Biol 333: Wetland Science and Management

What are the components of the Canadian Wetland classification system?

Mineral wetlands

1. Shallow open water

2. Marshes

3. Swamps

Organic wetlands

1. Swamps

2. Marshes

3. Bogs

4. Fens

How can we classify wetlands?

• Nutrient regime

• Water flow; water table

• Vegetation

• Soil type

How do wetlands recieve water?

precipitation, surface flow, groundwater flow, and tides

What can water table position and fluctuation affect?

• Nutrient availability and transformations

• Toxicity and pH

• Rate of decomposition and peat accumulation

How do wetlands influence input and output of nutrients and sediments?

• Wetlands as a sink/source/transformer

• Wetland productivity

• Delta formation, floodplain development

• Salinity

What are two key influences on wetland hydrology?

1. Climate

2. Basin geomorphology and water storage

What are some examples of the basin geomorphology influence wetland hydrology?

• Low Slope (poor drainage)

• Depression (not too deep)

• Confining layers preventing groundwater recharge

• Adjacent rivers, coasts and lakes

• Groundwater springs/seepage

What are two biological feedbacks that influence wetland hydrology?

1. Vegetation

• Vegetation have some control of ET

• Trees can increase transpiration by reaching water below the surface; increasing water losses

• Other vegetation can shade the water and reduce ET

2. Animals ‘Ecosystem engineers’

• Beaver initiation / destruction

• Geese, muskrat, carp remove vegetation

• Gator holes

What is wetland hydroperiod?

 The seasonal pattern of water level

What does wetland hydroperiod look like?

Periods of flooding (inundation) are important in describing hydroperiod

• Flood duration, flood frequency and flood depth are ways to describe hydroperiod

• Determines redox conditions in the soil surface

• Important determination of vegetation

How is hydroperiod used to differentiate between different types of marshes and SWW?

Temporary, seasonal, semi-permanent, permanent and intermittent

What does the hydroperiod of SWW look like?

• Permanent to Semi-permanent inundation

• Variable in hydroperiod

• Variable in pH

What does the hydroperiod of FWM look like?

• Permanent to temporary inundation

• Large fluctuation; intra- and inter- annually

• Alternate between dry and flooded
  Exceptions based on water sources

What does the hydroperiod of swamps look like?

• Seasonal to temporary inundation

• Large fluctuation: often due to surface water inflow

• Boreal trees need predominantly oxic soils for roots; do not tolerate long flooding durations

• Cypress and Mangrove trees have solutions to always live flooded (establishment requires non-flooded conditions)

What does the hydroperiod of peatlands look like?

• No inundation: Water table rarely above surface, higher after snowmelts and lower in summer

• Large fluctuation in water table position; especially in fens with dominant groundwater supply

• Peat characteristics prevent water table drop further

How do peat characteristics influence the water table?

Prevent water table drop further; 

• Below 40-50 cm peat is humified → slows water movement

• Below 40 cm evaporation is reduced

• Poor – Extremely rich fen = higher water table

What factors result in a wetland hydroperiod?

1. A surplus of water

• Excess water; water supply > water loss → Water balance

2. Capacity for water storage

• Geomorphology

• Landscape position

• A capacity to hold or bring water near the surface; dependent on soil properties

What do we need for a water budget?

• A defined wetland boundary

• A common unit of water: mm/yr or mm/day or mm/month

• Volume of water / area of wetland = depth of water

What is the difference between a water renewal rate and water residence time?

Water renewal rate = how often is water replaced within the wetland

• Sum of inflows / average total water in wetland

Water residence time = how long is water stored on average 

• 1 / renewal rate

What are the components of a water budget?

• Precipitation

• Surface inflows and outflows

• Groundwater

• Evapotranspiration

• Tides

What components of the water budget are driven by climate vs geomorphology?

Climate = precipitation and evapotranspiration

Geomorphology = everything else

Why is snow redistribution importat for wetlands? an example?

Snow drifts can increase snow storage 10x compared to surroundings

For Example: Prairie Wetland

Annual P = 300-450 mm ; 2m snow drift adds 600 mm!

What are three methods for measuring precipitation?

• Standard gauge = bulk measures

• Tipping bucket = continuous

• Snow measurement = bulk measures

Why is measuring precipitation difficult?

→ considerable uncertainty

+/- 20% for annual totals

• Instrument error

• Spatial variability

What is the general trend in precipitation across Canada?

Varies across Canada; generally decreases northwards, increases coastally

What does precipiation look like in Alberta vs Ontario vs British Columbia?

In AB = precipitation is not spread evenly; summer connective storms, ~25% from snow

In ON = precipitation spread evenly, ~40% from snow

In BC = precipitation from Oct-Mar, ~75% from rain

What is evapotranspiration?

= Evaporation + Transpiration

E = open surface water, or water available at soil surface

T = from roots, controlled by stomata on leaves // needles

→ Transpiration is linked to productivity; plants have stomatal control if water is scarce

What is potential evapotranspiration (PET)?

The maximum amount of water that would evaporate from the soil and transpire from plants if an unlimited supply of water was available

What causes PET to increase?

• Solar radiation

• Warmer air temperatures

• Lower air humidity

• Greater wind speeds

How is PET measured (directly)?

Using Evaporation pans: fill them with water and measure change in weight / depth in pan

What are the two ways PET is estimated?

• Thornthwaite equation

PET estimated using only the mean monthly temperature; accurate at large scales, not accurate at local scales

• Penman equation

PET estimated using information on net radiation, air humidity, air temperature and wind speed; better estimates

What is actual evaportranspiration?

The real-weight quantity of water that transfers from the land surface to the atmosphere, combining water evaporation from the soil and transpiration from plants

—> Considers the role of veg and soil

What is annual PET in Alberta?

600-700 mm/yr