Euro-limpacs Deliverables

ABSTRACT - DELIVERABLE 90

Report - Identification of biotic indicators of high/low flows in running waters

The main rationale for conducting the research within Euro−limpacs WP2: “Climate − hydromorphology interactions” is that in large parts of Europe hydromorphological alteration is the main stressor affecting rivers. Alterations include channel straightening, dam construction, disconnection of the river from its floodplain, and alteration of riparian vegetation. These changes also affect wetlands and lakes in the associated floodplain through, for example, a lowering of the groundwater level, increased siltation or changes in inundation regime. Under predicted future climate conditions further stresses will be introduced including the combined effect of changes in precipitation and climate induced changes in land−use patterns. These in turn may cause changes in catchment hydrology that will affect sediment transport and channel morphology, inundation frequency and extent, and impact on aquatic ecosystems at both the catchment and habitat scale. In this WP the focus is principally on rivers and their adjacent floodplain wetlands and lakes, and on shallow lakes sensitive to problems of sediment accumulation. Climate and global change scenarios will be adopted that link existing catchment specific hydrological conditions with existing regional land use data to derive two land−use scenarios per catchment and evaluate cause−effect relationships at habitat and catchment scale. Discharge regime and inundation pattern (frequency and duration) are the key hydrological parameters at the catchment scale, and current velocity pattern and water movement in space and time are the key parameters at the habitat scale. In order to bridge the gap between the two scales, particularly from an ecological perspective, the focus will be on sub−areas within the study catchments. Eight catchments have been selected: Vechte (NL/D), Eder (D), Taro (I), Ceno (I), Eman (S), Waldaist (A), Becva (CZ) and Lambourn (UK) representing a north −south and a west − east gradient to ensure that different ecoregions and land−use intensities are covered. Preference has been given to catchments for which data on land−use, hydromorphology and biological community composition are already available. For lake studies existing data on sediment accumulation rates from sites across Europe will be used. The key hypotheses are: (i) that global change may cause hydromorphological deterioration through intensification of land−use or through a more variable discharge regime that results in habitat modification and losses; and (ii) alternatively, that global change may cause significant improvement if, for example, human disturbances are withdrawn from floodplains due to more frequent flood events or as a result of floods that generate a near−natural habitat structure.

Task 2 “Hydromorphological changes and aquatic and riparian biota” of WP2 addresses the question of how the distribution of taxa and functional groups at the catchment scale is controlled by the environmental conditions described in Task 1. Characteristic taxa or functional groups to be used as response parameters to hydrological and morphological structures will be identified in all eight catchments i.e., Vechte (NL/D), Eder (D), Taro (I), Ceno (I), Eman (S), Waldaist (A), Becva (CZ) and Lambourn (UK). Different taxa and functional groups will be considered based on data for their distribution in space and time in the study catchments. Indicators reflecting key hydromorphological conditions at the catchment scale will then be studied in detail at the habitat scale. A subset of indicator species will be studied using autecological field and laboratory experiments to reveal the causes of habitat binding and tolerance to change. The habitats necessary for the occurrence of the key indicator species will be quantified at the catchment scale and linked to hydrology and stream morphology, and ultimately to catchment land−use. Existing time−series will be analysed to identify the effects of years with extremely high or low discharge on the fauna and flora.

The aim of task 2.5 “Identification of biotic indicators of high/low flows in running waters” is to answer the questions:
1. How large are seasonal and annual variability of hydrology, hydromorphology and biota?
2. What are the effects of extremely high or low discharges on the biology?
3. Can we identify indicators to feed into WP7?

These questions will primarily be answered using data from the eight study catchments if/where time−series data exists. At the start up meeting in Innsbruck, it was further decided that the focus will not only be on extreme events. Data with a clear shift in environment or biota are also selected and analysed.

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