Coupled Ecological Modeling for Improved Water Resources and Ecosystem Management

Estimating ecosystem impacts from alternative water management policies or practices involves an understanding of both engineering and biology, among other disciplines. However, the modeling approaches used by biologists and engineers to estimate these impacts are usually quite different. Engineers commonly use the Eulerian modeling framework to simulate bulk water flow and the biological, chemical and physical processes that affect lower trophic levels of ecosystems, such as bacteria, algae and protozoa. In contrast, biologists typically use an implicit Lagrangian modeling framework to simulate population dynamics or the influences of competitors, predators, and resource availability on populations of higher trophic levels, such as fish. These two modeling frameworks can be coupled together into a comprehensive coupled Eulerian-Lagrangian hybrid (CEL Hybrid) model to predict the interactions within, and the effects of water resources activities on, a wider range of ecosystem trophic levels than can either framework by itself. Our CEL Hybrid models use stimuli-response rules to transform neutrally buoyant objects into ‘smart' objects, or virtual organisms, emulating the movement behavior of individuals of an aquatic species in a simulated hydraulic and/or water quality environment. Standard calibration techniques are used to achieve movement behaviors in the virtual organisms that best emulate the movements of observed species. Once the movement behaviors of a higher trophic species are incorporated within a CEL Hybrid model, the model can be used to estimate the impacts of any water resources management activity on species population processes at any one of a number of trophic levels and spatial and temporal scales.