GLANCE

For the projection of changes in the stream communities, the knowledge of species preference for discharge and flow conditions is required

GLANCE is a formerly four-year (2014-2018) research project, which was extended by a fifth year, conducted at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin and funded by the German Federal Ministry of Education and Research (BMBF). GLANCE investigates the impacts of changing flow conditions in rivers on benthic invertebrates and fishes. Benthic invertebrates are organisms that live in or on the bottom sediments of rivers, such as insect larvae of mayflies, caddisflies or stoneflies, and other non-insect organisms such as mussels, snails, and worms.

GLANCE has considerably advanced predictive models for the effects of global change on riverine hydrology and organism groups including benthic invertebrates and fishes. GLANCE provided essential tool for future planning of monitoring programmes, improving the assessment of the potential success of restoration measures, or refining measures of forecast assuming that an increase in extreme hydrological events will affect different sectors such as agriculture, water infrastructure, and freshwater biodiversity. Our research has shown that discharge patterns and extreme events are related to climatic factors occurring at different temporal and spatial scales. Unlike ecological modelling, hydrological modelling is common practice in federal and state agencies, however, its application is still done separately among different sectors. Short- and long-term adaptations to hydrological changes require not only the further integration of climate forecasts and projections but the interaction between sectors to untap the full potential for management. GLANCE’s results allow, therefore, the integration of hydrological modelling across sectors for a holistic management of aquatic resources.

Climate change affects freshwater ecosystems in different ways, through increasing water temperature, changing discharge patterns, or decreasing dissolved oxygen concentrations. Rivers and streams are, therefore, considered particularly vulnerable to climate change due to their close interrelationship with the terrestrial environment and their heavy anthropogenic use. For example, we can expected longer periods of drought, more frequent and higher flood events, or reduced freshwater supplies. At the same time, species living in rivers are sensitive to changes in temperature, runoff, and water quality. However, up to date the recognition of relevant effects of global change in rivers has often remained limited to qualitative aspects. GLANCE aimed at investigating the effects of global change induced flow changes in rivers, taking multiple perspectives in terms of scale (regional to global) and approach (ecological and autecological). To achieve this goal, the following specific objectives were defined: First, to determine the preferences and tolerances of certain species of benthic invertebrates with respect to hydrological conditions. Second, to determine the impact of global change on hydrological conditions in different ecoregions of Germany. Third, to quantify relative importance of flow changes in a multi-stressor environment, where additional important parameters such as water temperature and land use are also included in the analyses. Fourth, to compare flow change effects in regions which are expected to react differently to global change, providing therefore tools for understanding changes at a global scale.

Catchments in three different ecoregions in Germany were selected as study areas to examine changes in flow conditions

The necessary data and knowledge bases were created in three data-rich and extensively studied catchments in Germany: Treene in the lowlands, Kinzig in the low mountain ranges, and Ammer in the Alps. These selected catchments are expected to react differently to climatic change (increase or decrease of annual precipitation, partly increased summer drought), and thus represent a gradient of potential hydrological changes. Based on the experience and established methods in these three catchments, hydrological changes in running waters in connection with ecological change were also investigated in other catchments and on larger scales.

GLANCE investigates the impacts of changing flow conditions in rivers on benthic invertebrates and fish in five sub-projects:

• Determination and quantification of flow traits of benthic invertebrates.
• Quantification of global change impacts on hydrological and hydraulic conditions.
• Improvement of climate change projections for benthic invertebrates.
• Analysis of flow related changes and possible ecological effects at large spatial scales.
• Synthesis and discussions with regard to water management applications. This fifth sub-project was added during the extension phase in order to maximize the impact of the project’s results and facilitate knowledge transfer towards water management practitioners.

Research results can improve water management

The results of GLANCE can help improve the management of rivers as required by the European Water Framework Directive (WFD), and in the long-run, support an optimal use of expenditures for water management. Three aspects play a particularly important role in this context: (1) an improved estimation of hydrological stress or effects of changes will reduce the uncertainty in river assessment and monitoring, (2) management plans should consider climate change impacts and their related uncertainty, but also an adaptation of monitoring programs to observe and determine the effects of climate change in running waters is needed, and (3) restoration measures might influence the hydrological and hydraulic conditions in restored river sections and more knowledge about preferences and tolerances of organisms could help to adjust expectations about possible effects. In the context of river restoration, multi-stressor analysis may also contribute to a better assessment of whether morphologically oriented restoration measures alone are really effective. It seems likely that any economic prospects will depend on further practical development of the GLANCE core approaches, such as developing ready-to-use-tools, teaching materials, as well as a thorough training of authority staff and external companies.

The annual meetings of the overarching Federal-State Working Group on Water (LAWA) and its Expert Group on Running Waters made it possible to inform representatives of all Fderal States and the German Federal Environment Agency (UBA), who are active in the management of running waters and the implementation of the WFD in Germany, about the project results and to discuss further ideas. This cooperation, which has been cultivated from the beginning of the project, resulted in a direct transfer of the results into water management practice. The results were also presented and discussed at the meetings of the LLUR Schleswig-Holstein for "Hydrological Discussion" and at the annual "Hydrology Workshop" of the University of Kiel. The project was presented in intensive half-day meetings with representatives of the three state offices (federal states in which the three study areas Treene, Kinzig, Ammer are located). Here, the research results were presented, the advantages and disadvantages for application were discussed and further application and research needs were documented. Results are also presented at national and international conferences, workshops and meetings, and are published in various journals.