There is no water quality data available for download. There are a few portals and reports but the actual data isn't there and not all the parameters are represented.
https://www.bafu.admin.ch/bafu/en/home/topics/water/info-specialists/state-of-waterbodies/state-of-groundwater/naqua-national-groundwater-monitoring/trend-and-spez-modules.html
https://map.geo.admin.ch/?lang=en&topic=bafu&X=190000.00&Y=660000.00&zoom=1&bgLayer=ch.swisstopo.pixelkarte-farbe&layers=ch.bafu.hydroweb-messstationen_grundwasser,ch.bafu.gewaesserschutz-chemischer_zustand_nitrat,ch.bafu.gewaesserschutz-chemischer_zustand_nitrit,ch.bafu.naqua-grundwasser_nitrat&layers_timestamp=,,,&layers_opacity=1,1,1,0.75&catalogNodes=2771,2772,2780,2822,2827,2832,2805,2828,2833
Your submission is valid. Thank you very much for contributing to the Global Open Data Index.