Field-scale transport through unsaturated soil is influenced by surface and subsurface boundary conditions, and the spatial variability of state soil variables. The objective of this thesis is to examine the relative importance of the spatial redistribution of surface water versus spatial variability of soil properties on long-term transient water flow and transport under semi-arid conditions. The field-scale transport (34 yr) of a surface applied tracer (chloride), spatial variability of other pedogenic tracers, and surface water redistribution over a 19 mo fallow period were measured in a catchment basin. In 1966 and 1971, a chloride tracer (KCl) was surface applied to plots (6.1 m x 90 m, Chernozemic soil) near Saskatoon, Saskatchewan. In 2000 and 2001, 262 soil cores were taken along and perpendicular to one KCl strip. Soil layering at each core was recorded and samples were analysed for chloride concentration, electrical conductivity, bulk density and water content. Sulphate and nitrate concentrations were measured on selected cores. The site is level by common definitions, with a very slight concave depression (1.8% grade) midway along the KCl strip and a slight grade (¡Ü2.1%) perpendicular to the KCl strip. Measured water recharge indicated slight differences in surface slope had a marked effect on redistribution of water and spatial distribution of the chloride tracer. An estimated 90% of redistributed water was subsequently used by plants and 10% resulted in an increase in deep drainage. A varved layer had a strong influence on the subsurface redistribution of water and chloride below the root zone. There were sharp horizontal transitions between areas of slow and faster transport, which corresponded to sharp increases in catchment area and water recharge. Small surface depressions, which controlled pedogenic transport and soil formation, have been filled in by tillage translocation. Spatial variability of soil horizon thickness (and associated hydraulic properties) had little effect on transport of chloride after 34 yr. Computer simulations also suggest substantial surface redistribution of precipitation and snowmelt. In contrast to the measured chloride data, the model was sensitive to changes in hydraulic properties and horizon thickness in the root zone. Surface water redistribution was the primary factor controlling long-term transport.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:SSU.etd-08232005-114954 |
| Date | 24 August 2005 |
| Creators | Woods, Shelley Anne |
| Contributors | Kachanoski, R. Gary |
| Publisher | University of Saskatchewan |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-08232005-114954/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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