbidity levels. Rain and melting snow flowing over the landscape can rapidly increase stream velocity and stir up and suspend loose sediments in streams, quickly raising their turbidity levels. Turbidity levels may also rise when construction activities, agricultural or forestry practices, logging activity discharges, or other land-disturbing activities occur on or near streams without sufficient erosion control measures in place.
Algal blooms can also contribute to increased turbidity by proliferating rapidly and producing large volumes of organic material that reduce visibility in water bodies, negatively affecting submerged vegetation rooted into their substrate. Such conditions are known as hypereutrophic conditions.
