# Step 3: Preparing the input data

As mentioned before, the input data can be classified into two types:

• Meteorological forcing: maps with timeseries for each model pixel, with values for precipitation, temperature, and potential evaporation. This data should be provided as a three-dimensional dataset, with the x, y and time dimensions.
• Static maps.

## Meteorological data

Meteorological data is provided as a single NetCDF file, with several variables containing the forcing data for precipitation, temperature and potential evaporation. The code snippet below shows the contents of the example file (downloaded here), and displaying the content with NCDatasets in Julia. As can be seen, each forcing variable (precip, pet and temp) consists of a three-dimensional dataset (x, y, and time), and each timestep consists of a two-dimensional map with values at each gridcell. Only values within the basin are required.

Group: /

Dimensions
time = 366
y = 313
x = 291

Variables
time   (366)
Datatype:    Int64
Dimensions:  time
Attributes:
units                = days since 2000-01-02 00:00:00
calendar             = proleptic_gregorian

y   (313)
Datatype:    Float64
Dimensions:  y
Attributes:
_FillValue           = NaN

x   (291)
Datatype:    Float64
Dimensions:  x
Attributes:
_FillValue           = NaN

spatial_ref
Attributes:
crs_wkt              = GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AXIS["Latitude",NORTH],AXIS["Longitude",EAST],AUTHORITY["EPSG","4326"]]
x_dim                = x
y_dim                = y
dim0                 = time

precip   (291 × 313 × 366)
Datatype:    Float32
Dimensions:  x × y × time
Attributes:
_FillValue           = NaN
unit                 = mm
precip_fn            = era5

idx_out   (291 × 313)
Datatype:    Int32
Dimensions:  x × y

Datatype:    UInt8
Dimensions:  x × y

pet   (291 × 313 × 366)
Datatype:    Float32
Dimensions:  x × y × time
Attributes:
_FillValue           = NaN
unit                 = mm
pet_fn               = era5
pet_method           = debruin

temp   (291 × 313 × 366)
Datatype:    Float32
Dimensions:  x × y × time
Attributes:
_FillValue           = NaN
unit                 = degree C.
temp_fn              = era5
temp_correction      = True

Global attributes
unit                 = mm
precip_fn            = era5
Note

Wflow expects right labeling of the forcing time interval, e.g. daily precipitation at 01-02-2000 00:00:00 is the accumulated total precipitation between 01-01-2000 00:00:00 and 01-02-2000 00:00:00.

## Static data

### List of essential static data

The list below contains a brief overview of several essential static maps required to run wflow. These NC variables names refer to the example data of the wflow_sbm + kinematic wave model (see here). Example data for the other model configurations can be found here.

DescriptionNC variable nameunit
Flow direction (1-9)wflow_ldd-
Map indicating the river cells (0-1)wflow_river-
The length of the riverwflow_riverlengthm
The width of the riverwflow_riverwidthm
Mask of the basinwflow_subcatch-
Land slopeSlopem m$^{-1}$
River slopeRiverSlopem m$^{-1}$

As mentioned before, the model parameters can also be defined as spatial maps. They can be included in the same NetCDF file, as long as their variable names are correctly mapped in the TOML settings file. See the section on example models on how to use this functionality.