A simulation model for the relationship among water flow, groundwater, wet meadows, and wildlife at central Platte River, Nebraska

Background/Question/Methods The Central Platte River Ecosystem, Nebraska, is vastly complex. The physical, chemical and wildlife elements of the river and adjacent wetlands are complicated because of intricate  relationships between river flows,  precipitation, ground water charge and discharge, evaporation and plant’s evapotranspiration, all influenced by  global and regional climate changes. The river is part of an ample system of dams, diversions, and canals that distribute water across the ecosystem. The river crosses, west to east, the Central Flyway, a main corridor for migratory birds, and the wetlands (wet meadows) associated to river flow-groundwater equilibrium provide valuable habitat for these, as well as other terrestrial and aquatic organisms. While several threatened and endangered species are known to use wet meadows, they are also severely threatened by changes in water regimes.  
We developed a model that simulates the effect of groundwater level and water flow on wet meadow changes. We also hypothesize through the model how fish and bird communities are distributed when changes in wet meadow conditions occur. 
The model is represented mathematically as a discrete-time model based on difference equations with a 1-day time step. Simulations are run using Stella 9.2 (High Performance System Inc., 2007)  
The models consists of 5 sub models representing (1) Precipitation - river flow – groundwater - evapotranspiration dynamics, (2) Emergent plant populations dynamics, (3) mesic and sedge meadows plants populations dynamics,(4) dry ridge plants populations dynamics, (5) fish community distribution and population dynamics, and (4) aquatic bird assemblage distribution and abundance dynamics.

Results/Conclusions

Preliminary simulations show that changes in water flow as well as ground water level generate changes in the dominance of plant species depending on water level from soil surface. Emergent and sedge meadow plants are dominant when water level is at least from 1.5 to - 0.5 feet on soil surface, mesic meadow plant are dominant when water level is from - 1 to - 3 feet, and dry ridge plants are dominants when water level is 3 or more feet under soil surface. Through the model we have hypothesized and discussed possible options for water and field management that will maximize fish and bird abundance and diversity.