Snow Hydrology - Glacier Hydrology Flashcards
What is a short-term benefit, and problem with glacial melt increases?
- Hydroelectric power
- Problem: What happens when the ice is gone, where will power come from? It is temporary.
Accumulation Mechanisms?
- Low subzero temperatures
- Precip that falls as snow
- Higher latitudes/altitudes
Ablation Mechanisms?
- Rain
- Melting
- Sublimation (enhanced by wind)
- Calving
- High Temperatures (lower latitudes/altitudes, near toe of glacier)
What is is a technique for finding rate of flow of a glacial stream?
- Dye tracing to find rate of flow from injection to terminus or outlet
What is the likely cause of supra glacial streams?
- Insolation at the surface of a glacier causing melt
What are 5 sources of water in a glacier?
- Ice melt
- Snow melt
- Rainfall
- Runoff from ice-free slopes
- Release of stored water
What are the primary permeabilities in glaciers?
- Intact ice and snow
- High for snow and firn (linked pore spaces)
- Very low permeability for ice
What are the secondary permeabilities in glaciers?
- Tunnels and passage ways (mm -m’s large)
- Most water drains through glaciers
Supra glacial water flow
- Surface of glacier
- Streams, lakes, the ‘snow aquifer’
Englacial water flow
- Inside the glacier
- Crevasses, Moulins, Fractures
- Stream channel network through/within glacier
Subglacial water flow
- Channels, Cavities, Sheets, Canals
- Underneath the glacier
- Under Pressure, may have artesian flow if tapped by a well
- Pressure may be higher in spring with increased melt and not enough spaces for water to flow
- Groundwater, mixture of pathways through the ice and the bed
How does meltwater enter the glacier system?
- Glacier ice is essentially impermeable
- So enters through moulins, crevasses, through-going fractures
What does the drainage of surface streams depend on?
- Potential depends on elevation
What does the drainage of basal streams depend on?
- Potential depends on elevation and pressure
How is direction of flow determined in a glacier?
Flow is determined by hydraulic potential and equipotential lines determined by ice thickness and underlying topography slope
- Flows to glacier snout at right angles to equipotential lines
How does subglacial drainage respond to the seasons?
- Shuts down in winter with little supply from the surface
- Ponds in lakes/cavities through winter and spring
- Bed is flooded in summer and channels form that melt through ice and flow to nearest exit on side or terminus
What marks the transition between distributed and channelized drainage?
- The equilibrium line altitude (snowline)
Distributed subglacial drainage system
- Series of linked cavities
- fed mainly by snowmelt
- slow transit
Conduit subglacial drainage system
- Rapid transit
- Fed by ice melt and distributed system
When does snow accumulate usually?
September to May
- Some ongoing groundwater drainage through fall
When does snow melt usually?
May through June
- Some runoff, mostly water storage due to poorly developed drainage system
- Some proglacial streams develop
When does intensified snow and ice melt happen usually?
July through August
- Well developed drainage
- Proglacial streams in full flow, peak discharge
- Meltwater throughput time ~ hours
Why is it important to know when peak output for a glacier will be?
- To manage water resources, especially in dry areas that rely on short period of glacial output
What percent of western Canadian glaciers have been lost over the last 20 years?
11%
What are glacier impacts on catchment runoff?
- Important in dry places where they act as natural reservoirs and release in late summer for a short period
- Can store water for decades to centuries and help buffer/regulate streamflow
- Significant in alpine regions where they contribute the most to summer flow
How can climate change affect glaciers?
- Amount of precip won’t change but type will (more rain, less snow)
- Changes time melt/runoff would be expected
- Storage decrease in snow and ice
