If the groundwater is used up

Hamburg's groundwater reserves are full

Lots of sun and hardly any heavy rain: It was the hottest June since weather records began. And many people still remember the summer of 2018 as an exceptional summer. Because of the persistent drought, drinking water became scarce in some municipalities in Germany. In Hamburg, too, all systems are fully utilized on hot days. There is basically enough groundwater available.

On June 25, around 432,000 cubic meters of water were fed into the drinking water network. A record figure - the average daily sales over the last 10 years is 322,000 cubic meters and even in summer it usually remains well below 400,000 cubic meters. Last year, more than 400,000 cubic meters of water were released on a total of 21 days. An unprecedented peak value. In Hamburg, however, there were no reasons for restrictions as in other cities in Germany, despite great thirst: “Basically, there is sufficient groundwater available in our extraction areas - even for days with peak consumption. However, sufficient extraction capacities must be available to cover the water demand on peak days. In the exceptional summer of last year, all available wells had to be operated for this, ”explains Frank Skowronek from the groundwater management department at HAMBURG WASSER. How much water can be pumped from the depths of the earth depends on the groundwater supply, which is constantly being renewed by rain. The wells also have an influence on the flow rate. So that the supply is also secure in the future, old wells that are declining in performance have to be replaced and new locations have to be found. Because consumption in Hamburg is increasing. It is not the hot summers that are to blame, but the population development. Because more and more people live in the Hanseatic city, the extraction capacities of the wells also have to be expanded.

Groundwater is created in the winter half-year

“We are currently assuming that the hot and dry summers will not have any notable effects on the formation of new groundwater,” says Skowronek. Because the rains in summer hardly contribute to the creation of groundwater. The rain between May and October evaporates or is used up by plants before it can contribute to the formation of new groundwater. The groundwater is formed almost exclusively from the rain that seeps away in the winter months. The water, which does not evaporate, is consumed by plants or runs off into bodies of water, seeps through the various layers of soil made of sand, gravel or even clay and is filtered and cleaned in the process. The downward movement of the seepage water ends when it hits the groundwater surface. To obtain drinking water, HAMBURG WASSER mainly uses deep, well-protected groundwater reservoirs between 100 and 400 meters below the surface of the earth. When the water is taken from the deep wells, it has been on the move for years, decades and even centuries. “The new groundwater formation in our extraction areas is more or less constant over the years and decades. A different impression can arise on the surface. During the course of the year, small streams sometimes dry out in hot summers. They feed themselves from near-surface groundwater resources, which are subject to seasonal influences. The deep reservoirs, which are mainly used for drinking water production, are little affected. These react to long-term events, for example the absence of winter precipitation for several years, ”says Frank Skowronek.

Every year, around 770 millimeters of rain fall on average in Hamburg, which corresponds to 770 liters per square meter. Of the 770 liters of rain, about 260 liters reach the groundwater. In the HAMBURG WASSER extraction areas in Hamburg, Lower Saxony and Schleswig-Holstein, a groundwater reserve of around 700 million cubic meters is available. HAMBURG WASSER takes around 120 million cubic meters of this annually to supply drinking water. In addition, there are commercial withdrawals, for example by agriculture or industrial companies.

As a local supplier, HAMBURG WASSER is particularly committed to protecting groundwater. Because clean, healthy water should continue to come from the tap in the future. One instrument for this is the establishment of water protection areas, especially where the groundwater is not adequately protected by surface layers. At the beginning of July, the Hamburg Senate designated a new protected area in Eidelstedt / Stellingen. This means that around 13 percent of Hamburg's area is now a water protection area.

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