The way forward

This project has been tightly constrained by time, and there has been little scope for detailed examination o f the data available from some wetland sites in the Phase 2 list. The expansion

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o f groundwater monitoring across a larger number o f wetland sites will offer the opportunity for a longer-term evaluation o f the methods proposed here, and for the development of alternative methodologies. Exploration o f the variation in the wetland leakage factor, and a more thorough interpretation o f fluctuations in wetland water levels in response to climate and hydrogeological factors, will add to the confidence with which these simple methods can be applied.

The effect o f varying the various parameters that have been used in the MIROS models to produce SEV estimates should be examined critically. This could take the form o f some sort o f sensitivity analysis. The parameters which could be varied include coefficients which are used to partition rainfall, the a-parameter used to lag the groundwater inputs and the drainage level in the wetland. The use o f values other than 20 cm for the SEV calculation could also be investigated.

The combination of the WETLWELL function and the MIROS model has not yet been fully investigated. It should be possible to combine the outputs of WETLWELL, in terms of flux reduction, to the inputs o f MIROS to give changes in SEV for existing and proposed abstractions.

Estimation o f cumulative drawdown due to existing and new abstractions has been carried out for the Phase 2 sites on the basis o f very simple assumptions. In particular the role of local features such as rivers and buried channels has not been considered. There is considerable room for improvement in the hydrogeological aspects of the proposed methodologies, and local knowledge may suggest, for example, the use o f image wells to improve the quality of predictions o f drawdown.

The workload in assembling, quality controlling and in-filling data for the MIROS model, and selecting and interpreting water level records from observation wells is considerable, taking several days for each site. This difficulty will also confront NRA staff trying to use the methodologies operationally. The enlarged database created by the wetland monitoring schem e will provide the potential for more detailed analysis, permitting a more individual approach to wetland sites, but there is little point in collecting water level information is time is not allocated for examination and interpretation. The value o f the data collection exercise w ill be directly related to the investment o f time and effort in analysis, cross-comparison and the dissemination o f results to those with an interest in the conservation o f wetlands.

7. A cknow ledgem ents

The authors of this report would like to thank the following for their assistance during the course o f this project:

Institute of Hydrology

Clare Coulson - freehand drawings

Ian Brightman, Claire Price - data processing

Stephen Loader - Responding to requests for data held at IH British Geological Survey

Brian Adams - Project Manager Andy Butcher - numerical modelling

Anna Matthews - producing data from the databases National Rivers Authority

Geoff Mason - Project manager David Seccombe - Project manager Angela Wallace - Data provision

Dave Burgess, Chris Taylor, Pat Soames - Background knowledge and useful discussions

English Nature

Ian Smith, Wanda Fojt - Provision of background information and reports Suffolk Wildlife Trust

Mike Harding - information on wetland sites

We are also grateful for the well balanced and helpful comments o f the reviewers from Birmingham University.

Part of the analytical work described in this report was funded by the British Geological Survey under R&D Project number E76CLR12.

8. References

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