Hydrologic effects of climatic change in west-central Canada (original) (raw)

Trends in timing of low stream flows in Canada: impact of autocorrelation and long-term persistence

Hydrological Processes, 2010

The annual timing of river flows might indicate changes that are climate related. In this study, trends in timing of low flows for the Reference Hydrometric Basin Network were investigated under three different hypotheses namely: independence, shortterm persistence (STP) and long-term persistence (LTP). Both summer and winter time series were characterized with scaling behaviour providing strong evidence of LTP. The Mann-Kendall trend test was modified to account for STP and LTP, and used to detect trends in timing of low flows. It was found that considering STP and LTP resulted in a significant decrease in the number of detected trends. Numerical analysis showed that the timing of summer 7-day low flows exhibited significant trends in 16, 9 and 7% of stations under independence, STP and LTP assumptions, respectively. Timing of summer low flow shifted toward later dates in western Canada, whereas the majority of stations in the east half of the country (except Atlantic Provinces) experienced a shift toward earlier dates. Timing of winter low flow experienced significant trends in 20, 12, and 6% of stations under independence, STP and LTP assumptions, respectively. Shift in timing of winter low flow toward earlier dates was dominant all over the country where it shifted toward earlier dates in up to 3/4 of time series with significant trends. There are local patterns of upward significant/insignificant trends in southeast, southwest and northern Canada. This study shows that timing of low flows in Canada is time dependent; however, addressing the full complexity of memory properties (i.e. short term vs long term) of a natural process is beyond the scope of this study. A significant increase in daily minimum temperature with the largest trend during winter and early spring was reported by which suggests a shift in timing of winter low flows toward earlier dates. A trend toward earlier occurrence of spring snowmelt in some of the more northerly rivers of Canada was reported by which was attributed to possible climate change. studied 11 hydro-climatic variables and found that break up of river ice and the resulting spring freshet were occurring significantly earlier.

Detection of hydrologic trends and variability

Journal of Hydrology, 2002

This paper describes the development and application of a procedure that identi®es trends in hydrologic variables. The procedure utilizes the Mann±Kendall non-parametric test to detect trends, a permutation approach to estimate the test distribution, and accounts for the correlation structure in the data in determining the signi®cance level of the test results. The research investigates 18 hydrologic variables that re¯ect different parts of the hydrologic cycle. The hydrologic variables are analyzed for a network of 248 Canadian catchments that are considered to re¯ect natural conditions. A selection of catchments identi®ed to have trends in hydrologic variables is studied further to investigate the presence of trends in meteorological variables and the relationship between the hydrologic and the meteorological response to climatic change. It is concluded that a greater number of trends are observed than are expected to occur by chance. There are differences in the geographic location of signi®cant trends in the hydrologic variables investigated implying that impacts are not spatially uniform. q

Climate Impacts on Hydrological Variables in the Mackenzie River Basin

Canadian Water Resources Journal, 2012

The research described in this paper examines changes in the hydrologic cycle in the Mackenzie River Basin (MRB) in northern Canada. The study focuses on temperature, precipitation, runoff, evapotranspiration and storage. A distributed hydrological model is used with two different climate input data sets: Environment Canada gridded observed data and the European Centre for Medium-range Weather Forecasting (ECMWF) reanalysis climate data (ERA-40). Both data sets were used to estimate runoff and evapotranspiration. The resulting hydrological variables were assessed for trends on a monthly and annual basis using the Mann-Kendall non-parametric trend test. The results reveal a general pattern of warming temperatures, and increasing precipitation and evapotranspiration. However, an overall decrease in runoff and in storage were detected for results derived from the Environment Canada data set while an overall increase in runoff and in storage were detected for results derived from the ECMWF data set. The sensitivity of mean annual runoff to changes in climate was also estimated using a non-parametric estimator. The results of the analysis can be used to better prepare for the potential impacts of climate change on water availability and water resource infrastructure in the MRB. Ré sumé : La recherche décrite dans la présente communication porte sur les changements dans le cycle hydrologique du bassin du fleuve Mackenzie dans le Nord du Canada. L'étude est axée sur la température, les précipitations, le ruissellement, l'évapotranspiration et l'emmagasinement. Un modèle hydrologique distribué est utilisé avec deux ensembles différents de données d'entrée climatiques : données observées sur grille d'Environnement Canada et données climatiques des réanalyses ERA-40 du Centre européen pour les prévisions météorologiques à moyen terme (CEPMMT). Les deux ensembles de données ont été utilisés afin d'estimer le ruissellement et l'évapotranspiration. Les variables hydrologiques qui en ont résulté ont été évaluées afin de dégager les tendances sur une

Recent Variations in Climate and Hydrology in Canada

Canadian Water Resources Journal, 2000

Climatic and hydrologic variations between the decades 1976-1985 and 1986-95 are examined at 210 climate stations for temperature,2Tl climate stations for precipitation, and 642 hydrology stations from across Canada. The variations in climate are distributed across a broad spatial area. Temperatures were generally warmer in the more recent decade, with many stations showing significant increases during spring and fall. Significant decreases in temperature were found during winter in eastern Canada. Significant increases in temperature were more frequent in western Canada than in the east. Significant decreases in precipitation were also more prevalent in the north, as were increases in the south, except for Ontario and Quebec where little or no change has taken place. The hydrologic responses to these variations in climate are classified into four hydrograph types and six patterns of shifts in streamflow between the two decades. The 642 hydrologic stations fall into pr6cipitations dtaient dgalement plus courantes dans le Nord, tout comme l'6taient Ies hausses dans le Sud, sauf en Ontario et au Qudbec, oil l'on a enregistrd que tEnvironment Canada, Vancouver, BC

The impact of climate change on seasonal floods of a southern Quebec River Basin

Hydrological Processes, 2001

Global warming predicted by general circulation models (GCM) is now a more and more generally agreed upon effect. The impact of climate change on summer and fall flooding on the Châteauguay River Basin (2500 km 2 ), located at the southern end of the Quebec province (Canada), was investigated using results from the Canadian GCM (CGCM1) and a coupled hydrology-hydraulics model of the basin. Three 20-year periods, corresponding to and 2080-2100, were used for the analysis. For each period, 24-h precipitation depths corresponding to the 20 and 100-year return periods were determined from a frequency analysis of the summer-fall maximum 24-h precipitations using a general extreme value frequency distribution. 24-h rainfall hyetographs were generated using region-specific cumulative distributions provided by the Canadian Atmospheric Environment Service. These hyetographs were then used as inputs to the hydrology-hydraulics model to simulate hydrographs, maximum discharge and maximum water levels at two sections of the river. Results indicate potentially very serious increases in the volume of runoff, maximum discharge and water level with future climate change scenarios. The changes get more drastic as longer return periods are considered. Increases of up to 250% of the maximum water discharge are encountered and water levels are significantly higher than the current flood levels. If realistic, these scenarios indicate that important decisions will have to be taken to alleviate future increases in flooding damages in what is already a flood prone river.

Detection of trends in hydrological extremes for Canadian watersheds

Hydrological Processes, 2010

The potential impacts of climate change can alter the risk to critical infrastructure resulting from changes to the frequency and magnitude of extreme events. As well, the natural environment is affected by the hydrologic regime, and changes in high flows or low flows can have negative impacts on ecosystems. This article examines the detection of trends in extreme hydrological events, both high and low flow events, for streamflow gauging stations in Canada. The trend analysis involves the application of the Mann-Kendall non-parametric test. A bootstrap resampling process has been used to determine the field significance of the trend results. A total of 68 gauging stations having a nominal record length of at least 50 years are analysed for two analysis periods of 50 and 40 years. The database of Canadian rivers investigated represents a diversity of hydrological conditions encompassing different extreme flow generating processes and reflects a national scale analysis of trends. The results reveal more trends than would be expected to occur by chance for most of the measures of extreme flow characteristics. Annual and spring maximum flows show decreasing trends in flow magnitude and decreasing trends in event timing (earlier events). Low flow magnitudes exhibit both decreasing and increasing trends.

Recent variations in seasonality of temperature and precipitation in Canada, 1976-95

International Journal of Climatology, 2002

A previously reported analysis of rehabilitated monthly temperature and precipitation time series for several hundred stations across Canada showed generally spatially coherent patterns of variation between two decades (1976-85 and 1986-95). The present work expands that analysis to finer time scales and a greater number of stations. We demonstrate how the finer temporal resolution, at 5 day or 11 day intervals, increases the separation between clusters of recent variations in seasonal patterns of temperature and precipitation. We also expand the analysis by increasing the number of stations from only rehabilitated monthly data sets to rehabilitated daily sets, then to approximately 1500 daily observation stations. This increases the spatial density of data and allows a finer spatial resolution of patterns between the two decades. We also examine the success of clustering partial records, i.e. sites where the data record is incomplete. The intent of this study was to be consistent with previous work and explore how greater temporal and spatial detail in the climate data affects the resolution of patterns of recent climate variations. The variations we report for temperature and precipitation are taking place at different temporal and spatial scales. Further, the spatial patterns are much broader than local climate regions and ecozones, indicating that the differences observed may be the result of variations in atmospheric circulation.

Assessing Climatic Drivers of Spring Mean and Annual Maximum Flows in Western Canadian River Basins

Water

Flows originating from cold and mountainous watersheds are highly dependent on temperature and precipitation patterns, and the resulting snow accumulation and melt conditions, affecting the magnitude and timing of annual peak flows. This study applied a multiple linear regression (MLR) modelling framework to investigate spatial variations and relative importance of hydroclimatic drivers of annual maximum flows (AMF) and mean spring flows (MAMJflow) in 25 river basins across western Canada. The results show that basin average maximum snow water equivalent (SWEmax), April 1st SWE and spring precipitation (MAMJprc) are the most important predictors of both AMF and MAMJflow, with the proportion of explained variance averaging 51.7%, 44.0% and 33.5%, respectively. The MLR models’ abilities to project future changes in AMF and MAMJflow in response to changes to the hydroclimatic controls are also examined using the Canadian Regional Climate Model (CanRCM4) output for RCP 4.5 and RCP8.5 sc...

Climate change effects on the hydrologic regime within the Churchill-Nelson River Basin

Journal of Hydrology, 1997

This paper evaluates the possible effects of climate change on four hydrologic variables pertaining to the magnitude and timing of hydrologic events within the Churchill-Nelson River Basin in westcentral Canada. By using the Mann-Kendall trend test, and a regionalization procedure, the severity of climatic effects within the river basin may be quantified and used to increase awareness of future consequences for water resource systems planning and management strategies. It was found that the magnitude of hydrologic events decreased over time while snowmelt runoff events occurred earlier.