Estimating groundwater evapotranspiration under pumping conditions using diurnal groundwater level fluctuations

Study region Hailiutu River catchment, semi-arid region of northwestern China. Study focus It remains challenge to estimate ETg during pumping. The White method estimates ETg from diurnal groundwater-level fluctuations and is widely applied in arid and semi-arid regions because of its simplicity and low cost. However, groundwater extraction substantially reduces the reliability of the White method and its variants. This study used numerical simulations to analyze groundwater diurnal fluctuation time-series components under different extraction conditions and evaluated an ETg estimation framework integrating Dynamic Harmonic Regression (DHR) with the Boussinesq equation. The effects of different extraction scenarios on groundwater diurnal fluctuation components and ETg estimation were systematically analyzed. New hydrological insights for the region Results indicate that groundwater evapotranspiration (ETg) in the study area is the primary discharge item of groundwater. Under non-pumping condition, estimation results indicate that average ETg is 6.92 mm/d. While, under continuous extraction conditions, the estimated mean value of ETg is 6.68 mm/d. Beyond documenting ETg estimation results, this study provides an operational perspective by integration DHR and analytical solution of Boussinesq equation to estimate ETg used under groundwater extraction condition. By relying on numerical simulation results from the research site, the study demonstrates how pumping patterns affect the estimation accuracy of ETg. The integrated framework offers an effective approach for ETg estimation to isolate pumping disturbance in semi-arid vegetation regions.