Land Cover Effects on Hydrologic Regime within Mixed Land Use Watersheds of East-Central Ontario

Description

Land cover change has the potential to alter the hydrologic regime from its natural state. Southern Ontario contains the largest and fastest growing urban population in Canada as well as the majority of prime (Class I) agricultural land. Expansions in urban cover at the expense of agricultural land and resultant ‘agricultural intensification’, including expansion of tile drainage, have unknown effects on watershed hydrology. To investigate this, several streams with a range of landcovers and physiographic characteristics were monitored for two years to compare differences of flashiness and variability of streamflow using several hydrologic metrics. Urban watersheds were usually the flashiest while agriculture had moderate flashiness and natural watersheds were the least flashy across all seasons, signifying that landcover effects were consistent across seasons. Tile drainage increased stream flashiness during wet periods, but minimized the stream response to an extreme rain event in the summer, perhaps due to increases in soil moisture storage. A sixty-year flow analysis showed that flashiness and streamflow increased (p < 0.05) above a development threshold of ~10% of watershed area. Flashiness was also greater in wetter years suggesting that climate shifts may enhance stream variability in developed watersheds.
Author Keywords: Agriculture, Flashiness, Hydrologic Metrics, Hydrologic Regime, Landcover Change, Urban