Management Options to Reduce Salt Loads from Tile Drainage in the Campaspe West Area

Introduction

Salinity management is one of the major environmental issues in the Goulburn-Murray Water region. Lowering the watertable below the root zone of the crops is identified as a measure of controlling salinity, which allows leaching of salt stored within the root zone. Lowering the watertable is normally achieved by removing groundwater either by pumping or by tile drains.

Saline groundwater from groundwater pumps and tile drains needs to be disposed either into channels or into drains. However, disposing of large quantities of the saline groundwater has a detrimental effect on the water quality for downstream users. Generally, groundwater pumps are allowed to dispose saline water during winter period to provide sufficient leaching of salts from the root zone. Unlike groundwater pumps, tile drains are normally operated throughout the year and deteriorate the water quality of receiving water bodies and also bypass irrigation water during irrigation events.

 

Research Project

In order to provide best management practice to design and operate tile drainage systems, a research project was formulated between G-MW and CSIRO in 2001 and a pilot site (irrigated pasture) was established in Campaspe Irrigation District at Rochester. The milestones of this research study are:

  • Evaluate watertable levels and soil properties underneath the study area and estimate generation of drainage effluent and salt load under normal conditions.
  • Test different flow-control devices and measure the resulting reduction in flows and salt loads. Assess these changes against soil salinity and watertable conditions.
  •  Assess the potential for crop water use from shallow watertables by analysing watertable dynamics and cropping patterns.
  •  Develop a computer model to simulate tile drainage system under different operation and management scenarios.
  • Conduct an economic analysis of tile drainage management in order to quantify the costs and benefits.

 

Output

  • Provide best management practice guidelines to design and operate tile drainage systems to control salinity for irrigated pasture.
  • Provide irrigation management guidelines for pasture in high watertable areas including adjusted crop factors.