With increasing pressure on natural resources of the world, irrigation is an indispensable technology used to augment agricultural production in the semi-arid and arid regions. However, due to poor water management, including unsuitable location of water reservoirs and supply channels, water logging, perched water tables and secondary soil salinisation are the consequent land degradation. This paper examines a) the problem of water use efficiency-particularly in terms of efficient water delivery to the irrigated fields from water reservoirs, and b) the information required to determine best-management practices. The study areas are southeast of Trangie and Warren in the lower Macquarie valley in central New South Wales, Australia. In the first instance rootzone information is necessary to determine soil types susceptible to excessive deep drainage (DD). We calibrate a root zone sensing electromagnetic (EM) induction meter (i.e. EM38) to estimate DD from soil properties under various irrigation (I) water scenarios (i.e. I = 300, 600, 1,200 and 1,800 mm/year) using a salt and leaching fraction model (SaLF). Maps of estimated DD are then produced from the detailed EM38 survey data. Maps of the spatial distribution of average clay and salt content to a depth of 7 m (i.e. vadose zone) are established using a deeper sensing EM34 at the 10 m coil separation distance. Based on a Geographic Information System analysis, these maps confirm the farmer’s experiences with the creation of perched water tables and incidence of soil salinisation. The results also identify areas where similar problems may occur if irrigation facilities were to be installed in certain parts of the Trangie and Warren irrigation districts.