CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Buttle, J.
Date : 2010.
Title : Reforestation revisited: streamflow response to headwater reforestation in the Ganaraska River basin, southern Ontario
Publication : CMOS-CGU Ottawa 2010. 44th Annual CMOS Congress, 36th Annual Scientific Meeting of CGU, 3rd Joint CMOS-CGU Congress. May 31-June 4, 2010. Ottawa, Ontario.
Issue :
Page(s) :
Abstract
The Ganaraska River basin (GRB) experienced severe soil erosion and flooding in the late 19th and early 20th centuries following deforestation along the crest of the Oak Ridges Moraine in the basin’s headwaters. A time-trend analysis (Buttle 1994, Can Geog 38: 240) suggested that headwater reforestation (doubling of forest cover from 1945 to 1960, with subsequent minor increases) led to decreased annual runoff and peak flows and increased low flows. The latter result is not consistent with reforestation studies in other landscapes, which indicate that low flows decline as a result of greater interception and evapotranspiration with an increase in forest cover. Reforestation effects on the GRB’s streamflow were re-examined using an extended hydroclimatic record and a quasi-paired-basin comparison with a nearby basin of similar size and physiography (Duffins Creek basin, DCB) that had not undergone headwater reforestation. Annual precipitation for both basins increased significantly since 1960, with no significant inter-basin differences in annual runoff or runoff/precipitation ratios. Peak daily streamflow from the GRB decreased relative to that from the DCB from the late 1940s to the early 1970s, with no significant inter-basin differences after this time. Low flows increased in both basins, particularly after 1960; however, the increase in low flows in the GRB significantly exceeded that in the DCB, suggesting that reforestation enhanced groundwater recharge beyond that attributable to trends in hydroclimatic drivers of streamflow behaviour. This appears to be the result of greater infiltration opportunities during spring snowmelt in forested areas along the ORM, which more than compensates for increased summer interception and evapotranspiration due to expanded forest cover. Thus, the influence of land cover change on the full suite of hydrologic processes in a particular forest landscape needs to be considered when trying to anticipate the hydrologic consequences of basin reforestation.
Bibliography of Canadian Geomorphology