Water Balance Lysimetry at a Nuclear Waste Site

by M. D. Campbell, Pacific Northwest Lab, Richland, United States,
G. W. Gee, Pacific Northwest Lab, Richland, United States,
R. R. Kirkham, Pacific Northwest Lab, Richland, United States,
S. J. Phillips, Pacific Northwest Lab, Richland, United States,
N. R. Wing, Pacific Northwest Lab, Richland, United States,



Document Type: Proceeding Paper

Part of: Lysimeters for Evapotranspiration and Environmental Measurements

Abstract: Lysimeters measure effects of soil, vegetation, and climate on water balance and groundwater recharge at a nuclear-waste site in arid-southcentral Washington State, USA. Data from 4 lysimeter sites illustrate water balance measurements taken over a period of 20 years. Soil sample, weight change, and neutron probe measurements monitored influences of vegetation and precipitation on water balance. Lysimeter drainage was measured directly where possible and was otherwise inferred from deep storage changes and soil moisture tensions. Apparently, deep-rooted plants prevented drainage from the 18-m deep, sand-filled lysimeter, as water storage fluctuated near the surface but not below the 5-m depth. In contrast, up to 120 mm of water drained from coarse sands in a 7.6-m-deep, bare-surface lysimeter and 100 mm drained from a 1.5-m-deep, vegetated (grass-covered) lysimeter when annual precipitation reached 281 mm. Lysimeters containing silt loam soil did not drain (i.e., zero recharge potential), even when total precipitation was 320 mm/y and the surface was bare. Soil water storage capacity, precipitation timing and amount, and vegetative cover and rooting depth affect water balance and groundwater recharge.

Subject Headings: Drainage | Waste sites | Water balance | Measuring instruments | Water storage | Water resources | Soil water | Vegetation | Groundwater recharge | Radioactive wastes | North America | United States | Washington

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