CIVE 633 - ENVIRONMENTAL HYDROLOGY WETLAND COMMUNITIES

HYDROPERIOD AND WATER REGIME

• The hydroperiod is the most important contributor to wetland type or class.

• Incorrect understanding of the hydroperiod and water regime limitations of wetland plant species is the most frequent cause of vegetation problems in natural and constructed wetlands.

• Measuring the hydroperiod is relatively easy.

• Selecting the optimal hydroperiod for wetland treatment design and performance is complex.

• The concepts of hydroperiod and water regime include two interdependent components:
  
  
  • the duration of flooded or saturated soil conditions
    (the hydroperiod defined as the percentage of time with flooding)

  • the depth of flooding.

• The duration and depth of flooding affect plant physiology because of soil oxygen concentration, soil pH, dissolved macro- and micro-nutrients, and toxic chemical concentrations.

• Plant types classified as wetlands by the USFWS have as few as 7 days of flooding or soil saturation each year (hydroperiod = 2 percent duration).

• Figure 7-11 shows the components of wetland hydroperiod and water regime.

• For any specific location, a depth-duration curve can be prepared to summarize the water regime and hydroperiod.

• Hydroperiod curves provide a convenient method for estimating the percentage of time that a wetland is flooded at any water depth and can summarize water level data over any period of record.

• Figure 7-14 shows idealized hydroperiod charts for general wetland types.

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