Modeling of Flow and Transport in Groundwater Systems

1. RESOURCE ASSESSMENT SUSTAINABLE MANAGEMENT CONTAMINANT MIGRATION Modeling of Flow and Transport in Groundwater Systems INTEGRATED MODELING M. SekharDepartment of Civil EngineeringIndian Institute of Science BIOREMEDIATION

2. Sustainable Groundwater Management Under Climatic & Anthropogenic Effects Cumulative Rainfall Departure & Groundwater Levels Water table fluctuation & Chloride mass balance methods Lower Kabini Basin ~ 1000 km2 CRD EOF Analysis GWL Groundwater discharge variations

3. Soil Moisture Retrieval & Modeling Using Assimilation Methods Numerical models for simulating profile soil moisture in soils using improved inversion (e.g. GLUE) and assimilation models (e.g. ensemble Kalman filter) are needed to characterize the land-surface fluxes under various soil cover conditions. Soil moisture prediction in plots for various crop types is developed. Near-surface soil moisture retrieval using ENVISAT satellite at watershed scale is under cropped areas is in progress. Field scale experiments to use future micro-wave Indian satellite (RISAT) are being developed. Example:Simulations in soil plots with grass cover for understanding the evaporation and recharge fluxes Data used: 29th April 2005 – 29th March 2007 60 cm 100 cm 200 cm Observed Simulated

4. Numerical modeling for stochastic analysis of flow and reactive solute transport in heterogeneous porous media Modeling of the effect of contaminant sources in groundwater is needed to predict the development of the plume characteristics. The random field modeling is required for analyzing the effect of heterogeneity in parameters (e.g. hydraulic conductivity, dispersivity, sorption and decay coefficient) 3-D stochastic flow and transport models are developed for analyzing the prediction uncertainty of concentration plumes due to the combined effect of randomness of system parameters and the input source conditions. Stochastic FEM Scale dependent dispersivity

5. Stochastic Modeling of Flow Conditional to Watershed Investigations 7 8 6 9 5 4 10 11 3 12 2 1 x2 x1 Stream outlet Blue colour = Top clay layer (Regolith) Green to yellow colour = Weathered rock (Fissured zone) Red colour = Fresh or fractured rock Top fissure surface Bottom fissure surface Random surfaces K high K low p(q)

6. Hydrogeochemical Modeling – Theoretical & Field Applications 3D Reactive Transport Model with equilibrium geochemical reactions (HYDROS) Example: Sulphide mineral oxidation and transport of oxidation products from pyrite ore mine tailing dump Multi-component transport of solutes in soil and groundwater system require modeling the geochemical reactions arising from the water-rock/sediment interactions. A multidimensional numerical model (HYDROS)based on the finite volume method for the multi-component equilibrium reactive solute transport is developed, which combines the transport model with equilibrium speciation module MINTEQA2 (US geological survey). HYDROS is evaluated and compared with the MINTOX simulations used to model the metal mobility in aquifers impacted by acid mine tailings discharge. HYDROS is then applied to the case study of the transfer of transition metals with organic colloids in the swamp groundwater of the experimental Nsimi watershed, representative of the humid tropical ecosystem of the South Cameroon Plateau.

7. Research Areas & Future Interests • Groundwater resources assessment under climatic variations and anthropogenic effects using numerical models, statistical tools and field studies. • Retrieval of near surface soil moisture through radar remote sensing (SAR) and estimation of profile soil moisture using modeling and assimilation at watershed scale. • Stochastic modeling of flow and reactive solute transport in heterogeneous porous media. Theoretical investigations and field scale experiments. • Integrated geochemical and hydrological studies in tropical regions using experimental watersheds.

8. Publications pertaining to the slides • Chaudhuri, A. and Sekhar, M. (2007) Stochastic finite element method for analysis of transport of nonlinearly sorbing solutes in 3-D heterogeneous porous media. Water Resources Research, 43, W07442. • Soumya, B., Sekhar, M., Riotte, J. and Braun, J.J. Non-linear regression model for spatial variation in precipitation chemistry for South India. Atmospheric Environment (In Press). • Mangiarotti, S., Sekhar, M., Javeed, Y., and Mazzega, P. Spatio-temporal analysis of groundwater dynamics due to climatic variability and land use changes. Hydrological Processes (Accepted). • Descloitres, M., Ruiz, L., Sekhar, M., Legchenko, A., Braun, J.J., Mohan Kumar, M.S. and Subramanian, S. (2007) Characterization of seasonal local recharge using Electrical Resistivity, Tomography and Magnetic Resonance Sounding. Hydrological Processes, doi. 10.1002/hyp.6608. • Sekhar, M., Braun, J. J., Hayagreeva Rao, K. V., Ruiz, L., Viers, J., and Dupre, B. (2007) Hydrogeochemical modeling of organo-metallic colloids in the Nsimi experimental watershed, South Cameroon. Environmental Geology (In Press). • Sekhar, M., Rasmi, S.N., Javeed, Y., Gowrisankar, D., and Ruiz, L. (2006). Modeling the groundwater dynamics in a semi-arid hard rock aquifer influenced by boundary fluxes, spatial and temporal variability in pumping/recharge. Advances in Geoscience, Hydrological Sciences (ed) Park, N., V. 4, p. 173-181