STREAMS + GROUNDWATER Flashcards
- Explain the hydrologic cycle
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
- The rock cycle
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
streams work depending on
Discharge – Q(m3/s)
Velocity – V (m/s)
Area – A9m2)
* Q=VxA
o How do streams erode
Dissolution
Hydraulic fracturing
Abrasion
o Transport material
Dissolved loas
Suspended road
Bed load
o Get energy
From slope and discharge
* A= “graded” (equilibrium) stream profile = base level
Stream gradient (m/km or ft/mile) varies along profile
o Excess energy stream: Erosion > deposition
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
o Balanced energy stream: erosion= deposition
Starts as a youthful downcutting stream
Floodplains and natural levees
Cuts banks and point bars indicate lateral erosion
o Variations in stream velocity
Max velocity near outside edge of meanders
Slower near gradual curve due to sediments and lower
o How do streams meander
Cut off meanders
Oxbow lakes
o Deficient energy stream
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)
- Understand how rejuvenation works
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
o Porosity :
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
o What controls the movement of groundwater through rock
Joints, fractures
Permeability: ]
Permeability
Permeability: the ability of a rock to transmit water depends on pore size and connection between pores eg sandstone and mudstone
porosity v permeability
Solid rock have more hydraulic conductivity and less porosity
Unconsolidated rocks have less hydraulic conductivity and more porosity
o Surface tension and permeability
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
o Sandstone vs mudstone
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
o Soil deposit
Most water is free to move
clay deposit
most of the water is unable to move
o Aquifer:
a body of permeable rock or sediment, saturated with groundwater and through which groundwater moves
Eg. Sand, gravel, sandstone, limestone (in humid climates only)
o Aquitard
rock or sediments that makes a poor aquifer (not permeable)
Eg. Mudstone, shale, most igneous and metamorphic rocks
o Water table:
level below which rock or sediment is saturated with water
Mimics
* Topography
Level varies with the season
Perched water tables create springs
- Groundwater
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
- Groundwater extraction
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
- What is an artesian system
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
- Groundwater interaction with streamflow
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
- Groundwater emerging at the surface
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
- Groundwaters geological activity
o Cementation
Eg. Sand vs sandstone
o Replacement
Petrified wood (opal SiO2- nH2O)
o Solution of carbonate rock in humid climates
Caves, karst
- Groundwater as a reaource
o A natural resource is something that exists without any action of humankind and can be used by individual or industry
Factor to consider it a renewable resource
time scale and supply and demand
time scale
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
supply and demand
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
