Citizen Science River Project

Surveys include observations on land use, recent rainfall, river flow, vegetation (including invasive plants) and wildlife. Measurements are made of the following:

Temperature

Temperature is a vital parameter within the river ecosystem. It controls many of the aquatic species' life cycles. Temperature fluctuates with the seasons and there is often variation within those, particularly in small rivers and streams. Monitoring temperature over the years will help track the impact of climate change on our waterbodies.

Total Dissolved Solids

Total Dissolved Solids (TDS) is directly related to the conductivity of the water. The more minerals, salts and metals that are dissolved in the water the more conductive it gets. Low levels of dissolved solids in waters such as those on Dartmoor or those near to the source of the river, are a result of very low levels of input from the surrounding landscape. The underlying geology will also influence the normal level of conductivity in a watercourse (e.g. areas dominated by granite generally give a lower conductivity than those with limestone). As the river runs down to the sea it collects material from many different inputs, some natural and some man-made such as farms, sewage plants, factories and residential areas and typically increases the amount of solids dissolved in the water leading to a higher reading. Harmful pollution from things like sewage, slurry and factory discharge will usually elevate the TDS reading, but some pollutants, such as oil can lower conductivity, so it should only be used as a general indicator of water quality not a specific measure of toxicity.  Regular monitoring will allow the detection of changes in conductivity which can indicate pollution.

Turbidity

Turbidity is a measure of the optical clarity of the water; water is viewed from the top of a long clear tube and emptied out until the black and white motif at the base is clearly visible. The more suspended particles there are in the water, the lower the clarity and the higher the turbidity. Often waterbodies gets more turbid after heavy rainfall due to soil run-off from the fields and sediment being mixed into the water column. This loss of topsoil is both a problem for farmer and river as it often contains chemicals from the fertiliser and pesticides used on the land. An increase in sediment level on the substrate of the river can potentially reduce light and oxygen and smother the riverbed habitat. Less mobile aquatic invertebrates and fish eggs struggle to survive in low oxygen conditions and without light, while plants are unable to grow. It is a good practice therefore to sample waterbodies after different weather conditions to better understand how it responds to rainfall or drought.

Phosphate levels

Phosphate occurs naturally within the river ecosystem, but in very low levels under 0.05 mg/l; levels higher than this may therefore indicate manmade input. Phosphate is found in animal and human waste, cleaning chemicals, industrial runoff and fertiliser, so this can be a good indicator of pollution. Raised levels of phosphate can lead to increases in plant growth within the watercourse, which leads to a depletion of oxygen and without oxygen aquatic species cannot survive and the river ecosystem collapses. On the other hand, it is important to note that phosphate is taken up by plants, so a low reading may be a result of high plant growth and algal blooms may be evident.

What Happens next?

The survey results are added to the Cartographer database kept by the Southwest Rivers Trust. Lydia and Simon at the Trust approve results and provide advice on any actions needed, such as reporting abnormal results to the Environment Agency or Cornwall Council. Recent concerns about high phosphate levels were reported and have since led to closer collaboration between the various agencies involved with the StARR project (for more information see the blog article for August 2020), which will hopefully lead to better understanding of possible causes of pollution.