Abstract
Water management and environmental protection is vulnerable to extreme low flows during streamflow droughts. During the last decades, in most rivers of Central Europe summer runoff and low flows have decreased. Discharge projections agree that future decrease in runoff is likely for catchments in Brandenburg, Germany. Depending on the first-order controls on low flows, different adaption measures are expected to be appropriate. Small catchments were analyzed because they are expected to be more vulnerable to a changing climate than larger rivers. They are mainly headwater catchments with smaller ground water storage. Local characteristics are more important at this scale and can increase vulnerability.
This thesis mutually evaluates potential adaption measures to sustain minimum runoff in small catchments of Brandenburg, Germany, and similarities of these catchments regarding low flows. The following guiding questions are addressed: (i) Which first-order controls on low flows and related time scales exist? (ii) Which are the differences between small catchments regarding low flow vulnerability? (iii) Which adaption measures to sustain minimum runoff in small catchments of Brandenburg are appropriate considering regional low flow patterns?
Potential adaption measures to sustain minimum runoff during periods of low flows can be classified into three categories: (i) increase of groundwater recharge and subsequent baseflow by land use change, land management and artificial ground water recharge, (ii) increase of water storage with regulated outflow by reservoirs, lakes and wetland water management and (iii) regional low flow patterns have to be considered during planning of measures with multiple purposes (urban water management, waste water recycling and inter-basin water transfer). The question remained whether water management of areas with shallow groundwater tables can efficiently sustain minimum runoff. Exemplary, water management scenarios of a ditch irrigated area were evaluated using the model Hydrus-2D. Increasing antecedent water levels and stopping ditch irrigation during periods of low flows increased fluxes from the pasture to the stream, but storage was depleted faster during the summer months due to higher evapotranspiration. Fluxes from this approx. 1 km long pasture with an area of approx. 13 ha ranged from 0.3 to 0.7 ls-1 depending on scenario. This demonstrates that numerous of such small decentralized measures are necessary to sustain minimum runoff in meso-scale catchments.
Differences in the low flow risk of catchments and meteorological low flow predictors were analyzed. A principal component analysis was applied on daily discharge of 37 catchments between 1991 and 2006. Flows decreased more in Southeast Brandenburg according to meteorological forcing. Low flow risk was highest in a region east of Berlin because of intersection of a more continental climate and the specific geohydrology. In these catchments, flows decreased faster during summer and the low flow period was prolonged. A non-linear support vector machine regression was applied to iteratively select meteorological predictors for annual 30-day minimum runoff in 16 catchments between 1965 and 2006. The potential evapotranspiration sum of the previous 48 months was the most important predictor (r2 = 0.28). The potential evapotranspiration of the previous 3 months and the precipitation of the previous 3 months and last year increased model performance (r2 = 0.49, including all four predictors). Model performance was higher for catchments with low yield and more damped runoff. In catchments with high low flow risk, explanatory power of long term potential evapotranspiration was high.
Catchments with a high low flow risk as well as catchments with a considerable decrease in flows in southeast Brandenburg have the highest demand for adaption. Measures increasing groundwater recharge are to be preferred. Catchments with high low flow risk showed relatively deep and decreasing groundwater heads allowing increased groundwater recharge at recharge areas with higher altitude away from the streams. Low flows are expected to stay low or decrease even further because long term potential evapotranspiration was the most important low flow predictor and is projected to increase during climate change. Differences in low flow risk and runoff dynamics between catchments have to be considered for management and planning of measures which do not only have the task to sustain minimum runoff.
The precipitation data of the Regional Climate Model CLM are used for the water management impact models within the dynaklim networking and research project. For this purpose, it is necessary to apply a bias correction to the CLM
precipitation data. First, the bias assessed for varying temporal resolutions and precipitation characteristics is described. Subsequently, a method for the bias correction is introduced. The developed methodology is a modified form of the socalled
quantile mapping. The focus lies on the corrections of the dry days and the heavy rainfall events. They are considered separately, deviating from other quantile mapping procedures.
One of the important parts of the final conference of ‘nordwest2050’ has been the scientific exchange sessions in the House of Science and the Industryclub Bremen. Contributions were based upon a call for papers from October 2013. The scientific committee received almost 100 abstracts where 36 were chosen for oral presentations and 15 for poster presentations (see overview tables below).
Four main topics were discussed in parallel workshops:
• Analysing Impacts and Assessing Vulnerabilities
• Designing and Testing Solutions for Regional Climate Adaptation and Resilience
• Implementing Climate Adaptation and Paths to a Resilient Future
• Resilience for Business: Climate Adaptation Challenge and Strategies of Sectors and Companies
Content:
Climate Change at the Baltic Sea Coast – The RADOST Project;
RADOST Annual Conference 2010;
Regional Activities:
Extractive Polyculture in the Kiel Fjord;
Kick-off meeting – RADOST focus network “Conservation and Land Use”;
Baltic Tourism Network for Climate Change Adaption is launched;
Kick-off for RADOST pilot projects for drainage management;
Geographic Information System (GIS) for RADOST online;
Stakeholder and institutional analysis in RADOST;
International Activities:
RADOST Side Event in Copenhagen;
Transatlantic Media Dialogue regarding;
Climate Policy in Europe and the US;
BaltCICA: 1st International Conference;
Dinner Dialogue;
Publications
Content:
Regional Activities:
Already adapted?
German coastal associations tackle climate change;
The IMK in RADOST;
Action Day in Rostock;
Climate Alliance Kiel Bay is launched;
First annual RADOST conference;
An Introduction to the RADOST advisory board;
Climate change on the German Baltic Sea coast;
International Activities:
Dinner Dialogue on America’s Climate Choices;
Global Oceans Conference 2010;
Publications
Content:
Regional Activities:
Symposium: Beach management;
The significance of regional networks;
Hanse Sail Business Forum;
RADOST-Workshop on Network Building;
Investing in beaches – Adaptation activities in Kühlungsborn;
Conference on extreme weather events;
International Activities:
UN Climate Change Conference in Cancún;
New project: Regional availability of climate data;
Summer School in Warnemünde;
Publications
Content:
Regional Activities:
Artificial Reefs as a Coastal Protection Measure and Diving Area;
Meadows and Forests in the Baltic Sea: RADOST Event at the LLUR;
Rocks for the Algae Forest;
Workshop ´´Municipal Coastal Protection under Modified Climate Conditions´´;
The Beach as Air Conditioner;
RADOST Workshop on Coastal Tourism in Hamburg;
International Activities:
RADOST at the UN Climate Conference in Cancún;
Using Synergies – the New Project BALTADAPT;
Publications:
First RADOST Annual Report Now Online;
Book Publication on the Impacts of Global Change on the Baltic Region
Content:
Regional Activities:
RADOST Annual Conference 2011 in Travemünde;
Research at Anchor;
Stakeholder Analysis;
RADOST-Workshop “Coastal Tourism”;
BSSSC/BALTEX Conference “Adaptation to Climate Change
on the Regional Level”;
Workshop “Baltic Sea and Baltic Sea Coast between Climate Change and Climate Adaptation”;
Mussel Workshop at the Institute for Baltic Sea Research Warnemünde;
International Activities:
Climate Change, the Science Policy Interface and Coastal Zone Management;
Workshops on Regional Availability of Climate Knowledge in the Baltic Sea Region
Content:
Regional Activities:
Workshop: Coastal Change as a Challenge for Society, Culture, and Spatial Planning;
RADOST on Tour: Baltic Sea Coast 2100 – On the Way to Regional Climate Adaptation;
Monitoring the Environmental Conditions in the Nearshore Area;
National Activities:
Outstanding Climate Adaptation;
International Activities:
RADOST in Exchange with Coastal Planners in the USA;
Short Film on Climate Change Adaptation in Germany, Poland,
and the Baltic States;
Publications:
Analyses of the Perception of Climate Change Along the
German Baltic Sea Coast;
RADOST Studies on Artificial Reefs