Chapter 2 - Wetlands Hydrology

Question 1

What is the importance of hydrology in Wetlands

Answer 1

Hydrological conditions are extremely important for maintenance of wetland’s structure and function. They affect soil anaerobiosis, nutrients availability, and salinity in coastal wetlands, these in turn determine the biota that develops in wetlands.
Hydrology also determines where wetland is established, wetland’s processes, chemical and physical reactions.

Question 2

Differences in wetland hydrology comes from differences in:

Answer 2

1. Water level
2. Water frequency
3. Flood duration
4. Water flow

Question 3

What is the hydroperiod?

Answer 3

Water level over a period of time.

It characterizes each type of wetlands that’s why it’s known as wetland’s signature.

Question 4

What are the possible hydroperiods for tidal wetlands?

Answer 4

1. Subtidal (permanently flooded).
2. Irregularly exposed (almost always flooded, surface exposed less often than daily).
3. Regularly flooded (flooded and exposed at least once daily)
4. Irregularly flooded (flooded less often than daily)

Question 5

What are the typical hydroperiods for non tidal wetland?

Answer 5

1. Permanently flooded.
2. Intermittently exposed.
3. Semi permanently flooded.
4. Seasonally flooded.
5. Saturated.
6. Temporarily flooded.
7. Intermittently flooded.

Question 6

The hydroperiod of a wetland is a result of three different factors, mention them.

Answer 6

1. Balance between inflow and outflow ( rain, runoff) .
2. Surface contours of the landscape (steep or flat) .
3. Subsurface soil, geology and groundwater conditions (type of soil, hydraulic conductivity, hydraulic gradient and storativity).

Question 7

What is the water budget of a wetland?

Answer 7

It is the balance between inflows and outflows (how much water the wetland recieve, what are the sources, and how much water the is flowing out)

Question 8

What determines the capacity of a wetland to conduct of store water?

Answer 8

1. Surface contours of the landscape.

2. Subsurface soil, geology and groundwater conditions.

Question 9

What are the components of the water budget for wetlands?

Answer 9

1. Precipitation.
2. Surface inflows and outflows.
3. Groundwater.
4. Evapotranspiration.
5. Tides

Question 10

What is the most important attribute of wetlands

(from the water budget components)?

Answer 10

The influence of wetland recharge and discharge on groundwater resources is often cited as the most important attribute (however this doesn’t hold for all wetlands types).

Question 11

The is the major hydrological feature of coastal wetlands?

Answer 11

Tides.

Question 12

How can Tides act as a stress?

Answer 12

By causing submergence, saline soils and soil anaerobiosis.

Question 13

How can Tides act as a subsidy?

Answer 13

By removing excess salts, re-establishing aerobic conditions and providing nutrients.

Question 14

What are the Riverine wetlands?

Answer 14

Those are wetlands located along the banks of river (the main source of inflow is the surface water).

Question 15

What is the residence time?

Answer 15

It is the ratio of throughput to average volume within a system, it indicates how long does the water stay in the wetland and the openness of a system.
( important in designing the treatment wetlands)

Question 16

How hydrology affect the biota?

Answer 16

1. Plant species :
   *Hydrology leads to unique vegetation compositions (i.e. water tolerant plants in wet conditions).
   * It can limit or enhance the species richness;
   long flooding - - > low species richness.
   Short flooding duration - - > high species richness.
2. Plant productivity :
   * Open wetlands to hydrological fluxes are more productive.
   * the productivity is highest when the hydrological conditions are normal (no extreme stresses).

Question 17

What are the effects of hydrology on physiochemical environment?

Answer 17

1. Accumulation of organic matters in wetlands is controlled by hydrology through its influence on primary productivity, decomposition and export of particulate orginc matters.
2. Nutrient cycling and nutrients availability are both influenced by hydrological conditions.

Question 18

What is the major difference between the hydroperiod of tidal wetlands and non tidal wetlands ?

Answer 18

Hydroperiods for tidal wetlands have large daily fluctuations, while the ones for nontidal wetlands have stronger seasonal fluctuations.

Question 19

Why do we need to calculate the water budget of a wetland ? Name one application.

Answer 19

For wetland restoration and conservation.

Question 20

How does the hydroperiod of a high productivity wetland looks like?

Answer 20

It characterized by fluctuation between aerobic and anaerobic conditions.

Question 21

How does the hydroperiod of a wetland with high low productivity looks like?

Answer 21

It can be permanently flooded (so there is no constant input of nutrients) = no fluctuations between aerobic and anaerobic conditions.

Question 22

Describe the interaction of wetlands with groundwater

Answer 22

Wetlands can either be:
1. Recharging wetlands : where water moves from the wetland into the groundwater.
2. Discharging wetlands : where water moves from groundwater to the wetland.
The fluctuating water table can cause wetlands to shift from discharging to recharging.