Geology Exam 4

Population Water resources Surface water Ground water

are population sizes similar among countries and continents

no

how do population distributions change over age groups

starts small, increases, then slowly decreases

carrying capacity

population size environment can sustain

logistic growth! “S” shape curve

linear population curve

constant slope

exponential population curve

increasing slope

geometric growth rate

increases in the size of the population depend on the population size

calculated using the 'compound interest formula'

linear growth rate

adding the same amount in each unit of time

y = mx + b

total fertility rate

average number of children a woman has over lifetime

replacement fertility rate

maintain a steady population size (zero growth)

ecological footprint

resources a person uses, can be considered as an area of land needed to produce these resources

how do humans alter the carrying capacity

migration, agriculture, medical advances, and communication

what is the current global population

8.1 billion people

projected carrying capacity of the Earth for humans

maybe 2, 9-10, 40, years no fixed number

what reservoirs contain the most fresh water

glacier ice !!

what reservoirs contain the most salt water

ocean

ocean residence time

3,200 years

glacier residence time

20 - 100 years

soil moisture shallow residence time

1 - 2 months

deep groundwater residence time

100 - 200 years

deepest groundwater residence time

10,000 years

lake residence time

50 - 100 years

river residence time

2 - 6 months

atmosphere residence time

9 days

river “off stream” uses

drinking water

river “on stream” uses

navigation through waterways

recreational boating and swimming

hydropower production

water balance equation

amount of precipitation compared to the water leaving the system as runoff or as evapotranspiration

mass of inflow - mass of outflow = change in stored mass

what/who is the biggest water user in the us

Thermoelectric power plants and irrigation

California

where does the largest portion of rainwater that falls on a drainage basin go

streams and rivers

what is a drainage basin

an area of land where water from rain or snow melt drains downhill into a body of water such as a river, lake, wetland or ocean

water budget

what is a drainage divide

water flowing on one side of a divide empties into one body of water, while water flowing on the other side empties into another

what direction does surface-water flow on a topographic map

downhill perpendicular to the contour lines

how do urban area’s impact recharge the subsurface

urbanization creates new pathways and sources of water for recharge, including leaking water pipes, sewers, septic tanks and irrigation

what are the advantages and disadvantages of the different sources of drinking water

groundwater well - close to user, filtered by geologic media, lower pumping rates, need recharge of water

surface water - requires distribution, exposed to surface contamination, soft, high pumping rates, low residence time

treated sea water - needs energy, expensive, generates wastewater

treated waste water

captured rain water

what factors impact runoff and infiltration(the velocity or speed at which water enters into the soil) rate

• relief/topography

• soil or rock type

• vegetation

• surface detention - portion of the storm rainfall that flows on the land surface toward the channel, but has not yet reached it

• storm intensity

laminar water flow

smooth parallel flow, no energy lost

turbulent water flow

chaotic flow, contains eddies(circular currents of water) that consume energy

hydrograph

discharge vs. time

identifies different hydrologic processes

recurrence interval

average time between events equal or greater than a discharge rate

based on rank of peak annual discharge rates

effects of urbanization on runoff and infiltration

less water infiltrates and more and more runs off

baseflow in channel of basin

water from long term (slow) sources - ground water, ponds, wetlands

storm-flow in channel of a basin

water to stream from a rain event

braided stream

contain intertwined channels flowing around sand and gravel bars

• steep slope

• high energy

• high competence (carry large particles)

• large width

meandering stream

curving path, erosion along outside bends, deposition on inside bends

• lower energy

• lower slope

• low competence (carry small particles)

• high capacity

form oxbow lakes, erosion causes river to break at the bend, making C shaped lakes

reasons for creating dams / consequences

• (+) flood control

• (+) energy production

• (+) drinking water source

• (-) restricts navigation and migration of organisms

• (-) sediment movement is impeded

• (-) increased erosion downstream

how do meandering streams evolve over time

erosion on the outside bend and deposition on the inside bend of a river, making C shaped lakes ‘oxbow lake’

how is river discharge determined

volume of water per time

measured using flow meter or engineered structure

stream competence vs capacity

stream competence - size of material stream can transport

stream capacity - mass of material a stream carries

bed load vs suspended load

bed load - sediment ‘pushed’ along bed of stream

suspended load - sediment that is carried by water

alluvium

sediment stream transports and deposits (clay, sand, silt)

levee

• raised river banks

• form naturally, sediments deposited along banks during flooding

• humans create/enlarge to protect flood plain

• increases downstream flooding

• traps water drain if overtapped

flood plain

an area of low-lying ground adjacent to a river, formed mainly of river sediments and subject to flooding

terrace

steep walls leading higher out of the valley

what is the purpose of retention ponds (ponds or pools designed with additional storage capacity)

to trap runoff from parking lots and roof tops to reduce peak flows in nearby streams

aquifer

capable of yielding significant/economic quantities of water

• unconfined aquifer - above is water table

• confined aquifer - above is aquitard

aquitard (confining unit)

impedes groundwater flow, horizontal layer between confined and unconfined aquifer

hydraulic head and its components

• the elevation of water in a tube open to the atmosphere

• three components - pressure, elevation, and velocity head

• measure of energy

• not needed in slow groundwater velocities

what direction does groundwater flow

• toward hydraulic heads

• toward pumping wells

• towards gaining stream (‘V’ angle)

• away from losing stream (‘V’ angle)

how does a pumping well impact groundwater levels

• produces a cone of depression

• water levels lowered

• altered aquifers may never fully recover

terms used to describe the different subsurface hydrolic zone and geologic units

1. water table

2. unconfined aquifer

3. aquitard

4. confined aquifer

Darcy’s law

an equation that describes the flow of a fluid through a porous medium

Q = -K x A h/l

Q = total discharge

K = hydraulic conductivity

H = hydraulic head

L = distance in direction of flow

spring water (FDA criteria)

water derived from an underground formation from which water flows naturally to surface of the earth

different classes of subsurface water

• meteoric - infiltrated from precipitation

• connate - water trapped in sediments during deposition

• juvenile - ‘new’ water, from interior of earth

• magmatic - cycled through igneous rocks

are groundwater and surface water related

yes!!!!!!!!!!!!!

what is the amount of pore space in a material called

POROSITY