#4 Hydrology (pt 1)

Hydrology

• The sources, velocity, renewal rate and timing of water in a system

• Inputs and outputs of water in a wetland

What are somethings you should be able to identify before one decides an area is a wetland?

• where the water is coming from

• how much water there is

• how long the water stays in the area

• how it leaves

What 2 physical factors determine a wetland’s hydrology?

• Geomorphometry (shape/depth)

  • Structure of wetland

• Inputs and outputs of water (Hydrology)

  • Climate/precipitation

  • Ground/surface water movement

What does hydrology determine in a wetland?

• Timing/duration/pattern of inundation

• Chemistry and nutrient concentration

What is the term used to describe the timing, duration, and pattern of water in a wetland?

Hydropattern / hydroperiod

What ecological factors are influenced by a wetland’s hydrology and chemistry?

• Plant species composition and productivity

• Animal use and life history patterns

How does climate in the Northern hemisphere affect hydrology?

• wetter and cooler = more wetlands. 

  •  In the tropics, most wetlands in uplands, riparian zones.

How does climate in the Tropics of Cancer and Capricorn affect hydrology?

• generally arid/semi-arid

  • Not as many wetlands

How do Geomorphometry affect wetlands?

• shape of wetland→ determines how much water it can hold

• a landscape’s shape affects where/how water accumulates as well as residence time of that water

• Slow water leakage -> bog may form

Where do discharge wetlands get their water from?

receives water from the groundwater table

• typically has a longer hydroperiod and higher salinity

Do recharge wetlands lose or gain water to the groundwater table?

lose

• usually has a shorter hydroperiod and fresher water

How does a wetland’s permeability affect its interaction with groundwater?

• High permeability allows greater exchange with groundwater

  • (e.g., sandy or porous soils)

• low permeability limits exchange and can trap water, extending hydroperiods

  • (e.g., clay soils)

Why do discharge wetlands often have higher salinity or solute concentrations?

• receive mineral-rich water from the groundwater table

  • increasing the amount of dissolved salts and nutrients

What determines whether a wetland is gaining or losing water to the groundwater system?

net movement of water

How can net movement of water determine a discharge wetland and recharge wetland?

• if water flows from the groundwater into the wetland

  • it’s a discharge wetland

• if water leaves the wetland and recharges the groundwater

  • it’s a recharge wetland

tidal

how much water is going in and out

How can nearby surface water bodies like rivers or oceans influence a wetland’s hydrology?

affect how much water enters or exits the wetland

• especially in tidal systems, where regular inflow and outflow of water can strongly shape the hydroperiod

What are 2 major factors that affect how much a wetland exchanges water with surrounding environments?

The permeability of the soil and the wetland’s position relative to groundwater and surface water sources

Hydroperiod

When/for how long water is present

Hydropattern

Where water is present

How do different plant species respond to variations in hydroperiod?

• require drought periods for seed germination

• some cannot survive prolonged drought

• others must survive being completely underwater

What happens to plant distribution as a result of hydroperiod variations in a wetland?

Plants form rings based on their flood tolerance

• Areas closer to the marsh-> true aquatic

• Farther from the middle-> more semi-aquatic plants

How do amphibians typically respond to the hydroperiod of wetlands?

Most amphibians prefer wetlands with intermediate hydroperiods, which provide suitable conditions for breeding and development.

What factors of inundation timing influence wetland biotic communities?

The frequency and duration of flooding events dictate which plants and animals can live in the wetland

Why do amphibians often prefer intermittently flooded habitats like vernal pools?

these habitats dry out periodically, reducing predators like fish and providing suitable breeding conditions.

Vernal pools

Depression in the ecosystem that is consistent with where it pops up and fills with water

How does water depth influence species use of wetlands?

Different species are adapted to use wetlands of varying depths

• determining which plants and animals can inhabit or forage in the area

Why does depth matter for wetland plant and animal communities?

Physiological adaptations limit species to certain depths, shaping the composition of the wetland community.

• ex:

  • Shorebirds prefer shallow water depths of 10 cm or less

  • Diving ducks can forage in wetlands that are 2 meters deep or more.

What is one main thing that influences wetland chemistry?

Water source chemistry

• oxygen, toxicity (salts**, pollutants), methane emissions, etc.

How does water chemistry affect wetland biodiversity?

influences which species can survive there

• wetlands with extreme chemistry often support fewer but more specialized species

  • e.g., high salinity or acidity

Why are salt marshes typically less diverse than freshwater marshes?

high salinity/acidic limits the number of species that can tolerate those conditions