Water budget
What Switzerland has, and where it goes
A water budget for the country, assembled only from what federal offices and their monitoring networks publish: how much falls, how much evaporates, how much leaves, how much is stored, how much is used, and where each of those stands this month.
Reading the latest official releases…
Where the budget stands now
The national balance is published once a year, about nine months after the year ends. These indicators fill the gap. Each compares the latest complete period with the same months of 1991–2020 at the same station, so a low reading means low for that place and season, not low in absolute terms.
Water leaving the country
Monthly mean discharge of the Rhine at Basel and the Rhône at Chancy, the two gauges where most Swiss water crosses the border, as a share of the 1991–2020 mean for the same month. Together they carry about five sixths of the national outflow; the Ticino, the Inn, the Doubs and smaller border rivers carry the rest.
Drought regions
The combined drought index of the federal drought platform for its 38 warning regions, week by week. It merges precipitation over one, three and twenty-four months, river flow and modelled soil moisture into five levels, from 1, not dry, to 5, extremely dry.
The annual balance
For the country as a whole the budget closes: precipitation and the water that flows in from abroad either evaporate, leave across the border, or change what is stored in snow, ice, soil, groundwater and lakes. BAFU publishes the terms for political Switzerland, 41’285 km², in millimetres of water over that area. Here they are also given in cubic kilometres; one millimetre is 0.041 km³.
A model constrained by measurement. The figures come from the hydrological model PREVAH on a 200-metre grid. Measured discharge is treated as exact and the model error is assigned to precipitation, which is the hardest term to measure in the mountains. Abstraction and use are not part of this natural balance. A negative storage change is water taken out of the country’s stores, above all glacier ice.
By catchment
The same table gives the twelve large catchments BAFU balances separately. Their figures are in millimetres over each catchment’s own area and are compared here with that catchment’s own 1991–2020 mean.
What is stored
The stores are larger than a year’s flow, but most of them are not a reserve that can be drawn on. The figures below are estimates of different ages and methods, and they do not add up to a total: the lake figure counts the whole of the border lakes, and the reservoir figure is a register of dam volumes, not the water in them today.
What is used
Only one use is counted every year: public drinking-water supply, from an extrapolation by the Swiss Gas and Water Industry Association (SVGW) published by the Federal Statistical Office. Every other national figure for abstraction describes 2006 or carries no year at all.
What is missing, and who holds it
A reliable budget needs each of the following. None is published in a form this page can read. Each row names the office that holds or produces the data; these are the requests to make.
| Missing | Why it matters | Holder |
|---|---|---|
| Annual balances for every year | BAFU replaces its table each year. Without the archive there is no national series to compare a year against. | BAFU, Hydrology Division, hydrologie@bafu.admin.ch |
| Snow water equivalent, Swiss-wide | Snow is the largest seasonal store. Published estimates disagree, and no current national figure is published. | WSL Institute for Snow and Avalanche Research SLF, operational snow-hydrological service |
| Actual evapotranspiration, gridded and current | The second-largest outgoing term. Only reference evapotranspiration at weather stations is open; that is atmospheric demand, not water lost. | MeteoSwiss; BAFU for the PREVAH model output |
| A Swiss mean precipitation series | The 1 km grids are open, but there is no official national monthly total to cite, so any aggregate would be this site’s own. | MeteoSwiss, customer service |
| Groundwater storage and recharge | The largest usable store rests on an estimate from 2012. Levels at monitoring sites say whether it is high or low, not how much it holds. | BAFU, NAQUA groundwater monitoring; the cantons |
| Abstraction by sector | Industry, cooling and agriculture were last counted nationally in 2006. Irrigation volumes are measured in only a few cantons. | The cantons, which grant abstraction rights; BAFU; Federal Office for Agriculture |
| Glacier volume as a national series | The annual national volume is published in a PDF bulletin; the open files are per glacier. | GLAMOS (Glacier Monitoring Switzerland) |
| Reservoir contents in cubic metres | The weekly series reports stored energy, not water. A volume per reservoir would show how much water is held back from the rivers. | Swiss Federal Office of Energy (SFOE); the operators |
If you hold any of this data, or know where it is published, please say so through the contribution routes.
How this page is built
- Every number is read at build time from the publishing office’s own file and carries that file’s date. The balance table must close term by term or the build stops.
- Only complete weeks and months are used. The drought platform dates a period by its first day and includes the running one; it is left out.
- A station is compared only with its own record for the same calendar month, and only when at least fifteen years of 1991–2020 exist. Low means below that record’s 20th percentile, high above its 80th.
- Levels and percentiles are not volumes. Nothing is converted to cubic kilometres except the national balance terms and the outflow, where discharge times duration is a volume.
- Old figures keep their year. A figure without a year says so.
Every source, its licence and its data state is listed on the
sources page. The scripts are build/19-budget.mjs
and build/20-conditions.mjs in the
repository.