This page traces the evolution of the three components of the
Kayak Belgique platform:
the
hydrological API (real-time open data), the
GPS app for river
navigation, and the
Balisage prediction algorithm (flow, comfort, difficulty, best day). Real-time entry point:
/api/index-app?format=json. Terms of use:
API License ·
Data License.
＋ Addition ✓ Fix ⟳ Change 🛡 Security
Our methods in brief
- Acquisition: open feeds from SPW Hydrométrie (KiWIS) + ODWB, readings every 15 minutes, validation and normalisation of the series.
- Flow forecast: weighted moving averages (60 d + 7 d) + effective runoff coefficient calibrated river by river on our history, modulated by basin saturation, mean reversion and a day-to-day rise cap at the 97th percentile.
- Indices: Comfort and Difficulty computed by weighting several criteria (flow, water temperature, windchill, wind, rain, level); navigability remains bounded by each river's legal thresholds.
- Quality control: automatic daily comparison forecast / actual flow (self-learning); error margins are published in the datasets.
- GPS mapping: routes assembled from OpenStreetMap hydrographic segments, with no hand-entered coordinates.
Full details: flow forecast methodology.
2026.09 September 2026 — current version Current Widget Security
Embeddable “water level” widget
- New partner widget embeddable with a single
<iframe> tag: live flow, level, temperature and navigation status, for the 6 rivers and in 4 languages (FR/NL/DE/EN). Configurator: /widget-niveau-eau.
- 7 visual styles (classic, border, gradient, shadow, frosted glass, minimal, neon), accent colour, light/dark/auto theme, adjustable width and height.
- PNG image version (
/widget/niveau-eau.png) intended for newsletters, regenerated each time the message is opened.
- Dedicated endpoint
/api/widget-niveau-eau.php (JSON, open CORS, read-only), designed for custom integrations.
- On the partner side, a “zero trust” model: cross-origin iframe in
sandbox, served with Content-Security-Policy: default-src 'none', no cookie, no third-party script run on the host site, referrerpolicy="no-referrer".
Dynamic social cards
- The
og:image of the “water level” pages (Facebook, LinkedIn, X, WhatsApp) is now a 1200×630 card generated live: it shows the day's flow, level and navigation status, refreshed daily.
Security & infrastructure
- HTTPS enforced with HSTS preload, TLS 1.3 and HTTP/3 (QUIC) across the whole domain.
- Strict Content-Security-Policy based on per-request nonces, complemented by a Trusted Types policy in report-only mode.
- Complete security headers:
X-Content-Type-Options, Referrer-Policy, locked-down Permissions-Policy, COOP/CORP.
- Tighter API CORS: an origin allow-list replaces reflecting the
Origin; public endpoints served with stale-while-revalidate.
schema.org vocabulary references switched to https:// in all structured-data blocks.
GPS app — social layer
- Real-time presence between kayakers on the map (anonymous position, automatic purge) and private messaging, with blocking, reporting and automatic muting on their side.
- Public profiles, shared achievements and synchronised challenges for linked accounts.
Balisage V10 August 2026 Prediction
- Fix for an optimistic bias in the flow predictor: the rain→flow coefficients overestimated the expected rise by a factor of 5 to 9. Recalibration river by river from our measurement history.
- Day-to-day rise cap per river, set on the real 97th percentile of observed flow changes, which acts as a safeguard even when extreme rain is forecast.
- Catchment saturation index (ratio of measured flow to reference flow, bounded): a dry basin absorbs the rain, a saturated one releases it.
- Reference flow = weighted moving average 60 days + 7 days, to which flow returns in the absence of rain; mean reversion at a fixed rate.
- Reactivation of the self-learning loop (daily comparison between forecast and actual flow), which had stayed inactive for lack of cron scheduling.
- The methodology also documents the calculation of thermal comfort (windchill) and of the Difficulty Score.
- Publication of the
Dataset “predictive flow model” (JSON-LD): measured variables, technique, time coverage D-60 → D+7.
GPS 2026 2nd quarter 2026 GPS
- Full-screen GPS navigation app (/map): real-time position on the river route, with points of interest, put-in and take-out points.
- Offline mode: map tiles and route to download before the descent, to navigate without a network deep in the valley.
- Personal waypoints, calculation of the road return route from the take-out point, SOS button with position sharing.
- System of achievements and challenges (badges) for the paddler's progression.
- River routes assembled from OpenStreetMap (official hydrographic segments) rather than hand-entered coordinates: the geometry faithfully follows the real riverbed.
- Single-language interface with injected internationalisation: touch targets ≥ 44 px, Leaflet controls moved away from critical action zones.
API v3 · Data v9 1st half 2026 API Data
- Coverage extended to 6 rivers: Semois, Lesse, Ourthe, Amblève, Bocq and Viroin.
- Comfort Index (/100) and Navigation Difficulty Score (/100) computed in real time: weighting flow 40 % + water temperature 15 % + windchill 15 % + wind 10 % + rain 10 % + level 10 %.
- The navigation safety status (low-water alert, flood, cold-water shock risk) is built into the API response.
- Estimation of trip times based on the day's flow, with personalised equipment recommendations.
- JSON-LD schema made Google-compliant:
Dataset, DataCatalog, Observation and Recommendation; creator/publisher typed as Organization.
- Dataset cache bumped (
v7 → v9) and regenerated from the corrected source.
- License links internalised:
license points to our own pages.
- Fix of the
creator/publisher object type (the array type, rejected by validators, was removed).
v2.0 → v2.3 2025 API Prediction
- Integration of water temperature and windchill (feels-like temperature) into the comfort calculation.
- Forecast of the best day to paddle in the coming days, by crossing forecast rainfall with historical flow.
- Flow forecast D+1 → D+7 by regression on history and rainfall.
- Data refresh raised to every 15 minutes from the SPW Hydrométrie and ODWB feeds (aligned with the KiWIS cadence).
- Navigability status bounded by each river's legal thresholds.
v1.x 2022 – 2024 API
- 2024 — Launch of the public API and the open data files (
/data/semois.json, .csv) under the CC BY 4.0 license.
- 2023 — Addition of real-time weather (air temperature, wind, rainfall) to the river dashboard.
- 2022 — First version of the KSA algorithm, which reads the flow (m³/s) and water level of the Membre-sur-Semois station (SPW 9434), and publication of the first real-time hydrological dataset for the Semois.
Source of the measurements: SPW Hydrométrie Wallonie & Open Data Wallonie-Bruxelles. Processing, forecasting and indices: Balisage algorithm (Kayak Belgique).