Technologies to model Ground water --- W Santosh kumar

Ground water Some pic here Groundwater is the water found underground in the cracks and spaces in soil, sand and rock. It is stored in and moves slowly through geologic formations of soil, sand and rocks called aquifers. Supplies drinking water. Helps grow food. Source of recharge for lakes, rivers etc.

Need for Modelling To place septic tanks far from water table. To predict the ground water flow. Discharge and recharge cycle can be regulated. The location of pumping and artificial recharge wells, and their rates. Ground water level measurements are very important for a wide range of applications in geosciences, agriculture, environment monitoring and mining industry. Flow model Transport model

Ground water Simulation Model The mathematical or the numerical models are usually based on the real physics of the groundwater flow. These mathematical equations are solved using numerical codes such as  MODFLOW, ParFlow, HydroGeoSphere, OpenGeoSys etc.  Inputs: Hydrological inputs, Operational inputs, External conditions: initial and boundary conditions, Hydraulic parameters

Ground water table, sedimentary structures (Hydrological inputs) Conventional (Wells) Ground Penetrating Radar Electrode sensor

Ground Penetrating Radar Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. This method uses microwave band(UHF/VHF frequencies) of the radio spectrum, and detects the reflected signals from subsurface structures. Modes of operation: Reflection mode Common Mid Point mode Wide Angle Reflection Refraction mode Transillumination mode determining the thicknesses of soil horizons and depth to water table; detecting air-filled subsurface cavities, buried channels and tunnels; mapping contamination plumes; investigating the condition of dam cores, masonry structures and bridge piers; detecting buried objects in archeological surveys; finding ice or permafrost thicknesses; studying the condition of the asphalt layer on roads, etc. (Reflection mode) However, the subsurface soil above the groundwater table may consist of several layers and the velocity in each layer can be different.

Reflection profiling The antennae are kept at constant separation, while they are moved along a profile The electromagnetic pulses are transmitted at fixed time or distance interval. Vertical axis is two way travel time in nanoseconds (ns) and the horizontal axis is distance along the measured profile. If there are topographic changes along the GPR profiles it is important that the topographic variation is surveyed precisely, so that the GPR profiles can be displayed with correct topography.

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Common Midpoint Surveying Antennas are moved away from each other by certain amount each measurement. Survey is performed over a horizontal reflector.

Electrode sensor Sequentially each electrodes is excited and adjacent ones are used for detection. High frequency current signal is passed and voltage generated at detection electrodes proportional to mutual impedance between the pair is measured. Thus, resistance measured with respect to interface position is monitored for change, which is due to water table.

Detecting Contaminated Soil with Ground Penetrating Radar Dielectric features of contaminated sand with leachate Dielectric features of contaminated sand with diesel oil

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Potential Sources of Groundwater Contamination Storage tanks Septic systems Landfills Chemicals and Road Salts Atmospheric Contaminants

Groundwater remediation techniques Physical Biological Chemical Bioventing Biosparging Bioslurping Phytoremediation Chemical precipitation Ion exchange Carbon absorption Chemical oxidation Air sparging Pump and treat