|Ayars, James - Jim|
Submitted to: 2nd International Conference and Workshop on the Coffee Berry Borer
Publication Type: Proceedings
Publication Acceptance Date: 1/30/2004
Publication Date: 3/17/2004
Citation: Christen, E.W., Hornbuckle, J., Herath, S., Ayars, J.E., Soppe, R.W. 2004. Integrating em survey, soil sampling and watertable data to manage subsurface drainage for salt discharge reduction:a base study.. 2nd International Conference and Workshop on the Coffee Berry Borer. No vol or pgs, on CD ROM. Interpretive Summary: Disposal of saline drainage water is one of the most vexing problems facing irrigated agriculture in the arid and semi-arid areas of the United States and throughout the world. The primary source of the drainage water is deep percolation from inefficient irrigation. The first step in reducing the volume is to improve irrigation efficiency. The next step is to actively manage the drainage system to control the outflow. Often drainage systems are designed based on the poor irrigation efficiency and the result is over drainage and excess discharge when the irrigation is improved. Salinity is frequently found in arid areas and the salt load is proportional to the flow volume, thus reducing flow will also reduce load. This paper described a study that characterized the salinity status in the soil and ground water in an irrigated pasture in Victoria, Australia and the management plan to reduce the salt load from the drainage system installed in the field based on the findings. An electromagnetic salinity survey of the site determined that only portions of the field continued to need drainage for salinity control. As a result of the survey, water table control was implemented on a portion of the field and the total flow was reduced. The water table control improved the irrigation efficiency and reduced the total drainage and salt load being discharged.
Technical Abstract: The performance of subsurface drainage systems is rarely evaluated after installation. Assessments regarding the completion of salinity reclamation are often not undertaken and hence the potential to move to a reduced drainage requirement after the initial reclamation phase is never realised. Reduced drainage requirements offer a number of economic and environmental benefits including reduced drainage operating costs, higher water use efficiency and reduced disposal problems. This paper provides a methodology based upon electromagnetic (EM) soil survey information, field calibrated with soil salinity sampling to provide a temporal and spatial analysis of the effectiveness of subsurface drainage in removing rootzone soil salinity. EM surveys were undertaken on a dairy farm in south-eastern Australia 2 years after the installation of a subsurface drainage system. This spatial assessment allowed analysis of the efficacy of the drainage system, in terms of uniformity of reclamation and time to reclamation. It was found that in some areas due to varying soil properties, topography and water management the soil had been fully reclaimed and so the drainage requirement could be reduced, whilst other areas still had high levels of soil salinity and as such reclamation needed to continue. Using EM, soil salinity and watertable data, differential management of the subsurface drains was implemented with the aim of minimising salt discharge and hence reducing the downstream impacts of subsurface drainage.