Identification of a hydrometric data network for the study of climate change over the province of Quebec
The 1980s and 1990s contained most of the warmest years since the beginning of worldwide temperature recording nearly 140 years ago. Widely accepted estimates project that the earth's average temperature might increase by about 2°C over the next 100 years. It is also expected that, as a result of global warming, the frequency and intensity of floods and droughts may change. However, despite the increasing attention that the issue of climate change receives, there has been little effort to develop a systematic approach for the collection of relevant data, and to establish observational networks specifically designed for the analysis of climate variability and change and their impact on hydrologic regimes and water resources in general. This task is particularly important given the major network reductions that result from recent cutbacks in the funding of monitoring programs in Canada and other countries. This paper presents the results of a rigorous study that was carried out recently, and aimed at establishing a hydrometric network for the study of the attributes of climate change and variability across the province of Quebec (Canada) and their impact on water resources. The approach is based on identifying and maintaining stations that can help provide an understanding of the physical processes within the hydrological cycle and account for climate variations across the province. This network will be of fundamental importance in establishing scientific evidence of the magnitude and direction of possible shifts in climate patterns across the province. These aspects are of global significance and must be considered during the rationalization of monitoring networks. The results of the application of this procedure to the hydrometric network of the province of Quebec are presented. The paper presents also a brief review of the various types of non-stationarities that can be observed in hydrologic data series, and some of the current approaches that can be used for the detection of these non-stationarities. Several statistical tests and procedures have been proposed in the literature for the analysis of the characteristics of data samples and for hypothesis testing, for various types of non-stationarity. A Bayesian procedure, proposed by Lee and Heghinian (1977) and generalized by Bernier (1994), for the detection of shifts in the mean of hydrological and meteorological time-series is selected based on its theoretical advantages (Faucher et al., 1997). The procedure is then applied for the analysis of all streamflow series of selected stations in the province of Quebec with the objective of extracting information on possible climatic changes. Results indicate the presence of significant non-stationarities for a number of the series analyzed. For five stations, the most probable date for the shift in the mean level falls in the period 1983-1985. Recommandations are made for future research activities.