Application of isotopes and water balance on Lake Duluti–groundwater interaction, Arusha, Tanzania OF ISOTOPES AND WATER BALANCE ON LAKE DULUTI-GROUNDWATER INTERACTION, ARUSHA, TANZANIA
Nancy P. Mduma1, Hans C. Komakech1, Jing Zhang2, and Alfred N. N. Muzuka11Department of Water and Environmental Science and Engineering, Nelson Mandela African Institution of Science and Technology, 23311, Tanzania 2State Key Laboratory of Estuarine and Coastal Research, Shanghai, 200062, China
Received: 14 Apr 2016 – Accepted for review: 26 Apr 2016 – Discussion started: 08 Jun 2016
Abstract. Water chemistry, and stable isotopes of oxygen and hydrogen (18O and 2H respectively), were used to characterize and quantify Lake Duluti–groundwater interaction. Physico-chemical parameters: temperature, pH, electrical conductivity, dissolved oxygen, total dissolved solids, alkalinity, major cations and anions were used to determine chemical characteristics of the lake and to assess its relationship with groundwater sources. Physico-chemical parameters showed abundance of major cation and anions in the Lake water in the following order Na > Ca > K > Mg and HCO3 > Cl > F > SO4 > NO3. The lake water was predominantly Na-HCO3 type in both wet and dry season, while spring waters were mostly of Ca-HCO3 type, and boreholes were of Ca-Na-HCO3 type during the dry season. In the wet season, springs and boreholes were mostly of Na-HCO3 and Na-K-HCO3 types respectively. Isotopic results indicate that evaporation-induced isotopic enrichment prevails in the lake and contributes significantly to water loss from the lake. The δ18O of the lake water averaged +6.1 ‰ while that of well/boreholes and springs averaged −1.2 ‰ and −2.1 ‰ respectively. Similarly, the δD of lake water averaged +24.2 ‰ while that of well/boreholes and springs averaged −12.9 ‰ and −12.2 ‰ respectively. Stable isotope calculations indicate that the lake loses it water to the groundwater aquifer. Water balance model equations used to quantify the level of lake–groundwater exchange found that the Lake Duluti receives and recharges more groundwater than it receives from precipitation and surface runoff. Groundwater thus plays a major role in the hydrological system of Lake Duluti. The findings in this research are of assistance to policy makers and management personnel to make use of the information provided for better management of the lake water.
Mduma, N. P., Komakech, H. C., Zhang, J., and Muzuka, A. N. N.: Application of isotopes and water balance on Lake Duluti–groundwater interaction, Arusha, Tanzania OF ISOTOPES AND WATER BALANCE ON LAKE DULUTI-GROUNDWATER INTERACTION, ARUSHA, TANZANIA, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-176, 2016.