Bias in streamflow projections due to climate‐induced shifts in catchment response

Abstract

Demand for quantitative assessments of likely climate change impact on runoff is increasing and conceptual rainfall‐runoff models are essential tools for this task. However, the capacity of these models to extrapolate under changing climatic conditions is questionable. A number of studies have found that model predictive skill decreases with changed climatic conditions, especially when predicting drier climates. We found that model skill only declines under certain circumstances, in particular, when a catchment's rainfall‐runoff processes change due to changed climatic drivers. In catchments where the rainfall‐runoff relationship changed significantly in response to prolonged dry conditions, runoff was consistently overestimated. In contrast, modeled runoff was unbiased in catchments where the rainfall‐runoff relationship remained unchanged during the dry period. These conclusions were not model dependent. Our results suggest that current projections of runoff under climate change may provide overly optimistic assessments of future water availability in some regions expecting rainfall reductions.

Lags in hydrologic recovery following an extreme drought: Assessing the roles of climate and catchment characteristics

“…Most recently, a prolonged drought occurred throughout southeastern Australia between ∼1997 and ∼2009 (noting that this period differs between studies due to different criteria for drought determination and different catchments being analyzed), which is the worst drought in the region since the instrumental era and is known as “the Millennium drought” (or “the Big dry”). The Millennium drought extended over all southeast Australia and resulted in very different hydrological behavior compared with shorter droughts in the same catchments [ Saft et al ., ]. Averaged over southeast Australian catchments, the Millennium drought was associated with ∼13% decrease in precipitation, amplified to be a ∼45% decline in streamflow with a ∼12% reduction in agricultural yield (i.e., measured per unit area) compared to predrought conditions [ Van Dijk et al ., ].…”

“…However, previous studies on the Millennium drought mostly take the entire Southern Australia as a whole (or the entire Murray‐Darling Basin), resulting in a lack of detailed spatial information on the drought characteristics and its impacts at the catchment‐level (exceptions are Saft et al . []). Moreover, recovery from the Millennium drought, especially the hydrological components (i.e., streamflow and base flow), which directly indicate the recovery of available water resources, has not yet been investigated.…”

“…in very different hydrological behavior compared with shorter droughts in the same catchments [Saft et al, 2016a]. Averaged over southeast Australian catchments, the Millennium drought was associated with 13% decrease in precipitation, amplified to be a 45% decline in streamflow with a 12% reduction in agricultural yield (i.e., measured per unit area) compared to predrought conditions [Van Dijk et al, 2013].…”

“…Considerable efforts have previously been made to understand different aspects of the Millennium drought, including its causes, duration, intensity and propagation, among other aspects [e.g., Ummenhofer et al, 2009;Verdon-Kidd and Kiem, 2009;Chiew et al, 2011;Potter and Chiew, 2011;Van Dijk et al, 2013;Bond et al, 2008;Van Dijk and Renzullo, 2009]. However, previous studies on the Millennium drought mostly take the entire Southern Australia as a whole (or the entire Murray-Darling Basin), resulting in a lack of detailed spatial information on the drought characteristics and its impacts at the catchment-level (exceptions are Saft et al [2015Saft et al [ , 2016aSaft et al [ , 2016b). Moreover, recovery from the Millennium drought, especially the hydrological components (i.e., streamflow and base flow), which directly indicate the recovery of available water resources, has not yet been investigated.…”

Climate Variability and Groundwater Response: A Case Study in Burkina Faso (West Africa)

“…Water 2016, 8,171 Saft et al [67] also suggested processes linked to groundwater as a possible explanation behind the change in the hydrological functioning of catchments in the context of a prolonged dry period. The underground flow, coming from deep aquifer through the spring, gives a more delayed and smother response to climate than surface and shallow groundwater flow [66].…”