About tauchplaetze.ch
A non-commercial project by divers for everyone who dives in Swiss lakes and rivers. No ads and no tracking.
How the forecast works
No reports needed: the lake tells us itself. Twice a day a job fetches data from four sources and calculates the dive index for every site for five days.
Temperature at every depth
Eawag lake models calculate up to four days ahead how warm it is at 0, 10, 20 and 30 m and where the thermocline lies.
Clarity and algae
Once or twice a week, satellite images show how clear the surface is and whether algae are spreading.
Wind, rain, discharge
Heavy rain makes inflows murky, wind stirs up the shore. Both go into the index.
Reports sharpen the model
Reporting the visibility after a dive improves the forecast. It is not required.
What goes into the index
The dive index combines four parts. Each part gives 1 to 10 points. The weight tells how much it counts.
| Part | Weight | Where the data comes from |
|---|---|---|
| Clarity | 35 % | Sentinel-2 and Sentinel-3 satellites (Eawag Alplakes) |
| Wind | 25 % | MeteoSwiss ICON-CH1 and ICON-CH2, DWD ICON (via Open-Meteo) |
| Inflows | 20 % | Rain (Open-Meteo), discharge and discharge forecast (FOEN) |
| Stratification | 20 % | 3D lake models and Simstrat (Eawag Alplakes) |
Clarity: how clear the water is near the shore
We estimate the visibility depth (Secchi depth) where people dive. First we use Sentinel-2 with 10 m pixels, 50 m from the shore, otherwise 100 m. Without this value we use Sentinel-3 from the middle of the lake. Near the shore the water is usually less clear, so only 70 % of it counts. An image counts fully for 5 days. After that it loses weight, and after 14 days it no longer counts. Many algae cost points. Rain and much water in the inflows since the image reduce the visibility by up to 40 %.
Visibility limits the index
Nice weather does not turn murky water into a top day. If the visibility near the shore is moderate (3 to 6 m), the index is at most 7. If it is poor (below 3 m), the index is at most 5. Without a visibility value it is at most 6.5.
Wind in the dive window
We take the strongest hour between 8:00 and 16:00. Up to 2 Beaufort gives full points, from 5 Beaufort there are none. On a lake, wind stirs up the shore and makes entry and exit harder.
Inflows and rain
Rain and floods carry mud into the lake. We count the rain of the last 72 hours. We add the discharge of the inflows compared with the usual discharge, the median of the last 30 days (at least 1 m³/s). For the next days we use the discharge forecast of the FOEN. An inflow counts fully up to 5 km from its mouth, then less, and from 15 km not at all. So a flood of the Ticino clouds Magadino, but not Brissago.
Stratification and thermocline
Lake models of the Eawag calculate the temperature at each depth: at the site with the 3D model, otherwise for the whole lake with Simstrat. From this we find the thermocline. Below it the water is often colder and clearer. Full points only come when the surface is good too (from 6 m visibility near the shore).
On a river
A river is mixed, so stratification does not count. We use the FOEN station of the site, with discharge, forecast and water temperature. Much water means a strong current. From 1.5 times the usual discharge we take off points, at 3 times 3 points. If the measurement is older than 6 hours, the forecast counts for today. With the forecast we also compute the index for the next days.
Current in the lake
The 3D lake model also calculates the current. We show the mean between 5 and 30 m depth as information. The current in a lake does not go into the index.
When we calculate
The forecast runs daily at 04:30 and 13:00 for 5 days. We fetch the discharge every 30 minutes, the FOEN forecast from 08:15 every 3 hours. Satellite images come when the sky is clear: Sentinel-3 almost daily, Sentinel-2 about every 5 days.
When data is missing
If a part is missing, we calculate with the others. Only clarity always counts: without a satellite value it counts carefully, and the index is at most 6.5. Without wind or without water data there is no index, only an outlook with wind and rain.
Rules rules-1.7. The numbers on this page come straight from the calculation.
How precise is the forecast?
Every site has a data level. It shows how close the data is to the site.
- Precise: temperature profile at the site from the Eawag 3D lake model.
- Water body: profile for the whole lake from the 1D model, for rivers a FOEN gauging station.
- Weather: only wind and rain at the site. An index exists only with a satellite image.
The dive index (0 to 10) is an indicator, not a guarantee of visibility. Check the conditions on site, and never dive alone.
Data sources
We show all data with attribution. The pages read only our own database; only the job queries the sources.
- Eawag Alplakes
- Lake models (3D and 1D) with the temperature at depth, plus satellite data on clarity and algae. © Eawag.
- MeteoSwiss via Open-Meteo
- Weather models ICON-CH1 and ICON-CH2 by MeteoSwiss (open government data) and ICON by DWD, retrieved via Open-Meteo (CC BY 4.0).
- FOEN hydrological data
- Discharge and water temperature of the measuring stations of the Federal Office for the Environment, fetched via existenz.ch, plus the discharge forecast directly from the FOEN. Open Government Data with attribution.
- swisstopo
- National map, aerial imagery (SWISSIMAGE) and lake depth data (swissBATHY3D) for the depth contours. Open government data, © swisstopo.
- OpenStreetMap
- Initial set of dive sites with name, location and some details. © OpenStreetMap contributors, Open Database License (ODbL). The data we took over is also available under the ODbL.
Legal notice
Operator
Marc DürstPanoramastrasse 34
5619 Büttikon
Schweiz
Contact
All information without guarantee. The forecast is an indicator; diving is at your own risk. The operators of linked pages are responsible for their content.
Contact
Questions, corrections or a site we do not know yet? Write to us. The message goes to the operator by e-mail and is not stored.
Privacy
We process as little personal data as possible, in line with the Swiss Federal Act on Data Protection (FADP).
Visiting the website
You do not need an account to visit. We set no tracking or advertising cookies. For troubleshooting, the app writes operational data (requested address, time, errors) to a log, without IP address. We keep it for at most 30 days. If you choose a place on the start page, a functional cookie (tp_area) remembers only the place and the radius for one year, for example «zuerich:25». «Use my location» asks for your location only when you click it. The coordinate stays in your browser; only the nearest place from the list is sent.
Hosting
Website, database and photos are hosted by Microsoft Azure in the Switzerland North region. We send emails through a Swiss email provider.
Account
Only contributors need an account: e-mail address, display name and the password as a hash. Signing in uses a technically necessary cookie, forms use a cookie that protects against misuse, and the editing pages a cookie with the language of the page. We also store when you registered and last signed in, without IP address or device. Confirmation and password reset mails go only to you.
Contributions, reports and photos
Changes appear in the versions of a site, with your name only if you agree. We show photos with the photographer’s name. The public image sizes contain no GPS or camera data; the original stays private. We show reports after a dive with date, visibility and temperature, the comment only after approval and your name only if you agree. If you delete your account, reports stay without name and comment.
Contact form
Name, e-mail address and message go to the operator by e-mail and are not stored in the database. The form uses a technically necessary cookie that protects against misuse. Against spam, we count messages per IP address, only in memory and for at most one hour.
Location and maps
«Near me» asks your browser for your location. The coordinate is only part of the search address and may therefore appear in the app’s log. We do not analyse it and do not store it in an account. Your browser loads map tiles directly from swisstopo (geo.admin.ch); swisstopo sees your IP address. Your browser remembers the choice of map or aerial image.
Routes
The links to Google Maps and Apple Maps only transmit the site’s coordinate when you click them.
Your rights
Under «My data» you see all data about your account and can download it. Under «Delete account» you delete your account: private photos and all originals are deleted, versions remain without a name. Questions and requests without an account via the contact form.