DAM AND IRRIGATION SITES FINAL DESIGN OF 4 SITES FOR LAND HUSBANDRY WATER HARVESTING AND HILLSIDES IRRIGATION (LWH) PROJECT (RWANDA)

The main project's component was the detail feasibility study of the dams and supplemental irrigation infrastructure necessary for hillside irrigation at four sites (Nyanza-23 Karongi-12, Karongi-13 and Gatsibo-8). For each dam and irrigation sites, the study included review of existing designs and studies, field visits and geotechnical investigations, detailed design of dams and irrigation networks, preparation of tender documents, design workshops with the Service and the Panel of Experts and dam safety calculations

 The four (4) schemes had the following characteristics:

• The Nyanza 23 scheme the study concerned a total area of 450ha corresponding to an annual irrigation water demand of 1.3 million cubic meters and included the design of a clay core earth fill dam of 19m height with a total embankment volume of 77,500m3, the reservoir capacity was 1.82 MM3.
• The Karongi-12 scheme the study concerned a total area of 255ha corresponding to an annual irrigation water demand of 0.65 million cubic meters and included the design of a clay core homogenous dam of 22.5m height with a total embankment volume of 118,850m3, the reservoir capacity was 0.68 MM3.
• The Karongi-13, scheme the study concerned a total area of 304ha corresponding to an annual irrigation water demand of 1.07 million cubic meters and included the design of a clay core homogenous dam of 22.5m height with a total embankment volume of 208,000m3 the reservoir capacity was 1.17 MM3.
• The Gatsibo-8 scheme the study concerned a total area of 90ha irrigation and included the design of a clay core earthfill dam of 17.0m height with a total embankment volume of 172,410m3, the reservoir capacity was 0.6 MM3.

Z&A was involved with the detailed design of the irrigation networks in all sites with a total area of 1099 ha, the geological investigations and the full hydro geological assessment of the four dam site areas.

Water transmission and distribution networks designed for this project consisted of: (a) 32,000 m HDPE DN500 water pipes for Karongi-12 area, (b) 48,000 m HDPE DN630 water pipes for Karongi-13 area and (c) 21,000 m HDPE DN450 water pipes for Nyanza-23 area.