Climate change impact on the water

The increased precipitation and temperature will affect the water cycle considerably. The water cycle is an important driving force in many natural ecosystems, which consequently will be affected.

The effects of a changing climate on the water cycle
The Danish drinking water supply is almost entirely based on unpolluted groundwater. Water management therefore has a specific focus on the quantity and quality of the groundwater resource. A reduced formation of groundwater in the summer period and an increased formation the rest of the year will, for example, affect the use of groundwater for drinking water and irrigation purposes as well as the long term development of flora and fauna in wetlands, watercourses, lakes and the sea. On a yearly basis more groundwater will be formed, but lack of water will occur in some subsystems in the summer period, especially if the requirements of households, agriculture, industry and the natural ecosystems all have to be considered.

The need for adaptation
There is a need for integrated water management of the entire water resource in order to accommodate the future demand for water from both humans and nature. Water falling as rain, infiltrates the soil and flows naturally as groundwater to lakes and water courses, ending up in the sea. This cycle can be diverted by pumping the water up in abstraction wells for human use, to end as waste water that after treatment also ends up in the sea. Adaptation therefore has to consist of an integrated approach to the water cycle to find solutions that best accommodate the various needs. 

There will be an increased demand for water for irrigation purposes in green areas in the cities and for agriculture in the summer period. This need for irrigation has, as far as possible, to be managed so as to minimize the effect on the natural ecosystems that will also be under stress in the summer period. It is therefore important to manage water abstraction so that it affects the discharge of groundwater to wetlands, lakes and water courses as little as possible.

The increased temperature will increase the excessive growth of algae in lakes, water courses and the sea. To counteract this it may be necessary to increase the flow of water in affected areas, which again may result in a need to reduce abstraction in certain areas. The increased temperature may also result in an increased demand for clean groundwater for irrigation and cooling purposes. The quality of drinking water will also be affected, as an increased temperature in the water pipes will expose the drinking water to growth of bacteria and at the same time make the taste less fresh. The water supply in coastal areas will, especially in the summer period, need to manage the risk of salt water intrusion into fresh groundwater.

Heavy downpours in the summer period and the increased precipitation in the winter may put pressure on municipal sewage and drainage systems. Handling an increased amount of water in these systems has to be considered when sewage and drainage systems are renovated or developed. The possibility of storing rain water in green areas should be considered as part of urban planning.

Urban areas are especially vulnerable to flooding, but the risk of flooding from high water in streams and rivers in rural areas and subsequent damages must also be considered. Adaptation measures such as removal of drains, weed cutting, water course maintenance and conversion of farmland to wetland are some of the measures that can reduce damages due to flooding in rural areas and at the same time improve the condition of the aquatic environment.