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Water restoration and remediation

since 2016 EU LIFE+ Project Urban Lake Old Danube – Groundfilter Wasserpark

As part of the project “EU-Life + Urban Lake Old Danube”, the measure “Soil Filter Water Park” was planned as a sustainable solution to improve the water balance of the Upper Old Danube and to increase the calcium content. Ca-rich water is extracted from the New Danube and passed through a soil filter in the water park to the Alte Donau. The supplied water is usually passed through the water park after passage the soil filter, in which a nutrient and suspended matter reduction is done, in the Upper Old Danube. The transfer quantities compensate the hydrological deficit of the Upper Old Danube. The soil filter was built in 2016 and the water law was applied for. The evidence-recovery program to verify the impact of the operation includes hydrological, aquatic ecological and hygienic aspects.

In cooperation with: Fa. Polyplan, Dipl.-Ing. Schattovits Ziviltechniker GmbH, Gruppe Wasser, TB Schuster

Tasks: Water law EOP, operating instructions, limnological preservation of evidence, supervision of online sensors and sampling collectors

Client: City of Vienna MA45

since 2010 Rehabilitation measures at Pöttschinger See

At the beginning of the extensive investigations, the mining lake Pöttsching was eu- to hypertrophic (dissolution of sedimentcomponents in anoxic deep water, high turbidity, intense red-brown coloration after the autumn circulation, unfavorable structure of the food chain, buoyant algae). Following the recording of the lakes morphometry, sediment, nutrient chemistry and food web, the following measures were implemented: sediment treatment and planting of macrophytes in restricted areas, fish stock survey and proposal for fishery management (spawning aids), as well as an installation of a deep water aeration system combined with online monitoring.

Client: Pan.Real Immobilienbeteiligungs GmbH


since 2006 Regulation of the pH buffer capacity of the Old Danube

In order to lower the pH values ​​and increase the buffer capacity in the Old Danube, a water law EOP for the discharge of New Danube water into the Old Danube (“water exchange”) was drawn up in 2006 and submitted to the authorities. The measure includes the discharge of water from the New Danube into the lower Old Danube at the transition structure “Seestern” in the amount of max. 500 L s-1 between 1 July and 30 November and to the same extent, the simultaneous discharge of water from the Old Danube at the diversion structure Floridsdorf in the drainage system of Vienna (MA 30 LDS). Each discharge is augmented by the increased groundwater inflow to “Wasserpark”, due to the lowered water level. Until 2017, the “water exchange” was carried out annually and accompanied by a monitoring program.

in cooperation with: Gruppe Wasser & Donauconsult

Tasks: Measurement of physico-chemical and nutrient-chemical parameters, phytoplankton analysis in the New Danube and Old Danube

Client: City of Vienna MA 45

since 2001 Water level regulation of the Old Danube

In the 1990s, the Old Danube was highly eutrophic. Low depths of visibility and blue-green algae blooms were associated with the near-disappearance of higher aquatic plants. In 1993, the MA 45 led to the preparation of remediation proposals. The aim of the project was i.a. to promote a repopulation with macropytes by a directed lowering of the water level in spring time. The measure, which was operated as a water management experiment in 2002-2005 and subsequently anchored as a water law, brought the desired success. The MA 45, in cooperation with ecologists, is currently pursuing a management and cultivation plan for underwater plants. The concept is to control underwater plant stocks by targeted mowing to the extent that boat and swimming operations can proceed undisturbed, but damage to the crop is avoided.

In cooperation with Gruppe Wasser & Systema GmbH

Contribution of DWS Hydro-Ökologie: limnological monitoring via measurements of physical, chemical and nutritional parameters of the Old Danube and groundwater

Client: city of Vienna MA 45


since 2001 Lake revitalisation via deep water aerator

The function of a deep water aeration system (in German ‘Tiefenwasserbelüftungssysteme’ or short ‘TIBEAN’) is to pump water from the bottom up with an ascending pipe, resulting in an oxygen boost. Via a downpipe the oxygen-enriched deep water is then – after  passing a degasser – channeled into a defined depth where it is distributed evenly in all directions. The goal of aeration is to restore sufficient oxygenation, thereby binding nutrients in the sediment, reducing the overall nutrient pool, and increasing the living space of higher organisms. The consequences are a general reduction in the trophic level, a reduction in algae growth and an improvement in the depth of visibility. In cooperation with Polyplan, DWS Hydro-Ökologie has carried out the planning, installation and preservation of the following TIBEANs in Austria: Pöttschinger See (Burgenland), Badesee Steinbrunn (Burgenland), Grundwassersee Watzelsdorf (Lower Austria), Tilgteich (Lower Austria), Bendateich/Buttinger Teich (Vienna), Schellensee (Vienna), Stubenberg (Styria).

Client: private property owners, municipals, associations, city of Vienna MA45

since 1997 Revitalisation and limnological monitoring of the Kahrteich (Wiener Neudorf)

Qualitative and quantitative changes in the groundwater inflow, intensive bathing as well as intensive fishing were probably the causes of eutrophication in the Kahrteich near Wiener Neudorf. First measurements in 1997 showed that in summer the deep water was oxygen free. High ammonium and orthophosphate levels above the sediment and the distinct smell of hydrogen sulfide were causally related to the reducing conditions. As progressive eutrophication would have caused significant damage to fish fauna (including fish mortality) and bathing quality, countermeasures were taken early by the municipality as in autumn 1999 a deep water aeration system was installed. Since then, regular on-site monitoring has been supported by continuous measurements via online probes.

Tasks: Morphometric survey, mapping of sediment thicknesses and estimation of sediment cubatures, physico-chemical measurements in the depth profile and nutrient chemical analyses, zooplankton and phytoplankton surveys, trophic indication based on chironomids, manangement recommendations, water law submission, installation of deep water aeration, monitoring

In cooperation with: Polyplan, TB Schuster and the diving club Wiener Neudorf

Clients: Municipality of Wiener Neudorf

2015 Elaboration of a revitalisation concept for park ponds in Vienna

The municipal authority “Wiener Stadtgärten” (MA 42) is responsible for daily horticultural care and design of various parks in Vienna. Many of these parks contain ponds in various designs, different ages and with diverse claims of utilization. For some of these ponds, the MA 42 found a need for remediation (problems were: sludge deposits, leaking basin or Clay seals, fish mortality) and thus contacted the WGM (Vienna Water Management) and the MA 45 in order to establish a rehabilitation concept. Subsequently the DWS Hydro-Ökologie was commissioned with the preparation of a rehabilitation concept.

Tasks: Research (data basis), inspections of the parks and verification of the remedial needs, deficit analysis, revitalisation concept

Client: City of Vienna MA42 and MA45


2010 Revitalisation of a meromictic lake – Badesee Steinbrunn

The almost 25 m deep Steinbrunner See is a meromictic lake. A strong chemocline prevents wind-induced mixing even in isothermal conditions. Below 10 m, the lake was oxygen-free year-round, just above filamentous blue-green algae accumulated. The goal of aeration in Steinbrunner See was to restore an oxygen-enriched deep zone. In the presence of oxygen, internal nutrient enrichment is blocked and the available nutrient pool for the low-light-adapted blue-green algae at the lower limit of the euphotic zone is minimized. Likewise, potentially catastrophic scenarios, such as fish stock damage due to lack of oxygen or hydrogen sulfide poisoning, can be prevented.

Tasks of the DWS Hydro-Ecology: Preliminary investigations, management plan, water law submission permit, installation of a deep water aeration facility in cooperation with the company Polyplan and an online monitoring in cooperation with the TB Schuster

Client: Municipality Zillingdorf

2010 Restoration concept Prater waters

under construction…

2006 Revitalisation of Unteres Heustadelwasser by Neptun plant

under construction…

1999-2002 Investigation and preparation of a management concept for Kuchelauer harbor

under construction…

1999 Feasibility Study for the restoration of the West Lake/Tai-ho (Hanoi, Vietnam)

Aim of the project was to draft a feasibility study for the rehabilitation of the West Lake (Tai-ho) in Hanoi. DWS Hydro-Ecology (formerly Donabaum & Wolfram OEG) was involved with key expert Dr. Georg Wolfram as limnological consultant.

Client: IC Consulenten