Heath.1 Flashcards
Hydrosphere
The term used to refer to the waters of the Earth and, in its broadest usage, includes all water, water vapor, and ice regardless of whether they occur beneath, on, or above the Earth’s surface.
Unconsolidated Deposits
Material derived from the disintegration of consolidated rocks.
Types of unconsolidated deposits (in order of increasing grain size):
Clay, Silt, Sand, Gravel
Consolidated Rocks
Rocks that consist of mineral particles of different sizes and shapes that have been welded by heat and pressure or by chemical reactions into a solid mass.
Bedrock
A really squishy term that in hydrologic circles refers to the layer of consolidated rock that underlies the surface layer/s of unconsolidated deposits.
Primary Openings
Voids existing within any rock structure that formed at the same time that the rock itself. Think pore structure in sand, gravel, etc. Even a lava-tube would be considered a primary opening.
Secondary Openings
Voids in a rock structure that form after the rock itself was formed. Think cracks in granite or the cavern systems within limestone.
Semi-consolidated Rocks
Rocks in which openings include both pores and fractures (both primary and secondary openings).
Unsaturated Zone
The region immediately below the earth’s surface (in any given area) that contains both water and air in its primary and secondary openings.
Regions of the Unsaturated Zone (top-down)
Soil zone, intermediate zone, capillary fringe (upper part).
Saturated Zone
Sub-surface region, below the unsaturated zone in which all of the interconnected primary and secondary openings have filled with water (no-air).
aka-Ground water
Water Table (simple definition)
Basically the dividing line between the saturated and unsaturated zones.
Water Table (technical definition)
The level in the saturated zone at which the hydraulic pressure is equal to atmospheric pressure. Represented by the water level in an unused well (no cone of depression).
Hydrologic Cycle
The constant (cyclical-ish) movement of water above, on, and below the Earth’s surface.
Parts of the Hydrologic Cycle
Evaporation, Transportation (via clouds), Precipitation, Infiltration/Runoff, Groundwater Movement/Overland Flow.
Biology complicates things here…
Infiltration
The absorption/movement of precipitated water down below the earth’s surface under the force of gravity (and capillary action).
Overland Flow
Surface movement of the precipitated water that falls in excess of the ground’s infiltration rate.
Aquifer
A rock unit that will yield water in a usable quantity to a well or a spring.
Confining Bed
A rock unit that having very low hydraulic conductivity that restricts the movement of ground water either into or out of adjacent aquifers.
Unconfined Aquifer
An aquifer in which the upper surface of the saturated zone is free to rise or fall without restriction. Most often located between the Earth’s surface and the first confining bed.
Confined Aquifer
An aquifer that is bounded by confining beds from both above and below.
aka-Artesian Aquifer
Water-Table Well
A well drilled down into an unconfined aquifer.
Artesian Well
A well drilled down into an unconfined aquifer.
Potentiometric Surface
The level of the water in a tightly-cased artesian well. Generally rises above the level of the top of the aquifer due to the pressure exerted on the water within the aquifer by the weight of the overlying rock.
Flowing Artesian Well
A well drilled down into an artesian well which has a potentiometric surface that is higher than the level of the ground at the top of the well. Thus the water coming out from the well flows out onto the surface of the Earth.
Porosity
The ratio of openings (voids) to the total volume of a sample of soil or rock.
Porosity Equation
n=(Vt-Vs)/Vt
n=Vv/Vt
n is porosity
Vt is the total volume of sample
Vs is the volume of the solids in a sample
Vv is the volume of the voids in a sample
Specific Yield
That portion of the water contained in a sample that will drain out under the force of gravity.
Specific Retention
The volume of water that remains within the voids of a sample (due to surface film cohesion and capillary action) after gravity drains the specific yield.
Relationship between porosity, specific yield, and specific retention
n=Sy+Sr
n is porosity
Sy is specific yield
Sr is specific retention
Equation for Specific Yield
Sy= Vd/Vt
Sy is specific yield
Vd is the volume of water that drains under the force of gravity
Vt is the total volume of the sample
Equation for Specific Retention
Sr=Vr/Vt
Sr is the specific retention
Vr is the volume of water retained in a sample after water is drained under force of gravity
Vt is the total volume of the sample
Vertical Datum of 1929
aka-Sea Level
Total Head
The depth to water in a non-flowing well subtracted from a specific measurement point (or datum plane, such as sea-level).
Components of a Total Head
Ht=z+Hp+Hv
Ht is the total head
z is the elevation head
Hp is the pressure head
Hv is the velocity head (functionally zero when dealing with ground-water, and thus typically ignored
Elevation Head
Distance from the bottom of a drilled well to a given datum plane (usually sea-level)
Pressure Head
Distance from the bottom of a well to the surface of the water in that well (aka-water table/potentiometric surface)
Head Loss
The decrease in the total head between two different wells drilled into the same aquifer.
Hydraulic Gradient
The change in the total head per unit distance in a given direction between wells in a given aquifer (hL/L).
Frequently given in inconsistent units such as m/km.
Hydraulic Conductivity
The quantity of ground water that moves through a given unit of aquifer per unit time. Expressed through “Darcy’s Law.”
Depends on the size and arrangement of the water-transmitting openings, and on the fluid dynamics of the water (kinematic viscosity, density, and the strength of the gravitational field).
Darcy’s Law
Q=KA (dh/dl)
Q is the quantity of water per unit time
K is the hydraulic conductivity of the sample
(dh/dl) is the hydraulic gradient
Darcy’s Law (rearranged as a definition of Hydraulic Conductivity)
K= (Qdl/Adh)= (m^3 d^-1)(m)/(m^2m) = m/d
Thus units of hydraulic conductivity are those of velocity: distance divided by time.
Isotropic Hydraulic Conductivity (K)
The situation in which the hydraulic conductivity is essentially the same in all directions within a given region of an aquifer.
Anisotropic Hydraulic Conductivity
That situation in which the hydraulic conductivity of an aquifer is different in different directions.
Ground-water Hydrology
A subdivision of the science of hydrology that deals with the occurrence, movement, and quality of water beneath the Earth’s surface.
