Balancing Reservoir

Designing a Reservoir with Breaklines and Calculating a Storage Volume Curve

Location: South Africa
Field Area: 14.4 ha or 35.6 acres
Irrigation Method: none
Crops: n/a

Figure 1. Google Earth Satellite image of the site.


A balancing reservoir was required to store water pumped from the Mokolo River on the west prior to irrigation. The existing topography is shown below.

Figure 2. Existing Topography.


The reservoir was designed using breaklines and earthworks was balanced using Re-calculate Cut/Fill Map feature. The proposed design is shown below.

Figure 3. Existing Topography (left) and Proposed Topography (right).

The earthworks were balanced to ensure the cut volume matched the fill required for the embankments. This is automatically done using the Re-Balance Cut/Fill tool. The earthworks required are 193,850 m³ for the cuts and 160,440 m³ for the fills.

Figure 4. Proposed Cut/Fill Map.

Below are some long section and cross sections through the proposed design.

Figure 5. Long Section Profile

Figure 6. Cross Section 1 Profile.

Figure 7. Cross Section 2 Profile.

Reservoir Storage Volume

The Reservoir Storage Volume tool calculates the volume of water stored in a reservoir at different elevations.

The inputs in the calculation are shown below along with the tabular results.

Figure 8. Reservoir Storage Volume Inputs.

Figure 9. Reservoir Storage Volume Results.

Below is the Storage Depth Map generated from the Reservoir Storage tool.

Figure 10. Proposed Topography (left) and Water Storage Depth Map (right).


OptiSurface Designer provides powerful tools and features to design earthen water reservoirs. The Reservoir Storage Volume feature allows to determine the water volume curve and map. The Re-Calculate Cut/Fill allows the balancing of earthworks. The design can even be displayed in 3D!

The machine control file was exported at 1m grid to capture all the details of the design and can be loaded into numerous machine control systems.

Below is the 3D representation of the proposed design with vertical scale exaggerated by 23x.


Figure 11. Proposed Topography in 3D.

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