Understanding the surface hydrology of low lying sugarcane fields for a basis of optimised surface drainage criteria – Macknade Mill

Level 1: General Description


The aim of this study was to develop field design criteria for surface drainage of low lying sugarcane fields. The criteria was developed by measuring and modelling the field scale hydrological processes that influence surface drainage of sugarcane fields that are subject to inundation and waterlogging in the Lower Herbert Valley, North Queensland.

The main objectivise of the research are the following:

  • To understand the underlying soil and field hydrological processes involved in the generation of runoff, interflow and waterlogging of the soil;
  • To use the measured field data from the study site to calibrate sustainable computer models to simulate the hydrological processes; and
  • To use the models to derive optimised field drainage design criteria through modelling of a range of climatic conditions and field design.


Field Treatments

A soil pit was dug at the Palma's site to a depth of 0.75 m and 2.0 m. Soil samples were removed for moisture retention and hydraulic conductivity determinations. Single ring infilrometers were used to measure the infiltration rate of key soil horizons which in turn used to establish the saturated hydraulic conductivity of the 4 soil horizons observed in the pit.

A series of experiments were conducted at the Palma's site to establish a depth discharge relationship, the resistance to flow of runoff and to measure in situ soil hydraulics properties. Flumes were installed to measure the runoff from the field and shallow wells were installed to observe and measure the fluctuating shallow watertable. Time domain reflectometer probes (TDR) were installed to measure the volumetric soil moisture content at several depths and redox probes were installed to measure the reduction potential of the soil at
two depths in the field.

Soil samples were collected from the study site and analysed in the laboratory for soil water retention and hydraulic conductivity curve.


A processes model, Storm Water Management Model (SWMM), a Unit Hydrograph and a watertable drawdown model were used to model the hydrology of the sugarcane field at the Palma's site. In addition two sugarcane yield-watertable response models (RC and GOYLE) were coupled to the watertable drawdown model.

Key Findings

The surface hydrological characteristics of three low lying sugarcane fields were measured and it was found that the regional drainage system controlled the runoff from the fields. The runoff from the fields was mainly submerged flow with free flow occurring only at the very beginning and at the very end of the runoff event.

The use of simple height stage recorders such as weirs, to measure discharge rates is not appropriate in environments such as the Lower Herbert Valley. Low relief slopes and non integrated drainage design complemented with high intensity and high volume of rainfall restricts the movement of water from low lying fields.

The inundation of sugarcane field was not the major cause of yield loss. The Rudd and Chardon model was found to be an excellent predictor of yield of sugarcane under conditions of excess water.

Manning's equation provided a relationship for the description of overland flow for sugarcane trash blanket. The surface water balance of the Main Palma's site shows that the water furrows act as a preferential pathway for runoff. The surface water balance revealed that on average 36% of the runoff from the field exits by the rows.


The third site is located at Macknade Mill (CSG Sugar Ltd) approximately 10km east of the Palma's site.


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