Wetup - A software tool to display approximate wetting patterns from drippers

For trickle irrigation systems to deliver improved water and nutrient use efficiency, distance between emitters and emitter flow rates must be matched to the soil’s wetting characteristics and the amount and timing of water to be supplied to the crop. Broad soil texture ranges are usually the only information related to soil wetting used in trickle system designs. WetUp allows calculation of wetting pattern dimensions for 29 individual soils covering a wide range of textures and soil hydraulic properties. The user is encouraged to use Wetup to assess the impact of soil texture and/or soil type on soil wetting patterns.

The soils came from two groups that differed in the extent to which hydraulic properties depended on soil texture. The first group of 18 soils has the field structure preserved (Verburg et al. 2001). In these soils there is no relationship between wetted dimensions and texture. For example, soils with a similar texture can have great variation in wetting patterns.

In the second group of 11 soils (Clapp and Hornberger 1978), which have little expression of field structure, the wetted radius increases and depth of wetting below the emitter decreases with increasing clay content, as is commonly accepted.

Vertical and horizontal wetted dimensions provided by WetUp are calculated from the infiltration solutions of Philip (1984), which have been found to provide good predictions of the radius and depth of the unsaturated wetted zone in a field study (Revol et al. 1997). Philip (1984) did not give a solution for radial wetting from a buried source, so one was derived (Thorburn et al. 2001, Cook et al. 2001).

References

• Clapp RB and Hornberger GM (1978) Empirical equations for soil hydraulic properties. Water Resources Research 14: 601-604
• Cook FJ, Thorburn PJ,Fitch P. and Bristow KL (2002a) WetUp - a software tool to display approximate wetting patterns from drippers. Irrigation Science (in press).
• Cook FJ Thorburn PJ, Bristow KL (2001) and Cote C, (2002b) Infiltration from surface and buried point sources: The average wetting water content. Water Resources Research (submitted)
• Philip JR (1984) Travel times from buried and surface infiltration point sources. Water Resources Research 20: 990-994
• Revol P Clothier BE Mailhol JC Vachaud G and Vauclin M (1997) Infiltration from a surface point source and drip irrigation. 2. An approximate time-dependent solution for wet-front position. Water Resources Research 33: 1869-1874
• Thorburn PJ Cook FJ and Bristow KL (2002) Soil-dependent wetting from trickle emitters: Implications for system design and management. Irrigation Science (in press)
• Verburg K Bridge BJ Bristow KL and Keating BA (2001) Properties of selected soils in the Gooburrum – Moore Park area of Bundaberg. Technical Report 09/01, CSIRO Land and Water, Canberra, Australia

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