How we handle your data.
LakeAlert, [email protected]. For the responsible person and address, see Imprint.
Telegram Bot: Telegram user ID, username (if set by you), first name (if set by you), selected lakes, creation and last activity timestamps. This data is stored to deliver warnings to you.
iOS App: Favourite lakes are stored locally on your device. Your location is evaluated exclusively on your device and is never sent to our servers.
Push Notifications (APNs): Apple device token (a pseudonymous identifier with no personal reference), your selected lakes and the app language (used to localize push notifications) are sent to our server to enable push notifications. Apple Push Notification Service additionally processes the push payload (lake name, warning level, title/body); Apple does not store payloads (details: Apple privacy notice for APNs).
Apple Watch: If you use an Apple Watch, the favorite lake and disclaimer acknowledgment status are synced locally between iPhone and Watch via Apple WatchConnectivity. No server involvement.
Email Signups: Email address, voluntarily provided on lakealert.ch. Optionally, the source (e.g. "seo_bielersee") is stored for analytics.
Feedback: If you send feedback via the bot or a form, we store the text along with your Telegram ID/username for the purpose of responding.
Website Tracking: No cookies, no cross-site tracking. Cloudflare Web Analytics is enabled (privacy-friendly, no personal data, no cookies). Clicks on primary CTAs are logged anonymously.
Server logs: IP address, timestamp, requested URL. Automatically collected by Cloudflare and deleted after 72 hours. Used for security and abuse prevention.
All collected data is used exclusively to deliver storm warnings for your selected lakes and to improve the service (anonymous click analytics). We do not sell data, do not use it for advertising, and do not share it with third parties unless legally required to do so.
Legal bases (GDPR Art. 6): Performance of contract (Art. 6(1)(b)) for delivering warnings and providing the service. Legitimate interest (Art. 6(1)(f)) for anonymous usage analysis and server security. Consent (Art. 6(1)(a)) for voluntary email signup.
Cloudflare, Inc. (USA): Hosting (Cloudflare Pages, Workers, D1 database, Web Analytics). Data processing may occur in the USA. Cloudflare participates in the EU-US Data Privacy Framework and uses Standard Contractual Clauses.
Telegram FZ-LLC (UAE): Bot and channel hosting. If you use the bot, your messages are processed by Telegram (see Telegram Privacy Policy).
Apple Inc. (USA): Apple Push Notification Service (APNs) for iOS push.
Bluesky Social, PBC (USA): Bluesky channel as a backup communication channel. Posts are public.
Your data is stored for as long as you use the service:
/stop. Inactive accounts are automatically removed after 12 months without activity.You have the right at any time to access, rectify, delete, restrict processing, and request portability of your data, as well as the right to object to processing. Send a brief email to [email protected].
In the Telegram Bot: /stop deletes all your data immediately. You may also file a complaint with the competent data protection authority at any time (Switzerland: FDPIC; EU: national data protection authorities).
Warning data comes from stwarn.ch (cantonal police of BE, ZH, LU), the cantonal police TG (Lake Constance, kapo.kttg.ch) and the MeteoSwiss App API. LakeAlert is not an official service of the cantonal police or MeteoSwiss. The legally binding signal is the warning light at the lake.
All data transmissions are encrypted (HTTPS/TLS). On the server, data is stored in Cloudflare D1 (encrypted SQLite database) and Cloudflare KV. Access only via authenticated Worker endpoints.
Swiss data protection law (nDSG) applies. For users in the EU/EEA, the GDPR additionally applies.
As of: April 2026