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The model

CoSWAT is a global hydrological model assembled from regional SWAT+ models. Each region is usually a large river basin. A smaller region is one model; a larger one is divided into subregions, each a separate model. The models are prepared with the CoSWAT framework and run by the platform with SWAT+ rev 62.0.1.

Model versions

At any time there is one current version, which receives contributions. Earlier versions can be released and are then frozen. The website offers CoSWATv2.0.0, the current version.

Regions and subregions

A region with subregions is run as one run. Upstream subregions run first, and the daily flow at each one's outlet enters the next subregion downstream as a recall inflow at its inlet, as in a run of the whole basin. The results therefore join up across subregion boundaries. A region without subregions is run as a single model.

Climate

Results are published for observed climate.

Run periods

A run simulates a run period: a span of years that begins with warm-up years. The warm-up lets the model's stores of soil water and groundwater settle, and its years are left out of the results.

The CoSWAT team sets the default run period in the dashboard. Runs with no period set use the default. The default is 1980 to 1986 with two warm-up years, giving results for 1982 to 1986.

If a run period is deleted, the runs made with it keep their years.

Live period

The website shows results for one run period, the live period, which the CoSWAT team sets in the dashboard separately from the default run period. The live period is 1980 to 1986 with two warm-up years, so the maps cover 1982 to 1986.

  • A region whose results cover the same years as the live period is shown as usual.
  • A region whose results cover some of the live period's years shows its yearly maps for those years only, and is left out of the annual average, which would otherwise mix different years. Explore notes this under the region's name.
  • A region whose results cover none of the live period's years is hidden from Explore, the Calibration page, the Data page and the API until it is run again for the live period.

Explore's time bar offers the live period's years and the annual average.

Results

Each run keeps:

  • a map for each year after the warm-up, for precipitation, evapotranspiration and water yield, from the yearly water balance of each HRU;
  • the mean annual total of each of these variables over the same years;
  • the monthly flow in every channel, used for evaluation.

Water balance variables are in millimetres per year. SWAT+ output beyond these is switched off or removed during the run, so daily and monthly HRU output is not available for download.

Global layers

There is one global layer for each variable, and one for its mean annual total, per model version and climate. A region's run supplies its part of each layer. Publishing a new run of a region replaces that region's part only, and the rest of the layer is unchanged. A region with no results shows no data.

The region's previous run is kept, so the CoSWAT team can return to it if a new run has a problem.