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wcswatin

Overview

wcswatin provides workflows to prepare weather and climate time series from gridded and station data for the Soil and Water Assessment Tool (SWAT). It supports data extraction, aggregation, interpolation, quality control, unit conversion, and export of per-location model input files.

The package provides two complementary workflows:

  • Raster/NetCDF processing: inspect NetCDF or GeoTIFF files, define study-area cells, extract gridded values, aggregate hourly or daily data, and write SWAT-style time-series files.
  • Station data interpolation: read station files, fill gaps, reorganize daily observations, interpolate values with trend surfaces, and write point-based SWAT inputs.

Developed with funding from the Critical Ecosystem Partnership Fund (CEPF).

Key Features

  • Inspect NetCDF variables, units, extents, layer counts, and time resolution with raster_info() and var_names()
  • Process NetCDF and GeoTIFF raster files from climate data providers such as ERA5-Land, GPM IMERG and PERSIANN
  • Extract gridded data for watershed cells or reference points
  • Support hourly workflows, daily NetCDF products, and local datacube aggregation with datacube_aggregation()
  • Use future-based parallel extraction through cube2table()
  • Prepare SWAT-style weather files and station interpolation outputs
  • Fill gaps and summarize station or gridded time series

Installation

Install the development version from GitHub:

# install.packages("devtools")
devtools::install_github("reginalexavier/wcswatin")

Quick Start 

library(wcswatin)

# Inspect a downloaded NetCDF file before choosing the processing route
nc_file <- system.file(
  "extdata/nc_data/hourly_multi_2days_2025.nc",
  package = "wcswatin"
)

raster_info(nc_file)
var_names(nc_file)

# Load a raster cube and extract values at reference stations
daily_nc <- system.file(
  "extdata/nc_data/daily_2m_temperature_daily_maximum_2025.nc",
  package = "wcswatin"
)
stations_file <- system.file(
  "extdata/pcp_stations/pcp.txt",
  package = "wcswatin"
)

station_values <- tbl_from_references(
  raster_file = input_raster(daily_nc),
  ref_points = stations_file,
  prefix_colname = "t2m"
)

head(station_values)

# Interpolate daily station tables to target points
interpolated_points <- ts_to_point(
  my_folder = "path/to/station_files",
  targeted_points_path = "path/to/centroids.shp",
  poly_degree = 2
)

ts_point_to_files(
  points_list = interpolated_points,
  output_folder = "path/to/swat_pcp",
  file_prefix = "pcp"
)

Workflow Overview

Conceptual workflow of the wcswatin package

Conceptual workflow of the wcswatin package

Main Functions

Data Input & Inspection

Raster/NetCDF Processing

Station Data Processing

SWAT-Specific Functions

Data Analysis & Utilities

Data Requirements

The package works with spatial data in WGS 84 geographic coordinate system (EPSG:4326), which is the standard format for most climate datasets. Reference point tables should include NAME, LAT, and LON columns. When possible, vector reference points are projected to the raster CRS before extraction.

For NetCDF inputs, inspect time metadata before processing. Hourly files can be processed through cube2table() and later aggregated with daily_aggregation(), while daily NetCDF products can often be extracted directly. For accumulated products timestamped at a specific hour, datacube_aggregation(mode = "value_at_hour") and daily_aggregation(mode = "value_at_hour") make that convention explicit.

Supported Data Sources

  • Climate Reanalysis: ERA5-Land, MERRA-2, NCEP
  • Satellite Precipitation: GPM IMERG, PERSIANN, CHIRPS
  • Station Data: Standard SWAT weather file format

Documentation

NetCDF files can be downloaded with any CDS workflow. The optional cds-downloader CLI can help create repeatable CDS download requests, but it is not required by wcswatin.

Getting Help

Citation

If you use wcswatin in your research, please cite:

Exavier R, Kawakubo F, Zeilhofer P (2026). wcswatin: Weather & Climate SWAT INput (WCSWATIN). R package version 0.1.1, https://github.com/reginalexavier/wcswatin

@software{
  title = {wcswatin: Weather & Climate SWAT INput (WCSWATIN)},
  author = {Réginal Exavier and Fernando Shinji Kawakubo and Peter Zeilhofer},
  year = {2026},
  note = {R package version 0.1.1},
  url = {https://github.com/reginalexavier/wcswatin},
}

License

GPL (>= 3)

Acknowledgments

This project is funded by the Critical Ecosystem Partnership Fund (CEPF).