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Barnett_Field Trip Presentation

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Barnett_Field Trip Presentation

  1. 1. Ground Water North of Cedar City, Utah in the Cedar Valley Drainage Basin Halley Barnett THE GREAT BASIN The Great Basin Region has the highest rate of population growth in the US. It is a large, semi-arid, cold desert that is prone to droughts and has limited water resources (Chambers et al., 2008). Water input into this region mainly comes from the melting of winter snow from adjacent mountainous areas (Chambers et al., 2008). The EPA estimates that the Great Basin will warm by 3-6 degrees by the end of the twenty-first century (Chambers et al., 2008). As temperatures continue to increase, the amount of snowmelt will decrease, which will limit the amount of available water. Aerial photo of Cedar City, Utah (AirPhotoNA.com, 2009). Below: Water level contours and fissure locations (Knudsen et al., 2014). Right: Map of the Cedar Valley Drainage Basin (Eisinger, 1998).Cedar City is circled in red in both images. Utah
  2. 2. CEDAR VALLEY DRAINAGE BASIN Within the Great Basin Region, the Cedar Valley Drainage Basin is a drainage basin with an area of 580 mi2 (1,502 km2 ) in southwestern Utah between the Basin and Range province and the Colorado Plateau (Eisinger, 1998). The valley is a graben that was formed through extension from Miocene to Quaternary normal faulting that was subsequently filled with quaternary alluvium eroded from adjacent horsts and volcanic deposits (Eisinger, 1998; Brooks and Mason, 2005). The basin sees eight to fourteen inches of precipitation annually along with moderately cold winters and warm, dry summers (Eisinger, 1998). Several smaller grabens exist within the larger graben, including the Enoch-graben-west fault (Knudsen et al., 2014). WATER RECHARGE AND DISCHARGE Recharge comes from seepage from perennial streams and springs, seepage from irrigation, infiltration from precipitation, and subsurface inflow from consolidated rock (Eisinger, 1998; Brooks and Mason, 2005). The majority of discharge comes from well pumping and has increased at a rate of about 600 acre-ft per year since 1964 (Eisinger 1998, Knudsen et al., 2014). As water levels decline, land subsidence occurs in this graben as sediments are compacted and fissures form (Knudsen et al., 2014). Fissures increase the permeability of the land surface, Top: Sprinkler System (Google Earth, 2015). Left: Road damage due to the EGWF1 fissure at the intersection of 5700N and 850E (Knudsen et al., 2014). WATER STORAGE Alluvial fill forms the dominant aquifer in the region and consists of sand, gravel, clay, and silt with many highly permeable beds (Eisinger, 1998). Quartz monzonite, volcanic rocks, and Navajo Sandstone are consolidated rocks known to provide water to wells (Brooks and Mason, 2005). Unconfined aquifers in this basin exist in coarse, unsorted sand and gravel, and confined aquifers exist in the middle of the basin where there are discontinuous lenses of impermeable clay or silt (Brooks and Mason, 2005). Groundwater flows northwest (Brooks and Mason, 2005). Cross-section north of Cedar City. This area shows characteristics of extension and basin fill and there are several faults running through the area (Hurlow, 2002).
  3. 3. which increases the ease at which runoff from will infiltrate into the groundwater system. Agricultural production is an important part of the economy in the Cedar City area (Knudsen et al., 2014). The majority of irrigation in 1992 and 1993 came from flood irrigation, but the majority in 2000 came from center-pivot sprinkler irrigation (Brooks and Mason, 2005). Water is also often diverted through canals and ditches or released into the atmosphere through evapotranspiration (Brooks and Mason, 2005). Evapotranspiration for 2000 is estimated at 3,000 acre-ft (Brooks and Mason, 2005). WATER QUALITY Well water was used for irrigation and livestock and municipal water came from springs from consolidated rocks in the mountains before the 1960s (Brooks and Mason, 2005). Effluent from waste-water treatment facilities has been used for field irrigation since 1976 (Brooks and Mason, 2005). Increasing population forced the city to rely more on groundwater for summer lawn watering and public water supply (Brooks and Mason, 2005). Dissolved solids range from 158 to 2752 mg/L with the majority being nitrate (Eisinger, 1998). This nitrate comes from deeper wells that extend to older basin fills rich in more soluble salts (Knudsen et al., 2014). Pollution comes mainly from septic tanks, fertilizer, and sewage lagoons (Eisinger, 1998). WATER RESOURCES AND FISSURES Cedar City and Enoch receive water from wells that collectively produce about 3000 acre-ft per year (Knudsen et al., 2014). Discharge in this basin has been greater than recharge since 1939, and the estimated storage decrease is estimated at 10,700 acre-ft for 2000 (Knudsen et al., 2014). Earth fissures increase the rate of infiltration of water and pollutants into the groundwater system (Knudsen et al., 2014). As fissures form through roads and livestock areas, potential for groundwater pollution increases (Knudsen et al., 2014). Increasing water resources may be The direction of groundwater flow has remained mostly constant since at least 1974 (Brooks and Mason, 2005). Wells had stopped flowing (without pumping) from the lowering of the water table by 1975 and confined pressures were not strong enough for flowing wells (Brooks and Mason, 2005).Water-level altitude contours show a lowering of the water table around Cedar City, which is a relatively highly-populated area.
  4. 4. accomplished by importing water from other basins and injecting it into the groundwater system in locations where infiltration rates are high, moving the high-discharge wells that populations rely on, and/or withdrawing less water (Knudsen et al., 2014).The most extensive fissures have been the Enoch-graben-west fissures, which are extending southward (Knudsen et al., 2014). REFERENCES AirPhoto (2009). Cedar City: Iron County, Utah, UT United States. Image #13295. http://www.airphotona.com/image.asp?imageid=13051&catnum=0&catname=All%20Categories&keywor d=&country=&state=&pagenum=229 Brooks, L. E. and Mason, J. L. (2005). Hydrology and Simulation of Ground-Water Flow in Cedar Valley, Iron County, Utah. US Geological Survey. Salt Lake City, Utah. Scientific Investigations Report 2005-5170. Chambers, J. C.; Devoe, N.; and Evended, A. (2008). Collaborative Management and Reasearch in the Great Basin – Examining the Issues and Developing a Framework for Action. Gen. Tech. Rep. RMRS-GTR-204. Fort Collins, CO: US Department of Agriculture, Forest Service, Rocky Mountain Research Station. 66 p. Eisinger, C. (1998). A Summary of the Geology and Hydrogeology of the Cedar Valley Drainage Basin, Iron County, Utah. Utah Geological Survey. Open-File Report 360. Hurlow, H.A., 2002, The geology of Cedar Valley, Iron County, Utah and its relation to ground-water conditions: Utah Geological Survey Special Study 103. Knudsen, T.; Inkenbrandt, P.; Lund, W.; Lowe, M.; and Bowman, S. (2014). “Investigation of Land Subsidence and Earth Fissures in Cedar Valley, Iron County, Utah.” Utah Geological Survey Special Study 150. Google Earth (2015). Cedar City, Utah. Water Quality of the Cedar Valley Drainage Basin (Brooks and Mason, 2005).

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