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Klaus, J., Külls, C., & Dahan, O. (2008). Evaluating the recharge mechanism of the Lower Kuiseb Dune area using mixing cell modeling and residence time data. Journal of Hydrology, 358(3-4), 304–316.
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Frumkin, A., & Gvirtzman, H. (2006). Cross-formational rising groundwater at an artesian karstic basin: the Ayalon Saline Anomaly, Israel. Journal of Hydrology, 318(1), 316–333.
Abstract: It is proposed that a geothermal artesian karstic system at the central part of the Yarkon–Taninim aquifer creates the ‘Ayalon Saline Anomaly’ (ASA), whose mechanism has been under debate for several decades. A 4-year-long detailed groundwater monitoring was carried out at 68 new shallow boreholes in the Ayalon region, accompanied by a comprehensive survey of karstic voids. Results indicate the rising of warm-brackish groundwater through highly permeable swarms of karstic shafts, serving as an outflow of the artesian geothermal system. The ASA area contains ‘hot spots’, where groundwater contrasts with ‘normal’ water hundreds of meters away. The ASA temperature reaches 30°C (∼5°C warmer than its surroundings), chloride concentration reaches 528mg/l (50–100mg/l in the surrounding), H2S concentration reaches 5.6mg/l (zero all around) and pH value is 7.0 (compared with 7.8 around). Subsequently, the hydrothermal water flows laterally of at the watertable horizon through horizontal conduits, mixing with ‘normal’ fresh water which had circulated at shallow depth. Following rainy seasons, maximal watertable rise is observed in the ASA compared to its surroundings. Regional hydrogeology considerations suggest that the replenishment area for the ASA water is at the Samaria Mountains, east of the ASA. The water circulates to a great depth while flowing westward, and a cross-formational upward flow is then favored close the upper sub-aquifer’s confinement border.
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Heaton, T. H. E. (1984). Sources of the nitrate in phreatic groundwater in the western Kalahari. Journal of Hydrology, 67(1), 249–259.
Abstract: Elevated levels of nitrate occur in phreatic groundwater in the western Kalahari, Namibia. Nitrate in water containing 0.4–3.1 meq NO−3l−1, of widespread occurrence, has δ15N values in the range +4.9 to +8.0‰, suggesting natural derivation from the soil. The sporadic occurrence of very high levels of nitrate (> 4 meq NO−3l−1), which has δ15N between +9.3 to +18.7‰, reflects pollution derived from animal waste. The importance of considering the possible isotopic effects of denitrification, and the significance of leaching in the nitrogen budget of the Kalahari soil, are also discussed.
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Heaton, T. H. E., Talma, A. S., & Vogel, J. C. (1983). Origin and history of nitrate in confined groundwater in the western Kalahari. Journal of Hydrology, 62(1), 243–262.
Abstract: Data are presented for nitrate, dinitrogen and argon concentrations and 15N14N ratios in groundwater, with radiocarbon ages up to 40,000 yr. for three confined sandstone aquifers in the western Kalahari of South West Africa/Namibia. The nitrate is probably generated within the soil of the recharge areas, and its production rate during the period 3000-40,000 B.P. has remained between 0.5 and 1.6 meq NO−3l−1 of recharge water, with ° 15N between + 4 and + 8‰. Variations in the amount of nitrate and of “excess air” in groundwater recharge are found, and can only reflect changes in the environmental conditions during recharge. They must therefore be caused by the climatic changes that have taken place during the past 25,000 yr.
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Heaton, T. H. E., Talma, A. S., & Vogel, J. C. (1983). Origin and history of nitrate in confined groundwater in the western Kalahari. Journal of Hydrology, 62(1), 243–262.
Abstract: Data are presented for nitrate, dinitrogen and argon concentrations and 15N14N ratios in groundwater, with radiocarbon ages up to 40,000 yr. for three confined sandstone aquifers in the western Kalahari of South West Africa/Namibia. The nitrate is probably generated within the soil of the recharge areas, and its production rate during the period 3000-40,000 B.P. has remained between 0.5 and 1.6 meq NO−3l−1 of recharge water, with ° 15N between + 4 and + 8‰. Variations in the amount of nitrate and of “excess air” in groundwater recharge are found, and can only reflect changes in the environmental conditions during recharge. They must therefore be caused by the climatic changes that have taken place during the past 25,000 yr.
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