Description

This area is in Wyoming (85 percent), Colorado (13 percent), and Utah (2 percent). It makes up about 33,005 square miles (85,525 square kilometers). The cities of Laramie, Pinedale, Rawlins, and Rock Springs, Wyoming, and Craig and Meeker, Colorado, are in this MLRA. Interstate 80 bisects the northern part of the MLRA. About 85 percent of this area is in the Wyoming Basin Province of the Rocky Mountain System, 5 percent is in the Middle Rocky Mountains Province of the Rocky Mountain System, and 10 percent is in the Uinta Basin Section of the Colorado Plateaus Province of the Intermontane Plateaus. The part of the area in the Uinta Basin Section is in Colorado. The Wyoming Basin is bounded on most sides by mountains. The Owl Creek Mountains, the Big Horn Mountains, and the Wind River Range are to the north; the Salt Range and Wasatch Mountains are to the west; and the Laramie and Sierra Madre Mountains are to the east. The part of the MLRA in Colorado is bounded on the south by the Roan Plateau, on the east by the Elkhead Mountains, and on the west by Dinosaur National Monument. In most of the MLRA, elevation ranges from 5,200 feet (1,585 meters) to 7,500 feet (2,285 meters). Small mountainous areas have an elevation as high as 9,200 feet (2,805 meters). The extent of the Hydrologic Unit Areas (identified by fourdigit numbers) that make up this MLRA is as follows: Great Divide-Upper Green (1404), 47 percent; North Platte (1018), 28 percent; White-Yampa (1405), 16 percent; Bighorn (1008), 6 percent; Bear (1601), 2 percent; and Powder-Tongue (1009), 1 percent. The Popo Agie, Sweetwater, Laramie, Green, and North Platte Rivers run through the northern part of this MLRA, and the Little Snake, Yampa, and White Rivers run through the southern part. This area is dominated by residual basin-floor geologic materials. Shale and sandstone are the dominant rock types. The Tertiary-age Bridger, Laney, Green River, Wasatch, Wind River, and Browns Park Formations dominate the MLRA. Cretaceous-age formations occur as small areas throughout the MLRA. The dominant Cretaceous formations are the Lewis and Lance Formations and the members of the Mesa Verde Group. Quaternary alluvial and eolian deposits occur throughout the MLRA. Glacial deposits occur primarily on outwash terraces in the vicinity of Pinedale, Wyoming. The small mountain ranges in this MLRA are made up of Precambrian igneous and metamorphic rocks. The average annual precipitation generally is 7 to 12 inches (180 to 305 millimeters), but it ranges from 7 to 32 inches (180 to 815 millimeters). Much of the precipitation occurs as snow from October through April and as rain from May through September. These precipitation events occur as a result of cold fronts moving through the area. Occasional convective thunderstorms produce small amounts of rain during the period June through September. The driest period is usually June through August. The average annual temperature generally is 40 to 44 degrees F (5 to 7 degrees C), but it ranges from 33 to 47 degrees F (0 to 8 degrees C). The freeze-free period averages 105 days and ranges from 45 to 160 days. The dominant soil orders in this MLRA are Aridisols and Entisols. Some representative suborders are Argids, Cambids, Calcids, Orthents, Fluvents, and Psamments. The most extensive and representative great groups are Haplargids (Forelle, Ryan Park, Ryark, and Maysprings series), Haplocambids (Poposhia, Kemmerer, and Chaperton series), Haplocalcids (Fiveoh, Langspring, and Tieside series), Torriorthents (Moyerson, Blazon, and Haterton series), Natrargids (Tisworth and Tismid series), Calciargids (Rock River and Cushool series), Torrifluvents (Cowestglen and Battlement series), and Torripsamments (Maybell and Kandaly series). The dominant soil temperature regime is frigid, and the dominant soil moisture regime is aridic. The soils receiving less than 8 inches (205 millimeters) of precipitation annually have an aridic soil moisture regime. The soils receiving 8 to 14 inches (205 to 355 millimeters) have an aridic soil moisture regime that borders on ustic. The soils receiving 14 to 16 inches (355 to 405 millimeters) have an ustic soil moisture regime that borders on aridic. On the lower slopes of the minor mountain ranges, the soils that receive 16 to 20 inches (405 to 510 millimeters) of precipitation generally have a frigid soil temperature regime and an ustic soil moisture regime. The soils at the highest elevations in the small mountain ranges have a cryic soil temperature regime and a udic soil moisture regime that borders on ustic. Some soils with a mesic soil temperature regime occur at the lowest elevations in the southern part of the MLRA. Soils with mixed or smectitic mineralogy are dominant. Many of the soils are shallow or moderately deep to shale or sandstone bedrock. Many formed in slope alluvium or residuum derived from shale or sandstone. Soils that formed in stream- or river-deposited alluvium are near the major waterways. Most of the soils are well drained. Most are calcareous.

Geographic subunits

Land Resource Unit 1. The Green River Basin LRU is located in the lower Green River drainage of Wyoming extending from Big Piney, Wyoming at the north to Manila, Utah in the south. It is located between the Bear River Divide on the west and the Rock Springs Uplift on the east, with an area of this LRU located in the Washakie Basin in the southeast corner of Sweetwater County, Wyoming as well. The total area of this LRU is approximately 4,230,000 acres. It shares boundaries with MLRA 47 and 46 (proposed). This LRU is dominated by the Green River and Bridger Formations, Eocene aged formations of sedimentation from ancient Lake Gosiute. These formations are well known to be fossil bearing. They are also the source of one of the largest trona (sodium carbonate) beds in the world, resulting in substantial mining activities (Dyni, USGS). The soils in the Green River Basin are dominated by older Aridisols containing thin argillic and calcic horizons and younger shallow undeveloped Entisols residing on raw parent geology. The Green River Basin has a heavy influence of sodium and other soluble salts on lower accumulation landforms and along dry to slightly wet drainage ways and alluvial flats. The soils in this LRU are very closely tied to their parent geology with some having either hard or soft bedrock contacts above a depth of 6 feet. This LRU has an ustic aridic soil moisture regime and frigid soil temperature regime. The precipitation pattern is fairly flat with a slight spike in the winter. Winter temperatures are cold allowing snow to accumulated and stay until spring. This precipitation pattern results in Wyoming Big Sagebrush domination with cool season grasses and forb understories. The mean annual soil temperatures are between 40-46° F (4.4-7.8 C) and average precipitation is between 7 and 9” (177-230 mm) annually. Elevations of this LRU range between 5800’ and 6500’ (1770-1980 m). The Green River and its tributaries flow through this LRU allowing for irrigated hayland production as isolated areas where the Bureau of Reclamation built dams and canal systems. The Green River is also a world class blue ribbon trout fishery. The largest agricultural land use in this LRU is grazing by livestock. Wildlife in this LRU are abundant, consisting largely of sagebrush obligate species. This LRU is home to large populations of Greater Sage Grouse, Sage Thrasher, Pronghorn, and Mule Deer. This LRU is distinguishable from other LRU’s in that it is home to a variety of salt desert shrubs, such as shadscale, spiny hopsage, and spiny horsebrush. The production potential for ES’s in this LRU are lower than those around it.

Land Resource Unit 10. The Browns Park LRU is situated in the south central portion of the MLRA on the Utah and Colorado border along the Green River. It is in a valley within the Uinta Mountains. The LRU is approximately 185,000 acres and shares a boundary with MLRA 47. The LRU is dominated by Tertiary sandstone, sitlstone, volcanic ash and Quaternary pediment surfaces. Major formations include: Browns Park fluvial siltstone, claystone and volcanic ash. Uinta Mountain group of dark red sandstone and green fluvial shales. Pediment surfaces of poorly sorted sand and gravel deposits from alluvial fans. The soils in the Browns Park LRU are dominated by younger Inceptisols and very young Entisols. The geology and wind patterns have created very sandy soils throughout this LRU. The sandy soils have minimized the impacts of salts to the plant communities and soils. The younger soils are naturally very erosional and not stable enough to develop argillic and calcic horizons. Some of the soils have formed on sandy alluvial fans and along the drainage ways with slight salt influence. The LRU has an ustic-aridic soil moisture regime and a mesic soil temperature regime. The precipitation pattern is fairly flat across the entire year. Summers are hot with little precipitation. The mean annual soil temperature is between 47 and 51° F (8.3-10.5 C) and the average annual precipitation is between 7 and 9” (177-230 mm). The elevational range is between 5350’ and 6450’ (1630-1965 m). Water resources in this LRU are good. The Green River provides irrigation along its flood plain. Along with its tributaries, the river provides ample amounts of surface water for livestock. Plant community potential in this LRU consist of a mix of cool and warm season grasses along with sagebrush and salt desert shrubs. Land uses in the LRU are typical of this MLRA with livestock grazing as the largest use of the land.

Land Resource Unit 2. The Pinedale Plateau LRU is located in the upper Green River Drainage from Pinedale, Wyoming at the north working southward to Farson, Wyoming and easterly to South Pass, Wyoming. It is situated between the Wyoming Range and Wind River Range largely in Sublette County with some areas in northern Sweetwater County and a small portion of Fremont County. The total area of this LRU is approximately 1,210,000 acres. It shares a boundary with MLRA 46 (proposed). This LRU is dominated by the New Fork Tongue of the Wasatch formation, a large artesian aquifer that is estimated to hold large amounts of water with relatively quick recharge (Dana, Smith 1973). It is also home to the Lance Formation, a cretaceous strata that is part of the Mesaverde Group, which holds large amounts of hydrocarbons, giving way to one of the largest on shore natural gas fields (Jonah Field) (Bowker et al 2000). The soils in the Pinedale Plateau are dominated by older Alfisols with thick argillic and calcic horizons and younger deep alluvial soils along drainage ways and in river bottoms. Salts are not a major influence in the Pinedale Plateau but do collect along wet catchment areas and are a mix of sodium, calcium carbonate, and other soluble salts. Soils are tied closely to their parent geology but are more developed and older so typically do not have bedrock contact within 6 feet. This LRU has an aridic ustic soil moisture regime and frigid soil temperature regime. The precipitation pattern is fairly flat with a slight spike in the winter. Winter temperatures are cold allowing snow to accumulated and stay until spring. This lends perfectly to cool season grasses and forbs to flourish, also allowing Big Sagebrush to establish and dominate the landscape. The mean annual soil temperatures are between 36-40° F (2.2-4.4 C) and average precipitation is between 9 and 12” (230-305 mm) annually. Elevations of this LRU range between 6500’ and 7500’ (1980-2280 m). The Green River and its tributaries flow through this LRU allowing for irrigated hayland production as isolated areas along live streams and established irrigation company canals. The Green River is also a world class blue ribbon trout fishery. The largest agricultural land use in this LRU is grazing by livestock. Wildlife in this LRU are abundant, consisting largely of sagebrush obligate species, this LRU is home to large populations of Greater Sage Grouse, Sage Thrasher, Pronghorn, Mule Deer and Elk. There is a large mule deer winter range in this LRU and is a major conduit for many big game species to migrate from the neighboring mountain areas to the lower elevations and back.

Land Resource Unit 3. The Basin Rims LRU is located on and around the Rock Springs uplift east of Rock Springs, Wyoming, it runs from Steamboat Mountain at the north to the border of the Browns Park LRU in the south, it includes the higher elevations between the Green River Basin and the Great Divide Basin. The LRU is approximately 2,260,000 acres and shared a boundary with MLRA 46 (proposed). The LRU is dominated by Upper Cretaceous rocks flanked by the Wasatch and Fort Union Formations. (Flores, Bader USGS) The Fort Union formation is a coal bearing formation resulting in several coal mining operations, including the Jim Bridger and Black Butte coal mines along with the Jim Bridger Power Plant which uses coal produced from these mines. The soils in the Basin Rim are dominated by younger un-developed Inceptisols with thin cambic and calcic horizons. The Basin Rim LRU also has a large amount of shallow young soils residing on raw parent geology. Some areas contain older more stable Alfisols with thicker argillic horizons on non-erosional surfaces. Quite of few of the soils in this LRU have either a soft or hard bedrock contact within 6 feet and are strongly tied to their parent geology. Salts are not a major influence in this LRU but do accumulate in closed basins and along dry to slightly wet drainage ways. The Basin Rim LRU also contains a very large active sand dune system moving west to east into the Great Divide Basin. The LRU has an aridic ustic soil moisture regime and a frigid soil temperature regime. The precipitation pattern is fairly flat with a slight spike in winter precipitation. There are inclusions of typic ustic and ustic aridic soil moisture regimes. Solar radiation and shallow soils on south and west facing slopes, these slopes support juniper where north and east slopes do not. The mean annual soil temperature of the LRU is between 40 and 44° F (4.4-6.7 C) and average precipitation between 9 and 15” (230-380 mm) annually. The elevation range is between 6500’ and 7500’ (230-2280 m). Water resources in this LRU are limited. Very few live streams are present in this LRU, with a few intermittent and ephemeral streams. Most of the stock water is provided from ground water through water wells. There is a fair amount of wildlife in this area, with a large desert elk herd that resides in the area and surrounding LRU’s year long. There are also herds of pronghorn and mule deer that reside in the area, although these species tend to migrate in and out of the area seasonally. Plant community potential in this LRU tend to be more like the foothills of the neighboring Uinta Mountains than that of the surrounding desert. There is a good population of Utah Juniper (with a mix of Rocky Mountain Juniper) and limber pine trees and understories of bluebunch wheatgrass with other cool season grasses. Land uses in the LRU are typical of this MLRA with livestock grazing and mineral extraction, in this case, coal mining, as the largest use of the land.

Land Resource Unit 4. The Great Divide Basin LRU is located in the heart of MLRA 34A. It extends from Baggs, WY in the south to near Jeffrey City, WY in the north. It is flanked by Delaney Rim on the west, Atlantic Rim on the east and Green Mountain on the north. This LRU is approximately 2,200,000 acres and shares a boundary with MLRA 48A. The LRU is dominated by the Battle Springs formation. Unlike the Green River and Wasatch formations, which are intertwined with each other, the Battle Springs formation is a single homogenous formation of Eocene age (Pipiringos, Denson 1970) which is known to hold uranium deposits. Uranium mining in this area was conducted until the mid-1990’s when uranium prices fell and was no longer economical. Since then, there has been some effort to again extract uranium from this area. The soils in the Great Divide Basin LRU are equally shared by old Aridisols with thick argillic and calcic horizons and shallow young Entisols on raw geology. Salts in the Great Divide Basin LRU play a major role in soil development with a lot of soils having a natric or sodium dominated horizon and very high salt concentrations on the surface. Most of the soils in the closed basin are very deep with high salt concentrations and neighboring soils on the hillslopes having either a hard or soft bedrock contact within 6 feet. The LRU has an ustic aridic soil moisture regime and a frigid soil temperature regime. The precipitation pattern, again, is fairly flat, however, unlike the Green River Basin LRU, this LRU has a slight spike in the summer precipitation, allowing for a reduction in the potential amount of sagebrush and the minor presence of some warm season grasses. The mean annual soil temperature is between 44 and 46° F (6.7-7.8 C) and the average annual precipitation is between 7 and 9” (177-230 mm). It elevational range is between 6200’ and 7000’ (1890-2130 m). Water resources in this LRU and very limited as much of the LRU is a closed basin between the Continental Divide, which splits and makes the borders of the LRU. There are a few live, intermittent and ephemeral streams in the LRU, however, most of the available water is from ground water sources in wells. There is a fair amount of wildlife in this area, with a large desert elk herd that resides in the area and surrounding LRU’s year long. There are also herds of pronghorn and mule deer that reside in the area, although these species tend to migrate in and out of the area seasonally. Plant community potential in this LRU consist of a mix of cool and minor amounts of warm season grasses and big sagebrush, with birdfoot sagebrush comprising most of the natric soils. Land uses in the LRU are typical of this MLRA with livestock grazing and mineral extraction as the largest use of the land.

Land Resource Unit 5. The Beaver Rim LRU is located largely in the southeast corner of Fremont County, Wyoming. It extends from Cedar Ridge near Lander, Wyoming on the west to the Rattlesnake Hills on the east, MLRA 32 to the north, and the Granite Mountains to the south. This LRU is approximately 1,500,000 acres and shares a boundary with MLRA 32. The LRU is dominated by the Wind River formation, an Eocene aged formation derived from deposition from the surrounding Wind River and Washakie Ranges and the Owl Creek and Granite Mountains uplift (Seeland, 1978). This formation is known to have deposits of hydrocarbons and uranium. There are other geologic inclusions in this LRU, such as the Cretaceous-aged Granite Mountains at the southern boundary. The soils in the Beaver Rim are dominated by older Alfisols with thick calcic and argillic horizons. The Beaver Rim LRU has more calcium carbonate influence then neighboring LRU’s due to limestone and volcanic tuft parent materials. Along the edges of the LRU, some younger Inceptisols are found with some having either soft or hard bedrock contacts, before 6 feet. Though the soils are closely tied to their parent geology, they are older and more developed than neighboring LRUs. The LRU has an aridic ustic soil moisture regime and a frigid soil temperature regime. The precipitation pattern is fairly flat with a slight spike in spring moisture. The mean annual soil temperature of the LRU is between 44 and 48° F (6.7-8.8 C) and the average annual precipitation is between 9 and 12” (230-305 mm). The elevational range of the LRU is 5400’ to 7500’ (1650-2280 m). Water resources in this LRU are good. The Sweetwater River allows for some flood irrigation along its flood plain near Jeffrey City, Wyoming. This river and its tributaries, supply ample amounts of ground water for water well pumping for livestock water. There are areas of the LRU where water becomes more scarce, making it a little more difficult to distribute livestock. There is a fair amount of wildlife in this area, with a large elk herd that migrates in and out of the area and surrounding LRU’s year long. There are also herds of pronghorn and mule deer that reside in the area, although these species tend to migrate in and out of the area seasonally. Plant communities in the LRU consist of a mix of big sagebrush and cool season grasses, this is the only LRU where bluebunch wheatgrass/Montana wheatgrass is the dominant cool season grass in the understory. Land uses in the LRU are typical of this MLRA with livestock grazing and mineral extraction (oil and gas) as the largest use of the land.

Land Resource Unit 6. The Lower Sweetwater LRU is in the northeast corner of the MLRA, mostly in Natrona County, Wyoming. It is bordered by Green Mountain to the south, the southern tip of the Big Horn Mountains to the north, MLRA 32 to the west and MLRA 58B to the east. The LRU is approximately 1,200,000 acres and shares a boundary with MLRAs 32 and 58B. The LRU is dominated by the Wind River formation, an Eocene aged formation derived from deposition from the surrounding Wind River and Washakie Ranges and the Owl Creek and Granite Mountains uplift (Seeland, 1978). This formation is known to have deposits of hydrocarbons and uranium. There are other geologic inclusions in this LRU, such as the Miocene-aged Split Rock Formation running though the LRU (Love, 1961). The soils in the Lower Sweetwater LRU are dominated by very deep old Alfisols with very thick argillic and calcic horizons. Other soils include slightly younger Alfisols with thinner argillc and calcic horizons and young Fluvent soils along the many dry to slightly wet drainage ways. The soils in this LRU are old on very stable landforms with minimal erosional surfaces creating the thick argillic and calcic horizons. Salts do not play a major role in this LRU, but do accumulate in a couple lower areas. Water resources in this LRU are good. The Sweetwater River allows for some flood irrigation along its flood plain near Independence Rock. Along with its tributaries, supply ample amounts of surface water for livestock water. There are areas of the LRU where water becomes more scarce, making more difficult to distribute livestock. The LRU has an aridic-ustic soil moisture regime, with a few typic-ustic inclusions (higher elevations) and a frigid soil temperature regime and a few mesic inclusions (lower elevations). The precipitation pattern is fairly flat with a slight spike in spring moisture. With warmer temperatures and more summer precipitation there is an increase in the amount of warm season plants in areas. The mean annual soil temperature of the LRU is between 44 and 48° F (6.7-8.8 C) and the average annual precipitation is between 10 and 15” (254-380 mm). The elevational range of the LRU is 5500’ to 7500’ (1670-2280 m). Plant community potential in this LRU is grass dominated with big sagebrush scattered throughout. There are areas where warm season grasses and forbs are present, giving this LRU different plant potentials than surrounding LRU’s. Land uses in the LRU are typical of this MLRA with livestock grazing and mineral extraction (oil and gas) as the largest use of the land.

Land Resource Unit 7. The Platte Valley LRU is in the eastern portion of the MLRA mostly in Carbon County, Wyoming. It is bordered by the Sierra Madre’s to the south and the Laramie Mountains to the east and north. It extends from the Rawlins Uplift on the west to the Shirley Basin on the north and east. This LRU is approximately 2,300,000 acres and shares a boundary with MLRAs 48A and 49. The LRU is dominated by the Hanna, Medicine Bow, Ferris and Mesaverda formations along with the Steele Shale. These are Eocene-aged formations known to be coal producing (Flores etal, USGS). Coal mining was a large part of this area’s history, however, most of the coal production in the area has since ceased. The soils in the Platte Valley LRU are a good mix of older Alfisols with moderate argillic and calcic horizons, younger parent geology dominated soils, and slightly wet to very wet drainage ways and basins. Salts have a moderate influence in this LRU with some areas accumulating enough sodium to have natric horizons and salt accumulation at the surface. Quite a few of these soils are dominated by parent geology and have either a soft or hard bedrock contact within 6 feet. The LRU has an aridic ustic soil moisture regime and a frigid soil temperature regime. The precipitation pattern is fairly flat with a slight spike in spring moisture. The mean annual soil temperature of the LRU is between 42 and 45° F (5.6-7.2 C) and the average annual precipitation is between 9 and 12” (230-305 mm). The elevational range of the LRU is 6500’ to 7500’ (1980-2280 m). Water resources in this LRU are good. The North Platte and Medicine Bow Rivers provides flood irrigation along the flood plains near the towns of Saratoga, Elk Mountain and Medicine Bow. Along with its tributaries, there is ample amounts of surface water for livestock water. There are areas of the LRU where water becomes more scarce, making it more difficult to distribute livestock. Plant communities in this LRU consist of big sagebrush and a mix of cool and minor amounts warm season grasses, with birdfoot sagebrush comprising most of the natric soils. Land uses in the LRU are typical of this MLRA with livestock grazing and mineral extraction as the largest use of the land.

Land Resource Unit 8. The Laramie Basin LRU is situated on the far eastern edge of the MLRA. It extends from the southeast boundary of the MLRA to Rock River, Wyoming in the north. It is settled in between the Medicine Bow Mountains and the Laramie Mountains in eastern Wyoming. The LRU is approximately 1,610,000 acres and shares a boundary with MLRAs 48A and 49. The LRU is dominated by alluvium and colluvium deposits from the surrounding mountains, along with the Wind River and Wagon Bed formations. The Wagon Bed formation is a middle Eocene aged formation that is known to hold fossil beds. Soils in the Laramie Basin LRU are dominated by very old Alfisols with thick argillic and calcic horizons. The LRU also has a quite few soils formed on wet drainage ways with minimal salt influence. The soils in this LRU are closely tied to their parent geology, but are old and very deep with very few having any bedrock contact within 6 feet. Most of the smaller clay sized particles have collected in heavier texture basins dotted throughout this LRU. The LRU has an aridic-ustic soil moisture regime, with a few typic ustic inclusions (higher elevations) and a frigid soil temperature regime. The precipitation pattern is fairly flat with a spike in summer moisture, giving way for more grass production and lack of big sagebrush and higher potential for warm season grasses. The mean annual soil temperature of the LRU is between 40 and 42° F (4.4-5.6 C) and the average annual precipitation is between 10 and 15” (254-380 mm). The elevational range of the LRU is 6900’ to 7500’ (2100-2280 mm). Water resources in this LRU are good. The Laramie River provides flood irrigation along its flood plain. Along with its tributaries, the river supplies surface water for livestock. Plant community potential in this LRU consist of a mix of cool and warm season grasses. With the influx of summer moisture, big sagebrush cannot compete with the grasses in this LRU. The only sagebrush of any significance is silver sagebrush, found in the heavier soils in the bottom lands (overflow). Land uses in the LRU are typical of this MLRA with livestock grazing as the largest use of the land.

Land Resource Unit 9. The Yampa Valley LRU is situated in the south central portion of the MLRA, mostly in Moffat County, Colorado. Powder Rim is the border in the north, the mountains in Moffat County from the other boundaries. The LRU is approximately 1,800,000 acres and shares a boundary with MLRAs 48A and 47. The LRU is dominated by Tertiary sandstone, mudstone, and shale with Cretaceous marine shales. Major formations include: the Wasatch pink sandstone, Fort Union brown sandstone and shale with coal beds, Lewis marine shale, and Mancos marine shale with calcareous sandstones. The soils in the Yampa Valley LRU are a good mix of older Alfisols with moderately thick arigillc and calcic horizons and slightly younger more parent geology dominated soils. These younger soils are closely tied to parent geology and many of them have either soft or hard bedrock contact within 6 feet. The older Alfiols are on more stable landforms with non-erosional surfaces. Some of the soils also formed in recent alluvium with a mix of sandstones and shales. Salt influence is minimal in the LRU, though some areas have accumulated enough to have natric or sodic horizons. The LRU has an aridic-ustic soil moisture regime, with isolated areas of typic ustic, and a frigid soil temperature regime. The precipitation pattern is fairly flat with a slight spike in winter precipitation. Summers are hot with little precipitation. The mean annual soil temperature is between 44 and 48° F (6.7-8.8 C) and the average annual precipitation is between 9 and 15” (230-380 mm). The elevational range is between 5740’ and 7200’ (1750-2200 m). Water resources in this LRU are good. The Yampa River provides flood irrigation along its flood plain. Along with its tributaries, the river provides ample amounts of surface water for livestock. Plant communities in this LRU consist of a mix of cool season grasses along with sagebrush. Land use in the LRU are typical of this MLRA with livestock grazing and mineral extraction as the largest use of the land.