Exam 1 Flashcards
What is the Fresh Water Conundrum?
- Fresh water is plentiful and cheap in many places
- But very difficult and expensive to move to places that need it most
Where is Earth’s water?
3% Fresh water
97% Saline (ocean)
Where is earths freshwater?
- 30% ground water
- 68% icecaps and glaciers
- .3% surface water (most of this is lakes)
How much of the worlds water is available for human use?
0.3%
How much water is needed per yearh for food, industries and the environment?
1,700m^3
1.7 million liters per person
Where is the worlds freshwater located?
- 60% is in the Amazon and Congo rivers
- 8% of Canada is lake
How often is atmospheric water recycled?
- 40x per year
- every 9 days
What is the catchment water budget?
a function of the hydrological cycle and watershed characteristics
Conservation of mass
• The time rate of change of mass stored within the
control volume equals the difference between the
inflow rate and the outflow rate
-=inflow’-outflow’
main components of hydrologic cycle
- precipitation
- ET
- Runoff
- Storage
Catchment water budget equation
P+G(in)-(RO+ET+G(out))=(delta)S
- Delta S is change in groundwater storage
- Through rearranging, P-ET=RO
- RO is what’s available for human consumption
How is runoff generated?
- when rainfall rate is greater than infiltration rate
- precipitation that can’t infiltrate becomes runoff
Hydrologic connectivity during dry season
-streams fed mainly by groundwater (hyphoreic)
Hydrologic connectivity during wet season
-tributary and mainstem runoff dominates streamflow
In what ways can runoff be measured
- Instantaneous discharge rate (units of V/t
- catchment annual water yield (units of Volume)
- Catchment-average depth (units of length)
For budgeting, water is most often meaured in units of _____
depth, (mm, cm, in)
V/A=D
The water year
- Surface water supple calculations
- from Oct 1 to Sept 30
- named based on the year the water year ends
Why is october the start of the water year
-Water inputs (P) exceed loss to evaporation (ET)
Precipitation supply depends on:
- Air mass circulation patterns
- Distance and direction from large water bodies
- Location with respect to mountains
- Altitude
______ is a major climate driver
Topography
When does precipitation occur
-when an air mass is lifted, becomes colled, and reaches saturation vapor pressure
Potential Evapotranspiration (PET)
- the amount of water that would be evaporated and transpired if there were sufficient water available
- Is higher in summer
- Occurs most where ET is high demand (southwest US)
Where does actual ET occur
-where it is hot and wet
When P>ET there is a
- surplus
- divide between surplus and deficit at 100 longitude
When P
deficit
-divide between surplus and deficit at 100 longitude
John Wesley Powell’s vision
- settlement denisty and land claim size should follow water supplies
- Stressed self-reliance, farmers should spend their money and not the gov’s on dams and canals for water
- Use of water tied to the land, no selling of water rights to distant entities
Flow Regime
- largely a reflection of climate
- integrates rainfall magnitude, amount and timing of ET, and snowfall
5 Characteristics of flow regime
- Magnitude of discharge
- Frequency of events
- Duration
- Timing
- Rate of change
What is the driver of flow regimes?
-Precipitation
Flow regime equation
-Q=P-ET+(delta)S
Exceedance probability
-the chance that an event of specified magnitude will be equaled or exceeded in any defined period of time, on average
Lag time on storm hydrograph
-time between peak precip and peak Q
Fluvial
– processes associated with rivers and
streams and the deposits and landforms created by them
Geomorphology
-scientific study of landforms and the processes that shape them
Factors affecting erosion and transport of sediment from land surfaces
- Wind, temp, rainfall runoff
- Soil character
- Topography
- Soil cover
What is a process domain
- predictable areas of a landscape within which distinct suites of geomorphic processes govern habitat type, structure, and dynamics
- Help us understand linkages between geomorphic processes and ecosystems
The Catchment-Channel Conveyor Belt
-dominant catachment zones of erosion, transport, and depostion
Basic geomorphic processes (erosion, transport, deposition) maintain a ____
- dynamic equilibrium
- over long time scales, the net effect is to transfer sediments from upslope areas to downstream areas
Erosion or deposition depend on:
-balance between sediment supply and sediment transport capacity
1) Capacity > load: __
2) Capacity < load:__
3) Capacity = load: __
1) Erosion
2) Deposition
3) no net erosion/deposition
Erosion
- dominant process in upper reaches of streams
- Occurs in 3 dimensions in stream channels (headward, lateral, and vertical erosion
Luna Leopold
- father of modern fluvial geomorphology
- defined common measures of stream dimensions
- Sinuosity (channel length/downvalley distance)
Equation for discharge
Q = WDV
Bankfull discharge
- discharge of a river which is just cnontained within the banks
- Max velocity in channel, max potential for transporting sediment
- in many streams, this represents the approx annual discharge
Some indicators of bankfull stage
- deposits of sand or silt at active scour mark
- top of point bars
- Changes in vegetation type
- topographic break in streambank slope
Effective discharge (ED) =
Freq*magnitude
What do we need to do to classify streams?
1) Collect empirical data about streams
2) select appropriate classification variables
3) Group samples into homogenous units
4) test the methodology on new data to verify if the method works
Quantifying a catchments sediment sources
- identify colluvial and fluvial sediment sources
- Estimate depth and extent of sediment storage pools
- Estimate fluxes out of basin
Measuring surface erosion
- Erosion plots
- Erosion stakes
- Reservoir surveys
- Tracers
What is a watershed
-an area of land that drains water,
sediment and dissolved materials to a common receiving body or outlet. It includes interactions with subsurface water.
Watershed ecology:
-the study of watershed as ecosystems (interacting abiotic and biotic components within watershed boundary)
Ecotone (ecosystem boundaries)
- determined by cycles and flux of energy, materials and organisms
- a boundary ecosystem, a transition zone between 2 adjacent systems
Floodway
-the channel of a river/stream, plus the adjacent land needed to carry away floodwaters
Floodplain
-a broader area surrounding the floodway, is inudated during a storm that has a ____% chance of occuring any given year
Geomorphic floodplains
- Functional systems that move water, sediment and organic material across the landscape
- defined by network of channels, land surfaces, and groundwater
Ecological floodplains
-Lowland ecosystems strongly shaped by river
hydrology and geomorphology
-hotspots of high biodiversity and ecosystem function
Hydrologic floodplains
-surfaces inundated with a defined flood recurrence interval
Catchment hydrology
- the science of water as it relates to the hydrologic cycle
- 3 states, solid, liquid, gas
Weather vs climate
- weather: air temp, clouds, precip, wind, etc
- climate: 30 yr average weather
Where does a channel network start?
-at the threshold where runoff becomes responsible for sediment transport
4 dimensions of a watershed
- Longitudinal connectivity
- Lateral
- Vertical
- Temporal
Channel drainage patterns are formed by :
underlying bedrock and tectonic history
Channel avulsion
- sudden change in alignment
- occurs over decades to centuries
- leaves complex landscape features
Long-term channel/network patterns
- Alluvial fans, constantly changing, eroding
- Mississippi river delta, formed over 700 years ago and is still evolving
Some watershed functions and services
- natural flood and erosion control
- water supply and quantity
- fish and wildlife habitats
The Anthropocene
A proposed epoch dating from
the start of significant human impact on the Earth’s geology
and ecosystems, including but
not limited to climate change.
What triggered the great acceleration
- the end of WW2
- inspired advnaces in engineering, aerospace, medicine, etc
Challenges to water management
- political and watershed boundaries rarely match
- acute stressors (droughts, floods, poor land use)
- persistant stressors (nonpoint source pollution, invasive species)
How do we deal with cumulative watershed impacts?
- must take a whole-watershed approach
- adaptive management
- understand how watershed processes interact to influence water quantity and quality
Some watershed management challenges
- water supply and quantity
- drinking water quality
- point source pollution
- nonpoint sources
- flood risk to people/infrastructure
- land use changes
- impacts from energy production
