Olszewski tube

This tube was first proposed by a Polish limnologist named Przemysław Olszewski in 1961 and helps combat the negative effects of eutrophication, high nutrient content, in lakes.

The basic concept behind the Olszewski tube is the reduction of nutrient concentration and destratification; the more specific goal is hypolimnetic withdrawal.

Other limnologists like Pechlaner and Gachter have reported successes in small lakes where the total phosphorus decreased, transparency of water increased, and less algae was present.

Short-term uses of Olszewski tubes have largely failed because it takes some time for the anoxic condition of the hypolimnetic layer to increase in dissolved oxygen.

If the Olszewski tube is operated slowly enough, the rate of water going in and going out will be fairly constant causing the thermocline to stay intact.

These include increasing dissolved oxygen, reducing nutrient concentration, and lessening the amount of algae and unwanted biomass in lakes.

Schematized cutaway view (elevation) of a lake, once without (upper illustration) and once with (below) Olszewski tube, to illustrate the functional principle of the Olszewski tube: The upper picture shows on the basis of the schematically outlined water flow that the main flow leads from the inflow to the outflow, only little mixing takes place with the deeper layers of water and thus mainly water near the surface flows off the lake. The lower picture shows the same lake, but with an outlet barrier and an installed Olszewski tube, the upper end of which passes through the barrier into the outlet and the lower end of which is at the lowest point of the lake. The outlined water flow illustrates that the inflowing water is now forced to advance into deeper layers of water and thus deep water is transported into the lower end of the Olszewski tube. This deep water is directed through the Olszewski pipe into the outlet.
Working principle of an Olszewski tube (below)