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Author Külls, C.; Schwarz, O. openurl 
  Title 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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  Area Expedition Conference  
  Notes Approved no  
  Call Number (up) THL @ christoph.kuells @ Serial 72  
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Author Castro, M.C.; Stute, M.; Schlosser, P. url  openurl
  Title 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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  Notes Approved no  
  Call Number (up) THL @ christoph.kuells @ castro_comparison_2000 Serial 109  
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Author Constantinou, C.; Udluft, P. openurl 
  Title Mapping the availability and dynamics of groundwater recharge. Part 2: Case studies from Mediterranean Basins Type Conference Article
  Year 2000 Publication Proceedings of Third Congress on Regional Geological Cartography and Information Systems Abbreviated Journal  
  Volume Issue Pages 163-168  
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  Notes Approved no  
  Call Number (up) THL @ christoph.kuells @ Constantinou2000mapping Serial 61  
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Author Gasse, F. url  openurl
  Title Hydrological changes in the African tropics since the Last Glacial Maximum Type Journal Article
  Year 2000 Publication Quaternary Science Reviews Abbreviated Journal  
  Volume 19 Issue 1 Pages 189-211  
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  Abstract Paleohydrological data from the African tropics and subtropics, including lake, groundwater and speleothem records, are reviewed to show how environments and climates from both hemispheres are inter-related. Although orbitally induced changes in the monsoon strength account for a large part of long-term climatic changes in tropical Africa, the Late Pleistocene–Holocene hydrological fluctuations rather appear to have been a series of abrupt events that reflect complex interactions between orbital forcing, atmosphere, ocean and land surface conditions. During the Last Glacial Maximum (23–18ka BP), most records indicate that generally dry conditions have prevailed in both hemispheres, associated with lower tropical land- and sea-surface temperatures. This agrees with simulations using coupled ocean–atmosphere models, which predict cooling and reduced summer precipitation in tropical Africa; the global hydrological cycle was weaker than today when the extent of large polar ice-sheets and sea-ice was a prominent forcing factor of the Earth’s climate. Glacial-interglacial climatic changes started early: a first wetting/warming phase at ca. 17–16ka BP took place during a period of rapid temperature increase in Antarctica. Next, two drastic arid-humid transitions in equatorial and northern Africa occurred around 15–14.5ka BP and 11.5–11ka BP. Both are thought to match the major Greenland warming events, in concert with the switching of the oceanic thermohaline circulation to modern mode. However, part of the climatic signal after 15 ka BP also seems related to the Antarctica climate. During the Holocene, Africa has also experienced rapid hydrological fluctuations of dramatic magnitude compared to the climatic changes at high latitudes. In particular, major dry spells occurred around 8.4–8ka and 4.2–4ka BP in the northern monsoon domain. Comparison with other parts of the world indicates that these events have a worldwide distribution but different regional expressions. In the absence of large polar ice sheets, changes in the continental hydrological cycles in the tropics may have a significant impact on the global climate system. Climate information gathered here allows to identify geographical and methodological gaps, and raise some scientific questions that remain to be solved to better understand how the tropics respond to changes in major climate-forcing factors, and how they influence climate globally.  
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  ISSN 0277-3791 ISBN Medium  
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  Notes Approved no  
  Call Number (up) THL @ christoph.kuells @ gasse_hydrological_2000 Serial 96  
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Author Klock, H.; Külls, C.; Udluft, P. openurl 
  Title 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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  Notes Approved no  
  Call Number (up) THL @ christoph.kuells @ Klock2000estimation Serial 33  
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Author Külls, C.; Salameh, E.; Udluft, P. openurl 
  Title 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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  Notes Approved no  
  Call Number (up) THL @ christoph.kuells @ Kuells2000assessing Serial 63  
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Author Külls, C. openurl 
  Title Resolving patterns of groundwater flow by inverse hydrochemical modelling in a semiarid Kalahari Type Conference Article
  Year 2000 Publication Tracers and Modelling in Hydrogeology: TraM’2000: Proceedings of TraM’2000, the International Conference on Tracers and Modelling in Hydrogeology Held at Liège, Belgium, in May 2000 Abbreviated Journal  
  Volume Issue 262 Pages 447  
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  Area Expedition Conference IAHS Press  
  Notes Approved no  
  Call Number (up) THL @ christoph.kuells @ Kuells2000resolving Serial 62  
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Author Külls, C.; Adar, E.M.; Udluft, P. openurl 
  Title Tracer Studies and Modelling of Regional Groundwater Systems-Resolving patterns of groundwater flow by inverse hydrochemical modelling in a semiarid Kalahari basin Type Journal Article
  Year 2000 Publication IAHS Publications-Series of Proceedings and Reports-Intern Assoc Hydrological Sciences Abbreviated Journal  
  Volume 262 Issue Pages 447-452  
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  Publisher Wallingford [Oxfordshire]: IAHS, 1981- Place of Publication Editor  
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  Notes Approved no  
  Call Number (up) THL @ christoph.kuells @ Kuells2006 Serial 31  
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Author Udluft, P.; Külls, C. openurl 
  Title Mapping the availability and dynamics of groundwater recharge. Part 1: modelling techniques Type Conference Article
  Year 2000 Publication Proceedings of the Third Congress on Regional Geological Cartography and Information Systems Abbreviated Journal  
  Volume Issue Pages 337-340  
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  Notes Approved no  
  Call Number (up) THL @ christoph.kuells @ Udluft2000mapping Serial 64  
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Author Zagana, E.; Külls, C.; Udluft, P. openurl 
  Title Der Wasserhaushalt des Aliakmonas Type Journal Article
  Year 2000 Publication Vom Wasser Abbreviated Journal  
  Volume 94 Issue Pages 29-39  
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  Notes Approved no  
  Call Number (up) THL @ christoph.kuells @ Zagana2000saa Serial 34  
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