Monthly irrigation, ETa, surface flux and groundwater storage change: Steenkoppies (2018–2021)

A set of remotely sensed and derived monthly data products was compiled and analysed for the Steenkoppies Dolomitic Compartment (South Africa) to enable near real-time monitoring of irrigated cultivation and aquifer stress. Monthly actively cultivated areas were identified from Sentinel‑2 imagery using an independently trained Random Forest classifier on seasonal median composites that captured crop phenological changes. The cultivated-area outputs were integrated with WaPOR actual evapotranspiration (ETa) data to estimate monthly crop water use at 250 m resolution, while monthly precipitation from CHIRPS was aligned and resampled to the same reference system. Monthly net irrigation water use was estimated as ETa minus precipitation (with negative values set to zero to indicate no irrigation requirement), and monthly surface water flux was estimated as precipitation minus ETa. Net groundwater storage change was estimated by combining downscaled GLDAS groundwater storage anomaly changes with irrigated areas, enabling comparison of surface water flux with groundwater storage dynamics. The outputs were used to quantify changes in irrigated cropped area and to examine seasonal patterns showing that irrigation demand and groundwater abstraction peaks coincided with low precipitation periods, while precipitation was the primary aquifer recharge source. The complete Google Earth Engine scripts (including datasets) were provided as part of the manuscript.