OPTIONS FOR ECOSYSTEM RESTORATION AND MANAGEMENT

SUmmARy oF HGm iNFoRmATioN NWR region. Annual variation in Green River flows and subsequent overbank and backwater flooding Information obtained in this study was suffi- likely caused significant annual variation in amount cient to conduct an HGM evaluation of historic and and distribution of flooded area and corre- current ecological attributes of the Seedskadee NWR sponding persistent emergent, and seasonal herba- ecosystem. Seedskadee NWR contains sections of the ceous wetland vegetation communities in the flood- Green and Big Sandy Rivers and their floodplains plain. A narrow linear riparian woodland comprised embedded within the extensive desert-type sagebrush of cottonwood and willow historically apparently was steppe community of southwest Wyoming. Histori- present along most areas of the Green and Big Sandy cally, annual surface water inputs to the Seedskadee Rivers on natural levee and point bar surfaces. Large NWR ecosystem were provided by highly pulsed and Green River flood events that exceeded 20,000 cfs dynamic discharges in the Green River during spring apparently were critical to periodically provide depo- and early summer. Discharge levels and resulting sition of fine alluvial sediments on natural levees flood flows into the Green River floodplain varied and point bar ridges and/or scour clean some flood- among years depending on annual snow pack and plain ridges where cottonwood and willow seedlings melt from surrounding mountains. The northern part could periodically germinate and have adequate soil of Seedskadee NWR was mainly influenced by Green moisture to survive (Ikeda 1989). River flows, while the southern part of the refuge also The primary changes to the Seedskadee NWR was influenced by flows from the Big Sandy River. ecosystem since major European settlement in the Historically, Green River discharges peaked in May late 1800s, have been: 1) alterations to the amount, or June in most years and were sufficient (8,000 to timing, duration, and extent of Green River flood 10,000 cfs) to cause at least some backwater flooding waters flowing into and through riparian woodland into old abandoned river channels, sloughs, and flood- and floodplain ; 2) management of the dis- plain swales over 50% of the years prior to Fontenelle tribution and retention of water in constructed and Reservoir. Larger flood events (> 14,000 cfs) appear altered wetland impoundments and natural basins; to have inundated deeper floodplain depressions and 3) reduced presence, regeneration, and health of occurred about every 5-10 years. Very large flood woody riparian vegetation; 4) altered sagebrush events > 20,000 were rare (only 3 times since the late steppe species composition and distribution; and 5) 1800s) but were highly important to create extensive increased presence of invasive species. A critical over- silt deposition and scouring, channel filling or riding issue that affects the future management of migration, nutrient deposition, and extensive areas of Seedskadee NWR is the annual operation of water floodplain connectivity. Similarly, regular flooding of storage and releases from Fontenelle Reservoir. A the Big Sandy River maintained important ecological major challenge for future management of Seed- processes in its floodplain. skadee NWR will be to determine how a reduced The regular river backwater flooding of low flood-driven river system, likely affected by unknown elevation floodplain wetlands every 2-5 years was future climate changes, will affect efforts to restore a primary driving process that sustained the flood- and provide critical habitats and communities for plain wetlands and wet meadows of the Seedskadee wildlife (Knopf et al. 1988, Meretsky et al. 2006, 49 50 Heitmeyer, et al.

Seavy et al. 2009). Past attempts to plan man- et al. 2006). Administrative policy that guides NWR agement of the refuge have largely been designed to goals includes mandates for: 1) comprehensive doc- continue more permanent water management among umentation of ecosystem attributes associated with wetland impoundments, which may or may not have biodiversity conservation; 2) assessment of each been consistent with objectives that seek to restore refuge’s importance across landscape scales; and 3) and emulate natural distribution, abundance, and recognition that restoration of historical processes is processes of endemic communities. Consequently, critical to achieve goals (Mertetsky et al. 2006). Most future management issues that affect timing, dis- of the CCPs completed for NWRs to date, including tribution, and movement of water on the NWR must the Seedskadee NWR CCP, have highlighted eco- consider how, and if, they are contributing to desired logical restoration as a primary goal, and choose his- objectives of restoring native communities and their torical conditions (those prior to substantial human processes on the refuge. Additionally, future man- related changes to the landscape) as the benchmark agement and possible expansion of the refuge must condition (USFWS 2002, Meretsky et al. 2006). seek to define the role of the refuge lands in a larger General USFWS policy, under the Improvement Act landscape-scale conservation and restoration strategy of 1997, directs managers to assess not only his- for the Upper Green River Basin and surrounding torical conditions, but also “opportunities and limita- sagebrush steppe ecosystem. tions to maintaining and restoring” such conditions. Furthermore, USFWS guidance documents for NWR management “favor management that restores or GeNeRAL ReCommeNdATioNS FoR mimics natural ecosystem processes or functions to eCoSySTem ReSToRATioN ANd achieve refuge purpose(s) (USFWS 2001). mANAGemeNT Given the above USFWS policies and mandates for management of NWRs, the basis for developing This study is an attempt to evaluate restoration recommendations for the future management of and management options that will protect, restore, Seedskadee NWR is the HGM approach used in this and sustain natural ecosystem processes, functions, study. The HGM approach objectively seeks to under- and values at Seedskadee NWR. Seedskadee NWR stand: 1) how this ecosystem was created; 2) the fun- provides key resources to meet annual cycle require- damental physical and biological processes that his- ments of many plant and animal species in the Upper torically “drove” and “sustained” the structure and Colorado River ecoregion of the western U.S. The functions of the system and its communities; and 3) Green River and its floodplains are an especially what changes have occurred that have caused deg- critical component of the river system that bisects radations and that might be reversed and restored an otherwise dry, semi-desert, ecosystem. Further, to historic and functional conditions within a “new the sagebrush steppe habitats adjacent to the Green desired” environment. This HGM approach also River in the Seedskadee NWR are part of the largest evaluates the NWR within the context of appropriate contiguous block of this habitat in the western U.S. regional and continental landscapes, and helps This habitat supports populations of many animal identify its “role” in meeting larger conservation species associated with this community in the Rocky goals and needs at different geographical scales. In Mountain ecoregion (USFWS 2010). Seedskadee NWR many cases, restoration of functional ecosystems on is an important area that also can provide opportu- NWR lands can help an individual refuge serve as nities for wildlife-dependent uses. These public uses a “core” of critical, sometimes limiting, resources are important values of the refuge, but they must be than can complement and encourage restoration and provided and managed within the context of more management on adjacent and regional private and holistic regional landscape- and ecosystem-based public lands. management. This study does not address where, or Seedskadee NWR contains a relatively sharp if, the many sometimes competing uses of the refuge contrast and dichotomy of communities/habitat can be accommodated, but rather this report provides types between the Green River and its floodplain information to support The National Wildlife Refuge and the adjacent upland sagebrush steppe landscape. System Improvement Act of 1997, which seeks to The primary ecological process that controlled the ensure that the biological integrity, diversity, and Green River ecosystem was rising water levels in the environmental health of the (eco)system (in which a Green River in spring and early summer that caused refuge sets) are maintained (USFWS 1999, Meretsky seasonal backwater flooding and inundation of at HGM EVALUATION OF ECOSYSTEM MANAGEMENT OPTIONS FOR SEEDSKADEE NWR 51 least some lower elevation floodplain sloughs, swales, this sagebrush community became heavily grazed and depressions in most years. Further, relatively by livestock, was burned more frequently, and many regularly occurring (5-10 year periodicity) large areas such as alluvial fans adjacent to floodplains flood events caused widespread inundation of flood- or riparian areas (such as at Seedskadee NWR) plain areas and alluvial deposition/scouring events were physically altered by roads, rail beds, fences, that formed dynamic topographic and water flow/soil and ditches. Although livestock grazing now is saturation patterns in the floodplain. Both seasonal reduced or eliminated on most of the uplands on and longer term inter-annual river flow and flooding Seedskadee NWR, the historical sagebrush steppe dynamics created and sustained a diversity of wetland habitat is still greatly altered from the past grazing types in the immediate floodplain and also created intensity that caused a reduction in abundance and and sustained sites for riparian woodland germi- distribution of native plant species including loss of nation and survival. The basic spatial and temporal native perennial bunchgrasses, expansion of some pattern of this spring-flood driven ecosystem remains shrubs such as rabbitbrush, introduction of many present, but operation of Fontenelle Dam has: 1) annual weeds and grasses such as cheatgrass, and reduced flood peaks and frequency of spring/summer soil/slope erosion. flows that caused extensive inundation and alluvial Clearly, Seedskadee NWR is, and will continue deposition/scouring in the floodplain; 2) caused arti- to be, highly affected by the presence and operation ficial high flows in late summer and early fall; and 3) of Fontenelle Reservoir and Dam. The impetus for created high base flows in winter. establishing Seedskadee NWR was to mitigate fish Floodplain topography and hydrology at Seeds- and wildlife habitat losses from the reservoir (and kadee NWR have been altered where extensive infra- other older proposed diversions of water from the structure has been constructed (e.g. dams, ditches, Green River). Consequently, future management of levees, water-control structures) to create and manage Seedskadee must attempt to sustain and restore his- impounded wetlands for more permanent water torical communities and resources in this region of regimes aimed at increasing waterfowl production. the Green River Valley and to manage all habitats Concurrently, vegetation in wetland impoundments (sagebrush steppe, floodplain wetlands, riparian was dramatically changed from historic conditions woodland, riverine) to provide historical resources where natural floodplain water regimes were predom- used and required by native animal species within inantly seasonal and at best seimpermanent in deeper the constraints imposed by the management of water depressions. Natural areas appear to be storage and releases from Fontenelle Reservoir. reduced in area and vigor on the refuge. In contrast, Given this management context, and based on the invasive species assemblages such as perennial pep- HGM context of information obtained and analyzed perweed are increasing. Riparian woodland at Seed- in this study, we believe that future management of skadee NWR is rapidly deteriorating with almost no Seedskadee NWR should seek to: recruitment of new cottonwood seedlings and poor 1. Maintain and restore the physical and hydro- survival of existing trees from combined effects of logical character of the Green River (below Fon- fire, herbivory, and drought induced stress caused by tenelle Reservoir) and the Big Sandy River as infrequent floods and rapidly declining soil moisture best possible. in summer. Former riparian woodland is shifting to upland/grassland vegetation composition. 2. Restore the natural topography, water regimes, Upland areas on Seedskadee are driven by the and surface water flow and flooding patterns relatively arid climate and geological history of the from the Green River into and across the Green region. Low annual precipitation, high evapotrans- River floodplain and sheetwater runoff into and piration rates, and sandy alkaline soils created a across adjacent terraces and alluvial fans. sagebrush steppe community throughout much of 3. Restore and maintain the diversity, composition, western Wyoming, southern Idaho, northern Nevada, distribution, and regenerating mechanisms of and southern Oregon (West 1988). Herbivory and fire native vegetation communities in relationship to were important ecological drivers in this ecosystem, topographic and geomorphic landscape position. but fire was relatively infrequent and grazing was mainly by seasonally present large browsers and The following general recommendations are low numbers of granivores. After European immi- suggested to meet these ecosystem restoration and gration and settlement in southwestern Wyoming, management goals for Seedskadee NWR. 52 Heitmeyer, et al.

1. Maintain and restore the physical and discharge with a unimodal late spring-early summer hydrological character of the Green discharge followed by gradual declines to low winter River (below Fontenelle Reservoir) and base levels, b) provide more regular (i.e., in ca. 50% the Big Sandy River as best possible. of years if possible) peak flows > 8,000 to 10,000 cfs that allow at least some backwater flooding into flood- The general physical position and geomor- plain sloughs, abandoned river channels, and swales; phology of the Green River below Fontenelle Dam and c) occasionally allow high peak flows > 15,000 cfs have not been altered greatly, although several rock that cause more extensive inundation of the Seeds- weirs and sills and other structures have been con- kadee NWR floodplain. Ideally, a flood discharge of structed to facilitate diversion of water into Seeds- > 20,000 cfs would occur about every 40 to 50 years kadee NWR impounded wetlands, provide watering to provide sediment and nutrient dynamics sufficient gaps for livestock, and stabilize channel banks. to create cottonwood regeneration sites, replenish Similarly, the physical nature of the lower Big Sandy nutrients and sediments in wetlands, and allow river River is only moderately altered from its historical migrations to occur. condition. The Green River channel below Fontenelle Ultimately, the hydrology of the entire Green Dam is not highly incised at present, but the reduced River ecosystem will depend on protecting the sediment loads in the river below the dam could integrity of the upstream watersheds of the Green potentially lead to eventual incision (Auble et al. and Big Sandy Rivers with special emphasis on 1997, Auble and Scott 1988, Glass 2002). The current the more immediate lands in their floodplains and low sediment loads in the Green River at Seedskadee drainages. This need will require coordinated efforts NWR have an effect on downstream alluvial depo- of land owners and managers to protect surface and sition in floodplains, which could alter nutrient levels subsurface landscapes of the region including the and replenishment in floodplains, establishment geohydrology of the system. Vigilance against efforts of germination sites for riparian woodlands, and to extract or divert more surface or subsurface water, creation of topographic/bathymetry diversity and alter flow patterns and pathways, and contamination dynamics in the river that influence water velocity, of soils and water in the watersheds and floodplain turbidity, and structural features and diversity. In corridors must be maintained. contrast, increased channel bank erosion that causes 2. Restore the natural topography, water bank destabilization and increased sediment loading regimes, and surface water flow and can occur where bank sites are altered by livestock, flooding patterns from the Green deforestation, and human activity. While no imminent River into and across the Green River large changes to the physical features of the Green floodplain and sheetwater runoff into or Big Sandy Rivers are foreseen, land managers and across adjacent terraces and must be vigilant to future proposals or actions that alluvial fans. would alter the physical nature of the rivers and their inherent dynamics of flow and sediments and to Many changes have occurred to the Seedskadee smaller, cumulative changes in the physical integrity NWR floodplain from alterations in topography, water of the river channels and their floodplains. movement patterns, and water regimes. Certain of In contrast to physical features, the hydrologic these changes have been directly caused by, or are character of the Green River is greatly altered from associated with, construction and management of the pre-Fontenelle Reservoir period. As currently Fontenelle Reservoir. These include some past infra- operated, Fontenelle Reservoir has relatively little structure that sought to move water to upland areas flexibility in water management as dictated by annual for irrigated croplands (e.g., the Hay Field area) and variation in watershed precipitation, water and land reduced spring discharge peaks that no longer flow use, and downstream needs in the entire Colorado into or through relict river channels, sloughs, and River system. Water flows in the Big Sandy River swales. Other changes occurred from construction of are less altered from historical periods, but still are roads, water gaps, ditches, weirs, and water-control affected to some degree by the reservoir on the river structures. Still other changes were purposeful channel near Farson, Wyoming. Working closely with attempts to modify natural flooding and drying the BOR and negotiating water management guide- regimes in wetlands to create more permanent and lines for Fontenelle Reservoir will be important to a) regularly occurring water regimes to increase open maintain a more natural seasonal pattern of river water and persistent emergent vegetation habitats HGM EVALUATION OF ECOSYSTEM MANAGEMENT OPTIONS FOR SEEDSKADEE NWR 53 and encourage waterfowl nesting. Collectively, these process of overbank and backwater flooding that was alterations have caused changes in vegetation com- so critical to sustain this ecosystem. munities and resources used and needed by select Third, water management objectives for the indi- animal groups. If a goal of the refuge is to restore vidual wetland impoundments on Seedskadee NWR the naturally occurring physical and biotic diversity should be reviewed. Historically, the Green River and productivity of the Seedskadee NWR ecosystem, floodplain at Seedskadee contained a diverse mosaic then at least some restoration of natural topography, of depressions that reflected past river migration, water flow pathways, and seasonal water regimes alluvial deposition, and current scouring. The LIDAR will be needed. This restoration will require changes maps for the refuge demonstrate this topographic in physical features and management of wetland diversity and the interrelationships of elevation and impoundments. relative flooding regimes. Very few deep depressions First, an evaluation of all roads, ditches, weirs, occurred in the Seedskadee floodplain except for a fence lines, water gaps, etc. on the refuge should be few remnant oxbows and abandoned channels such made to determine if they are necessary, beneficial or as was within the Northern units (Fig. 16). These detrimental to management objectives, and whether deeper wetlands apparently were regularly recharged they can be modified or removed. As an example, by floodwaters on average about every 2-3 years and some old small berms were constructed in floodplain they probably retained at least some surface water wet meadow and grassland areas in an attempt to throughout the summer and into fall. In very wet impound or divert water. If these structures disrupt years, water likely was present throughout the year, sheetflow of runoff or flood water, disconnect natural while in dry years these deeper depressions may swales or sloughs, or deter flood water movement into have had little if any water. Generally, few flood- floodplain depressions they should be removed. Other plain wetlands had water in late fall and winter at infrastructure such as ditches formerly constructed to Seedskadee NWR; the only open water would have move water across floodplains for irrigation purposes, been in the river channel. The inter-annual dynamic should be removed if they are not helpful to a desired flooding regimes in the deeper floodplain depressions wetland management need. Likewise, some internal helped maintain nutrient and vegetation cycling levees constructed in impounded wetlands create in these wetlands and attracted larger numbers of impediments to independent water management breeding waterbirds in wet years (see e.g., review in among wetland units/pools and disrupt, or actually van der Valk 1989 and Heitmeyer and Fredrickson prevent, most floodwater levels from entering and 2005). Most wetland depressions in the Green River flowing through the impoundments. floodplain at Seedskadee, however, were small swales Second, the “new” lower flood pulse peaks on in former ridge-and-swale river point bars. For the Green River now seldom reach levels where example, the ridge-swale topography complexes in the river water can back or overflow into floodplain Hamp, Pal, and Sagebrush units are marked (Fig. swales and depressions. Peak flows post-Fontenelle 6). These natural swales did not become inundated Reservoir average about 4,000 cfs lower than prior as often or as deeply as abandoned channel depres- to the reservoir (e.g., Fig. 23), which equates to about sions, and the swales had seasonal water regimes a 2-4 foot lower river stage elevation at Seedskadee that were recharged in spring and early summer and NWR during peak events. Where former river-flood- then dried relatively quickly into fall. Some higher plain connection entry points have been modified elevation swale sites may have only contained a small or artificially filled with sediment, they potentially amount of water from onsite precipitation or runoff could be reconnected and opened by excavating the in spring with rarer flooding by very large (and rare) fill material and lowering the natural levee entry flood events. Lower elevation swales likely flooded points by 2-4 feet. Additionally, sediment or debris more regularly from moderate Green River flood material that now obstructs or prevents flood flows events, especially those sites with connectivity to the in naturally occurring sloughs and swales should be river via backwater sloughs. Wet meadow habitats removed. Clearing, deepening, and restoring natural also were present in many floodplain locations that water flow pathways will require careful engineering received only short duration sheetflow of water across given the probability of new reduced flood flows in relatively flat floodplain areas during spring flood the Green River at Seedskadee NWR. While some and runoff events. These meadows did not impound deepening of sloughs and swales may be a bit arti- water, except in shallow depressions, which dried ficial, it is consistent with attempting to restore the quickly following inundation events. 54 Heitmeyer, et al.

Collectively, the HGM information for Seeds- other floodplain point bar ridge sites where alluvial kadee NWR indicate that most historical wetlands deposition occurred and porous soils provided more and wet meadows had seasonal water regimes prolonged and elevated groundwater during drying and that even the deeper depressions had regular, summer and fall periods. Uplands adjacent to flood- perhaps almost annual, drying in late summer plains, including alluvial fans that extended into the and fall. Consequently, wetland habitats were most floodplain supported sagebrush steppe communities. extensive and available during spring and early The above described community relationships summer and provided resources primarily to spring with abiotic ecosystem attributes provides a guideline migrant waterbirds. During wet years more flood- for determining which communities belong where in plain wetlands were inundated for longer periods the Seedskadee NWR ecosystem, and which sites in summer and attracted more waterbirds to stay are appropriate for restoration of specific community and breed locally. Current water management of types. For example, restoration of riparian forest, most wetland impoundments has overemphasized which is rapidly deteriorating, should be on rela- permanent and emergent vegetation for breeding tively recent alluvial deposition/scour sites near the waterbirds, and underemphasized seasonal flooding Green or Big Sandy Rivers (or seasonally connected regimes most important for spring migrants, relative abandoned river channels and sloughs) that have to historical pre-Fontenelle flooding regimes. Further, regular overbank/backwater flooding and prolonged artificial high water levels and river discharge in fall soil moisture in the tree root zone through the growing and winter may be providing more fall/winter habitat season. Further, if natural recruitment of cottonwood for waterbirds and in the area, but at some ecological cannot occur because of presently reduced occurrence cost of altered water regimes and seasonal produc- of large flood events that deposit alluvial material and tivity of the sites. create bare soil surfaces for seed set and germination, then direct plantings of seedlings may be successful 3. Restore and maintain the diversity, com- if they are in topographic and soil locations conducive position, distribution, and regenerating to higher groundwater tables along the river (Scott et mechanisms of native vegetation com- al. 1993, Braatne et al. 1996, Friedman et al. 1995). munities in relationship to topographic Future restoration and management of communities and geomorphic landscape position. at Seedskadee NWR will require a careful evaluation Seven major vegetation communities (sagebrush of site characteristics to determine what the site his- steppe, mesic upland, floodplain grassland-wet torically supported and now is capable of supporting meadow, seasonal herbaceous wetland, semiper- given alterations to the system. manent emergent wetland, riparian woodland, and riverine) historically were present at Seedskadee NWR and they were distributed along geomorphic, SpeCiFiC ReCommeNdATioNS FoR soil, topographic, and flood frequency gradients ReSToRATioN ANd mANAGemeNT (Table 8, Figs 20,21). Precise mapping of the opTioNS potential historical distribution of these communities on Seedskadee NWR was constrained to some degree maintain and Restore the physical and by coarse-scale soil mapping. In contrast, the recently Hydrological Character of the Green and Big completed LIDAR topographic information greatly Sandy Rivers enabled understanding of potential water regimes (Fig. 16). The spatial patterns of historical community The impetus for establishing Seedskadee NWR distribution are relatively distinct (Table 8, Fig. 21). was the need to mitigate and protect a portion of the Obviously, riverine habitats were/are within active Green River and its floodplain following construction river channels and seasonally connected river chutes of Fontenelle Reservoir. Consequently, management and sloughs. Deeper floodplain depressions, especially of Seedskadee NWR must seek to protect and restore relict abandoned channel oxbows, contained open the section of the Green River ecosystem below water-persistent emergent wetland habitats. Flood- Fontenelle within the constraints of the operation plain swales supported seasonal herbaceous com- of Fontenelle Dam. As such, restoration and man- munities while floodplain ridges and other relatively agement of the refuge must clearly understand the high floodplain area supported wet meadow habitats. ecological character of the river system prior to Fon- Riparian forest was present on natural levees and tenelle and identify the best options to protect and HGM EVALUATION OF ECOSYSTEM MANAGEMENT OPTIONS FOR SEEDSKADEE NWR 55 restore the physical and hydrological integrity of • Support programs to restore natural veg- the river, its floodplain, and the associated commu- etation communities in areas of the Green nities it supported. Clearly, many issues related to River watershed that are potentially subject to the future management of the Green River are not high soil erosion and water intensive land uses under the control of the refuge, but the USFWS does including marginal agricultural lands. have the opportunity and responsibility to manage 2. Cooperate with the BOR to manage Seedskadee NWR in an exemplary way that achieves water releases from Fontenelle its authorized purpose and contributes to the overall Reservoir in a more natural seasonal sustainability of the Green River system. Ultimately, and inter-annual flow regime. achieving the greatest sustainability possible will require efforts to protect the upstream watershed of • Seek to maintain a more natural seasonal river the Green and Big Sandy Rivers and work with BOR flow regime of unimodal late-spring to early- to manage water releases in the most natural flow summer peak discharges followed by gradual regime possible. Specific actions that seem important declines to low winter base levels in the Green to this end include: River. 1. Protect the physical integrity of the • Provide peak spring-early summer discharges Green and Big Sandy Rivers and their of > 8,000 cfs whenever possible to provide at upstream watersheds. least some connectivity of river flood water with Green River floodplain wetland and off-channel • Do not construct additional dams, levees, or depressions. channel-bank stabilization structures on the Green or Big Sandy rivers. • In very wet years, seek to provide spring flood pulses as high as possible, preferably with occa- • Remove and do not place hard point or bank sta- sional discharges > 15,000 cfs. bilization structures along the channel banks of the Green and Big Sandy rivers unless they • Attempt to provide a high discharge of > 20,000 protect critical property or structures. cfs about every 40 to 50 years. • Remove, or place spillways in levees along the • Reduce artificial high fall releases and dis- Green and Big Sandy rivers. charges. Preferably, more water would be released in spring-summer and less in fall. • Protect banks of rivers from physical distur- bance, especially from livestock. Restore Natural Topography, Water Flow • If river channel incision begins to occur, carefully patterns, and Water Regimes engineer rock weirs or other grade-control struc- The restoration of historic ecological commu- tures/measures, in the affected river area. nities and their key driving ecological processes at • Reconnect river channels with remnant side Seedskadee NWR will require at least some resto- channels, abandoned channels, sloughs, and ration of natural topography, water flow patterns, chutes. and water regimes (e.g., Stanford et al. 1996). As stated above, part of this restoration will require • Encourage and participate in sustainable range achieving water releases from Fontenelle Reservoir management programs throughout the Upper that are more natural, both seasonally and long term. Green River watershed. If these releases and more natural river flow regimes • Protect alluvial fans and terraces along the can be achieved, impediments to river-floodplain con- Green and Big Sandy River valleys from detri- nectivity on the refuge should not be intentionally mental development, mining, and topographic maintained, nor should present water management alteration and support private lands programs strategies in refuge wetland impoundments be to maintain natural topographic features and preferred over natural flooding and drying regimes. communities. The ultimate goal for Seedskadee NWR is to protect and restore natural integrity, functions, and values • Evaluate opportunities to expand the bound- of the unique western riparian corridor and adjacent aries and protection capabilities of Seedskadee sagebrush steppe, and not try to create unnatural NWR. artificial conditions or communities on the refuge. 56 Heitmeyer, et al.

The inherent geomorphic surfaces, soils, topography, abandoned channel at the downstream and former hydrology of wetland impoundments end of the river bend where floodwaters from should be considered when deciding management and the Green River historically entered this area development strategies. Specific changes to the Seed- (Fig. 6a). The unit was originally developed into skadee NWR system that seem helpful in this regard impoundments with the desire to create more include: permanent open-water emergent vegetation habitats for breeding waterfowl. Most of the 1. Restore natural topography and unit is a classic river point-bar ridge-and-swale reconnect natural water flow patterns geomorphic surface where only short duration and pathways where possible. seasonal inundation occurred, except during • Evaluate all levees, roads, ditches, and water- high flow conditions on the Green River (Fig. control structures to determine if they are 16a). Ideally, the unit should be managed as necessary, or are detrimental to, restoration of a more seasonally flooded wetland regime and natural water flow patterns and water regimes seasonal herbaceous/wet meadow community. in floodplains and uplands. Identify structures Infrastructure that deters floodwater entry from that can be used to help emulate natural flow the bottom end of the unit should be modified or patterns and conversely, remove or modify those removed to allow high flow events to back into structures that are not necessary or that are the abandoned channel sloughs and point bar deterring natural water flow patterns. swales. • Do not construct additional wetland impound- • The Hawley Unit contains several natural topo- ments, roads, levees, or water-control structures graphic depression features including a relict that alter water flow into and across the flood- abandoned channel oxbow (Figs. 6b,16b). The plain. Green River also has two side chute channels • Restore at least some natural topography in adjacent to the floodplain. This area appar- wetland impoundments, and former agricul- ently has been a site of relatively recent river tural lands that can be restored to native veg- migration. Development of the site has diverted etation. water into and through the unit to the more southern downstream impoundments and also • Remove islands and deposition sites in wetlands. created subdivided impoundments. The water • Improve water flow into and through historic management of impoundment pools typically floodplain abandoned channels, sloughs, and has sought to create more permanent open water depressions by removing or lowering obstruc- and emergent vegetation habitats. This man- tions, levees, weirs, sills, and dams across these agement seems appropriate, but more natural drainages and depressions. dynamics of spring inundation followed by summer and fall drying should be encouraged. • Evaluate the potential to “cut” fill material These semipermanent wetlands also periodi- at entry points of relict floodplain channels, cally dried every 3-5 years when Green River sloughs, and swales where the Green and Big peak flows in spring were low. Because water Sandy Rivers would back or overflow into these must be diverted into Hawley to supply water to sites. Also, remove or cut material from high downstream units, it is always flooded first and spots in these channels that prohibit water is flooded more regularly among years. Recog- movement through the floodplains and that nizing this “control” function, the unit should could potentially flood extensive areas during be occasionally dried to prevent the substantial high flow events. encroachment and filling of the unit with dense 2. Manage wetland impoundments and monocultures of emergent vegetation, especially natural floodplain depressions for more cattail. In the absence of more regular drying, natural seasonal and long-term water other vegetation controls may be needed. regimes based on their HGM-attribute • The Lower Hawley Unit contains former channels position. of the Green River and a point bar ridge-and- • The Hamp Unit is located on an inside-bend swale geomorphic surface on the south end (Fig. point-bar geomorphic surface with a relict 6c). The floodplain depressions in this area HGM EVALUATION OF ECOSYSTEM MANAGEMENT OPTIONS FOR SEEDSKADEE NWR 57

likely flooded regularly when the Green River high natural levees and probably ridges on point rose in spring and summer and the deeper relict bars contained riparian woodland, the swales oxbows may have been a large part of the more contained seasonal herbaceous wetlands, and permanent wetlands in the system (Fig. 16c). the old cutoff river channel was semipermanent Currently, water-control infrastructure moves emergent wetland (Fig. 16d). Water currently water from the Hawley Unit into and through the is moved to the Unit from the upstream infra- unit, through the Sagebrush Unit, and finally structure associated with the Hawley units, and to the southern Dunkle Unit. Several levees when river flows have been low, this and the create subimpoundments in the Lower Hawley Dunkle Unit have received less water. Conse- impoundment and they prevent high flows of the quently, the site has been developed to retain Green River from entering the unit. Managing water in deeper areas of swales and the old water regimes and wetland vegetation in Lower oxbow. Future management and redesign of Hawley in a manner similar to the Hawley Unit the unit should consider providing a complex seems appropriate, and should include rotational of riparian woodland on ridges and the natural flooding and drying of subimpoundments to levee along inside point bar bends of the river, emulate natural flooding-drying dynamics. Also, natural short duration seasonal flooding in the outside levees of the impoundment should be swales, and more semipermanent water regimes evaluated to find appropriate potential breach in the old oxbow depression. Water-control or spillway sites where high flows of the Green structures that prevent high flows of the Green River could enter the floodplain. River from entering and inundating swales and depressions should be removed or modified. • The Pal Unit is a slightly higher elevation point bar river bend surface on the east side of the • The Cottonwood Unit is a typical inside-bend Green River and it includes a relict horseshoe- point-bar surface that contains several ridge- shaped abandoned river channel on the northeast and-swale topographic complexes. The swales side (Fig. 6c). The Unit historically contained in these areas apparently became inundated riparian woodland along the river, seasonal her- when river discharges exceeded 14,000 to 17,000 baceous wetlands in swales and wet meadow cfs; the entry point of flooding was at the down- grassland on ridges. The higher elevation areas bottom ends of the river bends. In this in the unit historically apparently were flooded unit all water-control structures that prevent for short durations during spring flood events occasional river backwater from entering the (Fig. 16c). Only a few water-control structures point-bar swales should be removed or modified are present in the unit and they primarily are to allow river flows to cross them. used to hold water in swales. Higher elevations • The Dunkle Unit contains a point-bar bend of the in the unit are most suited for short duration Green River, crevasse splays on the upper bend seasonal flooding and wet meadow communities. area, and old relict channels behind the point In these areas existing water-control structures bar (Fig. 6e). The point bar bend has higher ele- should be removed or modified to allow natural vations and only shallow swales that probably sheetwater flow from floodwater and runoff historically supported riparian woodland and to occur. Deeper relict abandoned channel shrub wetland. Relict channels behind the areas apparently had frequent inundation point bar likely were flooded during high flow from high river flow events and probably had events of the Green River (Fig. 16e). The few semipermanent water regimes that supported water-control structures in the unit attempt to persistent emergent vegetation communities. capture and hold water that is diverted from the Infrastructure should be evaluated to make upstream Hawley units. Because the unit is sure river floodwater can continue to inundate the farthest from the Hamp diversion point, it these depressions frequently. has a less regular water source. Given the less • The Sagebrush Unit is within a widely mean- reliable source of water and its point bar setting, dering portion of the Green River and includes water-control structures should be removed if point bar ridges and swales on two inside bends they deter floodwater entry during high Green of the river with a cutoff abandoned channel River discharge times and where structures are behind the point bar (Fig. 6d). Historically, the retained, the water regimes should be seasonal. 58 Heitmeyer, et al.

Sustain and Restore Natural Vegetation • Carefully manage some decadent sagebrush Communities areas with select thinning and reduce the occur- The native mosaic of vegetation communities at rence and extent of rabbitbrush where it is arti- Seedskadee NWR were important components of the ficially high. Green River ecosystem and the entire Upper Colorado • Control invasive weeds and grasses. River ecoregion. Sustaining, and restoring where necessary, the distribution and types of historical 2. Restore linear bands of riparian habitats is important to the long term capability of woodland along the Green and Big the entire ecoregion to support system functions, Sandy Rivers. values, and services. The general types and distri- • Attempt to maintain existing areas of riparian bution of communities at Seedskadee NWR have not woodland with protection from extensive changed dramatically from historic patterns, but the browsing and trampling from native ungulates following major alterations have occurred: and livestock and suppression of fires. • Upland sagebrush steppe has altered species • Work with BOR to restore more natural flow composition including invasion by nonnative regimes in the Green River (see earlier recom- annual grasses and weeds. mendations section) that include: 1) occasional high discharges that can flood higher elevation Riparian woodlands are rapidly deteriorating • natural levees and ridges in floodplains, 2) and almost no natural recruitment of cot- gradual declines in water levels (< 4 cm/day) tonwood is occurring. in summer, and 3) low base flows in winter (to • Many floodplain wetland depressions have been prevent excessive water levels and ice scouring). impounded with more permanent water regimes • Target restoration sites that have sandy loam and open water-emergent vegetation and less soils on natural levees of active and relict river seasonal herbaceous and wet meadow commu- channels and sloughs and ridges in point bar nities. river bend areas where high, more sustained, • Off channel side and high flow channels, groundwater levels occur during summer. These sites typically are on inside bend point bar sites. sloughs, swales, and oxbows have been discon- nected with the Green River. • Evaluate some use of physical disturbance in the Restoration and maintenance of native com- above sites to provide bare-soil surfaces for cot- munities seems possible and desirable (at least to tonwood and willow seed set and germination. certain degrees) at Seedskadee NWR. Consequently, In sites where no seed source or bare soils are the basis for future conservation, restoration, and present, plant seedlings with protective wire management of plant communities on Seedskadee or wrap to prevent browsing and damage to NWR should be guided by ecological attributes iden- seedlings from ungulates and beaver (e.g., Glass tified in the HGM matrix and maps provided in this 2002, Breck et al. 2003, Scott et al. 2008). report based on geomorphology, soil, topography, and • Continue monitoring and evaluation studies hydrology features (Table 8, Fig. 21). Specific actions on biotic and abiotic components of riparian to assist this restoration include: woodland communities and restoration efforts. 1. Protect and restore native vegetation 3. Restore complexes of floodplain wetland composition to upland sagebrush steppe communities with natural water areas. regimes. • Protect all existing sagebrush steppe areas • Restore connectivity of the Green River and from conversion to other habitat types, frag- floodplain depressions and restore water flow mentation, and disturbance from livestock and pathways in floodplains as suggested previously. vehicles. • Change infrastructure and management of • Encourage natural fire regimes, with long wetland impoundments as listed above. return intervals, in uplands and especially in • Control invasive plants in floodplains and restore drainage areas and washes. native species composition to wet meadow areas. HGM EVALUATION OF ECOSYSTEM MANAGEMENT OPTIONS FOR SEEDSKADEE NWR 59

• Manage wetland impoundments for annually dynamic water regimes and reduce monotypic stands of tall emergents, especially cattail, to increase productivity of semipermanent wetland areas such as relict oxbows.

Adonia Henry 60 Heitmeyer, et al.

Adonia Henry