The influence of multiyear drought on the annual rainfall‐runoff relationship: AnAustralian perspective

Abstract

Most current long-term (decadal and longer) hydrological predictions implicitly assume that hydrological processes are stationary even under changing climate. However, in practice, we suspect that changing climatic conditions may affect runoff generation processes and cause changes in the rainfallrunoff relationship. In this article, we investigate whether temporary but prolonged (i.e., of the order of a decade) shifts in rainfall result in changes in rainfall-runoff relationships at the catchment scale. Annual rainfall and runoff records from south-eastern Australia are used to examine whether interdecadal climate variability induces changes in hydrological behavior. We test statistically whether annual rainfall-runoff relationships are significantly different during extended dry periods, compared with the historical norm. The results demonstrate that protracted drought led to a significant shift in the rainfall-runoff relationship in 46% of the catchment-dry periods studied. The shift led to less annual runoff for a given annual rainfall, compared with the historical relationship. We explore linkages between cases where statistically significant changes occurred and potential explanatory factors, including catchment properties and characteristics of the dry period (e.g., length, precipitation anomalies). We find that long-term drought is more likely to affect transformation of rainfall to runoff in drier, flatter, and less forested catchments. Understanding changes in the rainfall-runoff relationship is important for accurate streamflow projections and to help develop adaptation strategies to deal with multiyear droughts.

The 2010–2015 megadrought in central Chile: impacts on regional hydroclimate and vegetation

“…-2009(ca. , Cai et al, 2014Saft et al, 2015). The winter rainfall deficit during the socalled Millennium Drought caused major water crises, affecting river ecosystems and agricultural production as reviewed in van Dijk et al (2013).…”

Characterizing drought by change in precipitation-runoff relationship: a case study of the Loess Plateau, China

“…In the 15 times dry events under the regression line in the case of the total regression, there are 9 times significant change in the PRR (p < 0.05), accounting for about 60% of the total situation. This means that sustained drought results in lowered runoff generation rates for similar precipitation amounts (Saft et al, 2015). Thus in a continued years with decreased precipitation, we can conclude that lower runoff not only relate to the lower precipitation, but also less runoff than expected caused by the multi_yeat 5 drought period.…”

“…There are two main forms of the response of the PRR to multi-year droughts: no significant change and downward significant change. Saft et al (2015) have shown that there was also a significant upward trend in the PRR during a drought period in southeastern Australian watersheds, but the probability of 20 such events is small. It is also not clear whether the phenomenon is real or just sampling fluctuations.…”

“…To ensure that the dry periods are sufficiently long and severe, Saft et al (2015) only using dry periods with drought duration ≥7 years and severity ＜-5%. In this study, the duration of drought was limited to not less than 5 years.…”

“…This ecosystem service is of major concern in water-limited areas because it represents the water resource available to human beings. Studies have shown that protracted drought may affect runoff generation and cause changes in the PPR (Petrone et al, 2010;Saft et al, 2015). So the shift in PPR caused with an 30 extended drought will eventually have an adverse effect on the ecosystem service of water yield.…”