A Model for Evaluating Effects of Climate, Water Availability, and Water Management on Wetland Impoundments—A Case Study on Bowdoin, Long Lake, and Sand Lake National Wildlife Refuges

Many wetland impoundments managed by the U.S. Fish
and Wildlife Service (USFWS) National Wildlife Refuge
System throughout the northern Great Plains rely on rivers
as a primary water source. A large number of these impoundments currently are being stressed from changes in water supplies and quality, and these problems are forecast to
worsen because of projected changes to climate and land use.
For example, many managed wetlands in arid regions have
become degraded owing to the long-term accumulation of salts
and increased salinity associated with evapotranspiration. A
primary goal of the USFWS is to provide aquatic habitats for a
diversity of waterbirds; thus, wetland managers would benefit
from a tool that facilitates evaluation of wetland habitat quality in response to current and anticipated impacts of altered hydrology and salt balances caused by factors such as climate
change, water availability, and management actions.
A spreadsheet model that simulates the overall water and
salinity balance (WSB model) of managed wetland impoundments is presented. The WSB model depicts various habitat metrics, such as water depth, salinity, and surface areas (inundated, dry), which can be used to evaluate alternative management actions under various water-availability and climate scenarios. The WSB model uses widely available spreadsheet
software, is relatively simple to use, relies on widely available inputs, and is readily adaptable to specific locations. The WSB model was validated using data from three National
Wildlife Refuges with direct and indirect connections to water
resources associated with rivers, and common data limitations
are highlighted. The WSB model also was used to conduct
simulations based on hypothetical climate and management
scenarios to demonstrate the utility of the model for evaluating alternative management strategies and climate futures. The WSB model worked well across a range of National Wildlife
Refuges and could be a valuable tool for USFWS staff when
evaluating system state and management alternatives and
establishing long-term goals and objectives.