%0 Journal Article
%T Temporal and Spatial Variability of Water Surplus in Ontario, Canada
%A D. Murray Brown
%A Humaira Dadfar
%A David J. Fallow
%A Robert J. Gordon
%A John D. Lauzon
%A Gary W. Parkin
%J ISRN Soil Science
%D 2013
%R 10.1155/2013/362895
%X The temporal variability in estimated water surplus in 12 climatic regions of the province of Ontario, Canada, and its spatial distribution throughout most of the province are discussed in this paper. Surplus water is that which results from precipitation that runs off the land surface and that which drains through the soil profile to the water table and through subsurface drainage. A one-dimensional, deterministic model (DRAINMOD) that simulates soil water flow, including plant uptake, evapotranspiration, and freeze/thaw conditions, was used to estimate the water surplus. Simulations were performed using daily climatic data from January 1954 to December 2001 for each region. A reference corn crop and the predominant local soil conditions in each region, with the hydraulic properties for each layer in the soil profile, were used as model inputs. There was considerable year-to-year variability in annual water surplus in all regions caused by both precipitation and soil conditions. It was the least (~150£żmm) in three regions and it exceeded 350£żmm in another three regions, where winter snowfall is the greatest as a result of these regions being in the lea of one of the Great Lakes. The variability in water surplus generally increased as average water surplus increased. 1. Introduction At the end of most growing seasons in Ontario, soil water has been partially depleted from the plant root zone and deeper through evaporation from the soil surface and transpiration from plants. The growing season generally ends by mid-November in southwestern Ontario, by the end of October in the rest of southern Ontario, and by mid-October in northern Ontario as discussed in [1, 2]. As a result, from November to March in southwestern Ontario, from November to mid-April in the rest of southern Ontario, and from mid-October to April in northern Ontario, the soil water is replenished by precipitation and a water surplus occurs, as evaporation is less than precipitation. This surplus water either drains through the soil profile to the water table or through tile drainage lines (referred to collectively as deep drainage (DD)) or runs off directly into surface water (referred to as runoff (RO)), especially in the late winter and spring months as discussed in [3¨C5]. Large annual variability in soil water necessitates the use of long-term studies to adequately describe seasonal changes in water surplus as discussed in [6]. Since long-term field data are generally not available, modeling studies are necessary as discussed elsewhere [7]. The objective of this paper is to determine
%U http://www.hindawi.com/journals/isrn.soil.science/2013/362895/