Seasonal river channel water exchange and implications on salinity levels in sand dams: Case of semi-arid Kitui Region, Kenya
Seasonal river channel water exchange and implications on salinity levels in sand dams: Case of semi-arid Kitui Region, Kenya
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季节性河道水交换及其对沙坝盐度水平的影响：以肯尼亚半干旱基图伊地区为例
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发表时间：
2016
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通讯作者：
J. Kitheka
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作者：
J. Kitheka
本文介绍了肯尼亚半干旱地区季节性河流沙床盐度水平（及相关物理化学参数）变化的研究结果。该研究旨在调查河流沙床中的水与河岸蓄水之间的相互作用，以及这种相互作用如何影响半干旱地区沙坝和浅井的盐度水平。研究结果表明，干河沙床水质参数与浅井、沙坝相应水质参数之间存在显着的相关性。在河流沙床内，旱季盐度范围为0.9%至12.8%，雨季盐度范围为0.4%至1.1%。雨季总溶解固体(TDS) 浓度范围为77.8 至272 mgl -1 。旱季TDS浓度很高，范围为227至3,320 mgl -1 。然而，湿季水电导率较低，范围为 155.9 至 539 µS.cm -1 ，而旱季水电导率较高，范围为 455 至 6,640 µS.cm -1 。与河道沙床相比，浅井和沙坝水体的理化参数较高，盐度在1.5%～6.5%之间，TDS浓度在396～1680 mgl -1 之间。沙坝和浅井的盐度往往比河道沙床的盐度高得多。此外，除长期干旱时期外，河道沙床内的盐度水平大多在饮用水最低允许限值之内。相对较高的盐度、TDS 浓度和电导率归因于水的矿化，这是由于截留、地下水补给和土壤中矿物质的溶解造成的。研究表明，沙床基质内的水流具有低导水率和水通量的特点，这对季节性河流沙床的盐度水平具有重要意义。关键词：沙质河道；水交换；银行存储；盐度;肯尼亚基图伊
This paper presents results of a study on the variations of salinity levels (and associated physico-chemical parameters) in sandbeds of seasonal rivers found in the semi-arid region of Kenya. The study sought to investigate the interaction between water in river sandbeds and bank storage and how this interaction influences salinity levels in sand dams and shallow wells in semi arid lands. The results of the study show that there is a significant relationship between water quality parameters in dry river sandbeds and the corresponding water quality parameters in shallow wells and sand dams. Within river sandbeds, the dry season salinity ranged from 0.9 to 12.8% while the wet season salinity ranged from 0.4 to 1.1%. The wet season total dissolved solids (TDS) concentrations ranged from 77.8 to 272 mgl -1 . The dry season TDS concentrations were high ranging from 227 to 3,320 mgl -1 . The wet season water conductivities were however low ranging from 155.9 to 539 µS.cm -1 as compared to the dry season conductivities that were high ranging from 455 to 6,640 µS.cm -1 . As compared to the river channel sandbeds, water in shallow wells and sand dams was characterized by relatively high levels of physico-chemical parameters with salinity ranging between 1.5% and 6.5% and TDS concentrations ranging from 396 to 1,680 mgl -1 . The level of salinity in sand dams and shallow wells tends to be much higher than those in the stream channel sandbed. Also, within the river channel sand beds, the levels of salinity were mostly within the minimum allowable limit for drinking water except in extended drought periods. The relatively high salinity, TDS concentrations and conductivity were attributed to mineralization of water due to entrapment, ground water recharge and solubisation of minerals from soils. The study shows that the flow of water within sand bed matrix is characterized by low hydraulic conductivities and water fluxes and this has important implication on the salinity levels in sand beds of seasonal rivers. Keywords: Sandy river channel; water exchange; bank storage; salinity; Kitui, Kenya