groundwater final

modflow

numerical model developed by the USGS (United States Geological Survey) to simulate groundwater flow through aquifers

groundwater vistas

a graphical user interface for MODFLOW. It helps build, run, and analyze MODFLOW models more easily by offering visualization tools, data entry forms, and map-based input

recharge area

a location where water enters the ground and infiltrates down to the water table

discharge area

The area or zone where groundwater emerges from the aquifer. The outflow maybe into a stream, lake, spring, wetland, etc.

dynamic equilibrium

condition of continuous, random movement of particles but no overall change in concentration of materials

unsaturated zone

the layer of rocks and soil above the water table

porosity

ratio of volume of voids to total volume of sample

void ratio

Ratio of volume of voids to volume of solids.

gravimetric water content

Mass of water/mass of oven dry soil

volumetric water content

ratio of volume of water to volume of soil

saturation ratio

volume water over volume voids

dry bulk density

mass of solid/total volume

particle density

mass per unit volume of soil solids

capillary fringe

region above the water table with water drawn up by capillary action

unsaturated flow

how water moves through soil or rock pores that are not completely filled with water — that is, when the material is partially saturated

field capacity

The maximum amount of water held by soil particles against the force of gravity

wilting point

water content at which plants wilt

tensiometer

instrument used to measure soil moisture

field method

exploration for GW aquifers

fracture trace analysis

geologic mapping technique used to identify and analyze surface expressions of subsurface rock fractures

electromagnetic conductivity

is a geophysical property that describes how well a material can conduct electrical current when exposed to an electromagnetic (EM) field

Seismic Methods

sending waves into the ground to determine if there is a disruption in the soil

reflection method

find structural boundaries in the soil

refraction method

find thickness of unconsolidated materials

magnetometer

a device that can detect small changes in magnetic fields

ground penetrating radar

Specialist imaging hardware used to detect and visualise objects buried underground.

groundtruth

real-world, observed data collected directly from the field (or laboratory) that is used to verify or calibrate models

geophysical well logging

is the process of measuring physical properties of rocks and fluids in a borehole using specialized tools lowered into the well

caliper log

A well log that shows the variations with depth in the diameter of an uncased borehole.

temperature log

a measurement of temperatures along the wellbore

Single-Point Resistivity Log

A log that measures the resistivity using two electrodes and having a limited area of investigation of from 5 to 10 times the electrode diameter.

earth resistivity log

a measure of how strongly the ground resists the flow of electrical current

Spontaneous Potential log

measures Natural voltage differences, used to find Permeable zones, formation water salinity

nuclear logging

uses radioactive sources to measure the physical properties of rocks and fluids in a borehole

hydraulic investigation

surface mapping, surface geophysics, test holes

what do hydrologists do

plan and control field work, oversee driller, proper reporting

meq

milliequivalent, molar weight/charge

meq/L

milliequivalent concentration over eq. weight

common ion effect

a decrease in the solubility of an ionic compound caused by the addition of a common ion

law of mass action

The rate of a chemical reaction is proportional to the product of the concentrations of the reactants

solubility product

Ksp

chemical activity

A characteristic property of a substance that indicates its ability to undergo a specific chemical change

=the activity coefficient * molal concentration

Debye-Huckel equation

provides a method for obtaining activity coefficients for solutions that contain ionic solutes.

ion exchange

a process by which one ion is displaced by another

Sodium Adsorption Ratio (SAR)

The ratio of sodium to calcium that indicates how much calcium in the soil has been replaced by sodium

piper diagram

Graphical representation of groundwater chemistry.

retardation

slowing down of a contaminant's movement compared to the flow of groundwater