Abstract

Water BudgetThis chapter documents the hydrologic analysis of a watershed within the Windy Ridge mega-landslide of Central Utah to (1) create a water budget and (2) place a quantitative limit on the magnitude of climatic changes documented by Shurtliff et al. (2017) and Hudson et al. (2019). (1) A water budget was calculated over the last four years using instrumentation and weather stations both within and surrounding the watershed, In terms of precipitation input, 85% is released by the evapotranspiration of the Pinyon-Juniper forest, 4% discharges as surface water from the base of the watershed, and 11 % infiltrates the groundwater system. This infiltration rate is slightly lower than the 15% suggested by Maxey-Eakin method (Maxey and Eakin, 1949), likely due to the less permeable, clay-rich sediment. (2) Previous studies performed on Garden Basin Cattail (GBC) Fen at the base of its watershed suggest swings from pond-like to wetland environments (Shurtliff et al, 2017; Hudson et al, 2019). This study estimated precipitation values necessary to create standing water (pond) environments. Changes in annual precipitation, as well as input from North American monsoon (NAM), may cause these environmental changes. Each of these cases were examined. Trends in piezometer measurements compared to mean annual precipitation indicated that ‰¥ 644 mm of annual precipitation are required to sustain a wet (perennial standing water) environment. The change from wetland to pond conditions may depend on seasonal trends in precipitation. This study suggests an increase of 150-300 mm of precipitation in late summer (NAM) may be connected to perennially wet conditions. The higher annual precipitation values, largely accomplished by NAM fluctuations, caused a transition from wetland to pond (Hudson et al., 2019; Shurtliff et al., 2017). Chapter 2: Core AnalysisChapter 2 further documents the watershed's historical environmental and climate record by analyzing sediment and topography surrounding GBC fen, adding to the works of Shurtliff et al. (2019) and Hudson et al. (2019). A core was extracted from GBC fen at the base of the watershed and the sediment analyzed in terms of color, texture, environmental scanning electron microscope (ESEM) imaging, RockEval pyrolysis, and 14C ages. These results were then compared to pre-existing pollen and diatom proxies completed on a previous core by Shurtliff et al. (2019). This study suggests climatic variation, along with basin fill processes, was the driver of environmental change in GBC fen (Garden Basin watershed). Climate proxies show the basic trend from a particularly wet period (12-9 ka BP) of more stagnant or deeper water, to a much dryer period of much shallower water levels (9-3 ka BP), followed by a rebound in moisture levels, especially in the past few hundred years. Although climate was the driver of transitions within GBC2 core, a pollen record of sustained shallow water plants and MASW (Park et al., 1999) survey may suggest beaver activity.

Degree

MS

College and Department

Physical and Mathematical Sciences; Geological Sciences

Rights

http://lib.byu.edu/about/copyright/

Date Submitted

2019-11-01

Document Type

Thesis

Keywords

water budget, evapotranspiration, climate, weather station, piezometer, hydrograph, transpiration, outflow, precipitation, pyrolysis, radiocarbon ages, ESEM, core description, pollen

Language

english

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