The journey of the water into the Donauried of Baden-Württemberg
Rainfall quickly drains away from the plateaus of the Swabian Alps. Just under 3,000 litres per second, thus 87 million cubic metres flow annually into the widely ranged subterraneous fissures and seams of the White Jurassic towards the south-eastern Donauried. The water needs about 12 years for its journey. The Swabian Donauried, between Langenau and Sontheim, belongs to the few regions of Baden-Württemberg, which are abundant with water. This is where rich, natural ground water streams meet, flowing subterraneously alongside the Donauried and rising in the Swabian Alps.
The Donauried in Baden-Württemberg is one of the most important ground water reservoirs in the country. It contains about one billion cubic metres of water. The supply of water which is refilled within the Winter half-year is available for the hot, thirsty Summer months. Construction of water catchment No. 1 near Niederstotzingen started in 1912. Nowadays, 217 standpipes in six series of collection pools are available for withdrawing up to 2,500 litres of water per second, which corresponds to a maximum of 52 million cubic metres of water annually. Normally, the ground water which is extracted from the Donauried at a depth of about eight metres is of drinking water quality.
- The Donauried north-east of Ulm
Groundwater: Good quality from the start
Due to its good quality, the groundwater from six series of collection pools in the Donauried and from the deep wells near Burgberg can be delivered directly as drinking water with just one substream being softened in a decarbonising plant.
The ground and spring water sources used by the Landeswasserversorgung are fed from the karstified White Jurassic of the Swabian Alps. Due to the long period of time the water spends underground, the seeping precipitation water absorbs many minerals, lime, in particular. It is referred to as "hard" ground water.
If a ground water source is rich in minerals, it will be noticeable from its smooth taste. The ground water flowing in the Donauried has a natural total hardness of, on average, 22°dH and peak values of up to 28°dH.
Decarbonisation – a gentle process for reducing water hardness
A large portion of this delivered drinking water is used as service water for the most varying of purposes. Water hardness is an important factor when it comes to heating up the water due to the usually undesirable sediment accumulation processes or when dosing cleaning agents.
Customer behaviour and the economic and ecological benefits of softening local drinking water as opposed to having numerous small private softening plants resulted in the decision to construct a local decarbonising system in the Langenau Waterworks. The system was put into operation in 1989. To optimise operations, a pre-neutralising system was connected upstream of this system.
This makes it possible for ground water extracted from the Donauried to be softened by 9°dH and delivered as drinking water at 12.7°dH (hardness range 2) to customers.