Processes That Control Water Chemistry and Stable Isotopic Composition during the Refilling of Lake Ngami in Semiarid Northwest Botswana

摘要: Summary Lake Ngami in semiarid Botswana was dry until 2009 when it began filling with water because of regional increases precipitation and from redirection to the lake distributaries Okavango River. We measured physical, chemical stable isotopic composition collected at 25 cm below surface along a ∼18 km axial transect inflow river distal end lake. Our objective determine processes that control properties establish baseline values for future temporal spatial comparisons. The major ionic concentrations (e.g., Cl−, Na+, Ca2+) oxygen (δ18O) hydrogen (δD) isotope ratios show three distinct regions increasing enrichment, respectively transect. δ18O vs. δD data plot Delta evaporation line suggest modification by evaporation. proportions ions inlet were similar log Cl− log Na+ suggests an evaporative enrichment solutes. segmentation solutes into results differential recharge 2010, 2011 2012, are thus controlled residence time Unlike ions, dissolved inorganic carbon (DIC) (δ13C) DIC increase about midway lake, then reach steady state. δ13C organic matter averaged ∼−25.7 ± 0.3‰ while particulate decreased ∼−24‰ ∼−28‰ column productivity. Carbon cycling is which equilibration between atmospheric CO2(g). importance controlling solute chemistry dominance CO2(g) during stages lakes arid environments.