Frequently Asked Questions

Why sample phosphate levels?

The data collected by the River Detectives is used by BART to build a picture of what is happening at the rivers being monitored. The results help to build a picture of what is affecting the ecosystem and identifies key areas which may be in need of restoration or are clean and need protecting.

Nutrients, particularly phosphates, are amongst the most common pollutants of freshwater across the world. As a result of their wide-ranging effects, levels of phosphates are widely used as indicators of water quality. As shown on our Data Explorer, we have provided a scale of high, medium and low concentrations of phosphate.

Phosphate Levels

Phosphate legend in the Data Explorer

High nutrient levels in a river can encourage plant growth, particularly algae. Lots of algae uses up the oxygen in the river and blocks out light, which can cause a reduction in wildlife in the river.

Causes of high nutrients include:

Agricultural pollution which can be caused when livestock are kept in the vicinity of a river or through runoff from fertilisers.
Garden fertilisers are also sources of nutrients that can contribute to pollution when they are washed into our rivers, especially through the drainage network.
During periods of heavy rain, Combined Sewer Overflows (CSOs) are used to provide relief to the sewer system, preventing our homes from flooding. Unfortunately, when CSOs kick in, rainwater mixed with raw sewage, containing nutrients such as phosphate and nitrate, is discharged into our rivers.

The results can also be affected by weather conditions (e.g. rainfall) and the time of year that the sample is taken.

How can other recorded observations help?

The additional factors recorded by BART Detectives can indicate a river's health and water quality, such as:

Signs of pollution - this can help to explain a high concentration of nutrients and gives information on what is entering the system. Links may be possible between nutrient levels and the potential inputs. BART may arrange river cleans where litter is found.
Surrounding vegetation - recording what plants are present can also give an indication of how healthy the wider ecosystem is.
Surrounding land use - this helps to put the measurements into context, and enables a comparison of results in different landscapes, such as cities and the countryside.

How reliable is this tool as an indicator of river health?

Data collected by the BART River Detectives captures specific water quality measurements on a monthly basis throughout the year which provides a valuable dataset on the health of the river. Water quality data is collected alongside rainfall records and across each of the monitoring sites to allow comparisons, changes and synergies to be made. All this data is very valuable and can help us develop future river restoration strategies for that area.

Why are only certain catchments covered in this project?

The BART River Detectives project is currently covering the River Chew, Bristol Frome, and the Cam, Wellow and Midford Brooks. BART are trialling these three areas as a pilot programme and are likely to expand the ongoing project to more watercourses throughout the Bristol Avon catchment to develop a better understanding of the health of our rivers.

This tool looks great, can I set one up for my local area?

This interactive data viewer has been developed for us by Riskaware. If you would like to know more about what Riskaware do, and the products and services they offer, you can get in touch with them through their website, www.riskaware.co.uk.

If you have any questions not covered by this FAQs page then please get in touch at info@bristolavonriverstrust.org.