10. Hydrology of Canada and environmental change Flashcards
Problem for agriculture in wet agricultural regions (Quebec, Ontario, prairies)
High water tables
Why are high water tables a problem for agricuture?
- soils are too wet for heavy machinery
- excess water induces crop / plant stress
Solution to high water tables
Tile drainage
- it is a form of agricultural drainage system that removes excess sub-surface water from fields to allow sufficient air space within the soil, proper cultivation, and access by heavy machinery to tend and harvest crops.
- it is an extra flow pathway
- it decreases the likelihood of SSSF and SOF
- it decreases groundwater recharge
- it can enhance nutrient export to streams
Perculiarities of FLAT agricultural regions (prairies) (5)
- flat topography
- winter dynamics
- soils of variable depth
- fractured bedrock
- man made drains and diversions
Permafrost
Permafrost is ground that remains at or below 0°C for at least two consecutive years
Active layer
The active layer is the layer of soil above permafrost which freezes and thaws seasonally
Wetlands
Wetlands are lands that are seasonally or permanently covered by shallow water, including lands where the water table is at or close to the surface
Five types of wetlands
- marshes
- swamps
- bogs
- fens
- shallow open waters
What are fens and bogs
Peatlands
What are peatlands
Peatlands are terrestrial wetland ecosystems in which waterlogged conditions prevent plant material from fully decomposing
Fens
Fens are minerotrophic, ie, they receive their water and nutrients primarily from surface water flowing overland or groundwater flowing though mineral rich soils and rocks
Bogs
Bogs are ombrotrophic, ie they receive their water and nutrients only from precipitation
What are more nutrient rich, bogs or fens?
Fens
How are peat profiles divided?
into two layers: the acrotelm, and the catotelm
Acrotelm
Upper layer, contains living and dead plant material
Catotelm
Lower layer, contains dead plant material
Why does peat accumulate?
The presence of water creates anoxic conditions that limits the rate of decomposition
Consequences of peat accumulation (3)
- Plants that grow on peatlands tend to be less favorable to decomposition
- As peat accumulates, it creates its own aquifer and topography on the landscape
- The profile of decomposition creates a vertical pattern of subsurface hydraulic properties
Pothole wetland characteristics (7)
- subject to high and low temperatures (+40 and -40)
- can be subject to long periods of drought as well as deluges
- negative water balance (ET > P)
- periodically go dry
- freeze in the winter
- exhibit steep salinity gradients
- are geographically isolated from streams ( they are surround by uplands and do not have surface channelized connection to other water bodies)
Importance of pothole wetlands (4)
Ecosystem services:
- floodwater retention
- water quality improvement
- carbon sequestration
- biodiversity islands and corridors
Effects of deforestation on hydrology (3)
- decrease in ET
- decrease in infiltration
- increase in runoff
Effects of urbanization on hydrology (3)
- amplified fast runoff
- chemical and thermal pollution
- phosphorus pollution
Effects of agriculture on hydrology (4)
- irrigation can change water balance
- tile drainage modifies dominant runoff generation
- export of nutrients and pollutants
- runoff increases and worsening water quality with wetland drainage
Expected effects of temperature changes on hydrology (5)
- increase in potential evaporation (→ less runoff)
- smaller proportion of precipitation falls as snow
- earlier snow melt
- reduced freezing of lakes and rivers, earlier ice break-up
- increased melting of glaciers and permafrost
Expected effects of precipitation changes (↑) on hydrology (5)
- more runoff, but with strong temporal and regional differences
- complex change in magnitude, duration, variability, and frequency of flow events
- more extreme precipitation events will affect the dominant runoff generation processes
NELSON-CHURCHILL RIVER BASIN:
Increasing temperatures impacts (8)
- earlier snow melt
- glacier ablation
- near future: larger amounts of meltwater will feed river flows during the summer
- long term: high temperatures → less snowfall → melt → new snowfall → glacier retreat and disappearance
- permafrost melt → change subsurface flow dynamics and groundwater storage
- earlier snowmelt → changes river flow regimes and flood patterns
- vegetation stress → modify ET rates
- higher energy demand → river harnessing → threat to ecological flows
NELSON-CHURCHILL RIVER BASIN:
Low precipitation impacts (7)
- high evapotranspiration
- large abstractions → a lot of precipitation water does not reach streams
- rainfall mostly delivered through convective summer storms → HOF dominates
- more extreme droughts
- lower soil water and groundwater storage → crop failures
- mixture of convective and frontal storm systems
- climate change induced eutrophication
NELSON-CHURCHILL RIVER BASIN:
Impacts on wetlands and lakes (2)
- high ET → shrinkage of lakes / wetlands
- smaller wetlands can be permanently lost
NELSON-CHURCHILL RIVER BASIN:
Impacts of urban areas (2)
- Irrigation → threat to ecological flows
- existing water reservoirs will be less sustainable bc of high evap
