10. Hydrology of Canada and environmental change

Question 1

Problem for agriculture in wet agricultural regions (Quebec, Ontario, prairies)

Answer 1

High water tables

Question 2

Why are high water tables a problem for agricuture?

Answer 2

• soils are too wet for heavy machinery
• excess water induces crop / plant stress

Question 3

Solution to high water tables

Answer 3

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

Question 4

Perculiarities of FLAT agricultural regions (prairies) (5)

Answer 4

• flat topography
• winter dynamics
• soils of variable depth
• fractured bedrock
• man made drains and diversions

Question 5

Permafrost

Answer 5

Permafrost is ground that remains at or below 0°C for at least two consecutive years

Question 6

Active layer

Answer 6

The active layer is the layer of soil above permafrost which freezes and thaws seasonally

Question 7

Wetlands

Answer 7

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

Question 8

Five types of wetlands

Answer 8

• marshes
• swamps
• bogs
• fens
• shallow open waters

Question 9

What are fens and bogs

Answer 9

Peatlands

Question 10

What are peatlands

Answer 10

Peatlands are terrestrial wetland ecosystems in which waterlogged conditions prevent plant material from fully decomposing

Question 11

Fens

Answer 11

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

Question 12

Bogs

Answer 12

Bogs are ombrotrophic, ie they receive their water and nutrients only from precipitation

Question 13

What are more nutrient rich, bogs or fens?

Answer 13

Fens

Question 14

How are peat profiles divided?

Answer 14

into two layers: the acrotelm, and the catotelm

Question 15

Acrotelm

Answer 15

Upper layer, contains living and dead plant material

Question 16

Catotelm

Answer 16

Lower layer, contains dead plant material

Question 17

Why does peat accumulate?

Answer 17

The presence of water creates anoxic conditions that limits the rate of decomposition

Question 18

Consequences of peat accumulation (3)

Answer 18

• 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

Question 19

Pothole wetland characteristics (7)

Answer 19

• 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)

Question 20

Importance of pothole wetlands (4)

Answer 20

Ecosystem services:
- floodwater retention
- water quality improvement
- carbon sequestration
- biodiversity islands and corridors

Question 21

Effects of deforestation on hydrology (3)

Answer 21

• decrease in ET
• decrease in infiltration
• increase in runoff

Question 22

Effects of urbanization on hydrology (3)

Answer 22

• amplified fast runoff
• chemical and thermal pollution
• phosphorus pollution

Question 23

Effects of agriculture on hydrology (4)

Answer 23

• 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

Question 24

Expected effects of temperature changes on hydrology (5)

Answer 24

• 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

Question 25

Expected effects of precipitation changes (↑) on hydrology (5)

Answer 25

• 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

Question 26

NELSON-CHURCHILL RIVER BASIN:
Increasing temperatures impacts (8)

Answer 26

• 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

Question 27

NELSON-CHURCHILL RIVER BASIN:
Low precipitation impacts (7)

Answer 27

• 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

Question 28

NELSON-CHURCHILL RIVER BASIN:
Impacts on wetlands and lakes (2)

Answer 28

• high ET → shrinkage of lakes / wetlands
• smaller wetlands can be permanently lost

Question 29

NELSON-CHURCHILL RIVER BASIN:
Impacts of urban areas (2)

Answer 29

• Irrigation → threat to ecological flows
• existing water reservoirs will be less sustainable bc of high evap