L13: Hydrologic Cycle Flashcards
Define polar
More negative charge near the oxygen, more positive near the hydrogen
How is the water molecule formed
Formed by the covalent bond of 2 hydrogens to an oxygen; bent molecule at 104.5 angle
Phases of water
Ice, water vapour, liquid water
Transitions between phases _______ or _______ energy
- Absorb
- Release
When is energy absorbed by water?
While going from a more ordered to a less ordered phase
Properties of liquid water
- Polarity makes water an excellent solvent for ionic and polar substances, including many minerals
- Polarity causes water molecules to form hydrogen bonds with other water molecules in a solution; this is how it achieves high surface tension
How do water molecules achieve high surface tension?
Polarity causes water molecules to form hydrogen bonds with other water molecules in a solution
Properties of ice
- Ice is a mineral
- Expands as it freezes; ice has an open crystal lattice, which causes it to have a lower density than liquid water
Mineral properties
Fixed composition Defined structure Inorganic Naturally occurring Solid
What are some consequences of ice properties?
Ice is able to float in liquid water; expansion of freezing water can cause physical weathering (ex. The fracturing of rocks
Define hydrologic reservoirs
- Places in the water cycle where water is stored
Ex. Oceans, the atmosphere, lakes, rivers, etc.
Freshwater
- Useful for consumption and agriculture; 2.5% of all water on earth
- Of this, 75% is locked in ice
Where does water reside on the earth
Notebook
Define residence time
The average amount of time that a water molecule stays in a particular reservoir
Surface water bodies
- Lakes, rivers, wetlands
- Less than 0.01% total water on Earth
Define flux
- The rate at which water moves between reservoirs
- Earths reservoirs have hugely different reservoir times; check in notebook
Define hydrologic balance
Reservoir sizes, residence times, and fluxes combined
How does water flow at the surface?
- Overland flow
- Stream flow
Overland flow
- The initial sheet-like movement of water downhill with gravity
- Ex. Some of the rainfall and meltwater on the landscape begin to flow across the surface once the soil is saturated
Stream flow
- Once the flow of water occurs in an established channel
- Overland flow becomes channelized due to erosion, typically over relatively short distances
What are the 2 major sources of the flow of water in streams
- Overland flow contributions
2. Baseflow
Baseflow
The input of groundwater through the bed of a river, contributing to its flow
Streams are organized into _________
River systems
Define tributaries
Small streams; typically merge downstream
Define drainage basin
Area drained by a major river and its tributaries
How are drainage basins separated?
- By drainage divides
- Topographic highs (ex. Continental divides) typically separate water drainage basins that flow into different oceans
What is river behaviour controlled by?
- Width/depth of the channel: Both increase downstream as tributaries join
- Channel gradient: Or the steepness of the channel decreases downstream
- Average velocity: The average speed of the water in the channel increases downstream
- Discharge: The flux of water moving through the river at any given point, increases downstream
River behaviour properties change along the channel as . . .
We go from headwaters (upstream) to the mouth (downstream)
Discharge
- Determined by calculating the cross-sectional area of a river
- Notes
Why are river systems important?
- Important in physical erosion and weathering, as well as global transport routes for:
- Dissolved ions in solution
- Suspended sediments
- The bed load of a stream or a river - Intimately tied to the four physical properties
What is a dissolved load?
Major ions in rivers; primarily come from the dissolution of minerals
Suspended load
- Compromised of particulate matter (ex. clays) that remains in suspension in a river or stream
- Smaller particles settle more slowly than larger ones and so are transported farther
- Water often appears cloudy and opaque due to suspended load
Bed load
Compromised of the typically larger particle in a river system that are transported by moving along the bed
Hydrographs
A record of river discharge at one point in the river continuously over many years
What are particles in the bed load able to do?
- Roll: Rotate along the bed without leaving it
- Slide: Move along the bed without leaving it
- Move by saltation: Hopping along the bed, leaving it for short periods of time
Short periods of ______________ in a river, often cause most of the ______ transport over a year
- High discharge
- mass
Trends in the river mass transport
Notebook
How do we calculate discharge?
Width x depth x velocity of water
Faster flow = moves _______ particles
Larger
