Wetlands are dynamic ecosystems which often occur between deep water habitats and uplands. Wetlands are land areas that are inundated or saturated with water for part of the growing season. They are characterized by soils with little or no oxygen and plants that thrive in these conditions called hydrophytes. The term hydrophyte literally means plants that live in water, some examples are cattails, grasses, sedges, willows, marsh marigolds, and cottonwoods. Because of the unique features of wetland areas many species depend on wetlands for survival year around or seasonally. This section describes the background of terrain-based water resource and watershed management principles applied to created or constructed wetland systems.
1.1 Wetland Classification Systems
The National Resources Conservation Service (NRCS) [SCS, 1992] describes wetlands in three basic hydrologic classes: (1) Depressional, (2) Riverine, and (3) Tidal. Depressional or catchments wetlands are formed by terrain with cups or indentations where water can collect seasonally or year-round. Riverine systems are formed in areas alongside streams or rivers which are inundated with water seasonally or permanently. Tidal wetlands occur near the ocean where tidal fluctuations can saturate areas with water, such as the Everglades.Wetland classification systems have been developed using two popular approaches, both of which serve useful perspectives to the ecology, hydrologic regime, land forms present in the local setting of a particular region of the country:
- Hierarchical classification developed by the US. Fish and Wildlife Service. [Cowardin et al, 1979]
- Hydrogeomorphic classification developed by the US Army Corps of Engineers. [Brinson, 1993]
[Cowardin et al, 1979]describe the purpose of classification (1) to describe ecological units that have certain homogeneous natural attributes; (2) to arrange these units in a system that will aid decisions about resource management; (3) to furnish units for inventory and mapping; and (4) to provide uniformity in concepts and terminology throughout the United States.
The classification system developed by Cowardin et al has been adopted for cataloging use for the national mapping of wetlands. The US Fish and Wildlife Service, National Wetland Inventory (NWI) use the Cowardin system for the polygon identification within the DLG3 digital data products files. Understanding the hierarchy and detailed cataloging permits practical use of mapped wetland categories. This play an important role, since the entire Devils Lake Basin has complete NWI mapping products available.
1.2 Wetland Creation and Restoration
In the past, wetlands have been dismissed as noxious, unprofitable places, but wetlands are now commonly recognized as some of the richest ecosystems on earth. Over a 200-year period, wetlands in the continental United States have been drained, dredged, filled, leveled, and flooded. The continental United States once contained an estimated 221 million acres of wetlands (Dahl, 1990). But by the mid-1980's, only about 100 million acres of wetlands remained (Dahl, T.E. and C.E. Johnson, 1991).
Wetland restoration has impacts on municipal and agricultural water use. These impacts can include the diversion of water resources from traditionally municipal or agricultural uses to wetland restoration and wildlife habitat uses. Positive contributions towards improving water quality for agricultural and municipal uses through natural filtration can be obtained through wetland restoration programs.
Using wetland areas for improving water quality has been used successfully in locations around the United States, but can have disastrous consequences to wetland areas if water resources are not adequately provided. In the past, water resource managers had to invest large amounts of time and effort to accurately manage large amounts of spatial data to provide long-term solutions to the delicate balance of scarce water resources. Computer technologies may provide a way to develop realistic management plans that include the complexity and quantity of spatial data available. This data can be used to manage scarce water resources in an attempt to restore wetland areas while balancing the needs of agricultural and municipal water users with those of wetland habitat. Part of this effort includes NRWS and WetScape.
It should be kept in mind that wetlands may not always look like wetlands to the casual observer, many wetlands are seasonal and may only function as a wetland for part of the year. Wetlands can vary in size, from less that one acres to hundreds of acres. They can have mostly free water surfaces or water may not be visible at all. Wetland areas can provide critical habitat for wildlife, for example though prairie potholes are only 10 percent of the nation's inland wetlands, yet they provide habitat for over half of the waterfowl in North America.Wetlands are dynamic, serving many uses in nature or for human benefit. Wetlands cycle excess nutrients and chemical contaminants, store water during seasonal floods, provide clean water sources, and reduce erosion.
1.3 Previous Research
Resource managers are faced with difficult challenges when considering how to allocate and sustain vital ecological functions to optimize resources for competing uses. The need for integrated watershed management approaches (e.g. NRC, 1992, NRLC, 1992) is often cited as important to more effective resource management. In practice, the term "watershed management" is somewhat of a misnomer because it implies greater predictive capability than is typically appropriate in most watershed situations. Even with the benefit of detailed resource information, rarely would land ownership, political boundaries, and natural characteristics allow for comprehensive management of a watershed area of any appreciable size. More often, distinct strategies are applied to focus on defined classes of resource problems or discrete projects are undertaken at specific locations in the watershed.
Wetland ecosystems can be an important component in watershed management (NRC, 1992). Wetland functions are illustrative of the complex interactions commonly experienced in coordinated resource management. As transitional ecosystems connecting land and water, wetlands are inherently diverse and robust in nature. Due to their position in the landscape, wetlands are exposed to all manner of land and water use practices. As such, the conditions found in wetlands can reflect the properties of the adjoining ecosystems and in turn, can serve to attenuate or alter conditions downstream.
As discussed earlier, wetlands are frequently described according to hydrologic and biotic indicators that are used to classify their ecological properties (Cowardin, et. al., 1979) or to delineate wetland areas (FICWD,1989) for regulatory jurisdiction purposes. Functions such as wildlife habitat, water quality, and hydrologic modification are widely recognized (e.g. Mitsch and Gosselink, 1993), and wetlands are also described in reference to their hydrogeomorphic setting (Brinson, 1993), and with respect to watershed functions ranging from ambient values of natural wetlands to the potential application of created wetlands as "Best Management Practices" (BMP's) for non-point water pollution control (Olsen, 1993).
These common wetland-related activities indicate a discrepancy regarding how essential information pertaining to wetland mechanisms is derived from studies of fairly small sites or local areas, and yet the important application of this information to predict the influences of relevant functions is required at the systematic or watershed level. The same problem applies to other strategies such as vegetative buffers, land use modifications, or aquatic restoration efforts that are spatially distributed throughout a watershed area. Uncertainty arises from attempting to interpret the characteristics found at local sites, transfer information to other locations or larger areas, and derive predictive models to evaluate the potential effects of these watershed characteristics in resource management alternatives. Detailed investigations are often prohibitively expensive to undertake over watershed areas, and yet attempting large scale or widely dispersed resource management actions without careful consideration of the potential consequences is risky.
WetScape was undertaken to develop integrated tools to assimilate spatial data across local and systematic scope, and to allow refinement of the analysis in response to the sophistication of information available. Specific objectives were identified for individual planning tools including; to evaluate local site landform conditions and site alternatives; to allow local results to be compiled to examine the implications over larger areas based on user-defined scenarios, and finally, to provide assistance in review of spatial information, alternative development, and correlation of measured or simulated conditions. The overall framework is intended to allow flexibility in how the analysis tools are applied and accommodate development of additional capabilities in the future.
1.4 Previous Decision Support Efforts
Decision Support Systems (DSS) are a combination of advanced engineering models, analysis techniques, complex data, Geographic Information Systems (GIS), and Graphical User Interfaces (GUI). DSS can combine spatial data for elevation, land-use, agriculture data, hydrography, evaporation rates, climate data etc., as well as multi- criteria, optimization, habitat analysis, groundwater, and/or surface water models into one system. These DSS computer systems make available to the user large quantities of current spatial data, taking a comprehensive and interdisciplinary approach to water and natural resource management.
Spatially based analysis capabilities for wetlands planning and management in the San Joaquin Basin Action Plan (SJBAP) in central California has been implemented in a DSS for the analysis of wetlands at the planning level in several evolving phases known as the "Natural Resource Workstation" (NRWS) [Garcia et al., 1993], [IDS Group, 1993]. Efforts continue to support and extend the NRWS with custom modeling for the SJBAP continue.
The initial work provided in the NRWS DSS has been extended to provide an additional module specifically targeting wetland analysis. The improvements to NRWS and the module are used to simulate and represent the fundamental water resource processes associated with inland wetland facilities at the planning level. The work has been developed in phased approach, with phase II completion in fiscal year 1996. Additional specific technology has been developed to more conveniently analyze riverine and depressional terrain features with an emphasis on terrain based features as part of doctoral research underway by Steffen Meyer under the direction of Luis Garcia, CSU Department of Civil Engineering. Many of these findings and experiences have been implemented in recent contributions to WetScape DSS.
Recent research conducted by IDS group at CSU has identified terrain based features at the land form level to help predict the sustainability of wetlands in natural settings. This research has studied interaction between the character and form of wetlands within particular wetland categories. This research effort has been developed into a series of approaches (technologies) and a computer assisted semi-automated simulation environment has developed to assist scientists in analyzing, and planning wetland related water resources projects using techniques taken from information science including data base, GIS, and remote sensing as well as scientific visualization and modeling approaches from engineering, water resources planning and natural resources disciplines. The approach has been loosely formed into a collection of tools to assist the researcher in planning and studying the interaction of water resources sciences and wetlands. It is felt that when sustainable supplies of water can be delivered to settings, the cost and potential benefits of the wetland related projects may be more reliably and fully achieved. This effort is not intended to undermine the overall objectives associated with the biological, ecological, or economical goals of a particular analysis approach. This technology is an effort to make the hydrologic and hydraulic foundation on which those goals rest, firmly understood and practicably implementable and sustainable for moderate costs rather than requiring large support measures for the wetlands to be sustained once construction and implementation is completed.
2.1 Organization and Focus of WetScape
Wetland projects normally fall into the following categories [SCS, 1992]:
- Wetland Restoration - the rehabilitation of a degraded wetland.
- Wetland Enhancements - the improvement, maintenance, and management of existing wetlands for a particular function or value.
- Wetland Creation - the conversion of a non-wetland area into a wetland location.
- Constructed Wetlands - specifically designed to treat non-point and/or point sources of water pollution.
The focus of the WetScape system is on created and/or constructed freshwater wetlands in riverine or catchments situations that can be defined by terrain-based features. The system is not meant to be comprehensive for every type of wetland, but to specifically address wetlands that can be defined by terrain-based features. The following categories of wetlands have or could be addressed with Wetscape:
- Riverine - Wetlands that occur along creeks, streams, waterways, seeps, and springs. Typically these areas are called riparian wetlands, but not all riparian areas are wetlands.
- Depressional - This covers all other non-glacial water catchments formed by geologic or other processes. These can be characterized by seasonal or areas around permanent lakes in the arid and semi-arid West. During the spring months when water is available or when the water-level rises to flood surrounding areas, they can provide important habitat for wintering and migrating birds and some amphibians.
- Prairie Pothole - Wetlands were depressions in predominately flat areas left by retreating glaciers. They provide a majority of waterfowl production habitat in north-central North America.
- Leveed - Found in flat areas where water is supplied by gravity or pumping, they are most common in irrigated cropland areas. Typically the catchment is human made. These wetlands provide important habitat for wintering waterfowl in California's central valley and along streams in the Midwest.
- Floodplain - Bottomland wetland areas in remnant river channels and sloughs. Examples of floodplain wetlands can be found throughout the Mississippi River drainage and other rivers.
This foundational definition of wetland classes, wetland projects and distinctions of wetlands is particularly useful when developing technology to work with shared spatial characteristics. The operational distinction, for example between depressional and pothole wetlands is significant when considering the timing and availability of water, yet both these wetlands have similar general shape and appear on terrain mapping to be quite similar. The practical, project implementation side of definitions has influenced the basis of the technology that has been developed for the Reclamation in several efforts. The organization and emphasis has been derived to help meet agency mission goals has been largely influenced by the direction of Eric Stiles, US Bureau of Reclamation, Land Suitability and Water Quality group (Reclamation-LSWQ), Denver Technical Service Center.
No attempt is made to address wetlands outside the riverine or catchment wetland categories, such as tidal wetlands, alpine wetlands, the perma-frost wetlands of Alaska, etc. However, the principles and techniques used here could be applied other areas.
WetScape is a surface-water terrain-based system, but the viability of wetland ecosystems should be measured based on the hydrology, soils/geomorphology, and vegetation. These factors must be addressed in every wetland project regardless of its function or purpose (NRCS, 1992). Therefore long-term maintenance and monitoring of any wetland site located with these terrain-based methods is highly recommended. In no way is this system a substitute for hands-on maintenance and monitoring and this system does not attempt to address chemical processes, groundwater interactions, or vegetation which are critical to the success of any wetland ecosystem. Instead the WetScape system is a landscape ecological approach to identifying potential or critical issues for wetland locations based on terrain-based modeling.
2.2 Temporal and Spatial Context
WetScape address the categories of wetland creation and constructed wetlands, though much of the data could be used for long-term maintenance or management of these created or constitute wetland areas. In the future enhancing or restoring could be addressed with the WetScape system. These different analysis support activities are conducted with a framework having important two scopes: 1)Temporal scope and 2)Spatial scope. This frame work is described by [Meyer, Garcia, and Stiles, 1996].
Currently, the Reclamation focus in on the following elements:
- Temporal Scope: Existing Wetlands Projects vs. Projected Wetland Projects
- Spatial Scope: Local (Site Specific) vs. Basin Wide (Systematic)
Four general areas of research have been identified by the team for additional research, and are presented in a matrix of WetScape development activities in Table 1. In the matrix formed, several terms require interpretation to the research goals for constructed wetlands being undertaken by the Bureau of Reclamation.
Table 1: Framework for Areas of Reclamation Wetland Research
----------------------------------------------------------------------------- SPATIAL SCOPE TEMPORAL SCOPE EXISTING PROJECTED
----------------------------------------------------------------------------- LOCAL Case Study Analysis (CSA) Projected Wetland Analysis (PWA) Case Data Base (CDB) Local Site Evaluation (LSE) SYSTEMATIC Water Quality Loading (WQL) Basin Wide Siting (BWS) Hydrologic Loading (HYD) Basin Wide Analysis (BWA) -----------------------------------------------------------------------------
- 'SYSTEMATIC' - Refers to the spatial scope of the study area with a large physical dimension with many potential sites, such as a regional or basin wide scope.
- 'LOCAL' - Refers also to the physical dimension of the project and pertains specifically to a particular wetland site.
- 'EXISTING' - Refers to the temporal condition/existence of the wetland; Use of the corporate body of experience about the behavior of constructed, created, and restored wetlands in riparian environments.
- 'PROJECTED' - Refers to the temporal condition/existence of the wetland; A wetland complex that has not yet been designed and constructed and needs to be simulated.
- Basin Wide Siting (BWS) -initial phases complete
- Projected Wetland Analysis (PWA) -initial phases complete
- Basin Wide Analysis (BWA) -initial phases complete
- Local Site Evaluation (LSE) -researched
- Case Study Analysis (CSA) -researched
- Case Data Base (CDB) -researched
- Water Quality Loading (WQL) -possible future development
- Hydrologic Loading (HYD) -possible future development
WetScape Analysis Modules
The column and row titles used in the 2 X 2 matrix have a very specific meaning associated with the needs of freshwater wetlands:
The analysis modules in the cells of Table 1 are conceptually designed to address the temporal and spatial scope of terrain-based wetland siting. Currently the modules under the Projected column have seen the most development. A detailed presentation of these modules is given in Chapter C: Approach and Capabilities. Additional generic analysis modules not specific to wetland design will be included as need. Currently a water demand module has been implemented to determine the consumptive use associated with vegetation types. Identified analysis modules and their respective development status are as follows:
WetScape provides technical personnel with the opportunity to combine their expertise in a common, interactive analytical environment, as applied to wetland creation or construction. Because WetScape has been developed in a UNIX workstation environment, natural resource managers have access to a common interactive computer environment.
WetScape was developed as an interactive workstation (UNIX based) system to allow natural resource managers to combine their expertise in a readily accessible, interactive environment. WetScape modules and tools are presented in an easy to use graphical user interface (GUI) comprised of windows, icons, and menu selections that are designed to guide the user efficiently through various analysis, modeling, and simulation actions. The underlying spatial analyses modules utilize the Geographic Resource Analysis Support System (GRASS) version 4.1.5 (USACERL, 1993). The WetScape GUI operates under the SUN Microsystems UNIX operating system Sun OS and the X-Motif library. The existing WetScape workstation capabilities have been developed using the C programming language, TeleUSE by TeleSoft, Inc. (facilitating use/development of X-Motif), and makes use of the spatial analysis operations provided by the GRASS GIS libraries and shell environment.
To use WetScape the user should have a SUN Microsystems UNIX operating system Sun OS and the X-Motif library, with GRASS version 4.1.5 installed and knowledge of UNIX and GRASS. Future phases of the project may be developed in other environments and platforms.