APEM’s innovative new survey techniques combine aerial surveys and ground based surveys to identify potential sources of pollution in river catchments, notably large catchments or those that are hard to get to.

This allows us to identify potential pollution from sediment, priority substances, pesticides, nutrients and bacteriology, amongst others.

Field scientist gathering samples from a stream

Background to the project

APEM partnered with UK Water Industry Research (UKWIR) and piloted two projects for Yorkshire Water and Affinity Water, aimed at developing innovative new ways to hunt out hard-to-find sources of diffuse pollution. The techniques have subsequently been successfully applied for other water companies.

Water companies and others are under pressure to continue improving water quality in our rivers and water bodies, in order to meet their regulatory requirements. Having spent several decades successfully tackling the major sources of pollution, such as wastewater treatment works and combined sewers, they are increasingly turning their attention to diffuse pollution.

Aiding in this is a shift towards the catchment based approach – a way of managing river catchments and their many uses as a whole rather than piecemeal.

Aerial surveys and walkover surveys

Previously APEM has had considerable success in walkover surveys for catchment management. Our experience includes over 15,000 km of walkover surveys, in which teams survey river catchments on foot looking for a variety of issues, such as sources of pollution.

However, identifying and addressing diffuse pollution in catchments that are large, remote or otherwise difficult to access can be challenging.

Our new technique complements our ground based surveys by using satellite imagery and, where appropriate, our own aircraft and state-of-the-art cameras to survey catchments from the air. This is followed by targeted ground truthing.

As a first step we use existing satellite and aerial imagery combined with available GIS information to produce a risk map of potential sources of diffuse pollution. From these risk maps we identify high risk areas of potential diffuse catchment pollution. We then fly aerial surveys of these high risk areas to gather more detailed images. The high resolution images are examined by APEM’s image analysts for a variety of factors, including the signs of pollution.

The imagery allows us to send ground teams directly to the sites of concern, focussing efforts on the ground more efficiently and beneficially. It also allows us to identify sources of pollution that would be difficult or impossible to see from the ground.

Field team on a walkover survey for diffuse pollution

Our approach involves

  • Using readily available imagery from satellites and existing aerial surveys to produce a risk based map of a catchment.
  • Flying aerial surveys of areas where more detail is needed, gathering ultra-high resolution, multi-spectral images.
  • Analysing these images to identify potential sources of diffuse pollution and a range of other variables such as crop type and cover.
  • Using our field teams to assess and validate any likely sources of pollution.
  • Producing materials and imagery to highlight issues in the catchment.
  • Talking to stakeholders such as farmers, land owners and water companies to implement real change on the ground.

The Results

  • We produced a pollution risk map of the catchment, high resolution aerial imagery of high risk areas and carried out extensive surveys on the ground.
  • In one pilot project, we identified a 50 cm deep gully within a field and used 3D aerial imagery to calculate that 250 cubic metres of soil had been lost, at a cost of approximately £19,000 to replace.
  • The technique allows identification of rivers potentially being affected not only by sediment, but also polluted by nutrients and pesticides.
  • We engaged with farmers, using imagery and materials, leading to changed land use and greatly reduced run-off into the river.