Uncertainty in rainfall-runoff prediction, and subsequent streamflow, is a challenge for managers and policy makers when evaluating the future effectiveness of environmental water management decisions and investments. Assessments to evaluate potential outcomes from management interventions are typically undertaken using a historical climate sequence (e.g. 1890 to 2021 CE) that does not adequately represent potential future climate. The current strategy for managing water for the environment is guided by ecology-informed flow targets (flow magnitude, frequency, timing, and duration) at key sites, yet it is unknown if such targets can be consistently met under potential future climates.
Our work aimed to better understand this uncertainty by evaluating the ecohydrological impact of climate change, and the effectiveness of possible management interventions, for a plausible range of potential future climate sequences.
To model flows under potential future climates, 10,000 year-long daily stochastic climate datasets were input into a hydrologic model (built using eWater’s Source program) for the Murrumbidgee River (New South Wales, Australia). Data were then subsampled into 100-year periods and classified according to catchment inflow. Ecohydrological outcomes were then calculated using ecological response models and hydrometrics and aggregated for each 100-year period. This enabled the capture of predicted ecohydrological outcomes for a large number of catchment inflow sequences over a total of 20,000 years of historical and anthropogenically forced stochastic data representing a range of potential future climates.
Our work presents an approach for evaluating the ecohydrological response of rivers to flow regime changes that is robust against the uncertainty of future hydroclimate conditions and we demonstrate how this approach can be used to support environmental water decision making.