Water colour

The most reliable indices: irradiance cancels in a ratio, which also removes the camera's auto white balance and the unknown reflectance of the reference rocks. Green/Red rises as the water shifts toward green; Blue/Green falls as it becomes more turbid or more algal. Hover or tap a point to see the frame it came from.

Nechad single-band form driven by red-band reflectance. Not calibrated NTU — it is scaled by the unknown reflectance of the rock reference, and it still tracks illumination, so read trends only.

UK Met Office UKV 2 km model at the site. Shortwave radiation drives how much light reaches the water; cloud cover changes its diffuse/direct balance, which is the main thing the reference patch struggles to correct for.

Each stick points the way the wind is blowing towards, with north up and east right; stick length is speed. A run of sticks leaning the same way is sustained wind from one quarter, which is what builds fetch across the lough.

Rain drives runoff and sediment input; both typically lead turbidity by hours to days.

Each series keeps its own independent scale, drawn on a shared time base, so they can be compared for timing rather than magnitude. Each legend entry shows that series' own range.

Gauge level in metres, from the DFI Rivers Agency HydrometCloud network. Recorded every 15 minutes.

How to read this

• Each point is one photo. Zones are fixed rectangles — sky, open water, and a reference patch (shoreline rocks) standing in for a gray card — stored as fractions of the frame, so they survive a change of resolution.
• Pixels are linearised out of sRGB, then averaged over a luminance percentile band. Water and sky keep 5–90%, rejecting whitecaps and sun glint. The reference keeps 55–95%, so shadowed rock is excluded from the irradiance estimate that divides everything else.
• Values are normalised by EXIF exposure time and ISO to undo auto-exposure.
• Weather comes from the Open-Meteo UK Met Office UKV 2 km model at the site coordinates, matched to each photo on the exact UTC hour. Times shown are the site's local time.
• Hollow points are flagged suspect (clipped highlights, missing exposure data, or too little usable reference patch).
• Raw data: /api/series