Deep drainage (DD) - water that passes beyond the root zone - is an important process in irrigated cropping soils to ensure leaching of salts through the soil profile to deeper soil layers, the vadose zone (the zone between the rootzone and the watertable) or to groundwater. Salt can either be naturally present within some soils or be added through low quality irrigation water. Furthermore, excessive DD may cause water table rise to the rootzone with associated salts, so precluding the growth of salt sensitive species.DD is also an economic negative, as costs of pumping and storage are not realised in increased yields or possible increased area under production. The loss of irrigation waters to DD is particularly important in drought years where the rare water resource must be carefully utilised to ensure crops attain maximum yield per unit volume of applied water.The study reported here focused on DD water losses and the quality of those lost waters (in terms of salinity) on 7 irrigated cotton farms (all but one under traditional furrow irrigation management) in the upper Murray Darling basin (UMDB) near the towns of Boggabilla (2 sites), Dalby, Goondiwindi, Macalister, Pampas and St George.Many regarded the advent of low volume irrigation devices (eg lateral moves) with their known capacity to increase water use efficiency (bales of cotton/unit water applied) as a &quote;win win&quote; situation; making minimum water go further, particularly as DD is almost zero. However, minimal or no DD equates to a reduced leaching fraction. This in turn can lead to a potential for increased rootzone salinity.This project commenced in 2008 and monitored DD across irrigated cropping lands in the UMDP. There were 7 sites with lysimeters installed (each a commercial, irrigated cotton field) giving a total of 21 lysimeters. At each site, a lysimeter was installed near the head ditch, mid field and tail ditch in each field. One of these sites was irrigated with a lateral move and the remaining 6 with traditional furrow irrigation. One of the 6 furrow irrigated fields immediately adjoined the lateral move site, facilitating comparison of the two irrigation techniques in terms of DD. The water quality (salinity level) of all DD leachates was monitored at all sites. Several hydrological models were tested, to investigate their capacity to predict DD.Lastly, monitoring continued of the 16 &quote;wet&quote; inspection bores in the St George irrigation area (SGIA) to investigate their continuing dynamics and links withsurface water events. Principal results were:(i) In 2008-09, DD was collected only at the Macalister site under a rainfed barley crop; all other sites being fallow. Five sites (including the lateral move site) were irrigated in 2009-10 with DD values up to 104 mm measured, though most values were <20 mm and the lateral move (as always) being zero. All sites were under irrigated cotton in 2010-11 (high cotton prices) but DD collected were very low (all <12 mm) showing the incidence of very few irrigation events at all sites because of good and frequent in-season rains.(ii) The DD data and related soil Chloride sampling under the lateral move and in the adjoining furrow irrigated field suggest salt build-up under the lateral, due to the lack of DD (ie no leaching fraction). It is emphasised that the chloride data sets to date are small and sampling will continue in both fields to mid-2013 (just before a new Project ends) to assess further these soil chloride trends.(iii) As found previously, the EC of the leachates collected in the lysimeter collection bottles continued to be far greater than the EC of the irrigation waters applied to each field. This is seen as highlighting the potential for adverse off-site effects of poor water quality from DD. The maximum increases (60 fold) continued to occur at the St George site.(iv) Testing of the four hydrological models (SODICS, HowLeaky?, SaLF and SIRMOD/FAO-56) provided results at variance to the lysimeter-measured, DD values. The simulated outputs, though based on field collected parameters, had no relation to the magnitude, or seasonal or in-field trends of the lysimeter DD data. More work is required to fully investigate these anomalies. In particular, the simulations may benefit from more detailed inputs of evapotranspiration, rain and irrigation volumes that better reflect seasonal variability of irrigated cotton production.(v) Groundwater dynamics of the 16 &quote;wet&quote; inspection boreholes in the SGIA have been monitored since 1972 by manual dipping and since early 2007, by loggers set to log water levels on a 12 h interval. In the early to mid 1980s, the groundwater level in 50% of all the 16 wet inspection bores rose a range of 0.5 to 19 m towards the ground surface. Though these rises could have many causative factors, local growers linked them to the filling of on-farm water storages at approximately that time. These water levels have generally stayed at these elevated levels. Importantly, the water levels and their dynamics of the wet inspection bores illustrate more localised (small) groundwater mounds, rather than a broad groundwater mound under the SGIA. Two of the boreholes with the shallowest water levels showed a distinct rise in level, associated with the heavy rains and floods of March 2010 and January 2011. This result illustrates the continuing connectivity between surface water events and groundwater levels, at least for shallow, unconfined aquifers in the SGIA.