Lake Pfäffikon

Between Pfäffikon, Seegräben and Wetzikon, the lake occupies a basin shaped by ice-age glaciers. Reed beds, the Torfriet to the north and the Robenhauserriet to the south connect open water with extensive wetland habitats. The federal landscape inventory highlights this mosaic's value. Shoreline, open water and wetlands are not interchangeable habitats and respond differently to changes in the water balance.

The Chämtnerbach enters from the southeast, where it has built a delta. The Aa starts in the south, crosses the Robenhauserriet and continues towards Uster and Lake Greifen. This connection makes Aa stations useful for understanding the wider water system. They measure a river section, however, not automatically the level or temperature within Lake Pfäffikon.

Lake Pfäffikon is regulated: the canton of Zurich lists it alongside Lake Zurich as a lake whose level can be influenced by weirs. This explicitly distinguishes it from downstream Lake Greifen. Regulation can influence fluctuations, but cannot create water or release unlimited inflows. The annual pattern is therefore an interaction between water supply, outflow and management, rather than an unchanging target level.

When searching for stations, this is Pfäffikon in the canton of Zurich, not Pfäffikon beside Lake Zurich in the canton of Schwyz. Location still matters within this landscape: lake level, Aa discharge and wetland water levels describe different things. The lake's elevation is not its depth. Assessing the wetlands requires additional local observations; the lake level alone does not fully represent their water balance.

AWEL's January 2026 assessment rates phosphorus concentrations and algal abundance favourably, but still describes summer oxygen shortages in deeper layers. One good indicator cannot explain all living conditions. The former system supporting water circulation was stopped in spring 2011; this must not be confused with lake-level regulation, which remains in place. A shoreline temperature is still a local observation, not a substitute for a depth profile.