PNNL

Abstract

Water supplies throughout the world are rapidly diminishing in quantity and quality. Efforts over the next decade must focus on methods which use water more efficiently for agriculture, industry, and recreational purposes, and at the same time reduce the potential for groundwater pollution. To assist in this effort, we have developed an improved method to simultaneously measure drainage quantity and quality using a water fluxmeter. Our water fluxmeter is a wick-lysimeter fitted with a small tipping-spoon and a solution-collection system. The only moving part is the tipping spoon. We have tested our fluxmeters under a range of conditions, from non-vegetated desert settings in Washington State USA, to irrigated tea plantations in Sri Lanka. Conditions of over-irrigation have been documented with our fluxmeters. When 4200 mm of water was applied to sandy soil via drip irrigation, at the Washington State site, over 3100 mm of drainage occurred. In contrast, at the same site, in the absence of both irrigation and vegetation, drainage was found to range from 0 mm/yr for a 1-m-deep silt loam soil to more than 100 mm/yr for a coarse-gravel surface. Solute transport, related to nitrate leaching can also be analyzed using water fluxmeters. Water fluxmeters have provided a reliable and inexpensive method to assess both quantity and quality of drainage waters over a wide range of environmental conditions.