The Saltwater Intrusion Problem: Concepts, Challenges, Modeling, Experiments and Case Studies

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1 The Saltwater Intrusion Problem: Concepts, Challenges, Modeling, Experiments and Case Studies Manfred Koch Department of Geohydraulics and Engineering Hydrology, University of Kassel, Germany NITK, Surathkal, India, March 13, 2013

2 Overview 1. Saltwater Intrusion Problem: Basic concepts 2. Modeling Saltwater Intrusion 3. Laboratory Experiments 4. Case Studies 4.1 Saltwater Intrusion from brakish canals in Florida 4.2 Saltwater intrusion in the Bangkok Aquifer/ Thailand 4.3 Saltwater up-coning in Brandenburg/Germany

3 1. Saltwater Intrusion Problem: Basic Concepts Dynamical steps of saltwater intrusion

4 1. Saltwater Intrusion Problem: Basic Concepts Ghyben- Herzberg Law Natural head drop due to topography at the coastline. Hydrostatic equilibrium then leads to upconing of saltwater-fresh water interface Gyben- Herzberg Law => Sharp interface assumption: No consideration of hydrodynamic dispersion

5 1. Saltwater Intrusion Problem: Basic Concepts Example: Saltwater intrusion in the Florida coastal aquifer

6 1. Saltwater Intrusion Problem: Basic Concepts Example: Saltwater intrusion in the Mississippi River Mississippi River's volume of water flow has decreased to a quantity allowing salt water intrusion upstream into the river. The river's bottom profile is deeper than the Gulf of Mexico water surface level up to about 15 miles downstream of Natchez, Mississippi. Denser salt water flows upstream along the bottom of the River underneath the less dense river fresh water. This can ultimately affect municipal drinking water and industrial water supplies.

7 1. Saltwater Intrusion Problem: Basic Concepts Example: Saltwater up-coning in pumping wells Pumping leads to head drops around the well. Hydrostatic equilibrium then leads to upconing of saltwater-fresh water interface => Ghyben- Herzberg Law applies also 1m head drop leads to 40 m uprise Saltwater enters the well => Shut-off of wells required

8 2. Modeling Saltwater Intrusion The Henry Problem

9 2. Modeling Saltwater Intrusion Challenges in modeling saltwater intrusion 1. Possible presence of fissures and cracks and fractures in the aquifer, whose precise positions are unknown but have great influence on the saltwater intrusion. 2. Possible presence of small scale heterogeneities in the hydraulic properties of the aquifer, which are too small to be take into account by the model 3. Change of hydraulic properties by saltwater intrusion. As mixture of saltwater and freshwater is often under-saturated with respect to calcium, dissolution of calcium in the mixing zone may occur which changes hydraulic properties. 4. Cation exchange, which slows the advance and retreat of a saltwater intrusion 5. Saltwater intrusion often not in equilibrium. Aquifer dynamics tend to be slow and adapts only slowly to changes in pumping or rainfall 6. For long-term models, impact of the future climate change on sea levels and recharge not well-known.

10 3. Laboratory Experiments / density-dependent transport Sand tank at the University of Kassel Design of tank experiments

media: Effects of boundary conditions and at high concentrations, Second International Conference on Saltwater Intrusion and Coastal

11 3. Laboratory Experiments Analysis of mixing and dispersion in stochastically heterogeneous media Koch, M. and B. Starke, Experimental and numerical investigation of macrodispersion of densitydependent transport in stochastically heterogeneous media: Effects of boundary conditions and at high concentrations, Second International Conference on Saltwater Intrusion and Coastal Aquifers, Mérida, México, March 30 - April 2, 2003, Presentation Stochastic sand packing of tank with given geostatistical distribution of permeabilities

12 4. Case Studies 4.1 Saltwater Intrusion from brackish canals in Florida Koch, M. and A. Sharma, SUTRA and HST3D modeling and management of saltwater intrusion from brackish canals in Southeast Florida, Second International Conference on Saltwater Intrusion and Coastal Aquifers, Mérida, México, March 30 - April 2, 2003, Presentation (zipped) 4.2 Saltwater intrusion in the Bangkok Aquifer/ Thailand Koch, M. and P. Arlai, Deterministic and stochastic Modeling of Groundwater Flow and Solute Transport in the heavily-stressed Bangkok coastal Aquifer, Thailand, and Investigation of optimal Management Strategies for possible Aquifer Restoration, IAH 2007 Groundwater and Ecossystems Lisbon 2007, Lisbon, Portugal, September 17-21, Presentation 4.3 Saltwater up-coning in Brandenburg /Germany Voss, A. and M. Koch, Numerical simulations of topography-induced saltwater upconing in the state of Brandenburg, Germany, Physics and Chemistry of the Earth (B), 26, , 2001.

Manfred Koch and Bettina Starke. Department of Geohydraulics and Engineering Hydrology University of Kassel, Germany

Manfred Koch and Bettina Starke. Department of Geohydraulics and Engineering Hydrology University of Kassel, Germany Experimental and Numerical Investigation of Macrodispersion of Density-Dependent Transport in Stochastically Heterogeneous Media: Effects of Boundary Conditions and High Concentrations Manfred Koch and