In Colorado, Western Great Plains Saline Depressions are partially to fully isolated saline depressional basin herbaceous wetlands. Saline depressions are dispersed across the eastern Colorado plains river basins, sometimes directly adjacent to freshwater playas with a different water source or geologic influence. These closed depressions range from small playa-like basins to larger saline reservoirs and lakes, characterized by relatively impermeable-once-wetted clayey pond bottoms, shallow depressional topography, central sparsely vegetated zones or complete coverage of salt pans, and hydrology fed by both heavy precipitation events and groundwater discharge. Dominant, moderately salt-tolerant species include saltgrass (Distichlis spicata), common threesquare (Schoenoplectus pungens), and foxtail barley (Hordeum jubatum). Halophytes are generally also present with low to high cover in the active wetting/drying zones. Halophytic indicator species include red swampfire (Salicornia rubra), Mojave seablite (Suaeda moquinii), Pursh seepweed (Suaeda calceoliformis), verrucose seapurslane (Sesuvium verrucosum), salt heliotrope (Heliotropium curassavicum), and seaside arrowgrass (Triglochin maritima). Salt-tolerant shrubs such as greasewood (Sarcobatus vermiculatus), fourwing saltbush (Atriplex canescens), and winterfat (Krascheninnikovia lanata) may be present in low cover or around the saline wetland fringe. Concentric vegetation zonation is also related to duration of inundation.
Saline basins and lakes are discharge wetlands, with dynamic ponding regimes that vary from ephemeral and predominately dry, to perennially saturated and semi-permanently flooded. Hydroperiod depends on wetland size, proportion of groundwater vs. surface water sources, and human hydrologic alterations. Water depths are often shallow but can be deep in larger lakes and irrigated occurrences, and the surface substrate surrounding ponded areas can be soft muck in saline basins, unlike the hardened saturated substrate around the ponded zone of freshwater playas.

These are small- to lake-sized, highly saline depressional basins lacking a surface water outlet, often with visible salt crusts and saline water chemistry, presence of halophytes, and vegetation with concentric zonation in response to wetness and salinity. Saline depressions can occur in semi-isolated depressions similar to freshwater closed depressions, but are characterized by high salinity soils, an outer ring of halophytic (salt-tolerant) vegetation, and a central unvegetated zone.

This system can occur throughout the western Great Plains from Texas north into Canada but is likely more prevalent in the south-central portions of the division. Its distribution extends as far west as central Montana and eastern Wyoming where it occurs in the matrix of Northwestern Great Plains Mixedgrass Prairie, and south to Texas and New Mexico. In Colorado, this system occurs more prevalently within the Arkansas river basin north of the floodplain, specifically over the calcareous Niobrara formation. A more complete census is needed to determine the full distribution in the Western Great Plains.

Western Great Plains Saline Depression Wetland is a small patch type.

Saline lakes occur in similar landscapes to freshwater closed depressions and playas in the shortgrass prairie, and also occur in depressions below rolling vegetated sandhills and within salt-tolerant shrublands. They can occur as small herbaceous wetlands in saline headwater landscapes, or in larger complexes of saline groundwater discharge near large Colorado plains river floodplains. There are clustered occurrences north of the Arkansas River, such as the saline lakes known as the Great Plains Reservoirs. The surrounding environment can be stabilized sandhills and deflating dunes, shortgrass prairie, or irrigated areas outside of larger floodplains, and thus their substrate texture is more variable than freshwater playas with a mixture of coarse sandy and fine loamy to clayey soil textures. When wetted, soils in minimally altered saline depressions are relatively impermeable.

Species composition during the wet phase can be diagnostic most years. Species richness can be limited to very few species at any site, or restricted by species salinity tolerance, hypersaline water chemistry, and site conditions even where least altered. During exceptionally wet years, an increase in precipitation can dilute the salt concentration in the soils of some examples of this system and allow for less salt-tolerant species to occur. Conversely, species composition may fluctuate with lack of wetting, and upland species will populate and persist during dry phases.
Common species dominants are moderately salt-tolerant such as saltgrass (Distichlis spicata), common threesquare (Schoenoplectus pungens), and foxtail barley (Hordeum jubatum). Halophytes are generally also present with low to high cover where characteristic hydrology is intact. Halophytic indicator species are red swampfire (Salicornia rubra), Mojave seablite (Suaeda moquinii), Pursh seepweed (Suaeda calceoliformis), verrucose seapurslane (Sesuvium verrucosum), salt heliotrope (Heliotropium curassavicum), and seaside arrowgrass (Triglochin maritima). Salt-tolerant shrubs such as greasewood (Sarcobatus vermiculatus), fourwing saltbush (Atriplex canescens), and winterfat (Krascheninnikovia lanata) may be present in low cover or around the saline outer wetland fringe. Other common species are common spikerush (Eleocharis palustris), cosmopolitan bulrush (Bolboschoenus maritimus), chairmaker's bulrush (Schoenoplectus americanus), goosefoot (Chenopodium spp.), scratchgrass (Muhlenbergia asperifolia), and dropseed (Sporobolus spp.). Tamarisk (Tamarix spp.) and burningbush (Bassia scoparia) can invade the outer vegetation zones, particularly when hydrology is altered. Some freshwater-origin playas can have similar vegetation and salt accumulation to saline depressions, especially when irrigation leaches salts from surrounding upland soils into the feature. Saltgrass (Distichlis spicata) is the most consistently observed species in surveyed eastern Colorado occurrences, where it forms a wet meadow ring outside of the unvegetated salt-crust area, or a wide wet meadow fringe to saline lakes, similar in appearance to saltgrass-dominated eastern Colorado river floodplain meadows.
Saline depressions can be closely associated with greasewood and saltbush plant associations outside of the ponding zone. In addition to the surface water source, many or potentially all of the saline depressions in this region, including saline wet meadows, appear to receive groundwater input or subsurface irrigation secondary to their surface water source.

Numerous birds species flock to the larger and managed saline reservoirs, especially shorebirds, gulls, terns, and waterfowl, such as: piping plovers (Charadrius melodus), American coots (Fulica americana), American avocets (Recurvirostra americana), American white pelicans (Pelecanus erythrorhynchos), northern pintails (Anas acuta), grebes (Aechmorphorus spp.), and the ring-billed gulls (Larus delawarensis). Information is lacking on wildlife use in the non-irrigated saline playa-like basins in eastern Colorado. Saline depressional wetlands likely support unique invertebrate and brine-associated aquatic species, and provide habitat for a number of at-risk wildlife species outside of Colorado.

Saline depression hydrology is governed by wet and dry phases. Water sources are a combination of perched water from precipitation and groundwater discharge. Storm events or consistent wet years can cause water to pond on the surface of fine textured soils. Basin topography prolongs inundation, and as discharge wetlands, significant water is lost to evaporation. Microbial and algae mats can occur on the surface and their presence plays a role in water dynamics, photosynthesis, and salt concentrations. Natural saline basins and lakes function as discharge wetlands, with water from groundwater sources or downslope regional groundwater movement concentrating in shallow depressions.
There is little study on saline depressional wetland hydrodynamics in eastern Colorado. In more studied saline wetland regions of Canada and the southern United States, some wetlands depend on local artesian spring discharge, and plant establishment is associated with groundwater discharge areas. Other water sources include high water tables associated with unconsolidated surficial aquifers, lateral groundwater flow, and possibly shallow bedrock aquifers. The mineral and sediment sources supporting saline water chemistry can be highly diverse, with composition influenced by regional factors, basin geomorphology, and groundwater source and flow paths. Geologic studies outside of Colorado have attributed salt sources to deep bedrock geology rather than surface soil chemistry.

Maintaining an intact surrounding landscape with native plant cover is important to supplying overland runoff to small saline playas. Groundwater depletion poses a significant threat to all saline ecosystems, which can be compounded by droughts and increased evaporation associated with climate change. Water withdrawals and additions, and ditches in large saline playas can alter the timing and duration of wetting, which increases ecosystem sensitivity to sedimentation and exotic invasion. The larger examples of this system often have altered hydrology influenced by management and ditches or pipes. Some occurrences have evidence of declining groundwater levels and retracting wetted occurrence size Long-term irrigation and groundwater pumping can cause trends of increased salinity across the saline wetland populations.. However, if lowered water tables result in loss of wetland connection to an artesian spring source in salina wetlands (or groundwater-dependent saline wetlands), the wetland can dry or transform to a surface water-fed wetland with reduced hydrology.
Sedimentation from nearby tilled or irrigated land can impact wetland hydroperiods and water storage. Large saline reservoirs are frequently managed for irrigation storage, and in those cases, managing reservoir levels and fluctuations to mimic natural hydroperiods contributes to overall system health. Hydrologic alterations can also transform the substrate and support temporary herbaceous and long-term woody invasive species establishment. Due to the semi- to isolated nature of these features, chemical weed treatment has the potential to have cascading impacts on species composition. Overall, recognition and conservation of the wetland resource, groundwater inputs, and contributing basin landscape connectivity is needed for long-term sustainability. More research on the eastern Colorado saline wetlands is needed to better describe and understand their driving ecosystem processes, associated flora and fauna assemblages, and their importance for wildlife.