Project: An Integrative Approach to Managing the Dewatering of Estuaries

Project Summary:

Two key goals of the Comparative Analysis of Marine Ecosystem Organization (CAMEO) program are to: 1) integrate information from experimental, observational, human dimension, and modeling approaches and 2) provide science-based information to policy makers and managers. This proposal will meet both goals by performing ecosystem and human dimensions research to develop integrative decision-support tools that will provide decision-makers information for managing freshwater inflows to estuaries in the coastal zone.

An estuary is a transition zone where salt water from the sea mixes with fresh water draining from the land. Freshwater inflow to estuaries has a major influence on coastal ecosystems because it regulates salinity, nutrients, and sediments, and nothing is more fundamental to the functioning of an estuary than the freshwater inflow regime delivered to the mixing zone. However, change caused by climate and human systems is altering landscapes and the water cycle on Earth. One large manifestation of this change is dewatered estuaries caused by diverting freshwater flows away from the coast. Since 1960, the volume of water in global reservoirs has quadrupled, the volume of water withdrawn from rivers and lakes has doubled, and currently 60% of the Earth's runoff is captured. Given this unprecedented change, there is a clear need to manage water resources in the coastal zone to protect and sustain coastal environments and to provide ecosystem services that drive human prosperity and well being. No generic management tools exist and a strong scientific basis for an ecosystem approach to the stewardship of environmental flows is lacking.

There is probably no better place on Earth to compare effects caused by altered inflow than the Texas coast, because the major estuarine systems lie in a climatic gradient where runoff decreases 56 fold from the Louisiana border in the northeast to the Mexico border in the southwest. This results in a gradient of four subregions where the inflow balance in estuaries ranges from strongly positive, moderately positive, neutral, to negative. Thus, nature has provided a perfect experimental design to compare estuarine processes that change in relation to freshwater inflow. Assuming change along the inflow gradient is analogous to effects of dewatering over time, we can identify ecosystem change as a function of dewatering. Our transdisciplinary team of natural scientists and social scientists will: 1) use existing long-term observational data on climate, freshwater inflow, water column characteristics, sediment, and biological communities to predict how changes in water diversion and climatic variability influence the structure and function of estuaries, 2) identify value of ecosystem services, 3) create science-based policy alternatives that integrate science and socioeconomic values, and 4) create decision-support tools to aid policy makers, resource managers, educators, and the general public to understand the importance of freshwater inflow in ensuring long-term sustainability of coastal resources and ecosystems.