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water in nature

water in nature. Potable : 2,6%. water in nature. Groundwater Flow. Porous media Aquifer Properties: T: the rate of flow per unit width through the entire thickness of an aquifer, per unit hydr. Gradient (the more great the more permeable)

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water in nature

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  1. water in nature • Potable : 2,6%

  2. water in nature

  3. Groundwater Flow • Porous media • Aquifer Properties: • T: the rate of flow per unit width through the entire thickness of an aquifer, per unit hydr. Gradient (the more great the more permeable) • S: the volume of water released from storage (or added to it) per unit horizontal area of aquifer & per unit decline (or rise) of piezometric head, φ.

  4. GR Flow - The Problem • Darcy’s Law + Continuity (mass balance) Equation = Flow Equation (φ,T,S,x,z,y,t) • Aquifer’s Geometry • values of relevant physical coef. (K, S, ...) • Initial conditions (describe the initial state of the fluid in the domain) • Boundary cond. (how the fluid interacts with its surroundings)

  5. GR Flow - The Solution • Analytical Methods: seldom applied • Numerical Methods (FD, FE, MOC) (Computer Revolution Aid) - Models • Forecasting Problem: to obtain φ(x,y,z,t) u(x,y,z,t)

  6. Hydrologic Basin of Kastoria

  7. Geologic Map

  8. The model’s grid

  9. Map of Piezometric Heads

  10. Groundwater Velocities

  11. GW Quality Problem • Quality instead of pollution (GW already contains dissolved matter) • Increasing Demand - Decreasing quality • @@% men drink unclean water ~~~ concentration of dissolved pollutants > standards by the World Health Org.

  12. GW Pollution Sources A. Environmental • flow through carbonate rocks - dissolved rock • sea water intrusion (disturbed equillibrium) B. Domestic • accidental breaking of sewers • percolation from septic tanks • rain infiltrating through sanitary landfills • Biological contaminants (bacteria+viruses) also related to this source

  13. GW Pollution Sources C. Industrial • a single sewage disposal for both ind.-resident. • Waste disposal in non-protected constructions • Heavy metals, toxic compounds, radioactive materials B. Agricultural • irrigation water or rain water dissolving and carrying fertilizers, salts, etc. as they infiltrate through surface and replenish the aquifer

  14. Transport Phenomenon • Mass transport in porous media=the movement & accumulation of pollutants with the water in the interstices • 4 mechanisms affecting transport: • convection • mechanical dispersion • molecular diffusion • solid-solute interreactions, chemical reactions & decay phenomena

  15. Dispersion • Tracer gradually spreading & occupies a region>flow domain. Irreversible process • e.g. instantaneous point injection through a well, into an aquifer - spreading (longitudinal + transversal) • ellipsoidal contours of equal concentration • breakthrough curve in obs. well (C-t)

  16. Dispersion: reason • Mechanical Dispersion. Spread due to: • varying velocity distribution in the interstice • presence of the pore system (abnormal layout) • Molecular diffusion (low velocities) results from variations in concentr. In the liquid phase • production of an additional flux of pollutant particles from regions of higher C to those of lower ones • Mech.Disp.+Mol. Dif.=Hydrodynamic Dispersion

  17. GW Pollution Problem • Flow equation + transport equation • Numerical methods • h(x,y,z,t) + c(x,y,z,t) • E.G. Figure : Cases of aquifer pollution

  18. GW Flow & Transport Mathematic Models • Results • values of (x,y,z) • hydraulic heads • velocities • concentrations • value forecasting • (x,y,z,t) • aquifer’s volumetric budget Input Data • Aquifer Geometry • Boundary - Initial Conditions • Parameters • hydraulic • hydrogeologic • chemical • External stresses • Hydraulic contact (rivers-lakes-aquifers) ΜODEL

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