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Author Külls, C.; Salameh, E.; Udluft, P.
Title (up) Assessing water supplies for irrigation-availability of natural resources and sustainability indices Type Conference Article
Year 2000 Publication Tropentag Hoffenheim Abbreviated Journal
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Call Number THL @ christoph.kuells @ Kuells2000assessing Serial 63
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Author Castro, M.C.; Stute, M.; Schlosser, P.
Title (up) Comparison of 4He ages and 14C ages in simple aquifer systems: implications for groundwater flow and chronologies Type Journal Article
Year 2000 Publication Applied Geochemistry Abbreviated Journal
Volume 15 Issue 8 Pages 1137-1167
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Abstract 4He concentrations in excess of the solubility equilibrium with the atmosphere by up to two to three orders of magnitude are observed in the Carrizo Aquifer in Texas, the Ojo Alamo and Nacimiento aquifers in the San Juan Basin, New Mexico, and the Auob Sandstone Aquifer in Namibia. A simple 4He accumulation model is applied to explain these excess 4He concentrations in terms of both in situ production and a crustal flux across the bottom layer of the aquifer. Results from the model simulations suggest variability in the 4He fluxes, ranging from 6×10−6 cm3 STP cm−2 yr−1 for the Auob Sandstone Aquifer to 3.6×10−7 cm3 STP cm−2 yr−1 for the Carrizo aquifer. For the Ojo Alamo and Nacimiento aquifers an intermediate value of 3×10−6 cm3 STP cm−2 yr−1 was estimated. The contribution of in-situ produced 4He to the measured concentrations was also estimated. This contribution is negligible for the Auob Sandstone Aquifer as compared with both the concentrations measured at the top and bottom of the aquifer for most of the pathway. In the Carrizo aquifer, in-situ produced 4He contributes 27.5% and 15.4%, to the total 4He observed at the top and bottom of the aquifer, respectively. For both aquifers of the San Juan Basin in-situ production almost entirely dominates the 4He concentrations at the top of the aquifer for most of the pathway. In contrast, the internal production is negligible as compared with the measured concentrations at the bottom of these aquifers, reaching, at most, 1.1%. The model simulations require an exponential decrease in the horizontal velocity of the water with increasing recharge distance to reproduce the distribution of 4He in these aquifers. For the Auob Sandstone Aquifer the highest range in the velocity values is obtained (25 to 0.4 m yr−1). The simulations for the Carrizo aquifer and both aquifers located in the San Juan Basin require velocities varying from 4 to 0.1 m yr−1, and from 2 to 0.3 m yr−1, respectively. For each aquifer, average permeability values were also estimated. They are generally in agreement with results obtained from pumping tests, hydrodynamic modeling and previous 14C measurements. On the basis of the results obtained by calibrating the model with the measured 4He concentrations, the mean water residence times were estimated. They agree reasonably well with 14C ages. When applied as chronologies for noble gas temperatures in the same aquifers, the calculated 4He ages allow the identification of three different climate periods similar to those previously identified using 14C ages: (1) the Holocene period (0–10 Ka BP), (2) the Last Glacial Maximum (≈18 Ka BP), and (3) the preceeding period (30–150 Ka BP).
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ISSN 0883-2927 ISBN Medium
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Call Number THL @ christoph.kuells @ castro_comparison_2000 Serial 109
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Author Zagana, E.; Külls, C.; Udluft, P.
Title (up) Der Wasserhaushalt des Aliakmonas Type Journal Article
Year 2000 Publication Vom Wasser Abbreviated Journal
Volume 94 Issue Pages 29-39
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Call Number THL @ christoph.kuells @ Zagana2000saa Serial 34
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Author Klock, H.; Külls, C.; Udluft, P.
Title (up) Estimation of relative recharge values for the northern Kalahari catchment, Namibia Type Journal Article
Year 2000 Publication Journal of African Earth Sciences Abbreviated Journal
Volume 30 Issue 4 Pages 47-48
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Call Number THL @ christoph.kuells @ Klock2000estimation Serial 33
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Author Külls, C.; Schwarz, O.
Title (up) Grundwasseranreicherung in den Waldbeständen der Teninger Allmend bei Freiburg im Breisgau Type Book Chapter
Year 2000 Publication Beiträge zur Physischen Geographie Abbreviated Journal
Volume Issue Pages 67 - 78
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Corporate Author Fachbereich Geowissenschaften der Johann Wolfgang Goethe-Universität Frankfurt am Main Thesis
Publisher Werner-F. Bär Place of Publication Frankfurt am Main Editor
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Call Number THL @ christoph.kuells @ Serial 72
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