Groundwater recharge, circulation and geochemical evolution in the source region of the Blue Nile River, Ethiopia

摘要: Geochemical and environmental isotope data were used to gain the first regional picture of groundwater recharge, circulation its hydrochemical evolution in upper Blue Nile River basin Ethiopia. Q-mode statistical cluster analysis (HCA) was classify water into objective groups conduct inverse geochemical modeling among groups. Two major structurally deformed regions with distinct history identified. These are Lake Tana Graben (LTG) Yerer Tullu Wellel Volcanic Lineament Zone (YTVL). Silicate hydrolysis accompanied by CO2 influx from deeper sources plays a role chemical high TDS Na–HCO3 type thermal groundwaters these two regions. In basaltic plateau outside zones, recharge takes place rapidly through fractured basalts, flow paths short they characterized low Ca–Mg–HCO3 waters. Despite altitude (mean � 2500 masl) relatively mean annual air temperature (18 C) region compared Sahelian Africa, there is no commensurate depletion d 18 O compositions Ethiopian Plateau. Generally highland areas north east depleted groundwaters. Altitudinal 0.1&/100 m. The meteoric waters have higher d-excess Rift that White sister which emerges equatorial lakes region. geochemically evolved YTVL LTG isotopically when present day reflecting under colder climate their altitude. 2005 Elsevier Ltd. All rights reserved. 1. Background Surface Ethiopia not widely for supply because marked seasonality lack proper technology retain it. basin, most important source dominant domestic