Impacts of Climate Change
Water availability and heat
Climate change is likely to lead to changes in rainfall distribution in Germany. In summer, rainfall will tend to go back while it will tend to increase in winter. However, the degree of this effect will vary, depending on the respective location. These future developments have potential consequences, inter alia, for ecosystems, agriculture, forestry and groundwater recharge.
Particularly in areas with impermeable soils and a low soil storage capacity, the groundwater recharge is likely to decline due to climate change. This may lead to limited water availability and even droughts. Especially parts of eastern Germany can be affected. Low water availability leads to restrictions in agriculture and forestry and is detrimental to ecosystems and their biological diversity .
Although Germany is currently only using 24 percent of the total water resources and the daily water consumption per capita is declining, climate change can even affect the drinking water supply in some regions. In addition, very low rainfall during the summer months can lead to low water levels in waterways and thus affect the shipping industry.
Due to rising temperatures and stronger sunlight, the upper layers of surface waters warm up. This has an impact on the water quality in so far as warmer water has less oxygen, which again is detrimental to animals and plants. Oxygen deficiency and enriching nutrients can disrupt the ecological balance of the water (eutrophication). Particularly smaller water bodies are affected.
Also floods that may occur more frequently in the future can affect the quality of surface waters and groundwater.
As a result of climate change, it is expected that there will be a shift of precipitation from summer to winter. Furthermore it is expected that heavy rainfall will increase in winter. Due to the milder winters, the proportion of snow in the total precipitation will decline. Essentially this means that precipitation will rarely be stored in the form of snow, but increasingly cause an immediate discharge. This increases the likelihood of floods.
Urban conurbations are particularly at risk because sealed surfaces prevent the seepage of water into the ground. Even now, short but intense heavy rainfall already leads to problems in the drainage in urban areas.
During floods, pollutants such as fertilisers and pesticides can seep into the groundwater and surface water and impair the water quality. In the event of floods in industrial and sewage treatment plants or private oil tanks, pollutants can also seep into the water. This can lead to significant impairment of drinking water quality and thus damage health.
In addition, large and long-term economic damage can be caused by damage to or the destruction of buildings and infrastructure. The Elbe flood in August 2002, for example, caused damages amounting to 9.4 billion euros.
Coastal and marine protection
The melting of large quantities of inland ice and the expansion of warming ocean water leads to rising sea levels. It is estimated that by the end of the 21st century, the global sea level will rise by two to eight decimetres. The exact degree of the increase is still difficult to predict for the North and Baltic Sea.
Rising sea levels will lift the starting level of storm surges. In future, high storm surge levels will be reached more easily and last longer. It is expected that by the middle of the 21st century, floods that presently occur once in 350 years could then occur once in 100 years. In some coastal areas, such high water levels could occur even more frequently.
The height and weight of the waves that reach the coasts are affected by the water level and influenced by wind and sea conditions. In the North and Baltic Sea, more severe storms are expected especially in the winter months. Along the Baltic coast, the winter storm speed is expected to increase by up to 14 percent by the end of the century. By the North Sea, storm surges will be approximately 10 to 30 cm higher in 2030 than they are today. By 2100 even an increase of 30 to 80 cm is expected. This constitutes a challenge for coastal protection, which needs to be expanded significantly by the end of the 21st century according to the latest estimates.
Besides damage to buildings and infrastructure, the consequences of storm surges are that salt water seeps into inland areas and the fresh water of groundwater and surface waters. The rising sea level leads to a shift of the mixing zone of fresh and salt water, too. This impairs the regional water availability and quality significantly. Furthermore it alters soils and thus the conditions for forestry and agriculture. The salination of fresh water can also be a problem for industry and commercial sectors if the production is dependent on high water quality.
In the future, water shortage in Germany can be particularly acute during the summer months. It can affect energy production and industry as well as the forestry and agricultural sector. The agricultural sector has several ecosystem adaptation opportunities: plants whose largest water demand does not arise in summer should be sown in the affected regions. Also the cultivation of plants with low water requirements can counteract losses in agriculture.
In addition, it is expected that technical measures for the required adaptation in the water sector will be necessary. In order to secure water supplies in regions for which significantly less rainfall is expected during the summer months, long-distance water pipelines could be installed for example. In addition, the use of pumps can ensure that also deeper sources of groundwater can be accessed. However, environmental impacts have to be considered in that context. An adaptation of the capacity of channel systems to a decreased flow rate is crucial when it comes to avoiding stagnant water in the pipes as well as preventing potentially resulting damage, contamination or clogging.
In the future, periods of low water and water shortage could lead to temporary regional land use conflicts, for example between agricultural stakeholders who are dependent on sufficient water to irrigate their land, and industrial companies, whose demand for cooling water for their plants increases. The stability of the water supply and quality is cross-sectorally of great importance. For that reason, all adaptation measures should be well-coordinated and aligned inter-regionally.
The further development of water-saving methods and the use of rainwater or wastewater should be extended. Especially the so-called grey water, which is only marginally contaminated and accumulates in private households when people take showers, baths or wash their hands, offers great saving potentials. It can be processed locally in water recycling systems and then used, for example, to water the garden, clean the house or flush the toilet. For instance, there are systems for private households with low storage volume and moderate acquisition and operating costs that generate great saving results. In addition, it is important that industry, agriculture and forestry take sufficient precautionary measures against expected water losses and raise awareness in view of conscious, sustainable water consumption.
In addition to the water use, also the land use management has to be adapted to the changing availability of water to ensure a continuous availability of the valuable resource. An adapted dam management system can be used, for example, to allow a temporally and spatially differentiated management of reservoirs. Thus, dam facilities such as storage or retention basins can be integrated into the overall system of water management and contribute to the drinking water treatment as well as the water power and the flow regulation in the catchment area.
Floods and heavy rain
In addition to water shortage, it is expected that extreme events such as heavy rainfall and resulting floods will increase in the future. The range of possible climate changes should be considered in planning processes for drainage measures in particular. With regard to extreme events, water reservoirs and water treatment plants should be geared for larger amounts of water in future to prevent the flooding of combined sewer systems. Furthermore, customised area management should also restrict the sealing of surfaces – especially in settlements – and thus ensure that there are adequate infiltration possibilities in case of heavy rain events.
Furthermore, retention areas, which can be flooded at high tide, should be created. A natural management of surface waters and sufficiently broad floodplains and waters cross sections can also contribute to a reduction of flood risks. The European Water Framework Directive (WFD - Directive 2000/60/EC) and the EU Flood Risk Management Directive (FRMD - Directive 2007/60/EC) already stipulate an integrated management of river basins with coordinated protection and usage requirements.
As climate change advances, it should be examined whether and to what extent technical flood protection should be strengthened. For that purpose, the corresponding policy frameworks need to be created, for instance by the (partial) funding and implementation of adaptation measures that also promote private sector investment as examples of good practice. In addition, it makes sense for federal, state and local governments so revise their award criteria and rules in a way that ensures that impacts of climate change are taken into account in decisions and planning from the beginning. For example, new development areas should generally not be designated in floodplains. Furthermore, buildings should be designed so as to prevent potential damages resulting from high water. New construction designs, such as floating houses are currently tested especially in the Netherlands.
In addition it is especially important to raise awareness amongst the population regarding the risks of climate change and to call for individual precautionary measures, too.
There are several technical options that can be used in order to protect especially coastal regions against the consequences of an increased sea level. On the one hand, stronger and higher dikes can help to protect the existing shoreline. On the other hand, structural measures such as the erection of dwelling mounds (artificially raised, flood-protected settlements) - should be taken precautionarily. In general it has to be considered in the long term whether high-risk coastal areas can still be populated in the future.
In the future, the Integrated Coastal Zone Management (ICZM) of the federal government should coordinate the alignment of various adaptation measures in the context of coastal protection. In view of the expected climate conditions, the previous model of coastal protection "Defense at all costs" was further developed towards "Living with water”. In addition, a federal-state coastal protection secretariat along the lines of the Common Wadden Sea Secretariat could support the implementation of innovative coastal protection adaptation measures.
To further promote adaptation measures, financial means that will be awarded as part of the “Joint Task for the Improvement of Agricultural Structures and Coastal Protection" (GAK) in future can be linked more closely to criteria that support climate change adaptation.
Marine protection is another increasingly important issue to counteract the increasing acidification and warming of the oceans. In this respect, all measures that have the purpose of avoiding harmful greenhouse gas emissions are beneficial in principle. In addition, more conservation areas should be established to protect endangered species from climate-related stressors.