Water Table Lysimeter Data Interpretationby R. W. Hill, Utah State Univ, Logan, United States,
L. N. Allen, Utah State Univ, Logan, United States,
Abstract: Lysimeters were used to estimate seasonal water use of wet meadows and phreatophytes in northern Utah, southeast Idaho and southwest Wyoming (1983-1990). Twelve water table lysimeters (approx. 1 m square) were placed in high elevation irrigated meadows while others were used to estimate evapotranspiration (Et) of cattails, rushes, willows, grass and alfalfa (2 lysimeters in each) in a comparative study at Utah State University's (USU) drainage farm. The lysimeters in wet meadows were visited once each week during the growing season. Water levels inside and outside the lysimeters were measured, neutron probe readings taken and water was added or removed as needed. The weekly visits led to occasional significant fluctuations in water levels. The ten lysimeters at the USU drainage farm were visited daily. The water level in cattails and rushes was maintained at on above the soil surface allowing daily Et estimates. The water level in willows, grass and alfalfa was kept within desired limits by timely irrigations. Data analysis was confounded for the wet meadow lysimeters by calculated negative Et values occurring, on occasion, the week after heavy irrigations and by apparent disagreement between Et determined solely from neutron probe readings and Et from water level observations and estimated saturated soil water specific yield. Computation procedures were devised to account for these differences. A procedure was also developed to adjust lysimeter Et to better match meadow Et after harvest when the lysimeters continued to be irrigated, whereas, the meadows were dry.
Subject Headings: Measuring instruments | Irrigation | Water table | Soil water | Water level | Hydrologic data | Water resources | Vegetation | Seasonal variations | North America | United States | Utah | Idaho | Wyoming
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