WW-R-1: Water use index

The picture shows a water clock in front of water pipes.Click to enlarge
In summer, there may be peaks in the use of drinking water in the household, regionally different.
Source: Photograph: © Sashkin / stock.adobe.com

2019 Monitoring Report on the German Strategy for Adaptation to Climate Change

Table of Contents

 

WW-R-1: Water use index

In the course of the past 25 years, water usage has experienced a significant decline. 2004 was the first year in which the water usage index of 20% considered critical was undercut, i.e. no more than 20% of the potential water supply has been used since. However, there are distinct regional differences in Germany, and climate change confronts water providers with new challenges, for instance, in terms of meeting the demand at times of seasonal consumption peaks.

The dot graph shows the development of the water use index as a percentage of water use in the water supply from 1991 to 2016. In addition, the threshold for sustainable water use is marked with 20 percent in the graphic. The water use index fell below this threshold for the first time in 2024. The time series shows a significantly decreasing trend.
WW-R-1: Water use index

The dot graph shows the development of the water use index as a percentage of water use in the water supply from 1991 to 2016. In addition, the threshold for sustainable water use is marked with 20 percent in the graphic. The water use index fell below this threshold for the first time in 2024. The time series shows a significantly decreasing trend.

Source: UBA (based on data of StBA (water use) and BfG (water supply))
 

Water usage clearly in decline

Germany is a country rich in water where in current circumstances there are only limited restrictions to water availability at a regional and seasonal level. The long-term average shows that approx. 188 billion cubic metres of groundwater and surface water are potentially available whereas only a fraction of this volume is being used. Nevertheless, extended and more frequent drought phases and low-water periods, brought about by reduced water supply, can result in regional conflicts of usage regarding surface water and especially with regard to groundwater abstraction close to the surface. This is true, in particular, for central parts of eastern Germany, the north-eastern German lowlands and the south-eastern German basin where unfavourable climate- related water regimes occur; in other words where comparatively little rain falls while evaporation of water is high owing to high summer temperatures.

The water use index provides basic clues as to whether the usage of water resources in Germany is sustainable or whether water shortages are developing. Water abstraction can be termed sustainable as long as it does not exceed the threshold of 20 % of available water supply. Notably, the 20 % threshold is an internationally valid benchmark. Once water usage exceeds this threshold, this is regarded as a sign of water stress. Values of 40 % and above are termed high water stress. The causes for exceeding this threshold can be sought in an increased water abstraction or scarcity of naturally occurring water supplies.

Owing to a decline in both the commercial and private water usage in Germany, this 20 % threshold has been undercut regularly since 2004. Overall the values recorded in the water use index have been declining significantly since 1991. It follows, therefore, that according to internationally valid benchmarks, the extent of water usage can be considered sustainable. Energy producers as well as industrial and mining operations have contributed to this distinct decline; as these companies clearly have the greatest share (80 %) in water usage. Coolant abstraction by thermal power plants accounted for the lion share of commercial water usage. Consequently, efficiency improvements in terms of recycling or cyclical usage, had particularly favourable effects on the water regime, at least until 2007.

Likewise, water consumption by private households and by trade was reduced substantially since 1991 from 144 litres per person per day to 123 litres per person per day. It is nonetheless important to keep using drinking water sparingly.

The water use index used as an indicator so far does, however, have its limitations when it comes to illustrating the adaptation requirements and related activities in the water industry. An overview of the situation nationwide does not take into account any distinct regional differences within Germany. In future, the water regime may – owing to climate change and a further decrease in summer precipitation and increased evaporation e.g. in eastern Germany – become even more unfavourable thus reducing the availability of water in that area. At the same time, extended heat periods may lead to increased demand for water. With regard to private water usage it is to be expected that, especially in residential areas with a high proportion of detached houses and terraced houses which have their own courtyard or garden space, water consumption will soar in prolonged periods of heat without precipitation as major quantities of water will be used for garden irrigation.

The overall declining water usage on one hand and the climate-induced higher consumption peaks on the other as well as variations in regional distribution of water resources and water demand, confront water providers with certain challenges. In particular water providers in rural areas and in upland regions where largely decentralised and precipitiation-dependent water supply structures prevail, may be confronted with predicaments during prolonged drought periods. Nevertheless, with regard to central or pipeline-based supply, it has been possible so far to keep a balance in terms of regional and temporary differences in water availability and demand. In the case of several subsequent years of prolonged drought, it is important to ensure that there are always sufficient water resources available to meet the demand.

 

Interfaces

WW-I-1: Groundwater level

WW-I-4: Low water

EW-­R­-4: Water efficiency of thermal ower plants

IG-R-1: Intensity of water consumption in the manufacturing sector

 

 

Objectives

As far as demand management is concerned, technical methods and improvements for a more efficient use of water can be applied and this should be taken into account in accordance with the principle of proportionality (DAS, ch. 3.2.3)