Variability and Trend in Alberta Streamflow with a Focus on The
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Variability and Trend in Alberta Climate and Streamflow with a Focus on the North Saskatchewan River Basin 2011-12 Final Report Water Theme, Prairies RAC 31 March 2012 Dave Sauchyn, Jeannine St. Jacques, Elaine Barrow, Suzan Lapp, Cesar Perez Valdivia and Jessica Vanstone Prairie Adaptation Research Collaborative (PARC), University of Regina The North Saskatchewan River above Lake Abraham (Source: D.J. Sauchyn) 1 TABLE OF CONTENTS !"#$%&'(#)%" ******************************************************************************************************************************+! ,$-"&./0"&/10$)02)3)#4/)"/52.-$6-&/0"&/7-(%".#$'(#-&/8#$-09:3%;********************<! =$%>-(#)%"./%:/?'#'$-/@4&$%(3)90#-******************************************************************************* A<! B%"(3'.)%".***************************************************************************************************************************** CD! 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OY! 3 Partner Organizations With funding support provided by: !"#$%&'(#)%"/ This report documents the results of technical work conducted at the Prairie Adaptation Research Collaborative (PARC) from April 2011 to March 2012 under the Water Theme of the Prairies Regional Adaptation Collaborative (RAC). The Prairies RAC is a three- year federal-provincial program to advance adaptation to climate change. Water is one of the three major themes of the Prairie RAC and it is a significant component of the other two themes: Drought and Excess Moisture, and Terrestrial Ecosystems. A shift in the distribution of water resources between seasons, years and watersheds is the major risk from climate change in the Prairies region (Sauchyn and Kulshreshtha, 2008). Adaptation to avoid or reduce adverse impacts on communities, economies, and managed ecosystems requires knowledge of past and future trends and variability in surface and soil water balances. Nearly all of the existing information on future climate and water supplies is in the form of change scenarios, that is, the expected shift in mean conditions from the recent past (usually 1961-90) to a future 30-year period, typically 2040-69. The major challenge from climate change in our region is not a shift in average conditions but rather a change in the frequency and severity of climate extremes and departures from average conditions; in particular, excessive moisture and drought. Without a knowledge of the future tendencies in the distribution of water among years, decades and watersheds, most decision makers will have limited technical capacity to address adaptive management practices and appropriate policy for planned adaptation to climate change. The work reported in this report is the culmination of a three-year technical investigation of the climate and hydrology (hydroclimate) of the Prairie Provinces based on the statistical analysis of instrumental, proxy and climate model data. The geographic focus has been primarily, although not exclusively, Alberta river basins and gauges. The focus in Year 3 (April 2011 to March 2012) was the North Saskatchewan River Basin (NSRB), although to provide a broader context much of the analysis extended into adjacent river basins and, in come cases, across the Prairie Provinces. The climate forcing of hydrologic 4 systems is large scale and thus an understanding of trends and variability must extend over large areas, among river basins, and over long time frames including the pre- instrumental hydroclimate. The technical details of these analyses, and the results obtained over a larger area than the NSRB, are given in series of papers appended in Appendices B to F. In the following section of this report, we summarize the results our analysis of climate and streamflow for the NSRB. Increasing reliance on water from the North Saskatchewan River assumes a certain reliability of the source: mostly snowmelt runoff from the eastern slopes of the Rocky Mountains (Figure 1). Beyond the mountains, the main tributary is the Battle River, which originates in aspen parkland in west-central Alberta. In March and April snowmelt in the parkland and prairie produces an initial rise in the annual hydrograph. The major peak is from mountain snowmelt in July. While the net effect of glacier meltwater runoff on the annual flow of the North Saskatchewan River is small, it does sustain higher river levels in late summer and fall and during drought conditions. Most of the allocation from the North Saskatchewan River (NSR) is for industrial (83%) and municipal (8%) use (North Saskatchewan Watershed Alliance, 2007). The petroleum sector, which currently is allocated about 5% of the water from the NSR, is projected to account for most of the increase in withdrawals over the next 20 years largely for the processing heavy oil at a series of new or expanded facilities in the Edmonton Industrial Heartland. This water use could be as high as about 10 times the current allocation for the city of Edmonton. 5 Figure 1: The NSRB in Alberta; the sub-basins are identified (Source: NSWA, 2005) ,$-"&./0"&/10$)02)3)#4/)"/52.-$6-&/0"&/7-(%".#$'(#-&/8#$-09:3%;/ Water level gauges are the principal source of data for our analysis of hydroclimatic variability. Streamflow and lake levels integrate the effective precipitation across a watershed and over days to months. There is a relatively dense network of water level gauges in the southern Prairies since precipitation and the raw surface water supply is a limiting factor for agriculture and most other economic activities. This network was originally established in the early 20th century not for the scientific study of hydrology or climate, but rather to identify supplies of water initially for steam locomotives and irrigation (Greg McCullough, Water Survey of Canada, personal communication, June 2011). Therefore just a few gauges have operated continuously for more than 50 years. Fortunately some of these long records are from Alberta gauges including the North Saskatchewan River (NSR) at Edmonton (Figure