Water Table Lysimeter Data Interpretation

Hill, R. W.; Allen, L. N.; ,

Water Table Lysimeter Data Interpretation

by R. W. Hill, Utah State Univ, Logan, United States,
L. N. Allen, Utah State Univ, Logan, United States,

Document Type: Proceeding Paper

Part of: Grouting in Geotechnical Engineering

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 (E_t) 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 E_t 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 E_t values occurring, on occasion, the week after heavy irrigations and by apparent disagreement between E_t determined solely from neutron probe readings and E_t 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 E_t to better match meadow E_t after harvest when the lysimeters continued to be irrigated, whereas, the meadows were dry.

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