Gabriela Patricia FLORÈS AVILÈS
soutenance en 2019
Tracing nitrate sources and modelling Groundwater lake interactions in the coastal zone of the Titicaca Lake, Bolivia
Surface–subsurface flow modelling of groundwater–lake Interactions and transference of nitrogen pollutants in the aquifer of the coastal zone of the Titicaca Lake, Bolivia
Supervisors : Céline DUWIG and Yvan ROSSIER
Groundwater and surface water inﬂow play an important role in controlling lakes water chemistry, water quality, aquatic habitat and biodiversity. Numerous studies have shown that groundwater can contribute importantly to the nutrient budget of lakes (Shaw et al. 1990 ; Robertson et al. 2005 ; Özen et al. 2010) and in several cases have been observed where contaminant and/or nutrient-rich groundwater entering lakes has led to lake pollution and/or eutrophication (Zhang et al., 2010 ; Zhu and Schwartz, 2011).
In Bolivia the Titicaca Lake watershed, valued for its scenery, recreational activities and fishing, has experienced severe eutrophication problems associated with the degradation of water quality and a consequent disturbance in the ecological balance. The effects of groundwater on the nutrient budget are poorly elucidated, but may supply an important contribution on the ecological state of the Titicaca Lake. The exact sources of nutrients to the lake are not well known, but could include tributary streams and springs, septic efﬂuent, fertilizer application or geologic sources.
Characterizing groundwater–lake interactions may provide some insight into the possible sources of nutrients or processes controlling nutrient dynamics within the Titicaca Lake. However, the application of N and O isotopic ratios of NO3, can provide detailed information about the sources and potential transformations of NO3−in aquatic systems (Kendall, 1998).
For these reason, the overall objective of this thesis is to determine groundwater–lake interactions and transference of nitrogen pollutants in the coastal zone of the Titicaca Lake, through an integrated surface-subsurface flow modelling, which will allow the delineation and implementation of new environmental remediation systems for the preservation of the biological diversity.
Specific objectives of the thesis
• Develop a three dimensional surface-subsurface flow modelling of groundwater at a regional scale to delineate local study areas.
• Characterize the geometry and hydraulic properties of the aquifer interacting with the lake focused mainly in the coastal zone of the Titicaca Lake.
• Identify nitrogen sources and their behavior based on dual nitrogen and oxygen isotopic compositions and hydrochemical analysis in the coastal zone of the Titicaca Lake.
• Determine groundwater – lake interactions and transference of nitrogen pollutants through an integrated three dimensional surface-subsurface flow modelling of the coastal aquifer.
• Provide a scientific database on the implication of groundwater - lake interaction and nutrient dynamics, proposing different scenarios that may allow the development and implementation of new environmental remediation systems for biodiversity preservation.
Kendall, C., 1998. Tracing nitrogen sources and cycling in catchments. In : Kendall, C., McDonnell, J.J. (Eds.), Isotope Tracers in Catchment Hydrology. Elsevier Science B.V., Amsterdam.pp. 519–576.
Özen A., Karapınar B., Kucuk I., Jeppesen E., Beklioglu M., 2010. Drought-induced changes in nutrient concentrations and retention in two shallow Mediterranean lakes subjected to different degrees of management. Hydrobiologia, 646:61–72
Robertson D.M., Rose W.J., Saad D.A., 2005. Water quality, hydrology, and phosphorus loading to Little St. Germain Lake, Wisconsin, with special emphasis on the effects of winter aeration and groundwater inputs. US Geol Surv Sci Invest Rep 2005-5071.
Shaw R.D., Shaw J.F.H., Fricker H., Prepas E.E., 1990. An integrated approach to quantify groundwater transport of phosphorus to Narrow Lake, Alberta. Limnol. Oceanogr.,35 (4),870–886
Zhang, Y., Liu, X.J., Fangmeier, A., Goulding, K., Zhang, F.S., 2008. Nitrogen inputs and isotopes in precipitation in the North China Plain. Atmospheric. Environment. 42 (7), 1436–1448.
Zhu, C., Schwartz, F.W., 2011. Hydrogeochemical processes and controls on water quality and water management. Elements 7, 169–174.
directeur de thèse : Céline DUWIG
Thèse en cotutelle financée par xxx
Date de début de thèse : octobre 2016