Mountain lake diving

Diver in the Lai da Marmorera ( 1680  m above sea level )

In diving, mountain lake diving refers to a dive in which, due to the elevated location, different environmental conditions must be observed than during a dive at sea level.

The pressure conditions at high altitudes are different from those at sea level. In a mountain lake, longer decompression times must therefore be observed, while the no-stop times are shortened. For this purpose, there are special mountain lake decompression tables and calculation models tailored to the appropriate altitude . In diving training , mountain lake diving is often used from a height of 300 meters above sea level . Other definitions - such as the decompression model DECO 92 from Max Hahn - only provide for adapted calculation models from 700 meters above sea level.

Since the water contains fewer suspended particles due to the low temperatures, visibility of up to 60 meters is possible in mountain lakes, reservoirs and alpine rivers . In the temperate latitudes , the vegetation and thus the fish population decrease rapidly from a height of 1100 meters, which can also turn the underwater landscape into a wasteland . Alpine waters are mostly cold, which makes appropriate protection from the cold with semi-dry or dry suits essential.

Diving in mountain lakes places increased demands on both the diver and the diving equipment , which is why only sufficiently experienced divers should dive in high alpine waters.

Measurement of pressure

Depth gauges that determine the diving depth from the water pressure must be adjusted to the correspondingly low atmospheric pressure at high altitude before the dive if they are to display correct values. While modern dive computers measure the ambient pressure independently - before boarding - and include it in the calculations under water, some conventional depth gauges can be preceded by an adjusting screw. Quite a few of the conventional depth gauges used by divers today do not have this option. However, since they indicate a depth that is too shallow in high water bodies, the diver is always on the "safe side" - even with the deviation from the effective depth.

Decompression tables

Since the atmospheric pressure decreases with increasing altitude - by around 0.1 bar per 1000 m - the risk of diving illness increases during and after surfacing. Because of the lower external pressure / air pressure, gas bubbles can bubble out more easily, which is why the nitrogen enriched during the dive has to be broken down more slowly than would be the case at sea level. Therefore, decompression tables and calculation models adapted to the altitude must be used. This category includes waters from a corresponding height of 300 or 700 meters above sea level.

Dive planning with correction factor

Decompression tables for sea level can be used for dive planning if a correction factor is used:

${\displaystyle {\frac {\text{Atmosphärendruck in Meereshöhe}}{\text{Atmosphärendruck in der Höhe des Wasserspiegels}}}={\text{Korrekturfaktor}}}$

This factor must be multiplied by all the depths that are searched for in the decompression tables:

${\displaystyle {\text{Tauchtiefe }}\times {\text{ Korrekturfaktor}}={\text{in der Dekompressionstabellen zu suchende Tiefe}}}$

With this conversion one achieves a sufficiently conservative dive planning in order to exclude the risk of a diving illness.

Mountain lake decompression tables

Dive planning with a decompression table specially adapted for the altitude is more precise and therefore less conservative than the calculation with the correction factor. In the course of time, various such tables have been developed for different heights: The best known is the so-called "Bühlmann table", which goes back to Albert Bühlmann . Other tables are the Hennessy, Egi-Brubakk, and Paulev-Zubieta tables.

Mountain lake mode

Even less conservative diving than with mountain lake decompression tables is possible with computers that have a so-called mountain lake mode . While some dive computers automatically switch to this mode, other models have to be switched manually by the user. In such a mode, the computer uses a decompression table adapted to the altitude for its calculations.

Repetitive dives

If several dives are planned on the same day, these can also be calculated using a correction factor, whereby the next higher pressure group is selected. Dive computers include the surface interval in calculating the limits for a repetitive dive. The US Navy prohibits repetitive dives in alpine waters for surface-supplied diving and heliox dives .

Before and after diving

Especially in the case of reservoirs, the operator of the weir and power plant systems should be informed about the dive plans in advance . It is impossible for divers to escape the current caused by an underground inflow, a pressure pipe or an open weir. Since inflows and outflows can only be opened during the dive, the danger at the entrance may not yet exist and the divers may surprise underwater.

The low water temperatures in mountain lakes can lead to further dangers:

• Hypothermia .
• Icing of the regulator .

When planning the dive, you should therefore use diving equipment suitable for cold water.

The return journey from mountain lakes often requires crossing passes or other routes with steep inclines. Since the atmospheric pressure decreases with increasing altitude and nitrogen could bubble out in the body, there is a risk of diving illness. In principle, the return journey should not go over any point that is higher than the level of the mountain water being dived. There are models to calculate the maximum permissible safe ascent after diving in a mountain lake. Since these models do not allow large climbs, they are usually not used.

Mountain lakes are often difficult to reach for rescue services . In the event of a diving accident, rescue or transport by rescue helicopter is usually ruled out, because every ascent to greater heights means a renewed risk to the accident diver. Therefore, special attention should be paid to the emergency scenario when planning a dive.

Extreme mountain lake diving

Licancabur crater lake

Although there is no official evidence for this, it is believed that Charles Brush and Johan Reinhard's team carried out the highest dives in 1982 in one of the world's highest lakes, the Licancabur crater lake at 5916  m .

Individual evidence

1. ↑ Diving at higher altitudes - mountain lake diving. (No longer available online.) PADI, archived from the original on November 10, 2013 ; Retrieved February 11, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
2. ↑ Jochen van Waasen: DECO92 - 0-700m. Retrieved February 11, 2013 . 
3. ↑ ^{a b c d e f} Thomas Kromp , Hans J. Roggenbach , Peter Bredebusch : Practice of diving : 3rd edition. Delius Klasing Verlag, Bielefeld 2008, ISBN 978-3-7688-1816-2 .
4. ↑ Sea diving. dive.steha.ch, accessed on August 21, 2019 : “ Because most mountain lakes are rather cool, we recommend completing this course in a dry suit. " 
5. ↑ Bergseetauchen , GTÜM eV, BG-Unfallklinik Murnau office, accessed on February 2, 2012.
6. ↑ ^{a b c d} Bergseetauchen / Altitude (PDF; 1.0 MB) , Erwin Haigis 2007, accessed February 2, 2012.
7. ^ Albert A. Bühlmann: Decompression problems in diving in mountain lakes . In: Switzerland Z Sportmed . 37, No. 2, 1989, pp. 80-3; discussion 99-102. PMID 2799365 .
8. ^ Albert A. Bühlmann: Decompression during lowered air pressure . In: Switzerland Med Wochenschr . 114, No. 26, 1984, pp. 942-7. PMID 6087447 .
9. ^ Albert A. Bühlmann, Schibli R, Gehring H: Experimental studies on decompression following diving in mountain lakes at reduced air pressure . In: Switzerland Med Wochenschr . 103, No. 10, March 1973, pp. 378-83. PMID 4144210 .
10. ↑ Hennessy TR: Converting standard air decompression tables for no-stop diving from altitude or habitat . In: Undersea Biomed Res . 4, No. 1, 1977, ISSN  0093-5387 , pp. 39-53. PMID 857357 . Retrieved April 24, 2008.
11. ↑ Egi SM, Brubakk AO: Diving at altitude: a review of decompression strategies . In: Undersea Hyperb Med . 22, No. 3, 1995, ISSN  1066-2936 , pp. 281-300. PMID 7580768 . Retrieved April 24, 2008.
12. ↑ ^{a b} US Navy Diving Manual, 6th revision . US Naval Sea Systems Command, United States 2006 (Retrieved April 24, 2008).
13. ↑ D. Hothorn, H.-V. Ulmer: Icing of the regulator: Fatal danger when diving in mountain lakes. (PDF; 231 kB) Institute for Sports Science at Johannes Gutenberg University Mainz, accessed on February 13, 2013 . 
14. ↑ Brush Engineered Materials Mourns Loss of Dr. Charles F. Brush III, Director Emeritus . Retrieved March 26, 2010.