Despite the pressing environmental, economic and social issues surrounding water abstraction, scientific methods for managing its ecological impacts remain in their infancy. In this paper, we demonstrate statistically significant relationships between in-stream ecological condition using macroinvertebrates and the hydrological effect of groundwater abstraction on surface water flows in streams originating from Permo-Triassic sandstone aquifers in the English midlands. Ecological condition was most strongly correlated to the effect of abstraction on medium-low flows (Q75) compared with effects at other flows, water quality, habitat or seasonal effects. Ecological impacts occurred when the effect of abstraction on Q75 flows exceeded 60%. The same relationships were shown among individual macroinvertebrate taxa, validating the biological responses. The hydroecological model has provided a scientific basis for making local decisions on investigation sites and has helped to focus resources to areas at risk of not meeting Good Ecological Status under the Water Framework Directive because of abstraction.
To ensure that the environment is adequately protected and abstractors are fairly regulated, hydroecological assessment tools are needed that give local interpretation, indicate where ecological communities might not be resilient to current or future abstraction pressures, and take account of the effect of other stressors. These tools should ideally be transferrable across different river catchments. This study presents a hydroecological model indicating that macroinvertebrates were not resilient to long-term, steady-state levels of groundwater abstraction when flows at Q75 were reduced by more than 50% in unpolluted streams in the West Midlands of England. The proportion of silt and clay covering the substratum and distance from source were also significant predictors of ecological condition, but did not interact with the abstraction effect. Combinations of different biotic indices and supplementary field observations of catchment land use gave additional evidence of the impacts of excessive inputs of fine sediment overriding the effects of abstraction at some locations. This study has shown that regional hydroecological models can be used with existing environmental flow indicators and other local environmental information as a weight of evidence to identify where abstraction and excessive inputs of fine sediment need to be mitigated separately or together to achieve the full ecological benefits. Such regional hydroecological models can increase the certainty of regulatory decisions made at the local scale for licencing abstraction at current use and predicted future levels.
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