High-resolution annual irrigation maps for Namoi Catchment, Murray-Darling Basin, Australia (2019-2025)

This repository contains the processed geospatial and tabular data underpinning the study: Muturi, J. W., Majumdar, S., Ndehedehe, C. E., Agutu, N. O., & Kennard, M. J. (2026). An integrated satellite remote sensing approach for mapping field-scale irrigation dynamics to support water management in highly regulated semi-arid catchments. Agricultural Water Management, 333, 110653. https://doi.org/10.1016/j.agwat.2026.110653 The study applies a simple, transferable thresholding approach based on the fraction of reference evapotranspiration (EToF) and the Enhanced Vegetation Index (EVI), derived from freely available satellite data (Sentinel-2 and related products in Google Earth Engine), to discriminate irrigated cropland from rainfed cropland in the Namoi catchment of the Murray–Darling Basin, Australia, over 2019–2025. The method behaves as a conservative classifier that prioritises high-confidence identification of core irrigation activity, making it suitable as a low-cost screening tool for irrigation hotspot detection, baseline mapping of irrigation extent, and prioritisation of field-scale monitoring and compliance. Google Earth Engine (GEE) scripts The metrics used for classification (EToF, EVI, and rainfall) were derived using the following Earth Engine scripts: Catchment-wide EToF, EVI and rainfall (used for irrigation classification across the whole Namoi catchment): https://code.earthengine.google.com/cba013737d40f454d9e8f6db2cb1520e EToF, EVI and rainfall extracted over the training and validation polygons: https://code.earthengine.google.com/348d36b1cc2679121ae44c4ee4bfdf80 Google Earth Engine assets The same processed data are also hosted as public Earth Engine assets (readable by any Earth Engine user) under projects/irrigation-status-474718/assets/namoi_irrigation/: irrigated_area — ImageCollection of seven annual maps (2019–2025); each image carries a year property and the classification described below. cropland — the cropland mask (binary: 1 = cropland). training_polygons / validation_polygons — FeatureCollections of the manually digitised fields with their monthly variables and geometry. The catchment boundary used in the analysis is available at projects/jacklinemuturi/assets/Namoi_Catchment. Interactive Google Earth Engine app An interactive Earth Engine app is provided for exploring the dataset:https://irrigation-status-474718.projects.earthengine.app/view/namoi-irrigation-explorer The app source (GEE_App.js) is included with this record, is available in the Earth Engine Code Editor at https://code.earthengine.google.com/184ebdca945a0c5688d1b1759e1d9e5c, and can be pasted into the Code Editor (https://code.earthengine.google.com) and run. It reads the public assets listed above and provides: a two-map swipe to compare the annual irrigated-area maps of any two years (2019–2025); cropland mask, catchment boundary, and training/validation field overlays, with adjustable layer opacity; click any field to chart its monthly EToF and EVI time series; monthly water-balance charts — precipitation (CHIRPS), actual ET (CMRSET), reference ET (WaPOR), and EToF = AET/RET — both catchment-wide and per pixel. External collections used by the app: CHIRPS precipitation (UCSB-CHG/CHIRPS/DAILY), CMRSET actual ET (TERN/AET/CMRSET_LANDSAT_V2_2), and WaPOR reference ET (FAO/WAPOR/3/L1_RET-E). Files Mapped irrigated area Final Irrigated area_2019-2025.tif — Multiband GeoTIFF of the mapped irrigated area for the Namoi catchment, in which Bands 1–7 correspond to the years 2019, 2020, 2021, 2022, 2023, 2024 and 2025, respectively. Irrigated_area_2019.tif … Irrigated_area_2025.tif — The same mapped irrigated area provided as one single-band GeoTIFF per year (2019–2025), for convenience. Each single-year file is identical to the corresponding band of the multiband raster. For all of the above rasters, pixel values encode the classification: Value Class 0 Non-cropland 1 Non-irrigated (rainfed) 2 Irrigated Rasters are in geographic coordinates (WGS 84, EPSG:4326, 1 km spatial resolution). Pixels outside the catchment are stored as NoData (NaN). NamoiCropland.tif — Cropland extent for the Namoi catchment, used as the cropland mask within which the irrigated/non-irrigated classification was performed. Polygon variable tables TrainingPolygons_Monthly_AllVariables.csv and ValidationPolygons_Monthly_AllVariables.csv — Monthly, per-polygon values of the satellite-derived variables for the manually digitised training and validation fields used to develop and independently evaluate the EToF–EVI thresholding approach. The columns required to reproduce the analyses are: system:index — System-generated unique identifier for each polygon. Class — Class label assigned to each polygon (e.g., irrigated or non-irrigated). ETa — Mean monthly actual evapotranspiration (mm) within each polygon. (training table only) EToF — Mean monthly fraction of reference evapotranspiration within each polygon. EVI — Mean monthly Enhanced Vegetation Index within each polygon. Name — Polygon name assigned during manual digitisation. RET — Mean monthly reference evapotranspiration (mm) within each polygon. (training table only) Rain — Mean monthly rainfall (mm) within each polygon. .geo — Polygon geometry (coordinates defining the polygon boundaries). The remaining columns in the CSV files (e.g., altitudeMode, begin, description, end, extrude, icon, month, tessellate, timestamp, visibility) were generated automatically during processing (KML/feature export) and are not required for reproducing the analyses presented in the study. Application code GEE_App.js — Source code for the interactive Google Earth Engine app described above. Paste it into the Earth Engine Code Editor to run the app, or open the hosted viewer / Code Editor links in the previous section. It is bundled inside both zip archives. Coverage and units Region: Namoi catchment, Murray–Darling Basin, New South Wales, Australia. Temporal coverage: 2019–2025 (annual maps; monthly polygon statistics). Evapotranspiration and rainfall: millimetres (mm); EToF and EVI are dimensionless. Citation Please cite both the accepted article and this dataset (DOI: 10.5281/zenodo.21282411) when using these data.