The Ecohydrology Team is an interdisciplinary group of scientists and engineers led by the Environmental Laboratory, Engineer Research and Development Center, U.S. Army Corps of Engineers. The primary focus of our group is improving our understanding of the interactions between hydrological and ecological processes to improve the functioning, stability, and resiliency of degraded ecosystems and foster sustainable development through better design of Natural and Nature-Based Features (NNBF). Ecosystems and human communities are under increasing threat due to hydrological and climate extremes, development, and pollution. Better understanding of ecohydrologial processes at multiple spatial and temporal scales will help achieve the dynamic balance needed to improve these systems.

The principles of Ecohydrology are expressed in three sequential components:

• Hydrological (Framework): The quantification of the hydrological cycle of a basin, should be a template for functional integration of hydrological and biological processes. This perspective includes issue of scale, water and temperature dynamics, and hierarchical interactions between biotic and abiotic factors.
• Ecological (Target): The integrated processes at river basin scale can be steered in such a way as to enhance the basin's carrying capacity and its ecosystem services. This component deals with aspects of ecosystem resilience and resistance.
• Ecological Engineering (Method): The regulation of hydrological and ecological processes, based on an integrative system approach, is thus a new tool for Integrated Water Basin Management. This method integrates the hydrological framework and ecological targets to improve water quality and ecosystem services, using engineering methods such as levees, biomanipulation, reforestation, and other management strategies.

Three principal hypotheses were proposed by Zalewski et al., 1997:

• Hydrological processes generally regulate biota.
• Biota can be shaped as a tool to regulate hydrological processes.
• Hydrological and biological regulations can be integrated with hydro-technical infrastructure to achieve sustainable water and ecosystem services.

Considerations:

• Flow path of the water through the watershed
• Residence time, which is related to inflow and outflow rates and system storage
• Biogeochemical reactions, which may change the species and types of chemical compounds dissolved in the water (nutrients, dissolved oxygen, etc.)
• Connectivity of the system, including how system flows interact as well as how the hydrology, ecology, and biogeochemistry of the system interact