The research builds on many years of collaboration between aquatic ecologists at APEM and groundwater specialists at ESI. Together the researchers were able to refine their existing method for measuring the impacts of water abstraction and other environmental pressures.

The method used samples of invertebrates collected from nearly 40 stream sites across the West Midlands that are subject to varying degrees of abstraction pressure.

Analysing the types and numbers of invertebrates recorded in the samples, researchers used an index that measures how changes in water flow affect stream ecology. This was related to the proportional reduction in flow as a result of abstraction at medium-low flow levels.

The results suggested that consistent signs of low flow stress on invertebrates were shown only when flows were reduced by more than fifty per cent of natural levels by abstraction.

The study also looked at some other invertebrate indices that are sensitive to the effects of excessive fine sediment and water pollution, together with data collected by APEM’s walkover surveys and aerial surveys.

Using these, researchers were able to assess the effects of fine sediment pollution from agriculture and artificial channel modifications in relation to the impacts of groundwater abstraction.

The technique allows the ecological impacts of groundwater abstraction to be assessed more accurately at the local scale. It also shows how pressures from other sources can be measured in relation to the effects of abstraction and how this is crucial to being able to put in place the most cost-effective measures to achieve Good Ecological Status under the EU Water Framework Directive.

Fine sediment in stream

Fine sediment entering a stream.

Dr David Bradley, lead researcher at APEM, said: “Water companies have an obligation to mitigate abstractions that take water from rivers to the point that river flow does not support good ecological status under the Water Framework Directive.

“To justify the high costs involved there must be good evidence of what the problem is and how certain we are that any measures taken will solve the problem.

“Until now, scientists haven’t had the tools to measure how abstraction directly impacts ecology in rivers and how pressures from other sources, for example from agriculture, interact with this.

“Ultimately we want to help water companies maintain the supply of clean water to our homes and businesses, whilst ensuring that our rivers are adequately protected, and money is well spent on the most effective schemes.”

Reference:

Bradley, D.C., Streetly, M., Cadman, D., Dunscombe, M., Farren, E. & Banham, A. (2017) A hydroecological model to assess the relative effects of groundwater abstraction and fine sediment pressures on riverine macro-invertebrates. River Research and Applications. Version of Record online 16 Aug 2017. DOI: 10.1002/rra.3191.

If you have any queries, please contact Dr David Bradley, associate director.
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