Abstract
Abstract. Streamflow in south-central Chile (SCC, ∼ 37–42∘ S) is vital for agriculture, forestry production, hydroelectricity, and human consumption. Recent drought episodes have generated hydrological deficits with damaging effects on these activities. This region is projected to undergo major reductions in water availability, concomitant with projected increases in water demand. However, the lack of long-term records hampers the development of accurate estimations of natural variability and trends. In order to provide more information on long-term streamflow variability and trends in SCC, here we report findings of an analysis of instrumental records and a tree-ring reconstruction of the summer streamflow of the Río Imperial (∼ 37∘ 40′ S–38∘ 50′ S). This is the first reconstruction in Chile targeted at this season. Results from the instrumental streamflow record (∼ 1940 onwards) indicated that the hydrological regime is fundamentally pluvial with a small snowmelt contribution during spring, and evidenced a decreasing trend, both for the summer and the full annual record. The reconstruction showed that streamflow below the average characterized the post-1980 period, with more frequent, but not more intense, drought episodes. We additionally found that the recent positive phase of the Southern Annular Mode has significantly influenced streamflow. These findings agree with previous studies, suggesting a robust regional signal and a shift to a new hydrological scenario. In this paper, we also discuss implications of these results for water managers and stakeholders; we provide rationale and examples that support the need for the incorporation of tree-ring reconstructions into water resources management.
Highlights
Streamflow in south-central Chile (SCC, ∼ 37–42◦ S) is vital for agriculture, forestry production, hydroelectricity, and human consumption (Lara et al, 2003; Rubio-Álvarez and McPhee, 2010)
Our objectives were to (a) determine whether or not current summer streamflow changes in the Río imperial are unprecedented at the multicentury scale, (b) establish if the return period of extreme years of high and low streamflow has changed in the last few centuries, and (c) estimate the correlation between the multicentury variability of the Río Imperial streamflow and climate modes of natural variability such as the El Niño Southern Oscillation (ENSO), the Southern Annular Mode (SAM), and the Interdecadal Pacific Oscillation (IPO)
The significance of our findings for planning is related to the need to consider a long-term view of the natural variability that defines the discharge regimes across the region
Summary
Streamflow in south-central Chile (SCC, ∼ 37–42◦ S) is vital for agriculture, forestry production, hydroelectricity, and human consumption (Lara et al, 2003; Rubio-Álvarez and McPhee, 2010). With more than 55 % of Chilean agriculture and forestry production delivered from this region (Instituto Nacional de Estadísticas, 2007), the drought episodes that occurred in the last few decades and the associated hydrological deficit have had damaging effects (Garreaud, 2015). A. Fernández et al.: Dendrohydrology and water resources management in south-central Chile drought episodes have been linked to a significant decreasing trend in regional precipitation (Pezoa, 2003; Aravena and Luckman, 2009; González-Reyes and Muñoz, 2013), with amounts 40 % below the 1901–2005 mean (Trenberth et al, 2007). Drier and warmer summers may make SCC more vulnerable to water scarcity, given that this is the season of highest water demand in this region (Garreaud, 2015)
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