Circular Furrows

Best for Pivot Irrigation

Location: Southern Zambia
Field Area: 84 ha or 207 acres
Irrigation: Pivot Irrigation
Crops: Sugarcane

Background

A sugarcane farm is looking to design their pivot irrigated fields with circular beds/furrows for best efficiency of operations and most importantly, to eliminate standing water on depressions scattered across the field.

Existing Topography

The Existing Topography shows where the roads intersects the field: N-S and E-W as shown by the survey points.  But the natural topography's lowest area (shown as purple) points to NNE area, so this was recommended to be used as the basis to where the roads run, as this will also be where the tail drain will lie.

Existing Topography Drainage Analysis

Proposed Topography

An OptiSurface 2Way Circle was used to design the field.  This surface type has circular furrow that drains into opposite directions away from a defined ridge (or into a defined cross drain).

Roads will quarter the field into four section and this will also where water can drain out of the field through defined cross drains.

The red subzone shows where the ridge lie following the southern road.  The green subzones lie where the road crosses the field, this also where the cross drains for each quarter will be placed.  The east green subzone drains water out to the east and the west green subzone drains out to the western edge.

Proposed Cut/Fill Map

Furrow Profile

Conclusion

Designing with circular furrows is unique to OptiSurface.  A minimum slope of 0.05% was used for the main slope and the cross slopes are set to have -0.5% to 0.5%.  Smoothing of 100m/% for main slope and 200m/% for cross slope finishes the parameters.

Ridges and cross drains are defined using subzones and this resulted to a circular pivot design with provision to drain excess water from each quarter out of the field.  This resulted to 169m3/ha of earthworks, quite low for a complex design.

The client was happy to change the road orientation with the earthworks savings and reduced cuts.

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