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？mm) in three regions and it exceeded 350？mm 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 [3–5]. 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
References
[1]
D. M. Brown, G. A. McKay, and L. J. Chapman, “The climate of Southern Ontario,” Climatological Studies 5, Department of Transport, Meteorological Branch, Toronto, Canada, 1968.
[2]
L. J. Chapman and M. K. Thomas, “The climate of Northern Ontario,” Climatological Studies 6, Department of Transport, Meteorological Branch, Toronto, Canada, 1968.
[3]
H. Dadfar, D. J. Fallow, D. M. Brown, G. W. Parkin, J. D. Lauzon, and R. J. Gordon, “Estimation of annual and seasonal water surplus for five new regions in Ontario to identify critical regions for water quality monitoring,” Technical Memo 2010-1, University of Guelph, School of Environmental Sciences, 2010, http://hdl.handle.net/10214/2231.
[4]
D. J. Fallow, D. M. Brown, G. W. Parkin, J. D. Lauzon, and C. Wagner-Riddle, “Identification of critical regions for water quality monitoring with respect to seasonal and annual water surplus,” Technical Memo 2003-1, University of Guelph, Department of Land Resource Science, 2003, http://hdl.handle.net/10214/2204.
[5]
G. W. Parkin, C. Wagner-Riddle, D. J. Fallow, and D. M. Brown, “Estimated seasonal and annual water surplus in Ontario,” Canadian Water Resources Journal, vol. 24, no. 4, pp. 277–292, 1999.
[6]
R. De Jong and A. Bootsma, “Estimated long-term soil moisture variability on the Canadian prairies,” Canadian Journal of Soil Science, vol. 68, no. 2, pp. 307–321, 1988.
[7]
S. E. Allaire, E. van Bochove, J.-T. Denault et al., “Preferential pathways of phosphorus movement from agricultural land to water bodies in the Canadian Great Lakes basin: a predictive tool,” Canadian Journal of Soil Science, vol. 91, no. 3, pp. 361–374, 2011.
[8]
S. Dayyani, C. A. Madramootoo, P. Enright et al., “Field evaluation of DRAINMOD 5.1 under a cold climate: simulation of daily midspan water table depths and drain outflows,” Journal of the American Water Resources Association, vol. 45, no. 3, pp. 779–792, 2009.
[9]
C.-C. Yang, S. O. Prasher, S. Wang et al., “Simulation of nitrate-N movement in southern Ontario, Canada with DRAINMOD-N,” Agricultural Water Management, vol. 87, no. 3, pp. 299–306, 2007.
[10]
W. Luo, R. W. Skaggs, A. Madani, S. Cizikci, and A. Mavi, “Predicting field hydrology in cold condition with DRAINMOD,” Transactions of the American Society of Agricultural Engineers, vol. 44, no. 4, pp. 825–834, 2001.
[11]
R. W. Skaggs, “A water management model for shallow water table soils,” Tech. Rep. 134, Water Resources Research Institute of the University of North Carolina, North Carolina State University, Raleigh, NC, USA, 1978.
[12]
Soil and Water Management Group, DRAINMOD. North Carolina State University, Department of Bio and Ag Engineering, 2011, http://www.bae.ncsu.edu/soil_water/index.html.
[13]
R. G. Allen, L. S. Pereira, D. Raes, and M. Smith, “Crop evapotranspiration: guidelines for computing crop requirements,” FAO Irrigation and Drainage Paper 56., FAO, Rome, Italy, 1998.
[14]
W. Luo, R. W. Skaggs, and G. M. Chescheir, “DRAINMOD modifications for cold conditions,” Transactions of the American Society of Agricultural Engineers, vol. 43, no. 6, pp. 1569–1582, 2000.
[15]
S. Ale, L. C. Bowling, J. R. Frankenberger, S. M. Brouder, and E. J. Kladivko, “Climate variability and drain spacing influence on drainage water management system operation,” Vadose Zone Journal, vol. 9, no. 1, pp. 43–52, 2010.
[16]
M. A. Brevé, R. W. Skaggs, J. E. Parsons, and J. W. Gilliam, “DRAINMOD-N, a nitrogen model for artificially drained soils,” Transactions of the American Society of Agricultural Engineers, vol. 40, no. 4, pp. 1067–1075, 1997.
[17]
M. A. Brevé, R. W. Skaggs, J. W. Gilliam et al., “Field testing of DRAINMOD-N,” Transactions of the American Society of Agricultural Engineers, vol. 40, no. 4, pp. 1077–1085, 1997.
[18]
G. P. Gupta, S. O. Prasher, S. T. Chieng, and I. N. Mathur, “Application of DRAINMOD under semi-arid conditions,” Agricultural Water Management, vol. 24, no. 1, pp. 63–80, 1993.
[19]
M. B. Shukla, S. O. Prasher, A. Madani, and G. P. Gupta, “Field validation of DRAINMOD in Atlantic Canada,” Canadian Agricultural Engineering, vol. 36, no. 4, pp. 205–213, 1994.
[20]
S. Wang, S. O. Prasher, R. M. Patel et al., “Fate and transport of nitrogen compounds in a cold region soil using DRAINMOD,” Computers and Electronics in Agriculture, vol. 53, no. 2, pp. 113–121, 2006.
[21]
D. M. Brown and A. Bootsma, “Crop heat units for corn and other warm-season Crops in Ontario,” Ministry of Agriculture and Food Factsheet Agdex 111/31, 1993.
[22]
J. L. Hutson, “Applying one-dimensional deterministic chemical fate models on a regional scale,” Geoderma, vol. 60, no. 1–4, pp. 201–212, 1993.
[23]
M. E. Sanderson and D. W. Philips, “Average annual water surplus in Canada,” Climatological Studies 9, Department of Transport, Meteorological Branch, Ontario, Canada, 1967.
[24]
C. W. Thornthwaite, “An approach toward a rational classification of climate,” Geographical Review, vol. 38, pp. 55–94, 1948.
[25]
D. M. Brown, “Average Annual Water Surplus in Ontario,” 2010, https://atrium.lib.uoguelph.ca/xmlui/handle/10214/2230.
