Irrigation and piping system
Basic supply of irrigation water
The supply of our greenhouses by our heating system is – just like water supply systems of the garden – indispensable for our collection. Being able to ensure the basic supply of water for watering at all times was also one of the reasons why the area north of the Nymphenburg Palace Park was chosen for the relocation. Supplying the garden with water from the Würm River – via a direct transfer from the Würm Canal – was thus intended to create a secure water supply for the Botanical Garden. Arriving at the source at the beginning of the Farnschlucht, the Würm water follows the natural gradient into the pond located in front of the Alpinum, which has functioned as a water reservoir since the garden was founded. While the worm water is used unfiltered in the open field, it is purified in advance by a sand filter for use in the greenhouses.
In order to ensure the distribution of the worm water in the 21-hectare garden area up to the greenhouse facility, an electric pumping station was planned in addition to the pipelines – by no means a matter of course at the beginning of the 20th century. To this day, the use of water from the Würm River is the most consumed type of water in our garden. If necessary, the water is automatically drawn from the pond and further distributed via two centrifugal pumps.
The pump house – the heart of the irrigation system
The heart of the irrigation system is housed in a small, architecturally very attractive building, the so-called “pump house”. It was completed in 1910 and stands at the southeast end of the pond. In 2009, a faithful exterior renovation was carried out on the part of the building not open to the public, which has always aroused the curiosity of the public. The foresight at that time and the elegant solution of using modern technology, but keeping it hidden, is now – more than 100 years later – admired and honored.
In order to be able to water our plants even at the time of the annually recurring Nymphenburger Bachauskehr (for cleaning and repair of the canal system), as well as in case of possible pipe bursts, a municipal tap water connection was additionally created, which is also used for all sanitary facilities. However, even today, supplying the plants with municipal drinking water is only a stopgap solution for ecological and financial reasons. Just like worm water, tap water is not suitable for all horticultural purposes. Rainwater, which is largely free of minerals, still meets the requirements of even the most delicate plants.
Blending water for optimal irrigation
A certain basic admixture of mineral-rich water, currently in a ratio of 1:15, is also necessary in part to buffer the water against falling pH values and thus protect the metal piping from acid-induced pitting in the long term. Before being used in the greenhouses, this blended water is sent through a UV disinfection system to render any pathogens harmless. Since the middle of the last century, the garden’s rainwater storage capacity has been expanded to now include five larger cisterns with a total capacity of 1,500 cubic meters. The most recent major cistern additions were in 2007 and 2012, each with 300 cubic yards of capacity, and in 2018, with 500 cubic yards of capacity. One of the more recent cisterns – built in 2007 – is located under the Insect Pavilion, which was ceremoniously opened in the summer of 2011 by Markus Söder – then serving as Bavarian Minister of the Environment.
All in all, the founders of the Botanic Garden showed remarkable foresight in their planning of the basic technical facilities. Even after more than 100 years, these can still be operated by us largely successfully.