River Water Monitoring

Once a week students from Path Hill Outdoors visit the River Thames at the Oratory Boathouse Mooring and undertake a number of water quality tests. We have joined the Drinkable Rivers Citizen Science project which aims to have concerned citizens monitoring rivers throughout Europe.

Interpreting the Results

E. Coli bacteria

If this bacteria is ingested it can cause illness. The amount of E Coli in the river fluctuates according to rainfall. When it rains hard our sewage system can sometimes not handle the extra water. This can cause the sewage to overflow into rivers increasing the E Coli content. We use the results from the Thames21 initiative who send water samples to a laboratory to accurately measure E. Coli levels.

Low Quality – Over 1000+ CFU/100ml – The River has excess sewage in water.
Average Quality – Between 500 to 1000 CFU/100ml – levels of E. Coli are acceptable
Good Quality – Below 500 CFU/100ml – levels of E. Coli are good

Intestinal Enterococci

Enterococci are found in human and animal faeces, and their presence in water can indicate the presence of other disease-causing pathogens. This can be a health risk for people who swim in or eat raw shellfish or fish from contaminated water.

Low Quality – Over 200+ CFU/100ml – The River has excess Enterococci and sewage.
Average Quality – Between 200 to 400 CFU/100ml – levels of Enterococci are acceptable
Good Quality – Below 200 CFU/100ml – levels of Enterococci are good

Nitrates

Nitrate is an important nutrient for plants but too much allows certain plants such as algae, to dominate. Nitrates are used in fertilizers and put on the surrounding fields. When it rains the nitrates can flow from the land into the rivers.

Low Quality – > 4ppm. If it is over 10ppm then it is very low quality
Average Quality – 3 to 4 ppm.
Good Quality – 1 to 3 ppm.

Nitrites

Nitrites are toxic to aquatic plants and animals

Low Quality – > 5ppm.
Average Quality – 1 to 5 ppm.
Good Quality – 0 or less than 1ppm.

Ammonia

Ammonia occurs naturally in water at low concentrations. High concentrations of ammonia in the River suggests runoff from agricultural land as ammonia is present in fertilisers.

Low Quality – more than 0.39ppm
Average Quality – Between 0.39 and 0.1 ppm
Good Quality – Less than 0.1ppm

Phosphates

Phosphate is, alongside Nitrate, one of the most common polluters of rivers. High concentrations of Phosphate encourage the growth of algae and duckweed which in turns blocks sunlight and lowers the level of oxygen available to other aquatic life.

Low Quality – More than 1ppm
Average Quality – 0.15 to 1ppm
Good Quality – Less than 0.15ppm

Electric Conductivity

This is a measure of the amount of minerals dissolved in the River water. Too many minerals (high electric conductivity) will render the water undrinkable and unsuitable for watering plants. The water may taste salty. As the River Thames passes through chalk landscapes there will be higher electric conductivity than a river passing through sandstone of rock less susceptible to dissolving in water. EC is related to temperature. The higher the temperature the greater the conductivity.

Low Quality – More than 700 micro-Siemens per centimetre
Average Quality
Good Quality – 150 to 700 micro-Siemens per centimetre

Clarity

A measure of how much sunlight is penetrating the water and the effectiveness of photosynthesis. Water can become turbid after heavy rain (run off from surrounding fields) and can indicate high Nitrate and Phosphate levels.

Low Quality – Less than 40cm can be seen into the water.
Average Quality – Between 40 and 60cm seen into the water.
Good Quality – The Riverbed can be seen.

Rainfall

Heavy rain may result in the sewage system being unable to cope with excess water allowing raw sewage to enter the river. From this autumn our weather station will accurately measure rainfall at Path Hill Outdoors