Riparian zone equilibrium and actual evapotranspiration in a first order agricultural catchment in Southern Ontario, Canada

Agricultural landcapes are typically comprised of a mosaic of land uses, some of which include riparian areas. While the active management of riparian water resources may not be the primary objective of many agricultural water managers, the importance of riparian zone evapotranspiration (ET) to over all basin water losses and water quality has been stressed in the literature. However, ET from these areas is rarely known with great certainty. To this end micrometeorological and hydrological measurements were made over one growing season using automatic weather stations and weighing micro-lysimeters (18,716 cm3) at several locations within a multiple land-use agricultural catchment in Southern Ontario. This paper compares modelled equilibrium evapotranspiration (PETEQ) and measured actual evapotranspiration (AET) values obtained from the lysimeters in riparian zone in a multiple land-use agricultural watershed in Southern Ontario. Two sites were chosen in two different riparian areas of the watershed, representing the range in surface conditions dominant throughout the basin.The results yield a mean daily AET of 3.43 mm for the catchment's riparian zone, with virtually no differences between the upper and lower portions of the basin, which lost 3.36 and 3.49 mm d−1, respectively. Using these daily AET values along with coincident estimates of PETEQ produced Priestley–Taylor coefficients (α) of 1.10 and 1.18 at the upper and lower sites, respectively.