Tree-Ring Reconstructions of Streamflow in the Churchill River Basin, Northern Saskatchewan

Abstract

This study describes the development of 13 moisture-sensitive tree-ring chronologies from the Churchill River Basin of northern Saskatchewan, and their application to estimate streamflow prior to the initiation of direct monitoring in 1929. Most of these new tree-ring records extend back to the early or mid-19th century, with their length limited by the lifespan of trees growing in fire-dominated boreal forest environments. Ring-width index chronologies are significantly correlated with mean annual and summer streamflow across the watershed; those records that were highly (above 0.6) correlated with streamflow were chosen as potential predictors in linear regression models. Robust models (accounting for between 40 and 53 percent of total variance) were developed for three gauges in the basin and used to estimate annual streamflow at these locations since ca. AD 1840. Periods of above average annual flow include 1853 to 1882, 1894 to 1904, 1932 to 1936 and 1946 to 1979. Annual flows were consistently below average during 1840 to 1852, 1883 to 1893, 1905 to 1921, 1937 to 1945 and 1980 to 1997. Some of the most severe and sustained low flows have occurred in recent decades. Although these proxy hydrological records are relatively short compared to many other tree-ring estimates of past streamflow, they provide an expanded context for evaluating the variability recorded by stream gauges and the conventional reference hydrology for water supply planning and management in northern Saskatchewan.