Exam 3 Flashcards
What is groundwater?
Water found in the void spaces beneath the surface of the earth. Can exist within layers of saturated rock, in cracks of material, etc.
Water Budget Equation
P= R+ ET + I +(delta)S
P-Precipitation
R-Runoff
ET-Evapotranspiration
I-Interception
S-GW Storage
What percentage of water is groundwater? Answer both in terms of all water and in terms of freshwater
95% of liquid freshwater is GW, and 13% of all fresh water is liquid
Where does GW come from?
Precipitation recharges groundwater stores
Vadose Zone
All the material between Earth’s surface and the Zone of Saturation
Zone of Saturation
Area where GW flows beneath earth surface, all spaces between rock particles are filled with water
Water Table
The upper boundary of the Zone of Saturation in an unconfined aquifer
Capillary Fringe
Material of varying thickness that overlies the Water Table, water is drawn up into it through capillary action
When is the World Day for Water (UN)?
March 22, established in 1998
How does GW affect politics?
GW is an important resource for drinking water. Overpumping from one country could mean drought for another country, causing cross-border issues when it comes to aquifers. The distribution of water can dictate how much of a country’s budget goes towards purchasing or pumping drinking water
Lithology
Physical characteristics of a mineral composition (grain size, density of material)
Stratigraphy
described composition and age of sediment
Structures
Cracks folds, physical characteristics of geologic landscape
Is GW basic or acidic? (generally)
GW is ty[ically acidic, able to dissolve rock and carry minerals (carbonic acid from limestone)
Karst
Terrain composed of numerous depressions in the landscape-sinkholes formed due to dissolution of limestone; lack of surface drainage (streams)
What are caverns composed of? And how is it formed?
Dripstone; formed from the continual deposition of minerals which are dissolved in water and stay when water evaporates
Glacial Till
rock debris (clays, sands, gravel and boulders)
Glacial Outwash
deposits of rock transported due to the melting of glaciers
Alluvial Valleys
permeable formation which can hold a considerable amount of water
Alluvium
sediment deposited by flowing rivers
Tectonic Formations
Fissures/ fractures formed through tectonic activity
What is an issue with recharge in urban areas?
Impermeable surfaces, such as parking lots, prevent percolation through the vadose zone and reduce the rate of recharge, this can lead to downstream flooding
Pressure Surface/Potentiometric Surface
The level at which water appears when a confined aquifer is drilled through- due to release of pressure through small opening (the level to which the water will rise in a well)
Aquifer
Underground water bearing geologic formation that stores and yields usable water
Consolidated Rock
Tightly bound geologic material, impervious, does not allow GW to flow easily
Unconsolidated Rock
Loosely bound geologic material (sand or gravel) that allows GW to flow
Fractured Aquifer
In consolidated rock that has enough fractures and fissures to store usable water
Unconfined Aquifer
Aquifer with no confining layer between water table and earth’s surface
Confined aquifer
Aquifer overlain with confining layer
Saturated Thickness
Total water bearing thickness of an aquifer
Aquitard
Geologic formation that prevents water flow from one aquifer to another
Aquiclude
Formation containing water which does not transmit significant amounts of water
Aquifuge
formation that does not contain or transmit water
Perched Aquifer
Localized zone of saturation above water level held by impermeable layer
Ogallala Aquifer
Largest aquifer in US, about 175,000 sq mi, has been overpumped by US
Porosity Equation
Porosity= Vvoid/Vtotal
or Specific Retention + Specific Yield
Porosity
Ratio of void space to the total volume of formation, expressed in percentage
Primary Porosity
intergranular porosity formed during primary formation of rock
Secondary Porosity
Spaces created by tectonic activity (fractures and fissures) or anything post rock formation
Total Porosity
All pore space in the sample
Effective Porosity
Only interconnected pore space of the sample
REV
Representative elementary volume, a large enough sample size to define a mean porosity
Transmissivity
Rate at which water moves laterally through saturated thickness of aquifer (with hydraulic gradient of 1)
Transmissivity Equation
i=dh/dl=1
Specific Yield
ratio of the volume of water that drains from the saturated rock to the total volume of rock; can also be gathered from ternary diagram
Specific Yield Equation
S=V water drain due to gravity/V Total sample
Specific Retention
ratio of volume of water an aquifer can retain against gravity drainage per the total volume of aquifer
Permeability
k; the ability of a material to transmit a fluid, a measure of how fast a fluid can travel through sediment
The smaller the size of the sediment grains…
The larger the surface contacts
Increased frictional resistance…
decreased intrinsic permeability
Poorly sorted material is…
less conductive
Hydraulic conductivity (K)
The proportionality constant in Darcy’s law, which relates the amount of water which will flow
through a unit cross-sectional area of an aquifer under a unit gradient of hydraulic head
OR
Coefficient that describes the ratio at which water can move through a permeable medium
Bernoulli’s Equation
formulation of energy loss during fluid flow
Groundwater flows…
from the top aquifer to the bottom aquifer
Hydraulic Gradient
Slope of GW table
Darcy’s Law Equation
Q=A x K x delta H/L
a-cross sectional area of flow
k-hydraulic conductivity
delta h-change in height
L-length
Darcy’s Law Definition
rate at which a fluid flows through a permeable medium
Seepage/ Average velocity
specific discharge/ effective porosity
