Effect of watertable depth on evaporation and salt accumulation from saline groundwater
D. A. Rose A , F. Konukcu B and J. W. Gowing A CA School of Agriculture, Food and Rural Development, University of Newcastle, Newcastle upon Tyne, NE1 7RU, United Kingdom.
B Trakya University, Tekirdag Agricultural Faculty, Department of Agricultural Construction and Irrigation, 59030 Tekirdag, Turkey.
C Corresponding author. Email: J.W.Gowing@ncl.ac.uk
Australian Journal of Soil Research 43(5) 565-573 https://doi.org/10.1071/SR04051
Submitted: 20 April 2004 Accepted: 4 March 2005 Published: 8 August 2005
Abstract
When the evaporative demand is greater than the ability of the soil to conduct water in the liquid phase, the soil profile above a watertable exhibits a liquid−vapour discontinuity, known as the evaporation front, that affects the depth of salinisation and the rate of evaporation. We conducted experiments on a sandy loam with shallow saline watertables under high isothermal evaporative demand (24 mm/day), monitoring rates of evaporation from the soil and upward movement of groundwater, and observing profiles of soil water and salinity over periods of up to 78 days. Three zones were distinguished in the soil profile: a zone of liquid flow above the watertable, a zone of vapour flow close to the surface, and an intermediate transition zone in which mixed liquid−vapour flow occurred. The vapour-flow zone above the evaporation front appeared after a few days and progressed downward to depths of 40, 60, and 120 mm, while eventual steady-state rates of evaporation were 1.3, 1.1, and 0.3 mm/day for watertable depths of 300, 450, and 700 mm, respectively. Salts mainly accumulated in the transition zone, suggesting that the depth of the evaporation front should be a criterion to locate and prevent salinisation as a result of capillary flow from a watertable in arid regions.
Additional keywords: bare soil evaporation, capillary flow, salinisation.
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