WWRC 84-09
Design and Installation of a Weighing Lysimeter
Objectives
The purpose of this research was to develop and install an undisturbed
weighing lysimeter in the Laramie River Basin. This location will facilitate
providing the necessary management to insure continuous and reliable
operation.
The lysimeter contains an undisturbed soil profile with accompanying
vegetation. To the best knowledge of the authors, the lysimeter is the first
system of its type installed anywhere, particularly at high elevations.
Once operational, the lysimeter will be used to:
- Provide the best direct estimate of water use by meadows in the
Laramie area.
- Evaluate the role of rainfall in meeting plant water requirements.
- Provide comparative data to evaluate the accuracy of non-weighing
lysimeters. Results will be used to correct errors or bias
introduced into vegetative water use models through data obtained
from non-weighing lysimeters.
The key to a successful weighing lysimeter is to design a system capable
of detecting a change in weight equal to a millimeter of water when the
lysimeter itself weighs several kilonewtons. For example, a precipitation
event on the surface of a lysimeter equivalent to 1 mm of water may weigh
approximately 10 Newtons. To detect a change in weight equivalent to 1 mm of
water, the weighing system would have to be sensitive to approximately the
O.1% level. In actual practice, the lysimeter weighing system should be
sensitive to approximately 0.03%. This can be accomplished by making the top
area of the lysimeter large relative to its depth, by maintaining the water
table depth precisely and by using modern high technology sensors on the
weighing system and a computer controlled data acquisition system.
84-09 Table of Contents
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