Huntley Meadows

WETBUD

 

The type of wetland that is ultimately established in the park (e.g. forested vs. marsh) and the associated ecosystem functions are largely controlled by the seasonal pattern of water depths in the pond and the surrounding soils. This seasonal wetland hydroperiod is controlled by the wetland water budget, which is a summation of all combined inputs and outputs of water to/from the system over any given period of time (day, season, year). Inputs of water to a given wetland system include surface water additions from streams or local hillsides, local groundwater inflows, and precipitation falling directly onto the wetland. Wetland water outputs include losses back to the atmosphere via evapotranspiration (ET), seepage losses back to local groundwater, and surface water flowing out of the wetland in streams. The net difference between inflows and outflows at any point it time is referred to as storage, which is the total volume of water stored in the pond and the surrounding saturated soil. The total volume of water in the wetland is ultimately reflected in the water level observed in the wetland pond (or in the belowground water table if the pond is dry).

One of our research group’s major objectives is to develop and verify a water budget for the central wetland and the immediately surrounding forested areas at Huntley Meadows. Essential data for all water budget components are being gathered via an extensive network of soil, groundwater, surface water, and weather monitoring sensors. These data sets are being used to produce accurate estimates of each part of the water budget and to predict water surface elevations in the pond. We will compare the results of our water budget to actual measurements of the water surface in the pond to verify our calculations.

Our second major research objective at Huntley Meadows Park is to continue the development of our new wetland water budget modeling tool, Wetbud. Wetbud is a computer program for estimating wetland water budgets using available weather data and site-specific topographic, soil, and geohydrologic data. Wetbud is primarily intended as a planning tool for use in the design of new wetlands, but it can also be applied to native wetlands, such as the central wetland at Huntley Meadows. Wetbud can be run in the Basic mode where wetland topography, soil parameters, and groundwater flow rates are simplified in a 2-dimensional approach or in the Advanced mode where these flow rates are calculated using a more complex 3-dimensional approach.

Wetbud runs in a Windows™ environment with a user-friendly graphical user interface which allows for: (1) centralized data and project management using a client/server concept; (2) direct internet download and manipulation of weather data from the National Weather Service; (3) generation of two evapotranspiration estimators (Penman and Thornthwaite); (4) multiple options to estimate surface water and groundwater inflows and outflows; and, (5) easy data import from and export to Excel™ spreadsheets. Wetbud features 12 preloaded weather stations covering the state of Virginia, so that a project located anywhere in Virginia can be set up and run quickly. Inquiries regarding availability and use of Wetbud should be directed to W. Lee Daniels.

Evapotranspiration and Overall Water Budget
Complete April 2015 Report is available.