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Data resources

The SWAT+ hydrological model requires four key data sources for its application (digital elevation map, soil map, land cover map and weather data), and the GOTM-WET lake and reservoir model requires minimum two data sources (hypsograph and weather data). On this page, you can learn how to acquire data from free globally available sources, which will allow you to set up a model from scratch, for any location in the world. We have also produced a series of video tutorials, available on our training page, which demonstrate how you may process these global datasets by a series of GIS operations (e.g. clipping data for your area of interest), so that they can be applied in the SWAT+ model.

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Get the best workflow and documentation of your SWAT+ model application

When setting up a SWAT+ model, the model user will make a range of choices. To be able to reproduce a model set up, it is very useful have at least a minimum of documentation of the choices made. This includes information on the model code versions, input data sources, and model configuration choices. WaterITech have prepared a model protocol template, which seeks to document key aspects of a model application. This will enable an experienced SWAT+ user to reproduce the SWAT+ set up from scratch.

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There are several datasets with global elevation data. For watershed delineations, we have had good experiences with The Shuttle Radar Topography Mission (SRTM) data that is available globally and the EU-DEM for Europe, which is based partly on this. SRTM was initially produced through a partnership between NASA and the National Geospatial-Intelligence Agency (NGA), where the NASA Space Shuttle Endeavour orbited the Earth 16 times in 2000, collecting radar data over approx. 80% of the Earth's land surface. The SRTM data has since been refined to flatten water bodies, better define coastlines, remove spikes and wells, and fill voids, and the most recent version (v3) from 2014 provide worldwide coverage of void filled data at a resolution of 1 arc-second (30 meters). https://doi.org/10.5066/F7PR7TFT

Digital Elevation Maps

SRTM

To access and download the SRTM data, we recommend using the Earth Explorer system by USGS. This requires you to create a free EarthData account, which will enable you to download the dataset (choose the SRTMGL1 data, which is 30 meter resolution) for any location in the world.


Learn how to download and process SRTM data for your next SWAT + setup by watching our training video.

EU-DEM

EU-DEM is an elevation dataset covering Europe at a 25 m resolution. It is a hybrid product based on SRTM and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Map (GDEM), which is based on NASA’s Terra satellite. For the development of EU-DEM, SRTM and ASTER GDEM data have been fused by a weighted averaging approach. You can access and download EU-DEM through Copernicus, which  requires you to create a free account.

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Local soil properties can greatly influence the hydrology of a watershed. Complex hydrological models such as SWAT+ therefore also requires a large set of soil parameters to be able to simulate accurately the hydrology of a watershed. Parameterizing different soil types is often a cumbersome and difficult process that often requires application of a range of pedo-transfer functions, which can translate soil textural properties into the soil parameters needed by the model.

 

While the SWAT+ model comes with a global soil dataset, more detailed datasets are available, which could improve the performance of the model. We utilized the review of pedo-transfer functions by Abbaspour et al. 2019, and derived all the required soil parameters in SWAT+ format using the median output value for a range of different pedo-transfer functions available for a given soil parameter. These unique datasets will provide you with a good basis for your model application, no matter where you are in the world.

Soil maps

Openland
soil map

OpenLand Map is a global (except Antartica) soil map derived from machine learning methods and hundreds of thousands soil profile observations. The raster resolution is 250m and the map includes six soil layers. Soil properties needed for the SWAT+ soil database were derived by WaterITech in collaboration with UCAM using a wide range of pedotransfer functions. See López-Ballesteros et al. 2023 for further details.

The Digital SoiL OpenLand Map (DSOLMap) can be downloaded right here.

Soil Map (zipped raster, 725 MB)

Soil database (SWAT+ format, 0.2 MB)

Soil lookup table (SWAT+ format, 0.1 MB)

Soil taxonomy (Supplementary information, 0.1 MB)

HWSD

The most recent version of the Harmonized World Soil Database (HWSD) compiled by FAO and IIASA (v1.21) is from 2012. The map comes in a horizontal resolution of 30 arc-seconds (1 km), and two soil layers: topsoil (0-30 cm) and subsoil (30-100 cm). Soil properties needed for the SWAT+ soil database were derived by WaterITech using a wide range of pedotransfer functions.

HWSD global extent can be downloaded right here.

Soil Map (zipped raster, 12 MB)

Soil database (SWAT+ format, 8 MB)

Soil lookup table (SWAT+ format, 0.2 MB)

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Land cover maps

Land cover impacts the hydrology of a watershed, as it influences the permeability of the landscape, and also the level of evapotranspiration, which varies for different types of vegetation and management.

Land cover is also highly important for simulating sediment and nutrient processes within a watershed. There a several good global land cover maps available.

To be able to utilize these maps in a SWAT+ application, you need a lookup table that translates the land cover types into the corresponding SWAT+ land cover types available in the SWAT+ general database.

WaterITech has prepared lookup tables specifically for this purpose.

CORINE

Copernicus Land Monitoring Service (CLMS) provides the CORINE Land Cover (CLC) dataset, which was initiated in 1985 (reference year 1990). Updates have been produced in 2000, 2006, 2012, and 2018. It consists of an inventory of 44 land cover classes, and comes in a raster resolution of 100 m.

Land cover map (zipped raster, 80 MB)

Lookup table (SWAT+ format, 0.4 MB)

GlobCover

The European Space Agency started producing the global GlobCover maps based on the Envisat satellite in 2005. The most recent map is from 2015, which contains 22 land cover classes and comes in a resolution of 300 m.

Land cover map (zipped raster, 331 MB)

Lookup table (SWAT+ format, 0.2 MB)

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Weather data

Accurate weather data is a key to be able to simulate the temporal and spatial dynamics of hydrology in a watershed, and hydrodynamics in lakes and reservoirs. Ideally, local weather data is available, which can easily be formatted into SWAT+ or GOTM-WET format, and used as input to your model application.

If you do not have good weather data for your area, you can instead use reanalysis data, some of which is now provided at a detailed spatial and temporal resolution. One of the best globally available reanalysis datasets is the ERA5 data produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). ERA5 comprise hourly data of all the weather parameters required by SWAT+, and covers the entire Earth on a 30km grid for the period 1950 to present.

ERA5

ERA5 data can be downloaded directly in both SWAT+ and GOTM-WET format from a dataportal hosted by WaterWebTools. You can access the portal right here. SWAT+ weather data can be downloaded in both hourly and daily formats from the portal. Alternatively, ERA5 data can also be downloaded from the original Climate Data Store using an Application Program Interface (CDS API). Downloading and formatting the ERA5 data from CDS into SWAT+ format requires some programming skills

CFSR

Alternatively, you can download the somewhat coarser Climate Forecast System Reanalysis (CFSR) data from 1979-2014, through the SWAT website (https://globalweather.tamu.edu/). The raw CFSR comprise 6 hourly data at a resolution of approx. 38 km for the entire Earth. The advantage of this dataset, when downloading this through the SWAT website, is that it has already been formatted into SWAT format.

Want to know more?

Contact Dr. Anders Nielsen to learn more about how we may be able to assist you.

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Anders Nielsen, Ph.D.
an@wateritech.com

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