STREAMS + GROUNDWATER

Question 1

• Explain the hydrologic cycle

Answer 1

o Evaporation due to heat  rising vapour cools and molecules combine forming clouds,  condensation  precipitation
 Fresh water
* 69% is frozen
 Total water
* 97% salt water

Question 2

• The rock cycle

Answer 2

o Melting of magma  crystallization of magma  igneous rock  weathering of rock at surface  erosion and transport  deposition of sediment  burial and compaction  sedimentary rock  deformation and metamorphism  metamorphic rock  melting

Question 3

streams work depending on

Answer 3

 Discharge – Q(m3/s)
 Velocity – V (m/s)
 Area – A9m2)
* Q=VxA

Question 4

o How do streams erode

Answer 4

 Dissolution
 Hydraulic fracturing
 Abrasion

Question 5

o Transport material

Answer 5

 Dissolved loas
 Suspended road
 Bed load

Question 6

o Get energy

Answer 6

 From slope and discharge
* A= “graded” (equilibrium) stream profile = base level
 Stream gradient (m/km or ft/mile) varies along profile

Question 7

o Excess energy stream: Erosion > deposition

Answer 7

 High energy stream carrying lots of load- cuts vertically into landscape
 Unstable material collapse into stream, increasing load and erosive power. V shaped stream forms
 With time river beings to erode valley walls and widen the valley
 Youthful downcutting stream, V-shaped valley

Question 8

o Balanced energy stream: erosion= deposition

Answer 8

 Starts as a youthful downcutting stream
 Floodplains and natural levees
 Cuts banks and point bars indicate lateral erosion

Question 9

o Variations in stream velocity

Answer 9

 Max velocity near outside edge of meanders
 Slower near gradual curve due to sediments and lower

Question 10

o How do streams meander

Answer 10

 Cut off meanders
 Oxbow lakes

Question 11

o Deficient energy stream

Answer 11

 High energy streams exit the steep mountains and loose energy. They no longer can carry the load they have so they repidily deposit largest gain sizes. Briades rivers of channels
 At its base level, a stream loses all capacity to carry loa- and depsots everything, forming an alluvial fan or delta (ex: Fraser river)

Question 12

• Understand how rejuvenation works

Answer 12

o Tectonic influence of stream = rejuvenation
o Rejuvenation (due to chage is base level)  excess energy … leads to downcutting, stream terraces
 Ex- incised meanders, UT
 Stream terrace sets, MT

Question 13

o Porosity :

Answer 13

amount of open space in a rock
 Depends on grain size, sorting
 Primary porosity- present when a rock forms
* Eg. Gravel  conglomerate, sand  sandstone, clay  shale

Question 14

o What controls the movement of groundwater through rock

Answer 14

 Joints, fractures
 Permeability: ]

Question 15

Permeability

Answer 15

Permeability: the ability of a rock to transmit water  depends on pore size and connection between pores eg sandstone and mudstone

Question 16

porosity v permeability

Answer 16

 Solid rock have more hydraulic conductivity and less porosity
 Unconsolidated rocks have less hydraulic conductivity and more porosity

Question 17

o Surface tension and permeability

Answer 17

 Hygroscopic= absorbed water (the particles are wet
 Capillary water= held to the particles by surface tension
 Gravitational water= flws downwards under the influence of gravity

Question 18

o Sandstone vs mudstone

Answer 18

 Grains are well rounded, well sorted  both have high porosiy but mudstone has a low permeability
 Surface tension causes water to stick to the surfaces of grains, so it will only flow through the larger, interconnected pores

Question 19

o Soil deposit

Answer 19

 Most water is free to move

Question 20

clay deposit

Answer 20

most of the water is unable to move

Question 21

o Aquifer:

Answer 21

a body of permeable rock or sediment, saturated with groundwater and through which groundwater moves
 Eg. Sand, gravel, sandstone, limestone (in humid climates only)

Question 22

o Aquitard

Answer 22

rock or sediments that makes a poor aquifer (not permeable)
 Eg. Mudstone, shale, most igneous and metamorphic rocks

Question 23

o Water table:

Answer 23

level below which rock or sediment is saturated with water
 Mimics
* Topography
 Level varies with the season
 Perched water tables create springs

Question 24

• Groundwater

Answer 24

o Flow is from high elevation to low elevation and from high pressure to low pressure
o Rate of flow depends on porosity and permeability
o Seasonal variations

Question 25

• Groundwater extraction

Answer 25

o Controlled by permeability
 Water moving towards the well horizontally
o Controlled by secondary porosity
 Water moving in diagonal lines
o Effect of pumping
 Non-pumped well
* Close small well as still useable
* Existing water table
 Pumped well
* Cone of depression
* Close small wells are dry

Question 26

• What is an artesian system

Answer 26

o Concept of a confined aquifer (in a heterogeneous sedimentary rocks)
 Artisan wells: flows without pumping
* Water rises to elevation
* Large water table under the confining table (sits above the confined aquifer
o Confined aquifer is bounded above and below by impermeable layers
o Aquiclude is an impermeable body of rock
o An artesian aquifer is a confined aquifer containing groundwater that will flow upward through a well without the need for pumping
 They are under the pressure of their own weight, so water is forces upward without the need for pumping

Question 27

• Groundwater interaction with streamflow

Answer 27

o Humid climate- effluent conditions
 The water table is higher than the stream channel so water flows out from the surrounding ground into the stream
o Dry climate- influent conditions
 The water table is lower than the stream channel so the stream’s water flows into groundwater

Question 28

• Groundwater emerging at the surface

Answer 28

o Springs- Groundwater moves from areas of higher pressure and elevation toward areas of lower pressure and elevation
o Hot springs in BC are formed by water in the mountains percolating downwards along fractures and heating up below the surface, becoming pressurized and moving along faults

Question 29

• Groundwaters geological activity

Answer 29

o Cementation
 Eg. Sand vs sandstone
o Replacement
 Petrified wood (opal SiO2- nH2O)
o Solution of carbonate rock in humid climates
 Caves, karst

Question 30

• Groundwater as a reaource

Answer 30

o A natural resource is something that exists without any action of humankind and can be used by individual or industry

Question 31

 Factor to consider it a renewable resource

Answer 31

time scale and supply and demand

Question 32

time scale

Answer 32

o Recharge area- the ground surface where water soaks into he ground
o Discharge area- where the water table is at the ground surface and water flows out of the ground

Question 33

supply and demand

Answer 33

o Lower water table  deeper wells, more $$
o Land subsidence  flooding, structural damage
o Loss of recharge area due to urbanization
o Saltwater intrusion
o Pollution- toxic waste, sewage, pesticides, herbicides, fertilizer, heat
o Cleanup- Sewage—bacterial cleanup depends on porosity, permeability, distance
 Behaviours of pollutants depend on
* Porosity and permeability of aquifer rocks
* Underground structure
* Density/chem comp. of the pollutants