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Hydraulic considerations in sampling the unsaturated zone with inclined gravity lysimeters

Water-Resources Investigations Report 83-4005

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Abstract

Inclined gravity lysimeters as deep as 5.39 meters below land surface designed for sampling soil water in coarse sand under continuous ponding conditions, were shown to be capable of collecting 10 liters per hour at an infiltration rate of 0.5 meter per hour. This represents a capture efficiency of approximately 50%, a value observed in two similar but shallower lysimeters. When lysimeters are installed from a trench or observation manhole, soil-water samples can be taken under virtually undisturbed conditions, avoiding the soil disturbance and filtration associated with porous-cup vacuum lysimeters. Successful operation requires that the sampler be designed for the hydraulic characteristics of the soil from which the water sample is to be extracted. Criteria for lysimeter dimensions can be established on the basis of pressure heads experienced during sampling, can be induced to flow into the lysimeter by gradient manipulation. Observed head gradients outside the lysimeter ranged between 1.7 and 2.2 times those across the lysimeter, which would seem to explain the observed capture efficiency. (USGS)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Hydraulic considerations in sampling the unsaturated zone with inclined gravity lysimeters
Series title:
Water-Resources Investigations Report
Series number:
83-4005
Edition:
-
Year Published:
1983
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
iv, 21 p. :ill. ;28 cm.