Researchers have discovered a significant relationship between reduced flows in streams and ecological conditions within them.

The research looks at streams in the English midlands and was co-authored by Dr David Bradley, APEM’s head of hydroecology; Dan Cadman, APEM’s head of hydrology; groundwater experts from ESI Ltd; and the client, Severn Trent Water.

Field team scientist gathering samples in a river

Water quality and quantity

Substantial investment by the water industry has resulted in widespread improvement in river water quality in Europe and North America over recent decades.

By contrast, the ecological issues associated with the quantity of water in rivers have received far less attention. The balance is being redressed as the growing use of freshwater resources by humans increasingly conflicts with major legislation that focuses on the protection of aquatic ecosystems.

Developing hydroecological models 1

Flow requirements

There is therefore an urgent need for aquatic ecologists and water scientists to work together, with the aim of quantifying the flow requirements of riverine ecosystems needed to support good ecological status, as defined under the Water Framework Directive.

Advances towards a tool for setting ecologically based flow targets in UK rivers have been led by the development of macroinvertebrate indices, such as the Lotic invertebrate index for flow evaluation (LIFE; Extence et al. 1999).

The first paper published shows a ground breaking relationship between flow reductions caused by groundwater abstraction and ecological conditions (as measured by LIFE) in streams in the midlands of England (Bradley et al. 2014)

In a second paper, the authors combine this relationship with hydrological indices derived from calibrated regional groundwater models to assess river reaches that are likely to be ecologically impacted by abstraction and might consequently be at risk of failing to meet Water Framework Directive standards (Streetly et al. 2014).

The method is then demonstrated within the framework of the Ecological Limits of Hydrologic Alteration (ELOHA) approach to making water resource decisions. The article provides examples of how this approach can be used to assess the implications of different groundwater abstraction scenarios for river water bodies where there are few or no monitoring data.

References

Bradley, D.C., Streetly, M.J., Farren, E., Cadman, D. & Banham, A. (2014) Establishing hydroecological relationships to manage the impacts of groundwater abstraction. Water and Environment Journal, 28, 114-123.

Streetly, M.J., Bradley, D.C., Streetly, H.R., Young, C., Cadman, D. & Banham, A. (2014) Bringing groundwater models to life: a new way to assess water resource management options. Hydrological Sciences Journal, 59, 1-16.

Extence, C.A., Balbi, D.M. and Chadd, R.P. (1999) River flow indexing using British benthic macroinvertebrates: a framework for setting hydro-ecological objectives. Regulated Rivers: Research and Management, 15:543–574.