Freshwater water ways such as ponds, streams and lakes are inherent for life on earth and an important storage system in the water cycle.

The impacts of humans through pollution linked to farming practices, industry and water sewage treatment can be investigated in these habitats using measurements of the physical conditions and looking for indicator species.

This investigation can also be used to develop pupils’ fieldwork and map skills which are also key elements of the KS3 National Curriculum.

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Assessing water pollution

Aim: to assess the health of a freshwater ecosystem.

Access required: To deliver this fieldwork, you will need access to a pond, lake edge or river which has safe access sites either to dip nets from the bank or to stand in safely.

Method

• Using relevant scale OS maps, identify a suitable location to make water quality assessments. Using different scales of OS map from ArcGIS map viewer learners can pinpoint a location to sample and also annotate possible sources of pollution within the landscape.

• Learners could give coordinates on the annotated map to determine features of the landscape and sources of pollution which might affect the health of the ecosystem.
• Download the free OPAL Water Survey booklet to complete during the survey and determine the health of the ecosystem.
• Once a site has been determined, assess suitable sites for dipping, either from a platform, low bank or shallow water edge.
• Set up a bucket or tray with water in ready to home the samples of invertebrates. A couple of small plastic spoons, sample pots and a magnifying lens are useful to help identify.
• Take multiple samples of the invertebrate life in the water (dragonflies, snails, beetles, leeches etc). Using a sampling net, such as this one, to either sweep the net sample (from outside the water) or kick sample (from within the water). See the Field Studies Council freshwater sampling methods for more information on kick sampling and sweep netting.
• Once you have a sample of invertebrates use the free download Freshwater Invertebrate Identification Guide from the OPAL survey, to identify and categorise invertebrates into red, green and blue and fill in the chart on the downloaded survey booklet.

Considerations

• Be careful to risk assess the water as a hazard.
• Ensure pupils wash their hands after sampling and before eating.
• In the winter months there is less to look at and invertebrate numbers are smaller making it hard to identify.

Questions

• What abiotic or physical factors could also be measured?
• How might this data be averaged? Mean? Median? Or mode?
• How many invertebrate samples should be made? How much of the pond, stream or lake can be covered? Is your sample representative?

Data presentation and analysis

In the The OPAL Water Survey Booklet there is a table to fill out to categorise the invertebrates found into indicators of healthy, normal and polluted water. A simple bar graph of the numbers of invertebrates in each quality category would suitably show the range of indicator species found. The table can then be used to assign scores to the invertebrate families and assess the pond health.

Consider how the landscape, environment and human impact in the area, might impact this freshwater ecosystem. This can be linked to climate change and future environmental changes and their impacts on important ecosystems.

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