Public water reading
Pregny-Chambésy, Geneva, 1292
Pregny-Chambésy, Geneva, Switzerland · 46.2356, 6.1682 · 1,159 hectares of water
Good water, pressed at the margin.
This body of water is sound water with clear regenerative upside at its edge, scoring 71 out of 100. The rain that feeds this water has been falling for twenty years. The water reads clear from orbit. 10 of 12 sources answered; the silent ones lowered confidence, not the score.
Five readings
10 of 12 sources answered · 100% of pillar weight read · silent: the water trace, the hazard screen
The water
What this body is, how it reads from orbit, whether it stays, and the basin it sits in.
The body
Clarity · from orbit
One Sentinel-2 pass, 2026-09-15, 0% cloud in the scene. Indices, not concentrations: a bottle to a lab decides; this says where to dip it.
Permanence · 1984–2021
The basin
The edge
What the shore is made of, what lives here, what presses on the water, and what the climate does to it.
The shore · 300 m ring
- Tree cover 55%
- Built-up 36%
- Grassland 9%
- Bare / sparse 1%
Life
Most recorded: Myotis daubentonii · Sciurus vulgaris · Himantoglossum hircinum · Anacamptis pyramidalis
Pressure
Climate · to 2050
Expect is the honest verb: the middle of a range of futures, one scenario, not a certainty. Warmer air means warmer, more stratified water and more evaporation.
The reading
What the figures mean together, what to do first, how to check it, and what only the water itself can answer.
Findings
- Risk
The rain that feeds this water has been falling for twenty years.
For a standing water body the trend in inflow matters more than the total: a falling trend is a shrinking budget, felt first at the shallow edge and in the dry season.
Twenty-year rainfall trend -15.9% over the water (reanalysis grid, ~9 km). · medium confidence
- Opportunity
The water reads clear from orbit.
Clear water is the rarest condition to keep and the cheapest to lose; it says the catchment above is still holding its soil.
Turbidity index -0.6, chlorophyll index -0.1 over 3,314 water pixels. · medium confidence
- Permanence
This water has stayed, year after year, for four decades.
Permanence is the first property of a water asset: what stays can be planned around; what comes and goes must be designed for.
99% permanent, 0% seasonal; where water was seen it was present 97% of the time (JRC Global Surface Water, Landsat 1984–2021). · high confidence
- Clarity
100% of the boundary read as open water on the latest clear pass.
The share of the drawn boundary the scene classifies as water says whether the reading is about the water or about its edge.
Sentinel-2 scene classification, 2026-09-15; turbidity clear, chlorophyll low. · medium confidence
- Climate
The surface of the water read 21.4 °C on the latest clear thermal pass.
Surface temperature governs how much oxygen the water can hold and how fast it stratifies.
Landsat Collection 2 surface temperature, 2026-09-12; a skin reading from orbit, warmer than the water a metre down. · medium confidence
- The shore
The shore is substantially built.
The edge decides what reaches the water: a wooded or wetland shore filters runoff; a built or cropped shore delivers it.
300 m ring: Tree cover 55% · Built-up 36% · Grassland 9% · Bare / sparse 1% (ESA WorldCover 2021, land pixels only). · high confidence
- Life
This water is well recorded by naturalists.
Occurrence counts measure where people have looked as much as what lives here; a thin record is an unknown, not an absence.
31,310 GBIF occurrence records inside the boundary; most recorded: Myotis daubentonii, Sciurus vulgaris, Himantoglossum hircinum. · medium confidence
- Climate
Expect the seasons here about 1.4 °C warmer by 2050, with 15% less rain.
Warmer air means warmer, more stratified water and more evaporation; less rain means less inflow. Expect is the honest verb: this is the middle of a range.
CMIP6 (MPI-ESM1-2-XR, SSP5-8.5) 2045–2049 against the 2004–2024 record; longest dry spell expected 26 days. · medium confidence
- The body
100% of the boundary is open water in the land-cover record; the public map does not name it.
An unnamed water is not an unknown one — the archive still says how much of the boundary is water and whether it stays — but its kind, its operator and its rights are yours to establish.
100% open water (ESA WorldCover 2021). · low confidence
- The basin
The water surface sits at about 371 m above sea level.
A lake's altitude sets its temperature regime and tells you how far its water has to fall to the next basin.
AWS Terrarium z12 (ETOPO1 below sea level), 36 samples. Bathymetry is ETOPO1-grade (~1.8 km): a screen, never a chart. · medium confidence
What it means together
About 1,306 mm of rain falls on this water in a year, and the water stays: most of the boundary has held water through four decades of passes.
The shore is 36% built, so runoff reaches the water unfiltered — and the water reads clear, which says the edge is doing its job.
This body of water is sound water with clear regenerative upside at its edge; the weakest reading is climate resilience, and that is where the leverage is.
What to do first
- 1
Take a baseline in four bottles before anything changes.
Every figure here is read from orbit or the public record; a baseline on the water is what makes the next reading a trend.
On the water · Temperature, dissolved oxygen, pH and conductivity at the surface and one metre down; Secchi depth; one bottle for E. coli. Same three points every time. · first visit
Open questions
- —Who holds rights to this water — to take from it, to discharge to it, to fish it — and who enforces them?
- —What is in the sediment on the bottom — the memory of everything the catchment has sent down?
- —What is the land above doing this year that the satellite has not caught up with yet?
Sources & method
Pregny-Chambésy was read from public satellite and open-data records; the sources are named below with their licence and grain. The weights that turn them into the Water Score are not published — the data is public, the lens is the product.
- Place — OpenStreetMap / Nominatim · Nominatim reverse geocodesettlement · live · ODbL 1.0
- Climate — Open-Meteo · Archive 2004–2024 + MPI-ESM1-2-XR to 2050~9 km · 2004–2024 / 2045–2049 · CC-BY 4.0 (data); non-commercial API tier
- Surface water — JRC Global Surface Water · Global Surface Water v1.4 — occurrence & seasonality30 m · 1984–2021 · Copernicus / open (attribution)
- Biodiversity — GBIF · Occurrence records (count + top species)point · live · Mixed CC0 / CC-BY / CC-BY-NC (per dataset)
- Body & shore cover — ESA WorldCover · WorldCover 2021 v200 inside the boundary and in a 300 m shore ring10 m · 2021 · CC-BY 4.0 (commercial promotion: notify due@esa.int)
- Basin — AWS Terrarium (Mapzen) with ETOPO1 bathymetry · Terrarium elevation tiles sampled inside the boundary~10–30 m on land; ~1.8 km below sea level · 2017 (ETOPO1: 2009) · Open (attribution)
- Water optics — Copernicus Sentinel-2 · Scene classification water mask; MNDWI, NDTI (turbidity proxy), NDCI (chlorophyll proxy) over the water pixels of one clear pass10–20 m · live (latest clear scene, ≤ 120 days) · Copernicus Sentinel data — free, full and open
- Surface temperature — Landsat Collection 2 Level-2 · Landsat C2 L2 surface temperature (ST_B10) over the boundary, latest clear scene100 m (resampled to 30 m) · live (≤ 365 days) · US public domain
- Watershed — Global Watersheds (MERIT-Hydro) · Upstream basin + downstream flowpath (screening hydrography)~90 m · MERIT-Hydro 2019 · Open service, no warranty; engine open source (delineator)
- Population — WorldPop · Gridded population 2020 (parcel + 5 km ring sums)~100 m · 2020 · CC-BY 4.0
Read 2026-09-17 21:00 UTC in 19.0 s · lens v1