PT Journal AU Külls, C Adar, EM Udluft, P TI Tracer Studies and Modelling of Regional Groundwater Systems-Resolving patterns of groundwater flow by inverse hydrochemical modelling in a semiarid Kalahari basin SO IAHS Publications-Series of Proceedings and Reports-Intern Assoc Hydrological Sciences PY 2000 BP 447 EP 452 VL 262 ER