Olszewski pipe

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An Olszewski pipe is a device used to drain deep water from lakes; it is a simple method to prevent lakes from eutrophication or even from tipping over or to remediate eutrophic lakes . The prerequisite is that the flow rate of the lake is sufficient to achieve a restorative effect. It is named after the limnologist Przemysław Olszewski , who first used the procedure in the 1950s on Lake Kortowo in Poland. The idea for this was published in 1944 by the Swiss biologist Eugen A. Thomas.

Construction and working method

Schematic sectional view (elevation) of a lake, once without (top view) and once with (bottom) Olszewski tube, to illustrate the functional principle of the Olszewski tube: The top picture shows, based on the schematically sketched water flows, that the main flow from the inflow to Runoff leads, there is only little mixing with the deeper water layers and thus mainly near-surface water flows out of the lake. The picture below shows the same lake, but with a barrier at the outflow and an installed Olszewski pipe, the upper end of which extends through the barrier into the drain and the lower end of which is at the deepest point of the lake. The outlined water currents illustrate that the inflowing water is now forced to penetrate deeper water layers and thus deep water is transported into the lower end of the Olszewski pipe. This deep water is channeled through the Olszewski pipe into the drain.
Functional principle of an Olszewski tube (below)

A pipe is laid between the deepest point at the bottom of a lake and the point of superficial drainage. The natural surface drainage is closed by a barrier, so that only the nutrient-rich deep water can drain through the pipe. No pump power is required for this. The deep water flows off by itself according to the principle of communicating pipes according to the natural inflow.

Occasionally, the drainage barrier is also designed as an overflow so that more water can leave the lake than the Olszewski pipe can hold.

The same principle of drawing off deep water is used in the carp pond through the construction of the drainage structure, the so-called monk . Here the deep water rises between two rows of boards. The row on the pond side contains a grille above the bottom to allow the water to pass through, which then overflows over the upper edge of the outer row of boards into the drain.

Purpose of deep water drainage

A temperature-related density stratification usually forms in a lake in summer and also in winter . In the areas close to the surface, the nutrients, especially phosphorus and nitrogen, are bound in biomass particles through primary production . In this form, some of these nutrients sink into the deeper water layers. They remain trapped there until the next full circulation occurs , even if they partly assume a dissolved form again due to degradation processes. So the water layers close to the ground are enriched with these nutrients. A withdrawal of this water through the Olszewski pipe therefore removes the nutrients from the ecosystem particularly efficiently.

See also

literature

  • M. Tarmann-Prem: Share of the Piburger Bach in the nitrogen and carbon input into the Piburger See. Nitrogen and carbon elimination through selective drainage of water from different depths of the Piburger See via the modified Olszewski pipe. In: Annual report of the Limnology Department at the Institute of Zoology at the University of Innsbruck. 1977, pp. 197-201 ( PDF on ZOBODAT ).
  • Peter Schaber: The effects of a light source on the extraction of zooplankton with the help of the Olszewski tube in Lake Piburg. In: Annual report of the Limnology Department at the Institute of Zoology at the University of Innsbruck. 1981, pp. 83-101 ( PDF on ZOBODAT ).

Individual evidence

  1. ^ Roland Pechlaner: The restoration of the Piburger See (Tyrol). In: Carinthia II. Sonderheft 31, Klagenfurt 1971, pp. 97–115 ( digitized on uibk.ac.at).