Duffins Creek - Toronto and Region Conservation Authority

Introduction toSurface Water QuantityWater quantity refers to the drainage of water through theDuffins Creek watershed under various rainfall and snowmeltconditions. There are many complex factors at play indetermining the amount of precipitation that eventually endsup flowing in Duffins Creek. These factors include: soil types(with varying abilities to both hold and transfer water),topography, and land use. Obeying the laws of gravity, waterabove and below the ground surface flows down gradienteventually entering Lake Ontario at the Ajax waterfront.Figure 1 illustrates the linkages between the major watercomponents of a watershed and the factors or processescontrolling this movement of water. A significant component ofthe precipitation falling on the watershed cycles back into theatmosphere through evaporation or transpiration (moisturereleased by plants). When the land surface is impermeable (e.g.urban built and paved), surplus water runs directly towardsdepressions (i.e. ponds, swales, swamps) and streams orevaporates back into the atmosphere. On permeable soils,however, the runoff component of precipitation is very small.Water that remains after evapotranspiration drains overland orinto the ground. The subsurface movement of water begins thecomplex sequence of events associated with the groundwaterflow system.In managing the Duffins Creek watershed, great care is taken toensure a natural balance to the movement of water. The studyof the movement of water through the hydrologic cycle is animportant element of our conservation work in the watershed.In the same manner, as one manages household or businessfinances, the amount of water flowing through the watershed iscarefully accounted for in a water budget. As a result, themonitoring of precipitation, along with surface andgroundwater levels, is an essential component of water quantitymanagement in the Duffins Creek.2