Salinization hazard in a polder soil of Belgium
Van Meirvenne, M.; Hartmann, R.; De Boodt, M.; De Breuck, W. (1989). Salinization hazard in a polder soil of Belgium. Natuurwet. Tijdschr. 70(1-4): 85-94
In: Natuurwetenschappelijk Tijdschrift. L. Walschot/Natuur- en Geneeskundige Vennootschap: Gent. ISSN 0770-1748, meer
Ook verschenen in:De Breuck, W.; Walschot, L. (Ed.) (1989). Proceedings of the 10th Salt-Water Intrusion Meeting Ghent (Belgium), 16-20 May 1988. Natuurwetenschappelijk Tijdschrift, 70(1-4). Natuurwetenschappelijk Tijdschrift: Gent. 408 pp., meer
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Hazard assessment
Polders
Properties > Chemical properties > Salinity
Water > Ground water
België, Vlaanderen [Marine Regions]
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| Auteurs | | Top |
- Van Meirvenne, M.
- Hartmann, R.
- De Boodt, M.
- De Breuck, W., meer
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| Abstract |
Hydrogeological surveys carried out in the polder area of northeastern Flanders (Belgium), showed the presence of saline water at varying depths. Mostly this saline water occurs too deep to have a direct influence on agriculture. At some places however, salts are present at shallow depths and agricultural use could be restricted. An experimental field design was set up in order to investigate the salt distribution and evolution of a soil with a shallow brackish groundwater and to evaluate the impact of salinization on agricultural exploitation. In this soil, mercury tensiometers as well as soil-moisture extractors were installed. A piezometer was used to measure the groundwater table and a pluviometer allowed the recording of the rainfall. Tensiometers and pluviometer were recorded 6 days a week, the piezometer weekly and the soil-moisture extractors were sampled every 2 weeks. The electrical conductivity of the soil-water samples was measured as well as the chlorine concentration. Measurements started April 3 and were terminated October 26, 1986. The land use of this soil was pasture. The tensiometer recordings allowed the calculation of the hydraulic potential gradient, indicating the direction of water movement in the unsaturated zone, and water samples showed the salt distribution in this soil. Despite very rainy periods, drainage throughout the entire unsaturated zone was found to occur only during 18 (of which 12 in April) of the 207 days observed. Mostly an upward water movement was measured in the biggest part of the unsaturated zone, indicating water losses by evapotranspiration . Salt distribution was found to be rather stable. An electrical conductivity of 2000 µS/cm (at 20 °C) varied between a depth of ca. 80 cm (beginning of April) and ca. 60 cm (end of August). At the same moments, an E.C. of 8000 µS/cm was encountered between ca. 110 cm and ca. 95 cm. Nevertheless, a reduction of the non-saline zone by 20 cm between April and August means a serious limitation of the agricultural use of this soil. Upward water movement was found to be the major cause of this increase in salt content. At the end of the growing season (October), the grass showed chlorosis and necrosis. Analyses of these leaves showed a Cl-concentration of 1,69 % (on dry matter). Literature mentions concentrations between 0,5 and 1,5 % as toxic Cl-levels, indicating Cl-toxicity as a possible cause of these phenomena. Agricultural use of this soil is restricted to pasture. Winter cereals could be considered as an alternative (barley being less salt sensitive than wheat), but beets and maize are to be expected to yield substantially less than optimal due to the saline groundwater. |
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