Calculations of the effects of climate change on the water cycle in Denmark show that Denmark can expect great changes in the distribution of water resources available to people and nature in the future. Some places will see more frequent flooding, while others will experience water shortages.
GEUS’ activities in brief
GEUS is conducting research and consultancy into the hydrological impacts of climate change in Denmark and abroad, including in developing countries. This work includes use of data from climate scenarios in hydrological modelling and quantification of climate change impacts. Calculations are performed primarily with a nationwide hydrological model, called the DK-model; a model which is being run and developed by GEUS.
GEUS describes and quantifies a broad range of impacts and problems associated with climate change in the hydrological cycle, including:
- Groundwater resources and discharge in watercourse
- Changes in groundwater extraction for irrigation
- Flooding caused by rising groundwater levels, high water levels in watercourses or by sea-level rises.
- Intrusion of salt-water into groundwater aquifers due to rising sea levels
- Leaching of pesticides and nutrients to the aquatic environment
- Protection of catchment zones and of well fields
- Occurrence of water in the landscape, including surface runoff and wetlands.
Determining the uncertainty linked to projections is an important aspect of climate work. Greenhouse gas emission projections, climate models as well as hydrological models contain a considerable element of uncertainty, and climate change impacts can therefore only be predicted with great uncertainty.
Climate and water – examples of efforts
Efforts include surveys of future groundwater recharge, water-table height, groundwater pressure level in deep-lying aquifers, as well as watercourse discharge, all of which are important parameters for good future management of water resources and the aquatic environment. GEUS also works with calculations of the impact of future climate change on leaching of pesticides to groundwater, lakes and watercourses. This climate work includes ongoing development of model tools, and a third example of efforts is the development of methods to couple climate models directly with the national hydrological model, so that calculations can take into account the fact that the Earth’s surface and atmosphere are constantly influencing each other.
Reconstructing the aquatic environment of the past
GEUS is also working to map the effects of climate change on the aquatic environment over a period dating back thousands of years. The aim is to gain an understanding of how the aquatic environment will react to future climate change. Lakes and bogs are natural archives of changes in nature and the environment, and through studies of lake sediments and their contents of plant and animal residues, it is possible to form a clear picture of how the environment has changed over thousands of years.
National hydrological model
GEUS runs and develops a national water resources model, the so-called DK-model, which is used to estimate the exploitable water resources available for water supply. The DK-model is a large-scale model, which calculates the overall water balance as well as the degree of utilisation and extent of the groundwater resources, taking into account the climate, land use and current water abstraction strategies.