Potential impact of large scale abstraction on the quality of shallow groundwater for irrigation in the Keta Strip, Ghana

Q4 Environmental Science
Bk Kortatsi, E. Young, A. Mensah-Bonsu
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引用次数: 9

Abstract

The potential impact of large-scale groundwater abstraction on the shallow groundwater and crop production within the Keta Strip was examined. The assessment was based on geophysical data, data on groundwater quality, soils, irrigation water requirement and hydrogeology of the Strip. The results indicate that the shallow groundwater can support only medium to high salt tolerant crops. This is consistent with the medium salt tolerant crops especially shallot and onion currently grown in the area. Large-scale irrigation of the Strip will require at least 2 x 107 m3 of water during the dry season. Abstraction of such large volume of water from the shallow aquifer will result in the lowering of water table by approximately 1.0 m per year. The consequence of this will be the up coning of the fresh/saline water interface probably by as much as 4.7 m, resulting in salinisation of the fresh water lenses particularly around the lagoon end where most of the shallot farms are situated. Apart from up conning, salinisation may result from ingress of brackish/saline water from the lagoon and sea into the fresh water lenses. Though post irrigation rainfall will be adequate to nullify the water table depression, once the fresh water is contaminated, it is extremely difficult to decontaminate. Consequently, the shallow groundwater will evolve from medium through high to very high salinity hazard to crops. Specific ions toxicity will also increase due to increment in the concentrations of individual ions. Thus, the previously freshwater will become unsuitable for the production of even high salt tolerance crops. This will effectively halt the lucrative shallot and other vegetable farming in the Keta Strip and thus signify socio-economic disaster for the Keta Strip in particular and Ghana in general.
大规模抽取对加纳克塔地带浅层地下水灌溉质量的潜在影响
研究了大规模抽取地下水对克他地带浅层地下水和农作物生产的潜在影响。评价依据的是地球物理数据、地下水质量、土壤、灌溉用水需求和加沙地带水文地质数据。结果表明,浅层地下水只能支持中至高耐盐作物。这与该地区目前种植的中等耐盐作物,特别是大葱和洋葱是一致的。加沙地带的大规模灌溉在旱季至少需要2 × 107立方米的水。从浅层含水层抽取如此大量的水将导致地下水位每年下降约1.0米。其结果将是淡水/咸水界面可能上升4.7米,导致淡水透镜盐碱化,特别是在大多数葱养殖场所在的泻湖末端。除了上升外,盐碱化可能是由于咸水湖和海水中的微咸/咸水进入淡水透镜所致。虽然灌溉后的降雨足以消除地下水位的下降,但淡水一旦受到污染,就很难去污。因此,浅层地下水对作物的危害将从中等盐度到高盐度再到极高盐度。特定离子的毒性也会因单个离子浓度的增加而增加。因此,以前的淡水将变得不适合生产甚至是高耐盐作物。这将有效地停止克塔地带利润丰厚的葱和其他蔬菜种植,从而对克塔地带特别是对整个加纳来说意味着社会经济灾难。
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来源期刊
West African Journal of Applied Ecology
West African Journal of Applied Ecology Environmental Science-Ecology
CiteScore
0.80
自引率
0.00%
发文量
0
期刊介绍: This research journal has been established by the Ecological Laboratory Unit of the University of Ghana, Accra to publish original papers, invited articles and book reviews in English on general ecology. Papers are peer reviewed by consulting editors. The journal is targeted at scientists, policy makers and the general public. The subject areas to be covered include the following: -Theoretical and Applied Ecology- Environmental Studies- Environmental Management- Population Studies- Sustainable use of Natural Resources- Atmospheric Science- Aquatic Sciences and Oceanography- Terrestrial Ecology- Soil Sciences- Human Settlements- Disaster Preparedness and Disaster Reduction- Sustainable Development- Traditional Knowledge on Biodiversity and its sustainable use- Application in Agriculture and Land Use- Health and Environmental Protection
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