Analytic Method to Derive Wetland Stage-Storage Relationships Using GIS Areas

The relationship between the depression area $\left(A\right)$ , volume $\left(V\right)$ , and depth of water $\left(h\right)$ for wetlands, ponds, and lakes is often required for model studies. Area-depth $\left(A\text{-}h\right)$ and volume-depth $\left(V\text{-}h\right)$ relationships for wetlands, ponds, and lakes, which are important inputs to hydrologic models can be developed from detailed surveys and/or bathymetric maps that are costly and labor intensive to produce, or the use of simple geometric models. An analytical approach is introduced to describe wetland stage-storage $\left(V\text{-}h\right)$ relationships using a single shape parameter, simple geometric data available from geographic information system coverages or field studies, and a power-function model. The dimensionless shape parameter defines the wetland prismatic conic shape, and together with the reference wetland pool area and associated maximum pool depth defines the $V\text{-}h$ relationship to a high degree of accuracy. Shape parameters were developed for 42 wetlands to generate $V\text{-}h$ relationships for each wetland. The study findings were: (1) there is little variability in the dimensionless shape parameter; (2) the mathematical model accurately represents the $V\text{-}h$ relations for all wetlands analyzed; and (3) only the upper 80% of the wetland storage is needed to develop accurate stage-storage predictions using this approach. The developed wetland storage equations should prove useful in field studies, theoretical investigations, and surface/groundwater modeling.