Abstract
Abstract. Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Québec (Canada), leading to the reconstruction of flow time series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir and compare the obtained streamflow time series against time series derived from dendrohydrology by other authors on the same catchment and study the natural streamflow variability over the 1881–2011 period in that region. This new reconstruction is based not on natural proxies but on a historical reanalysis of global geopotential height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall–runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, in terms of both monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows and the other on spring floods. In terms of mean annual flows, the interannual variability in the reconstructed flows was similar (except for the 1930–1940 decade), with noteworthy changes seen in wetter and drier years. For spring floods, the reconstructed interannual variabilities were quite similar for the 1955–2011 period, but strongly different between 1880 and 1940. The results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions and, finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.
Highlights
1.1 Challenge of decadal hydrological variabilityTime series of streamflow observations, which constitute the basis for all hydrological analyses, are generally characterized by a relatively short record period, typically ranging from several years to several decades
A daily hydro-climatic reconstruction is proposed for the Caniapiscau Reservoir for the 1881–2011 period
This reconstruction was generated by firstly applying the ANATEM method (Kuentz et al, 2015), combining large-scale atmospheric information with local climatic observations – when such series are available – to produce a daily ensemble of climatic series
Summary
Time series of streamflow observations, which constitute the basis for all hydrological analyses, are generally characterized by a relatively short record period, typically ranging from several years to several decades. The short record period is a major issue for hydrologists since it may be insufficient to capture and provide a clear understanding of the decadal variability in hydrological processes. After studying a 90-year-long daily streamflow series of the Po River (Italy), and highlighting significant natural variability at the decadal scale, Montanari (2012) stated that “more research efforts are needed to improve the interpretation of such long-term fluctuations”. Studying natural variability requires long instrumental records (typically longer than 100 years), but such long time series are non-existent in remote regions such as northern Québec (Canada). The few decades of observations available for this region are not sufficient to allow a robust analysis of multi-decadal hydrological variability and raise the issue of the reconstruction of past hydrology, i.e., occurring before the systematic recording of streamflows
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