Coordinating Deep Drainage Research in the Northern Darling Basin - Final Report 2008-09-12T07:34:06Z 2009-07-09T04:26:38Z Coordinating Deep Drainage Research in the Northern Darling Basin - Final Report Nicky Schick Nicky Schick <p>A key issue identified by the research community working with the cotton industry was the lack of understanding and acceptance of the concept of deep drainage. Deep drainage is defined as the part of the water (applied to the surface and as rainfall or irrigation) that moves past the rootzone. In general the existing paradigm was &ldquo;cotton soils don&rsquo;t leak&rdquo;. However, the research community related to the Australian Cotton CRC (ACCRC) was well aware of observations and simulations indicating significant deep drainage under irrigation. Examples of such studies include the PhD work by J. Montgomery in the Gwydir Valley, measurements by Willis et al. (1997) in the Macquarie valley and estimates by Weaver et al. (2004) in the Namoi valley. However, the estimates range widely and there was some disagreement about the magnitude of deep drainage and its impact. However, from logical considerations based on water quality and leaching fractions (Vervoort et al., 2003) it could be expected that at least 10% of the applied irrigation water is lost below the rootzone.<br /> <br /> While it was unknown what the future implications of this deep drainage might be in terms of landscape salinity, it was agreed that there was a need for more accurate measurements and that there was a need to create awareness about deep drainage in the cotton industry and forge linkages with researchers from other industries. Rather than reinventing the wheel, it was important to link to research on deep drainage in other agricultural industries. But due to the differences in climate and soils between the northern and southern part of the Murray Darling Basin, not all established research was directly useful.<br /> <br /> The Northern Murray Darling &ndash; Water Balance Group (NMD &ndash; WBG) was conceived as a partnership of researchers and extension personnel to exchange ideas, create awareness, and debate the issue of deep drainage. This project provided logistical support to help the group achieve these goals.</p> PN21997 PN21997