What makes them pump? Factors influencing groundwater extraction for cattle grazing in a semi-arid region

Quantifying groundwater extraction and understanding the factors that affect groundwater extraction are critical for improving water productivity and effectively managing groundwater resources. Groundwater extraction for cattle grazing is particularly poorly quantified and understood, despite groundwater being an important water source in many grazing regions globally. To address this knowledge gap, a world-first voluntary program of bore (well) metering in the Surat Basin, Queensland, Australia, collected extraction data for 54 bores that are used fully or partially for cattle grazing. Data on factors potentially affecting extraction were gathered for each bore through landholder interviews and government database searches. Multiple regression analysis examined 18 variables and found strong evidence that 5 factors influence annual extraction from the metered bores: cattle numbers, bore purpose, type of water storage infrastructure, aquifer pressure, and annual rainfall. Together these factors explained more than 78% of the variance of the annual extraction estimates. The results provide the basis for generalising extraction estimates to bores without meters in the same region and indicate the priority vari-ables to explore in other regions. The results also provide evidence of the importance of cattle breed and water storage infrastructure in improving water efficiency.