1 Effects of Seasonality upon Water and Solute Movement in The Unsaturated Zone Sleem Kreba and Charles Maule Department of Agricultural and Bioresource Engineering

2 Introduction  Soils of semi-arid to sub-humid climates, vertical water movement may seasonally vary in direction. (Zebarth and De Jong 1989; Armstrong et al. 1996)  In semi-arid regions, downward water flow is low ( mm yr -1 ). (Christie et al. 1985; Zebarth and De Jong 1989; Joshi and Maule 2000)  Tracer profile methods are recommended for quantification of unsaturated flow and solute transport in dry regions. (Gee and Hillel 1988; Allison et al. 1994; Scanlon et al. 1997)  The effects of seasonality on the tracer profile shape need to be investigated.

3 Objective The purpose of this paper is to investigate the effect of different seasonal regimes of directionally-varying flow upon solute profile shape and position under controlled laboratory conditions.

4 Soil and groundwater definitions Water Table Vadose zone Groundwater zone Soil root zone (0-1.2 m) Study region (1.2->10 m)

5 Seasonal flow regimes  Downward seasonal flow = upward seasonal flow  Downward seasonal flow > upward seasonal flow  Downward seasonal flow < upward seasonal flow

6 The KCl peak shape and location with three conditions Depth Concentration KCl peak Downward flow = upward flow Downward flow > upward flow Downward flow < upward flow

7 Materials and methods Beaver Creek sand Three columns Time Domain Reflectometry (TDR) Rain system Evaporative system Draining system Temperature loggers

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9 Methods of objectives ColumnsRegimes Water table depth (m) Number of cycles Study period (day) C1 Downward = upward C2 Downward > upward C3 Downward < upward

10 Physical and hydraulic sand properties Columns Bulk density (kg m -3 ) Porosity (m 3 m -3 ) K sat (mm min -1 ) C C C

11 Average concentration as a function of time

12 Shape of concentration profiles for the regime of upward flow = downward flow (C1)

13 Changes of the concentration profile shape under cycling conditions of upward seasonal flow = downward seasonal flow (C1) Parameters Number of cycles Peak depth (m) conc. (g L -1 ) Wideness (m) Mean (g L -1 ) SD (g L -1 ) Skewness Kurtosis conc. = concentration Wideness refers to the distance between the rising point depth and the falling point depth.

14 Shape of concentration profiles for the regime of downward flow > upward flow (C2)

15 Changes of the concentration profile shape under cycling conditions of downward seasonal flow > upward seasonal flow (C2) Parameters Number of cycles Peak depth (m) conc. (g L -1 ) Wideness (m) Mean (g L -1 ) SD (g L -1 ) Skewness Kurtosis conc. = concentration Wideness refers to the distance between the rising point depth and the falling point depth.

16 Shape of concentration profiles for the regime of downward flow < upward flow (C3)

17 Changes of the concentration profile shape under cycling conditions of upward seasonal flow > downward seasonal flow (C3) Parameters Number of cycles Peak depth (m) conc. (g L -1 ) Wideness (m) Mean (g L -1 ) SD (g L -1 ) Skewness Kurtosis conc. = concentration Wideness refers to the distance between the rising point depth and the falling point depth.

18 Comparison of relative change in profile shape among the three different regimes Parameters Total change % C1C2C3 Peak depth (m) conc. (g L -1 ) Wideness (m)42027 Mean (g L -1 )18311 SD (g L -1 )8223 Skewness Kurtosis conc. = concentration Wideness refers to the distance between the rising point depth and the falling point depth.

19 Conclusions  The solute profile shape and position clearly changed under the three repeated regimes of downward and upward seasonal flows. under the cycling conditions  The peak concentration decreased in columns 1 and 2, but it increased in column 3.  The distance between the rising and falling points got wider for columns 1 and 3, and there was no change in column 2.  Skewness shows that the profile in the three columns became skewed upward under the cycling conditions.  Kurtosis shows that the profile in columns 1 and 2 got flatter, but it was peaked in column 3.

20 Recommendations  Increasing the length of the sand column.  Having sand with no precipitated salts.  Having replicate regimes within different columns.  Being able to verify packing homogeneity with depth.

21 Acknowledgements The Libyan Ministry of Education (scholarship) Saskatchewan Agriculture Fund (materials) Swise, A. and Herzog, I. (help)

22 THANK YOU