Zieselsmaar Badestrand

Germany Lake 1 - Excellent

Zieselsmaar is an artificial lake created in 1966 located in the Rhein-Erft-Kreis region. It has been designated as a bathing water under EU regulations since 1989. The lake covers 4.5 hectares with an average depth of 4.5 metres and a maximum depth of 10.1 metres. Water quality has been rated as excellent for four consecutive years from 2020 to 2023.

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Water

Artificial lake with a surface area of 4.5 hectares. Average depth is 4.5 metres with a maximum depth of 10.1 metres. Water exchange time exceeds 30 days, with water renewal occurring through groundwater infiltration. The water body is stratified with a loamy substrate and naturally structured shoreline. Water temperature ranges from 15.2 to 22.7 degrees Celsius with an average of 19.6 degrees. Water transparency ranges from 0.8 to 1.5 metres with an average of 1.1 metres.

Location

The bathing area is located near Bergheim and Kerpen in North Rhine-Westphalia, Germany. The bathing beach covers a shoreline length of 1,000 metres. The water body is situated in lowland terrain below 200 metres elevation.

Water Quality

Water quality classified as excellent for 2020, 2021, 2022, and 2023. The pH value is exceptionally low, averaging 2.89 (range 2.7–3.08), due to pyrite and marcasite-bearing spoil materials from brown coal mining. Limestone is regularly added to maintain pH above 3. Conductivity averages 348 µS/cm (range 323–473 µS/cm). Heavy metal enrichment has been observed, particularly cobalt and nickel. From a microbiological perspective, the water is ideal due to the low pH preventing microorganism survival.

Risks

The water has an unusually low pH value due to sulfide oxidation from mining-related contamination, resulting in rust-brown discolouration. Significant enrichment with cobalt and nickel has been documented. A warning notice advises persons with sensitive skin, particularly those with nickel or cobalt allergies, against prolonged water immersion. Maintaining water transparency above 1 metre has become increasingly difficult due to regular lime additions. No cyanobacteria blooms have been observed in the past four years, and no risk of future mass development is anticipated.