The Importance of Hydroperiod in Wetland Assessment


A guide for community officials, planners, and natural resource professionals

A 25-page guide produced in cooperation with the University of New Hampshire Cooperative Extension, the UNH Department of Natural Resources, and the NH Fish and Game Department. This project was supported by funds from the sale of the Conservation License Plate (Moose Plate) under the NH State Conservation Committee grant program. 


The hydroperiod of a wetland (the length of time and portion of year the wetland holds ponded water) is largely responsible for determining what amphibian species can breed successfully in the wetland. Hydroperiod determines not only the length of time that amphibian larvae have for developing to the point where they can leave the water for land, but also the number and types of predators to which they are exposed. Wetlands can be grouped into three major hydroperiod categories (short, intermediate, and long). Wetlands within each category support a unique collection of amphibian species and together they support the entire diversity of pond-breeding amphibians in New Hampshire. To maintain a diversity of pond-breeding amphibians, we must maintain a diversity of wetlands with different hydroperiods across the landscape. Additionally, upland habitats provide amphibians with wintering and feeding habitat, as well as critical dispersal corridors between wetlands. We must protect uplands if we want to maintain functioning populations of pond-breeding amphibians into the future.

Table of Contents

  • Abstract
  • Introduction
  • Basic life cycle of pond-breeding amphibians
  • Wetlands occur along a hydrologic gradient
  • How hydroperiod affects amphibian use of wetlands
  • Role of amphibian larval period
  • Role of aquatic predator
  • Amphibian defenses against predators
  • Which wetlands support the greatest diversity of amphibian species? .
  • Maintaining amphibian diversity
  • Maintain wetlands of every hydroperiod
  • Identifying wetland hydroperiod
  • Suggestions for assessing wetland hydroperiod
  • Site indicators for predicting wetland hydroperiod
  • When to conduct hydroperiod assessments
  • How many wetlands must be protected?
  • Conserving wetlands across the landscape
  • Wetland size is a poor indicator of importance
  • Importance of amphibian dispersal
  • Maintain intact uplands around and between wetlands
  • Other Resources
  • Works Referenced
  • About the Authors

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