Growing evidence that plants play a role in hydrological non-stationarity

A new study has found that vegetation plays a key role in driving hydrological non-stationarity across the Australian continent. The recent research, conducted by a team of scientists from Australia and the United States, showed runoff ratio’s sensitivity to annual fractional vegetation cover is similar or greater than sensitivity to annual precipitation in catchments with a non-stationary hydrologic response. Therefore, it highlights the role of vegetation dynamics in long-term hydrologic prediction.

The paper, published in Hydrology and Earth System Sciences, presents the first-ever data-based framework for explaining why catchments behave in a non-stationary manner by using data from 166 anthropogenically unaffected catchments (


Location of catchments (from Ajami et al. 2017).



“These catchments provide the ideal natural laboratory to assess the impact of climate variability and vegetation dynamics on hydrologic response.” Said lead author Professor Hoori Ajami.

The researchers characterised non-stationary hydrologic behavior by assessing long-term trends in annual runoff ratio (ratio of discharge to annual precipitation) across hydrologic reference stations in Australia.
In their work, the team also formulated a novel ecohydrologic catchment classification framework. They did this by using information about the inter-annual variability of the catchment water balance (precipitation and annual evapotranspiration), and annual vegetation fractional cover obtained from remote sensing vegetation products.

In this classification, annual precipitation-fractional vegetation cover relationship provides the “first-order groupings” of the catchments. Further distinction within a group, depends on the catchment derived annual ET.

“This classification framework will inform future modeling experiments for determining contributing factors to non-stationary hydrologic response, and has important implications for hydrologic prediction and water resource management.” Said Professor Ajami.


Article: ‘On the non-stationarity of hydrological response in anthropogenically unaffected catchments: An Australian perspective’, Ajami, H., Sharma, A., Band, L., Evans, J., Tuteja, N., Amirthanathan, G. and Bari, M., Hydrology and Earth System Sciences, doi:10.5194/hess-2016-353

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