The Munich gravel plain
Over the course of 780,000 years, over the last four ice ages, an outwash plain was formed from deposits of ice-age glaciers: the Munich gravel plain. Along with it, great water resources were enclosed under ground. This gravel plain forms an extensive triangle around the city of Munich, divided into two more or less even halves by the river Isar.
Towards the end of the different glacial periods, the Alpine ice streams and piedmont glaciers, which had tongues that extended all over the region where Munich is now located, started melting down. The glaciers transported debris and huge amounts of water to the plains around Munich. Here the gravel was deposited while the water seeped away. The different layers of rock reach far below the earth’s surface. Between the sediments and the gravel, the glacial water has been preserved to this day.
The lowest solid layer is 640,000 years old, having been formed during the oldest of the four glacial periods; the upper strata are made up of various types of debris and gravel from the three younger ice ages. Between these strata there are thinner layers of clay, which was deposited during the interglacial periods. These rock layers from four ice ages are a natural shield and filter.
The deep water of the ice age has been like this for thousands of years before man-made impurities protected. To this day, the pollution and radiation exposure is below the detection limit and is regularly checked by independent institutes. Durch Niederschlag bekommen die eiszeitlichen Wassermassen neuen und natürlich gefilterten Zulauf: Regen, der heute fällt, wird in circa 5.000 Jahren in diesem Wasserspeicher angekommen sein. Angereichert mit den verschiedenen Mineralien aus dem Gestein, die das Wasser auf dem Weg passiert.
La régénération des ressources en eau de la plaine de gravier de Munich a donc commencé avec les pluies il y a des milliers d’années et perdure sans interruption.
Questions about the Gravel Plain
Prof. Dr. Wilfried Hagg is a glaciologist (glacier researcher) and a specialist in hydrology and in the physical geography of alpine mountains. We asked the head of the geological department at Hochschule München some questions about the Munich gravel plain and the Aqua Monaco mineral water below.
How was the Munich gravel plain formed?
The Munich gravel plain was formed by deposits left by the meltwaters of the Isar-Loisach glacier and the Inn-Chiemsee glacier over the course of several ice ages. The top layer was formed during the last ice age known as Würm, which ended 10,000 years ago. These deposits are known as glaciofluvial sediments. As the Alps are fairly close to Munich, and the rock was thus transported for short distances only, most of the material found here is different types of gravel ranging from 2 mm to 6.3 cm in size and featuring mostly rounded shapes formed by the flowing water that they were transported in and that smoothed their edges.
What was life like in these parts during the final days of the different glacial periods?
During the ice ages, the Alpine foothills had a tundra climate. Low temperatures prevented the growth of trees, and, similar to the Arctic regions of modern-day Canada and Russia, the land was characterised by tundra vegetation on permafrost. There was also plant migration from subpolar zones and Central Asia, with the edelweiss flower being the region’s most well-known ice-age immigrant. The era also saw large mammals including the mammoth, the woolly rhinoceros, and the cave bear.
How can we tell that our modern-day landscape was formed during the ice ages?
The ice ages left the landscape with very distinctive features. The piedmont glaciers left large hollows known as tongue basins, which are surrounded by forested ridges, the moraines, and often filled with water, thus forming lakes.
What is the difference between deep water and spring water from the mountains?
Deep water takes considerably more time to form and, for this reason, stays underground for much longer. As a result, deep water tends to be fairly well cleaned from any pollutants and contains less oxygen than spring water, which is sourced closer to the surface.
Some people may wonder what the difference between tap water and Aqua Monaco Mineral Water is. What is the difference in quality?
In general, Munich tap water is sourced from a variety of springs located in the Mangfalltal and Loisachtal valleys and is supplied to Munich households using a pipe and reservoir system. Aqua Monaco Mineral Water, on the contrary, originates from one single spring and is sourced and bottled right there and then. Moreover, mineral water is Germany’s most strictly controlled food product
So how exactly does the water get filtered when flowing through the different layers of rock?
When water trickles down through the fine pores present in loose rock, the layers act like a mechanical filter similar to a sieve, holding back even the tiniest particles including dirt and pollutants. In addition, even dissolved or gaseous pollutants can be bound by the surfaces of certain rock particles in a process known as ion exchange.
Is the water reservoir finite?
The groundwater balance depends on how much water is withdrawn (by humans and plants) and replenished (by new water trickling down). Sustainable management means that you should not remove more water than can be replenished. If you pump up more, the water volume will shrink and the reservoir will dry up in the long run. Aqua Monaco Mineral Water is sourced sustainably. This is tested by running a still water level test every month, where water levels are not allowed to fall while the pump runs at its maximum.
Prof. Dr. Wilfried Hagg
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