The Challenges in Assessing Effectiveness of Natural Water Retention Measures on a Catchment Scale

The good ecological status of surface water in EU in 2015 has improved by 10 % since 2009. However, there is still a lot of work to be done in order to achieve a better status of fauna and flora, as well as favourable hydrological and chemical characteristics. Various types of measures listed under the name Natural (Small) Water Retention Measures (N(S)WRM) can have significant positive effects on solving environmental problems such as hydrological extremes, nutrients’ transport and decreased biodiversity. Number of restoration and conservation projects show the positive effect of a single measure: river re-meandering, lake restoration, wetland restitutions, floodplain revitalisation etc. on water storage, sediment trapping or nutrients capturing. We observed, however limited integration of N(S)WRM in river basin and flood risk management plans in Europe. We assume, that it is caused mainly by lack of knowledge base and tools on how to plan, assess and implement the multiple benefits of number of measures applied in the catchment.

FramWat (INTERREG Central Europe) project ambition is to bring a new approach to the implementation of the N(S)WRM in the River Basin Management Plans. Project is developing new tools to be used by water authorities for: (1) valorization of the river basin for choosing the best location for a set of measures to help achieving the water quantity (mitigation of droughts and floods) and/or quality (decreasing the N and P loads) goals; (2) assessment of effectiveness of those measures and (3) guidelines for how to apply N(S)WRM in the River Basin Management context.

Valorisation method has been developed for identifying locations in a river basin where N(S)WRM are needed. It is based on multi-criteria analysis of topographic, hydrological, meteorological and land use data. A GIS software helps in choosing a sub-catchments where N(S)WRM may improve current water and/or nutrient balance and where the water resources are available for such measures.

The cumulative effects of N(S)WRM’s on water balance and/or nutrient can be assessed, when applying catchment hydrological model in appropriate scale. The question arises if setting up, calibrating and validation of the detailed catchment model is not too expensive for this task. It means we should propose also the simpler approach which can be accepted by a water authority. The simpler method is based on assumption that set of measures applied should improve valorisation status of the catchment. This solution is now tested in six catchments located in Central Europe.