FLOTEMERSCH, J. E., J. H. Thorp, AND B. S. Williams. Application of the riverine ecosystem synthesis (RES) and the functional process zone (FPZ) approach to EPA environmental mission tasks for rivers. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-11/089, 2010.
The shift to watershed management of rivers from a more reach-based approach has had far-reaching implications for the way we characterize and classify rivers and then use this information to understand and manage biodiversity, ecological functions, and ecosystem services in riverine landscapes. At the same time, we are faced with inherent challenges of how to best take advantage of past studies (e.g., the many projects on river classification funded by the U.S. Environmental Protection Agency’s [EPA’s] Science to Achieve Results [STAR] program) while we shift to the higher hierarchical scale necessary to manage at the watershed level. To meet these challenges, we require a model that links the physical structure of a river with its ecosystem functioning and allows us to evaluate past, present, and future river conditions. Such a model would ideally be cost effective, easy to employ, and capable of answering questions at different hierarchical scales in river basins of varying sizes. One model that meets all these criteria, while also accommodating many of the prominent approaches used by and/or developed in collaboration with the EPA, is the Riverine Ecosystem Synthesis, or RES (Thorp et al. 2006, 2008). Contrasting with earlier views of rivers as simple, continuous gradients in physical conditions from headwaters to great rivers (i.e., river continuum concept [RCC]), research and conceptual models in the last decade support the conclusion that rivers are more accurately portrayed as downstream arrays of large hydrogeomorphic patches formed by factors such as hydrologic patterns, geomorphic structure of the channel bed and valley, climate, and riparian conditions (e.g., Montgomery 1999; Poole 2002; Thoms and Parson 2002, 2003; Thorp et al. 2006, 2008). These patches are described in the RES, at the critical valley-to-reach scale, as functional process zones (FPZs). FPZs are named based on statistically-derived features of the channel and surrounding valley along with geological and precipitation features, but some widely known examples of channel types in different FPZs are constricted, meandering, braided, anastomosing, and distributary. According to the RES, FPZs are repeatable along the longitudinal dimension of rivers and only partially predictable in location (Fig. 1), especially at scales above the ecoregional level. Because of physicochemical habitat differences, ecosystem structure and function vary significantly (and predictably) among FPZs. Use of the RES model in river management is just beginning to expand, especially as it relates to tasks characteristic of EPA’s mission. The FPZ approach is being applied at present to the Kansas, Kanawha, and Neuse rivers in the U.S. and has previously been applied to dryland rivers on other continents. However, this approach needs to be applied and evaluated for a fuller spectrum of ecoregions, such as those characterizing the humid through arid regions and/or northern through southern portions of the U.S. Starting with a foundation of ideas from “river typing” work in Australia, we have now been able to accelerate the river typing process and are starting to explore its use in multiple environmental tasks in the EPA mission. While we are now involved in the planning and execution phases for some applications of the RES (e.g., the physical classification of rivers), more research and development is needed to firmly establish links between the physical and ecological portions of the RES. We propose to research, develop, pilot, and implement the products necessary to successfully apply the RES concept and FPZ approach to the mission tasks facing EPA.
This report presents some of the high points of the RES model, describes its uses in meeting tasks in EPA’s environmental mission, and integrates it with both current and past classification and management techniques, as a way of improving implementation of mission tasks.