TITLE:
Groundwater Residence Time Modelling in the Aquifers of the Ampasindava Peninsula, Northwestern of Madagascar
AUTHORS:
Lahimamy Paul Fareze, Joël Rajaobelison, Voahirana Ramaroson, Falintsoa Fanantenana Asombola Razafitsalama, Christian Ulrich Rakotomalala
KEYWORDS:
Isotopes, Groundwater, Model, Age, Madagascar
JOURNAL NAME:
Open Access Library Journal,
Vol.9 No.8,
August
30,
2022
ABSTRACT: This study concerns the use of isotope techniques to assess groundwater resource management in mining area. The objective of the study is first to estimate the groundwater residence time in the peninsula of Ampasindava and secondly to determine the relationship between wastewater from mining activity and groundwater resource in the study area by using environmental isotopes. It will contribute to clarifying the impact of the mining activity waste water on the groundwater in the study area. The stable isotopes of oxygen and hydrogen were used to understand groundwater recharge process and its origin. Tritium was used to estimate the groundwater residence time and hydrochemical tools helped identify the groundwater chemical facies. A simulation based on mathematical model was applied to estimate the groundwater residence time using the tritium concentration value of each groundwater sample. As results, the groundwater geochemical characteristics in the Ampasindava peninsula show two different water types. This assumption was confirmed by the isotope signature of the water samples. The results of the simulation run under exponential and dispersion models showed higher values of groundwater age for the spring waters compared to the groundwater age using a piston flow model. It suggests that spring waters are older than groundwater in the alluvium plains. The spring water seems to be protected from rare earth mining exploitation pollution. On the contrary, the mining exploitation could be a source of contamination of the groundwater in the alluvium plain.