Exploring possible connections between hydrologic extreme events and climate change in central south Chile

Abstract

Motivated by recent extreme flow events in the Mataquito River located in the Mediterranean regionof Chile, we performed a detailed trend analysis of critical hydroclimatic variables based on observed daily flow,precipitation and temperature within the basin. For the period 1976–2008, positive trends in temperature wereobserved, especially during spring and summer months. At the same time, we found negative trends in the frequencyand intensity of precipitation, especially during spring months. We observed an increasing differencebetween average streamflow in the rainy season as compared to the snowmelt season. Part of this trend is causedby larger flows during autumn months, although no positive precipitation trends are observed for these months.Finally, significant reductions in minimum flow during spring/summer and a disproportionate concentration ofhigh-flow events occurring in the last 10 years were also identified. These high-flow events tend to happen duringautumn months, and are associated with high precipitation and high minimum temperatures. Based on a simpleassessment of changes in irrigated agriculture and land use, we concluded that other non-climatic factors seem notto be as relevant to the detected flow trends. All these results are in accord with future climate change scenariosthat show an increase in temperature, a reduction in average precipitation and a reduction in snow accumulation.Such future scenarios could seriously hamper the development of economic activities in this basin, exemplifyingalso a fate that may be shared by other similar basins in Chile and in other regions of the world.