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Algeria is the largest African and Mediterranean country. It is located in the southern seashores of the Mediterranean Sea. Its climate conditions are ranging from relatively wet to very dry which makes it confronted to high levels of rainfall deficits. The future rainfall evolution may be critical for human activities since increased temperatures may further exacerbate droughts and water shortages. In this study, the regional climate simulations RCA4 are evaluated over historical period 1951–2005 and then used to examine the rainfall and temperature projections over the end of the twenty-first century under two Representative Concentration Pathway (RCP4.5 and RCP8.5) scenarios. The historical simulations are evaluated against observations coming from the recent data sets of Climatic Research Unit (CRU). The trends in precipitation and temperature over historical (1951–2005) and projected future scenarios (2006–2060 and 2045–2100) was depicted by the estimation of the shifts of the three main climate zones existing in Algeria (Koppen-Gieger classification): warm temperate climates (C), steppe climate (BS), and desert climate (BW). Comparative to the mean climate zone surface areas derived from observations (1951–2005), all model simulations predict an expansion of desert climate zone at the expense of the temperate and steppe climate zones. This shift seems to particularly increase by the end of twenty-first century (2045–2100) under RCP8.5 scenario.

Significant changes in regional climates have been observed at the end of the twentieth century, taking place at unprecedented rates. These changes, in turn, lead to changes in global climate zones with pace and amplitude varying from one region to another. Algeria, a country characterized by climate conditions ranging from relatively wet to very dry (desert-like), has also experienced changes in its climate regions, notably in the country’s wet region, which represents about 7% of its total surface area, but is home to 75% of its population. In this study, the pace of climate zone changes as it is defined by Koppen–Geiger was analyzed for the period from 1951 to 2098 using climate data from observation and regional climate simulations over Algeria. The ability of the CORDEX-Africa regional climate models simulations to reproduce the current observed climate zones and their shifts was first assessed. Future changes over the whole of the twenty-first century were then estimated based on two Representative Concentration Pathway (RCP4.5 and RCP8.5) scenarios. Analysis of the shift rate of climate zones from 1951 to 2005 found a gradual but significant expansion of the surface area of the desert zone at an approximate rate of 650 ± 160 km2/year along with the abrupt shrinking, by approximately 30%, at a rate of 1086 ± 270 km2/year, of the warm temperate climate zone surface area. According to projections for the RCP8.5 scenario, the rate of expansion of desert climate will increase in the future (twenty-first century), particularly during the period from 2045 to 2098.

The goal of this study was to analyse the impacts of the sequence of 1 El Nino (2009–2010) and 2 La Nina (2007–2008 and 2010–2011) events on the interannual variability of daily streamflow during the growing season (April to September) and grass species abundance downstream from the Taureau reservoir (4,070 km2) on the Matawin River (Quebec, Canada). This reservoir has inverted the natural annual cycle of streamflow: Maximum flows occur in winter and minimum flows in springtime during snowmelt. Comparison of daily flows over the period from 2006 to 2011 using various statistical tests revealed a significant increase in flows released downstream from the reservoir during the 2 La Nina events, with a particularly large increase in the growing season (April to May) during the 1st La Nina event (2007–2008). In contrast, during the El Nino event (2009–2010), streamflow decreased significantly. As far as the abundance of plant species is concerned, the total number of obligate wetland species increased significantly after the 1st La Nina event and then decreased after the El Nino event, along with the total number of terrestrial species. The study shows that relatively intense El Nino Southern Oscillation events can have significant implications for the management of flows released downstream from reservoirs in Quebec and hence affect plant species abundance on islets.

The objective of this study is to use two hydrological indices (coefficients of variation and immoderation) to analyze the impacts of dam management methods on seasonal daily flow rate change downstream of three dams: Manouane (diversion-type management method), Ouareau (natural-type management method) and Matawin (inversion-type management method). The results show that this change is far greater downstream of the Matawin dam (characterized by an inversion-type management method) than downstream of the two other dams. Moreover, downstream of the Matawin dam, this daily flow rate change increases significantly over time, while decreasing downstream of the two other dams and in natural rivers. Lastly, this change is better correlated with climate downstream of the Ouareau dam than downstream of the two other dams. It is positively correlated with winter and spring temperatures as well as summer and fall rain. Contrary commonly accepted hypothesis, this study shows that the impacts of dams generally result in an increase of the seasonal flow rate change in Quebec.

Many studies have highlighted breaks in mean values of temperature and precipitation time series since the 1970s. Given that temperatures have continued to increase following that decade, the first question addressed in this study is whether other breaks in mean values have occurred since that time. The second question is to determine which climate indices influence temperature and rainfall in the coastal region of Northern Algeria. To address these two questions, we analyzed the temporal variability of temperature and annual and seasonal rainfall as they relate to four climate indices at seven coastal stations in Algeria during the 1972–2013 period using the Mann–Kendall, Lombard, and canonical correlation (CC) analysis methods.The annual and seasonal maximum, minimum and mean temperatures increased significantly over that time period. Most of these increases are gradual, implying a slow warming trend. In contrast, total annual and seasonal rainfall did not show any significant change. CC analysis revealed that annual and seasonal temperatures are negatively correlated with the Western Mediterranean Oscillation (WeMOI) climate index that characterizes atmospheric circulation over the Mediterranean basin. On the other hand, rainfall is positively correlated with a large-scale atmospheric index such as the Southern Oscillation Index.

The goal of this study was to analyze the impact of agriculture on the spatial and temporal variability of flow rate change indices from 1930 to 2008. The two indices used are the coefficient of immoderation (CI) and the coefficient of variation (CV). Values of these two indices are higher for the L’Assomption River agricultural watershed than for the Matawin River forested watershed due to higher runoff in the former than in the latter. The difference in these values between the two watersheds is greater for winter, but it is lower for summer, when the difference in runoff between the two watersheds is strongly attenuated by the presence of crops. Regarding the temporal variability, a difference between the two watersheds is observed in the fall. For the agricultural watershed, mean values of neither index show a break in slope, while a break is observed for the forested watershed. In both watersheds, both indices are positively correlated with maximum temperature and total rainfall in winter, but only to this latter climate variable in the fall. In springtime, the two indices are negatively correlated with minimum temperature in the forested watershed, but only CV is correlated, positively, with this same climate variable in the agricultural watershed.

In this study, we compared the frequency and timing of drought and wetness indices of annual mean water levels in the North American Great Lakes as they relate to teleconnection indices over the period from 1918 to 2012. In terms of timing, drought occurred in the Great Lakes watershed during the 1920, 1930 and 2000 decades, and was very intense in the East during the 1930’s and in the West during the 2000 decade. The main cause of extreme drought episodes in the 1920’s and 1930’s was a decrease in precipitation, while the 2000 decade drought is thought to be caused by increased water temperature (enhanced evaporation) due to a significant decrease in winter ice cover. The 1970 and 1980 decades were very wet over the whole watershed as a result of increased precipitation in the region. The succession of these dry and wet episodes did not have the same impacts on the stationarity of annual mean water levels in the five Great Lakes. Lake Superior shows an abrupt shift in mean in 1999, but a smoothed shift in variance since 1994, whereas Lake Erie shows four abrupt shifts in mean. Lake Ontario also shows the two first abrupt shift in mean and one abrupt change in variance. Extreme drought indices are negatively correlated with the North Atlantic Oscillation (NAO) for the two shallowest lakes (Ontario and Erie). In contrast, extreme wetness indices are positively correlated with PDO (positive correlation) and SOI (negative correlation) for Lake Superior only.

Summary The temporal variability of winter climate in southern Quebec is characterized by increasing temperature and rainfall, but decreasing snowfall. The goal of the study was to analyze the impact of these changes on the magnitude and timing of winter maximum daily flows. Hydrologic series for seventeen tributaries of the St. Lawrence River were analyzed over the period from 1934 to 2010. The most noteworthy result, obtained using the Lombard method, was to highlight a nearly generalized shift in mean values of the series in the early 1970s. This shift reflects a significant increase in the magnitude of winter maximum daily flows after that decade, interpreted to result primarily from snowmelt, which is increasingly frequent at the end of winter. The frequency of the dates of occurrence of winter maximum daily flows increased significantly during the last winter decade (ten days) after the 1970s for most rivers in southern Quebec. The copula method did not, however, reveal any significant change in the dependency between the timing and magnitude of winter maximum daily flows over time. Finally, canonical correlation analysis revealed that the magnitude of winter maximum daily flows is positively correlated with the Pacific Decadal Oscillation (PDO), while their dates of occurrence are correlated with the North Atlantic Oscillation (NAO).

This study presents a comparison of the spatio-temporal variability of characteristics (magnitude, duration and timing) of annual minimum daily extreme flows (AMEF) as a function of land use and the mode of management of dams. Streamflow measured at stations not affected by dams at Joliette, along the L’Assomption River (agricultural watershed, 1340 km2), and at Saint-Michel-des-Saints, on the Matawin River (forested watershed, 1390 km2) on one hand, and downstream from the Rawdon dam (regulated natural-type management mode), on the Ouareau River (1260 km2), which is the main tributary of the L’Assomption River, and from the Matawin dam (inverted-type management mode), on the Matawin River (4070 km2), on the other hand, were compared over the period from 1930 to 2010. As far as the spatial variability of natural rivers is concerned, the magnitude and duration of AMEF are higher in the forested watershed than in the agricultural watershed. In regulated rivers, AMEF magnitude is higher downstream from the dam characterized by a natural-type management mode than downstream from the dam characterized by inversion-type management. However, downstream from the latter, AMEF occur much more frequently and very early in the year. As for temporal variability, the Lombard method did not reveal any influence of land use differences on the stationarity of series of AMEF characteristics. In contrast, differences in dam management mode result in occurrences of AMEF downstream from the inversion-type dam progressively earlier in the year. The duration and timing of AMEF are not correlated with the same climate variables, be it in natural rivers or downstream from dams.

Although numerous studies have looked at the long-term trend of the temporal variability of winter temperature and precipitation in southern Quebec, no study has focused on the shifts in series means and the dependence between these two types of climate variables associated with this long-term trend. To fill these gaps, we used the Lombard method to detect the shifts in mean values and the copula method to detect any change in dependence between extreme (maximum and minimum) temperatures and precipitation (snow and rain) over the periods 1950–2000 (17 stations) and 1950–2010 (7 stations). During these two periods, the shifts in mean values of temperature and precipitation were recorded at less than half of the stations. The only significant change observed at the provincial scale is a decrease in the amount of snowfall, which occurred in many cases during the 1970s. This decrease affected stations on the north shore (continental temperate climate) more strongly than stations on the south shore (maritime temperate climate) of the St Lawrence River. However, this decrease in the amount of snowfall had no impact on the dependence over time between temperature and precipitation as snow.

We analyze the relationship between four climate variables (maximum and minimum extreme temperatures, rainfall and snowfall) measured in winter (December to March) at 17 stations from 1950 to 2000 in the three hydroclimate regions of southern Quebec, and six seasonal climate indices using canonical correlation analysis (CCA) and the copula method. This analysis yielded these major results: (1) extreme temperatures are not correlated with the amount of winter rain or snow in southern Quebec; (2) winter seasonal climate indices show better correlations with climate variables than do fall climate indices; (3) winter extreme temperatures are best correlated (positive correlation) with the Atlantic Multidecadal Oscillation (AMO) in the eastern region, but show a negative correlation with the Arctic Oscillation (AO) in the southwestern region; (4) the total amount of winter snow is best correlated (negative correlation) with the Pacific Decadal Oscillation (PDO) in the three hydroclimate regions; (5) the total amount of winter rain is best (negatively) correlated with PDO in the eastern region, but shows a positive correlation with AO in the southeast region. Finally, the copula method revealed very little change in the dependence between climate indices and climate variables in the three hydroclimate regions.

Five characteristics (intensity or magnitude, duration, frequency, timing, and variability) of drought, defined using the threshold level method (TLM) and recorded in mean annual water levels in Lake Ontario and the St. Lawrence River from 1918 to 2010, were compared. Timing is the only characteristic that is different for the two water bodies. For Lake Ontario, the most intense drought occurred in the 1930s, whereas in the St. Lawrence River, intense droughts took place in the 1960s and 2000s. The Lake Ontario drought produced two shifts in mean before (decrease) and after (increase) the 1930s. The change in variance that took place in the 1960s is thought to be related to the construction of locks during the digging of the seaway. The droughts that affected the St. Lawrence River had no impact on the stationarity (mean and variance) of the annual mean water level series. Analysis of the correlation between drought severity and climate indices revealed that years characterized by very weak to moderate drought are significantly correlated with PDO (Pacific Decadal Oscillation), while those characterized by intense drought are correlated with NAO (North Atlantic Oscillation). Both climate indices are negatively correlated with Lake Ontario water levels, while they are positively correlated with St. Lawrence River levels. The study suggests that NAO may be used to predict the driest years for the two water bodies.

Although climate models predict that the impacts of climate change on the temporal variability of water levels in the St. Lawrence River will be seasonally-dependent, such a seasonal effect on the current variability of extreme water levels has never been analyzed. To address this, we analyzed the temporal variability of three hydrological variables (monthly daily maximums and minimums, as well as their ratio) of water levels in the St. Lawrence River measured at the Sorel station since 1912, as they relate to climate indices. As for stationarity, the shifts in the mean values of maximum and minimum water levels revealed by the Lombard method took place prior to 1970 for spring water levels, but after that year, for winter water levels. Changes in the winter stationarity are thought to mainly relate to the decreasing snowfall observed in the St. Lawrence River watershed after 1970. In contrast, for spring, these changes are likely primarily related to human activity (digging of the St. Lawrence Seaway and construction of dams). Two shifts in the mean values of fall minimum extreme water levels were highlighted. The first of these shifts, which occurred in the first half of the 1960s decade, can also be linked to human activity (digging of the St. Lawrence Seaway and construction of dams), whereas the second shift, observed after the 1970s for the months of November and December, can be linked to decreasing amounts of snow in winter. AMO (Atlantic Multidecadal Oscillation) is the climate index that is most frequently correlated negatively with the hydrologic variables, mainly in winter and spring.

Various manmade features (diversions, dredging, regulation, etc.) have affected water levels in the Great Lakes and their outlets since the 19th century. The goal of this study is to analyze the impacts of such features on the stationarity and dependence between monthly mean maximum and minimum water levels in the Great Lakes and St. Lawrence River from 1919 to 2012. As far as stationarity is concerned, the Lombard method brought out shifts in mean and variance values of monthly mean water levels in Lake Ontario and the St. Lawrence River related to regulation of these waterbodies in the wake of the digging of the St. Lawrence Seaway in the mid-1950s. Water level shifts in the other lakes are linked to climate variability. As for the dependence between water levels, the copula method revealed a change in dependence mainly between Lakes Erie and Ontario following regulation of monthly mean maximum and minimum water levels in the latter. The impacts of manmade features primarily affected the temporal variability of monthly mean water levels in Lake Ontario.

Underwater light characteristics (quality and quantity) are important drivers of many ecological processes in aquatic systems. However, the mechanisms driving the underwater light climate in large rivers are poorly understood due to the complex interactions among color-producing agents (CPAs), which can vary in space and time. A compelling example of such a complex interaction among CPAs concerns the St. Lawrence River, where chromophoric dissolved organic matter and suspended inorganic particulate matter interact to structure the underwater spectral environment. Because such interactions can be complex, the combined net effect of CPAs on water color is not intuitive and remains to be evaluated. To resolve the spatial and temporal dynamics of the spectral profile in the St. Lawrence River, we analyzed a series of 44 Landsat 5 and 7 images, distributed between 1984 and 2009, which cover the main freshwater section of the river. Rather than following linear trends along the longitudinal axis, the spectral profiles on spectral bands (blue, green and red) presented three distinctive spatial patterns. We argue that matter injected by tributaries and discontinuous zones of the river strongly impacts water color by modulating the balance among CPAs. We also clearly demonstrate a marked trend between 1984 and 2009 toward decreasing reflectance values on bands 1, 2 and 3, presumably in response to changes in land use in the surrounding watershed.

We compared the interannual variability of annual daily maximum and minimum extreme water levels in Lake Ontario and the St Lawrence River (Sorel station) from 1918 to 2010, using several statistical tests. The interannual variability of annual daily maximum extreme water levels in Lake Ontario is characterized by a positive long-term trend showing two shifts in mean (1929–1930 and 1942–1943) and a single shift in variance (in 1958–1959). In contrast, for the St Lawrence River, this interannual variability is characterized by a negative long-term trend with a single shift in mean, which occurred in 1955–1956. As for annual daily minimum extreme water levels, their interannual variability shows no significant long-term change in trend. However, for Lake Ontario, the interannual variability of these water levels shows two shifts in mean, which are synchronous with those for maximum water levels, and a single shift in variance, which occurred in 1965–1966. These changes in trend and stationarity (mean and variance) are thought to be due to factors both climatic (the Great Drought of the 1930s) and human (digging of the Seaway and construction of several dams and locks during the 1950s). Despite this change in means and variance, the four series are clearly described by the generalized extreme value distribution. Finally, annual daily maximum and minimum extreme water levels in the St Lawrence and Lake Ontario are negatively correlated with Atlantic multidecadal oscillation over the period from 1918 to 2010. Copyright © 2013 John Wiley & Sons, Ltd.

Summary Redundancy analysis (RDA) and Canonical correlation analysis (CCA) were used to examine the complex links between the five characteristics of flow (magnitude, duration, timing, frequency, and variation), defined as part of the “natural flow regime” ecological paradigm, for spring heavy flood, and five climate indices (Atlantic Multi-decadal Oscillation (AMO), Arctic Oscillation (AO), Nord Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO) and Southern Oscillation Index (SOI)) in southern Quebec, over the period from 1934 to 2004. The two methods yield similar results. AMO and NAO appear to be the main index correlated with the following four flow characteristics: duration, timing, frequency and coefficient of variation. Thus, positive AMO and NAO anomalies are associated with delayed timing, higher frequency, relatively long duration and relatively weak variability of spring heavy floods in Quebec. This relationship reflects sustained climate conditions characterized by low temperature in winter and early spring in eastern Canada during negative phases of AMO and positives phases NAO. No link was noted between climate indices and the magnitude of spring heavy floods in Quebec.

The interannual variability of streamflow affects the composition and species richness of vegetation in low-flow channels and alluvial plains. Although climate conditions in 2003 and 2004 were nearly identical, large differences in streamflow were observed downstream from the Matawin dam. These differences resulted in numerous days without flow (no water release) during the growing period (May to August) in 2003, leading to man-made hydrological drought. While this drought had no effect on abiotic variables (grain-size distribution and nutrient concentrations in sediments), a significant decrease in the number of terrestrial species was observed in 2004 (year without drought) relative to 2003 (drought year) on three sand bars studied. This decrease is interpreted to result from prolonged submergence of the sites in 2004. Principal component analysis highlighted the effect of individual sites (first principal component) and of the interannual variability of streamflow (second component) on the number of species. The study suggests that, from a flow management standpoint, it is advisable to release enough water downstream from the dam during the growing season to prevent low-flow channel colonization by invasive terrestrial species.

[1] The relationship between the color (measured with Landsat Thematic Mapper and Enhanced Thematic Mapper sensors in bands 1, 2, and 3) of St. Lawrence River (SLR) water and water levels (in SLR and Lake Ontario) was first analyzed, followed by the analysis of the relationship between water levels and four climate indices for the period from 1984 to 2009. Although there is a statistically significant relationship between these first two variables, this link depends on the strength of two factors: the type of color (band) and inflows from tributaries. Bands 1 (blue) and 2 (green) were negatively correlated with water levels. This correlation, however, is spatially influenced by water inflows from tributaries. Band 3 (red) showed no significant correlation with either water level. Over the same period, water levels were negatively correlated with the Atlantic multidecadal oscillation index. Results suggest that the color of waters in the SLR may be used as an indicator to monitor environmental and climate changes in its watershed.

The goal of the study was to compare the modes of management of seasonal floods for different dams and to constrain their impact on the relationship between climate variables and streamflow downstream from the dams. At the Rawdon dam, downstream from which the Ouareau River is characterized by a natural-type regulated flow regime, a ‘type A’ flood management mode prevails, in which the same rainfall and/or snowmelt events account for seasonal floods both in the unregulated (natural) stretch of river upstream from the dam and in the river downstream from the dam. As a result, seasonal floods in the natural setting and downstream from the dam are nearly synchronous. In contrast, downstream from the Matawin dam (Matawin River), which produces an inversion-type regulated flow regime, the prevalent flood management modes are of types B and D, whereby seasonal floods observed upstream and downstream from the dam are not caused by the same rainfall and/or snowmelt events and, as a result, are not synchronous. This difference in seasonal flood management modes affects the interannual variability of the magnitude of seasonal daily maximum flows related to the seasonal floods. Thus, the interannual variability of these flows downstream from the Matawin dam differs significantly from that of flows upstream. No correlation is observed between climate variables and streamflow downstream from the Matawin dam. This absence of correlation disappears gradually at the annual scale, at which streamflow is correlated with rainfall, as is observed upstream from the dam. Copyright © 2013 John Wiley & Sons, Ltd.

The goal of this study is to demonstrate the usefulness of the Lombard method for analyzing dam-induced hydrologic impacts. The method was used to accurately detect the effects of the construction of a diversion dam in 2003 on annual and seasonal maximum and minimum daily flows in the Manouane River, Quebec, Canada, measured from 1980 to 2014. The Lombard method yields results that are nearly identical to results obtained using the monitoring (Kruskal-Wallis test) and long-term trend (Mann-Kendall test) methods. The Lombard method revealed a shift in mean values of annual and seasonal minimum daily flows in 2003, the year the dam was built. This shift is sharp for all four seasons. The dam induced a significant decrease in minimum daily flows in all four seasons. As far as maximum daily flows are concerned, unlike the monitoring method, the Lombard method detected a significant decrease only in the mean values of annual and spring maximum daily flows. This decrease occurred two years prior to the construction of the diversion dam. Instead, this decrease is interpreted to be the result of a significant decrease in spring precipitation after 1997. These hydrological changes are different from those induced by other types of dams in Quebec.

Erosion, sediment transport, and deposition result in agricultural soil degradation, dam siltation, and significant and costly damage. In Algeria, despite a decrease in total rainfall, especially in the central and western parts of the country, dam siltation and erosion are on the rise according to recent studies by the National Agency of Dams and Transfers. Developing a map of the spatial variation of rainfall erosivity will provide a powerful tool for land and dam managers. Erosivity can be quantified using the R factor from the Universal Soil Loss Equation. The purpose of this work is to develop a model for estimating rain erosivity based on the modified Fournier index (MFI), longitude, altitude, and mean maximum daily rainfall, and then to produce a map of the spatial distribution of erosivity in Northern Algeria. The R factor reaches a maximum value of roughly 905 MJ mm ha−1 year−1 in the Jijel area of Mediterranean Eastern Algeria and a minimum value of 37 MJ mm ha−1 year−1 in the southern portion of the study area. The study of the temporal evolution of annual rainfall erosivity index (R) and I max over 30 min showed that R recorded a negative trend and I max recorded no trend.

Comparison of the interannual variability of five characteristics (magnitude, duration, timing, frequency, and variability) of spring heavy floods was carried out for 17 natural rivers in Quebec for the period from 1934 to 2004 to detect any effect of climate warming on these characteristics. This was done using the Lombard method and Copula. Changes in the mean and variance of all characteristics of streamflow were observed, and all these changes are abrupt. Whereas little significant change was observed in the magnitude, duration and variability (CV) series of spring flood flows. A significant change was noted in the frequency (diminution) for five rivers and in the timing of spring floods for six rivers. However, the change in mean timing is the only one that has a hydroclimatic significance in time and space. This change was observed, on the one hand, in the Eastern hydrological region, located on the south shore of the St. Lawrence River, north of 47°N, and characterized by a maritime climate and, on the other hand, in the South-west hydrological region, located on the north shore and characterized by a continental climate. In both cases, the change took place after the second half of the 1970s and is characterized by the early occurrence of spring floods. In addition, in both hydrological regions, the timing of spring floods is correlated with the same hydroclimatic indices, showing a positive correlation with the North Atlantic Oscillation (NAO) and a negative correlation with the Atlantic Multidecadal Oscillation (AMO). Frequency is the only characteristic for which mean and variance changed significantly over time for the same rivers (4), all located north of 48°N, on both shores of the St. Lawrence. For all flow characteristics, the change in variance can predate, postdate or be synchronous with the change in mean. Finally, the dependence between the various characteristics of spring floods as determined using the Kendall tau statistic remained constant in time for most of the rivers.

The aim of this study was to test three main hypotheses about the interannual variability of streamflow downstream from dams: (1) an almost similar long-term trend in interannual variability, (2) low variability of flow, and (3) its independence (no link) from climate variability. To test these hypotheses, the interannual variability of winter and spring streamflow downstream from three reservoirs (Gouin, Manouane, and Matawin) which induce an inversion of the natural cycle of streamflow (maximum flows in winter and minimum flows in spring) was compared to the interannual variability of streamflow in natural rivers (measured at the Matawin and Vermillon stations) over the period from 1932 to 2008 in the St-Maurice River watershed. As far as the interannual variability of flow is concerned, its long-term trend is not homogeneous downstream from the three reservoirs in both seasons. However, downstream from two reservoirs, changes in streamflow were observed to be different from those in natural rivers (no significant trend downstream from the Taureau reservoir, on the Matawin River, and significant decrease in spring flow downstream from the Manouane reservoir). Finally, coefficient of variation values for minimum flows are higher downstream from reservoirs than in natural rivers, despite the fact that watershed surface area is larger for regulated rivers than for natural ones. As for the link with climate variability, analysis of the correlation between climate variables (temperature and precipitation) and mean winter and spring daily streamflow reveals that winter streamflow downstream from the Taureau reservoir is not correlated with any climate variable, whereas spring streamflow is positively correlated with rainfall and negatively correlated with maximum temperature. Thus, downstream from reservoirs, the interannual variability of streamflow depends on climate during the spring, but not during winter.

The interactions between precipitation, streamflow and groundwater are very complex. In cold temperate regions characterized by harsh winters, winter streamflow is mainly derived from aquifers that are recharged in the spring, during snowmelt, and in the fall, when evapotranspiration is subdued. Despite this complexity, the modes and trends in the interannual variability of spring (April, May, June and July) streamflow and fall (August, September, October and November) precipitation and streamflow were compared to the modes and trends in the interannual variability of winter (December, January, February and March) streamflow in southern Quebec from 1950 to 2000. Results indicate that the variability modes are identical for all four of these hydro-climatic variables: two modes (south-east and east modes) on the south shore of the St. Lawrence River on either side of the 47°N and a single mode (south-west mode) on the north shore. As for the trend, a significant increase in winter streamflow was observed on the north shore. This increase is comparable to that observed in spring streamflow, which suggests that winter streamflow on the north shore is mainly derived from groundwater recharge during the spring. Moreover, both spring and winter streamflows are positively correlated to the North Atlantic Oscillation climate index. On the south shore, south of the 47°N, a significant decrease was observed in the trend of the interannual variability of winter streamflow, this in spite of a significant increase in fall precipitation and streamflow. An increase in evaporation (decreased infiltration) due to a shift from forest cover to agricultural land cover in this region could account for this. However, fall precipitation and streamflow and winter streamflow are significantly correlated to the Atlantic Multidecadal Oscillation winter index. This correlation is negative with the first two variables but positive with the third. This study suggests that, in southern Quebec, the interannual variability of winter streamflow is mainly affected by spring recharge in non-agricultural catchments (east and south-west modes) and by farming in agricultural catchments (south-east mode). Copyright © 2011 John Wiley & Sons, Ltd.

Winter and summer 7-day low flows of eighteen natural rivers in the St. Lawrence River watershed of Quebec were analyzed over the period from 1934 to 2000. The rivers were first subdivided into three modes using principal component analysis. Two of these modes are located on the south shore of the St. Lawrence River, respectively south (Southeast mode) and north (East mode) of the 47°N, and the third (Southwest mode) is located on the north shore. The Southeast mode shows a significant increase in 7-day low flows in winter and summer due to increasing summer and fall precipitation, whereas the Southwest mode shows a significant decrease in summer 7-day low flows due to an increase in evapotranspiration. No significant change in winter and summer 7-day low flows is observed in the East mode. Results show that the variability of 7-day low flows and their link with climate indices are mainly seasonally dependent. The North Atlantic Oscillation (NAO) is the only index which is correlated to 7-day low flows in all three modes. This correlation is positive for north shore rivers and negative for south shore rivers. Furthermore, only north shore rivers are correlated to NAO in both winter and summer.

Erected in 1930, the Matawin Dam caused an inversion of the hydrologic regime of the Matawin River: snow-melt water in spring (April to June) is stored in the reservoir and then released in winter (January to March) to feed the hydroelectric generating stations built downstream on the Saint-Maurice River. Thus, heavy floods occur upstream from the dam in spring but downstream in winter. We compared the interannual and interdecadal variability of the heavy flood characteristics (magnitude, duration, frequency and variability) both upstream (spring floods) and downstream (winter floods) from the dam during the 1934–1994 period. This comparison revealed that the principal change observed downstream from the dam translates into a strong increase in the duration (in days) of heavy floods. The average duration of these floods quintupled. This change in duration occurred around the mid-1960s and thus led to a significant decrease in the magnitude, frequency and variability of heavy floods. It also altered the relationship between the climate indices and these fundamental characteristics (magnitude, frequency and duration). Downstream from the dam, the magnitude and frequency are positively correlated to the Atlantic multidecadal oscillation (AMO), whereas upstream they are negatively correlated to the same index. However, the AMO index is negatively correlated to the duration downstream from the dam, whereas upstream this characteristic is no longer significantly correlated to any climatic index. Two factors have been invoked to explain this change observed downstream from the dam. The cooling observed since the 1960s at the station located at the dam. However, this cooling was not observed on the scale of the entire watershed. This reduces its plausibility. The increase in hydroelectric power production in the watershed after nationalization of hydroelectric power in 1962. This increase would be explained by the expansion of the market for hydroelectric power (national and international markets). Before nationalization, the hydroelectric power produced in the watershed was intended only for regional industries. Copyright © 2010 John Wiley & Sons, Ltd.

According to the concept of “natural flow regime,” introduced and developed in the 1990's in aquatic ecology, streamflow can be described using five basic characteristics: magnitude, frequency, duration, period of occurrence and variability. A sixth could be added to these, namely, distribution curve. Our study, which focused exclusively on the temporal variability of these six characteristics, had these objectives: (1) to compare their stationarity, (2) to determine the links among these characteristics and (3) to analyze, for the first time, their relationship to six climatic indices (Atlantic Multidecadal Oscillation, Artic Oscillation, North Atlantic Oscillation, Nino3.4, Pacific decadal Oscillation and Southern Oscillation Index). To do this, we used the Vermillon River (2670 km²) as an example, analyzing the streamflow of heavy spring floods (equal to or greater than the annual flood streamflow), as measured between 1934 and 2000. The comparison of the stationarity of these six characteristics by means of linear regression analysis and Mann-Kendall test revealed that flood duration has increased and flood frequency has decreased during the 1934–2000 period. As for the link among the six characteristics, magnitude, the primary fundamental characteristic, is correlated to all the other characteristics, except for the coefficient of skewness. The AMO (Atlantic Multidecadal Oscillation) climatic index is correlated to all the characteristics, except for frequency and coefficient of skewness. This last characteristic is correlated to AO (Arctic Oscillation). This example shows that this concept can serve to link climatology, hydrology, fluvial geomorphology and aquatic ecology for a better understanding of the interactions among the different components of the aquatic ecosystems. The understanding of these interactions is important for better watercourse management and could serve as a potential framework for predicting the evolution of river ecosystems in light of climate change, using a combination of these various disciplines.

We analyzed the temporal variability of annual precipitation measured at five stations in the Macta (14,380 km2) and Tafna (4,949 km2) catchments located in northwestern Algeria, in connection with climate indices over the 1950–2004 period. Analysis of the temporal variability using linear regression and Pettitt test revealed a significant decline in annual rainfall in the mid-1970s in both basins. Furthermore, a decrease of at least 20% of total annual rainfall is also observed at all five stations. As for the relationship between climate indices and variability of annual precipitation, canonical correlation analysis shows that, from 1950 to 2004, precipitation at the five stations are negatively correlated with NINO4 and, to a lesser degree, with NAO.

This paper, based on an analysis of the mean annual flow (MAF) of 16 natural rivers over the period 1934–2000, has the following goals: (1) to determine the different temporal variability modes of the MAF in the St. Lawrence watershed, (2) to describe the temporal variability of the streamflow in each mode and (3) to analyze the influence of the AMO (Atlantic Multidecadal Oscillation) on the interannual and interdecadal variability of mean annual flows in this Quebec watershed. This paper shows that the interannual variability of mean annual flow was not synchronous on both sides of the river. During the period analyzed, MAF variability was characterized by a tendency to decrease on the south shore (right bank) but to increase on the north shore (left bank). A correlation analysis reveals that the influence of the AMO was limited exclusively to the north shore of the river, which is characterized by a continental climate. This correlation is negative. On the south shore, streamflow is correlated negatively to the AO (Arctic Oscillation).

Summary Introduced in the early 1990s in aquatic ecology as a new paradigm for restoration of rivers modified by anthropic activities, the “natural flow regime” concept has allowed the formulation of new problems in dam hydrologic impact studies. Within the context of this study, we posed two problems: (1) selection of the hydrologic variables most modified by dams and (2) identification of the factors that influence the extent of the hydrologic changes. Resolving these two problems necessitated the application of multivariate statistical analysis methods, in this instance, principal component analysis and canonical correlation analysis. These two methods thus are being applied for the first time to analysis of the hydrologic impacts of dams. The first method allowed selection of the hydrologic variables most modified downstream from dams in Quebec. These are the variables best correlated to the first two principal components. As for the factors influencing the magnitude of these changes, canonical correlation analysis exposed the influence of the type of regulated regime (dam management mode), and to a lesser degree, the watershed size.

Summary We have compared the monthly flow characteristics between natural rivers (76 stations) and reservoir-regulated rivers (25 stations) based on watershed size, using regression analysis on the monthly flows observed in Quebec. The flow characteristics, defined according to the “natural flows regime” paradigm, are as follows: the periods of occurrence of the monthly maximum and minimum flows and their inter-annual variability, the magnitude and its inter-annual variability, the frequency, and the coefficients of skewness and kurtosis. This study revealed that dams alter all monthly flow characteristics but the extent of these modifications is variable. Two factors influence this extent: the watershed size and the season. The behaviour of large watersheds (>10,000 km 2 ) seems to be different from that of small and medium-sized watersheds. Large watersheds are characterized by a greater inter-annual variability of the timing of maximum monthly discharges but a lower inter-annual variability of the timing of the minimum monthly flows than smaller basins. Concerning the monthly winter flows, large watersheds also exhibit an increase in the magnitude and a smaller variability in between years of discharges. Concerning the season, the hydrological changes were mainly observed in winter and spring. However, in both seasons, the extent of these hydrological changes varies from month to month. These results show that the dam-induced hydrological changes render the method of estimating minimum flow requirements in winter and spring inapplicable to reservoir dams in Quebec to protect Quebec fish habitats effectively. In winter, the method would underestimate the flows released downstream from the dams, while overestimating them in the spring. Moreover, the method cannot be applicable to all watersheds in certain months, because the hydrological changes during those months only affect either small watersheds or large watersheds.

We have analyzed relationships between environmental factors (physiographic, climatic, geological, geographic and land use) and extreme minimum flow characteristics. We have defined 18 hydrological variables on the annual minimum flow series according to the "natural flow regime" paradigm. Application of the principal component analysis (PCA) to these 18 variables allowed us to extract five principal components, each associated with a fundamental characteristic (magnitude-frequency, timing, inter-annual variability of magnitude and timing, shape of distribution curve) of the annual minimum flows. The analysis of indices and values of the loading of the five PC revealed a spatial difference in the annual minimum flow characteristics between stations on the north and south shores of the St. Lawrence River (Quebec, Canada). South shore stations are generally characterized by lower magnitude, later timing, and sharper inter-annual variability of magnitude and timing of the annual minimum flows than those on the north shore. The analysis of correlations (simple correlation and canonical correlation) between the five hydrological PC and the seven environmental PC, also extracted by means of the PCA, revealed that the spatial difference between the annual minimum flow characteristics observed between the north and the south shore stations is mainly due to precipitation (climatic factor) based on a highly complex relationship, which mainly involves the timing of annual minimum flows.

Despite the presence of numerous dams in Qu´ ebec, no study has yet been devoted to their impacts on flood levels. To compensate for this deficiency, we have compared the impacts of dams on the five characteristics (magnitude and its interannual variability, timing and its interannual variability, and asymmetry) of the maximum annual flows between natural rivers and regulated rivers by means of several statistical approaches (analysis of variance, chi-square test, nonparametric tests, etc.). In the course of this study, we analysed 88 stations on pristine rivers and 60 stations on regulated rivers. The latter group was subdivided into three regulated hydrologic regimes, i.e. inversed flow regimes (25 stations), homogenization flow regimes (15 stations) and natural-type flow regimes (20 stations). The following observations emerge from this study. (1) In inversed and homogenization flow regimes, generally associated with reservoirs, all the flow characteristics are modified. These modifications notably entrain a decrease in magnitude, a significant reduction in the frequency of the maximum annual spring flows when the snow is melting and an increase in skewness of the distribution and interannual variability of the magnitude and dates of occurrence of the annual maximum flows. We also observed the disappearance of most flows with a recurrence of over 10 years. All these changes particularly affect watersheds larger than 10 000 km 2 . (2) In natural-type flow regimes, often associated with run-of-river dams, very few changes were observed compared with pristine rivers. These changes primarily affected watersheds smaller than 1000 km 2 . Copyright  2006 John Wiley & Sons, Ltd.

The monitoring station method, which is based on comparing data before and after dam construction, is commonly used to quantify the hydromorphological impacts induced by dams. However, in the absence of pre-dam construction data, other analytical methods may be used to detect changes downstream from dams that remain more or less constant over time. The study used one such method, the control station method, to constrain changes which may be linked to construction of the Rawdon Dam, in 1913, on the Ouareau River. Thus, a comparison of the hydrological (seasonal daily maximum flows) and morphological (mean bankfull width and sinuosity) evolution of the Ouareau and L'Assomption Rivers during the period 1930 to 2008 was carried out. The surface area as well as the climatic, lithological, land use and physiographic features of the two watersheds are nearly identical in the study area. The comparison revealed three changes that may be linked to the Rawdon Dam: an increase in the magnitude of daily maximum flows downstream from the dam for all four seasons, which is inferred to have resulted in extensive widening and low sinuosity of the Ouareau river channel downstream from the Rawdon Dam relative to the L'Assomption river channel. These types of morphological changes are consistent with changes observed downstream from some dams. The Rawdon Dam had no effect on the interannual variability of daily maximum flows, which are characterized by a significant increase in mean in winter in both watersheds. This increase, which is abrupt, occurred in 1973 for both rivers. Copyright © 2012 John Wiley & Sons, Ltd.

Summary Studies looking at the effects of forest land cover on streamflow in Quebec have shown that a decrease in forest cover in a watershed leads to an increase in minimum flows. However, in many watersheds, such a decrease in forest cover is primarily due to an increase in agricultural land use. The goal of the study was to analyze the impact of a change from forest to agriculture land cover on the spatial variability of maximum and minimum extreme flows measured in summer (May–October) in 36 watersheds with surface areas between 200 km 2 and 4000 km 2 , over the period from 1960 to 1990 using the canonical correlation analysis and analysis of covariance methods. The main result of this study is the fact that, in watersheds characterized by relatively high agricultural land cover (>20%), daily minimum flows are relatively small. The decrease in daily minimum flows associated with an increase in agricultural land cover is likely the result of relatively extensive evaporation due to the low-permeability (clayey) and nearly flat substrate in the farmland-dominated St. Lawrence Lowlands, as well as by high summer temperatures and, at times, relatively long dry spells. Hence, in Quebec, agricultural land use results in an inversion of the hydrological effects of a decrease in forest cover on extreme minimum flows. As for daily maximum flows, an increase of agricultural land cover results in a significant increase in the variability (coefficient of variation) of their magnitude, although this is only observed during the last part of the summer season (September–October), likely as a result of the diversity of factors which cause floods (tropical cyclones, polar fronts, convection, etc.).