5. overview of category B interventions
5.1. Surface Water Abstraction
5.1.1. Public Water Supply
This intervention is described in
Section 4.1.1 (damming for public water supply).
5.1.2. Industrial Water Supply
This intervention is of economic
importance in the Continental region of France.
This intervention is described in
chapter 4.1.2 (damming for irrigation - Atlantic region).
5.1.4. Fish Farming
This intervention is described in chapter 4.1.5 (damming for fish farming).
Fish farms are a main "consumer" of surface water in Denmark by diverting water from the river which has a significant ecological impact on the river sections by reducing flow ("the dead rivers"). These "dead rivers" are the sections between the inlet (upstream of the dam) and the outlet of the fish farm.
The size of the water reduction
varies between fish farms from river sections which dry up for several months each year,
to river sections with more than 50 % of the summer water flow through the year. The
affected rivers are of reduced ecological quality and even the natural continuum is
Surface water abstraction for
generating hydropower was reported from mountainous areas and is described in chapter
4.1.3 (damming for hydropower) and chapter 4.5.3 (lake regulation for hydropower).
5.1.6. Inter-basin Transfer
Inter-basin transfer is often
enforced in connection with hydropower purposes in mountainous areas. See section 4.1.3
(damming for hydropower). It is also important on the Iberian Peninsula (water supply,
5.2. Groundwater Abstraction
The major reasons for groundwater
abstraction and usage are for public and industrial water supply and for irrigation
purposes. Information has been provided for the Atlantic and Continental region.
5.2.1. Public Water Supply
This intervention was reported for the Atlantic, Continental and Mediterranean regions.
Groundwater in Denmark makes up to 99 % of the total public water supply. It secures a high quality and stable supply of drinking water to large populations.
In France this intervention is required because of a lack of surface water of sufficient quality in the certain areas (e.g. Lille and Paris). Nationally, groundwater abstractions represent 57 % of total public water supply abstractions, but in some parts of northern Atlantic France, this figure is much higher (88 % in Artois-Picardie water agency area which includes Lille).
In Portugal 70 % of total water supply is met by groundwater. Groundwater quality will deteriorate because of deficiencies in waste water collection systems and treatment, and in industrial waste disposals.
Problems from groundwater abstractions may occur by reducing groundwater levels which in turn may reduce river base levels, too. As a result wetlands disappear and river ecosystems get disturbed.
Particularly for groundwater
abstractions in coastal areas there is a risk of salt water intrusion into groundwater.
For example this occurs in Denmark and Portugal. As a result, for example, in Denmark
groundwater has to be abstracted some distance away from the larger coastal cities.
The contributions to this report show that groundwater abstraction for irrigation purposes is one of the major interventions in the hydrological cycle especially in the Atlantic, Continental and Mediterranean regions. For example, the water cycle can be massively affected by the high consumption rate of the water (differences between abstraction and recharge can be around 70-80 %).
Irrigation increases agricultural productivity, secures a highly stable agricultural production and permits agricultural development in climatically disadvantageous areas. High amounts of groundwater are abstracted for irrigation and the demand is still increasing.
Groundwater abstraction for irrigation is in some regions a significant problem, especially in dry summers. Groundwater abstraction contributes significantly to the fact that the rivers cannot meet the politically decided quality objectives. If the groundwater renewal rate is low and the total water demand is higher, groundwater level drops, river levels decrease and aquatic and riparian ecosystems will massively be influenced.