CO₂-vegetation feedbacks and other climate changes implicated in reducing base flow

Changes in the hydrological cycle have a significant impact in water limited environments. Globally, some of these regions are experiencing declining precipitation yet are simultaneously becoming greener, partly due to vegetation feedbacks associated with increasing atmospheric CO₂ concentrations. Reduced precipitation together with increasing rates of actual evapotranspiration diminishes streamflow, especially base flow, a critical freshwater dry-season resource. Here we assess recent changes in base flow in Australia from 1981–2013 and 1950–2013 and separate the contribution of precipitation, potential evapotranspiration, and other factors on base flow trends. Our findings reveal that these other factors influencing the base flow trends are best explained by an increase in photosynthetic activity. These results provide the first robust observational evidence that increasing atmospheric CO₂ and its associated vegetation feedbacks are reducing base flow in addition to other climatic impacts. These findings have broad implications for water resource management, especially in the world's water limited regions.