FARMING-SYSTEM SPECIFIC EXTENSION CONTENT FOR ENHANCING CLIMATE CHANGE ADAPTATION AND RESILIENT FOOD SYSTEMS IN SORGHUM-BASED DRYLAND FARMING SYSTEMS OF TANZANIA AND BURKINA FASO
BUNDS ALONG THE CONTOURS AND SPILLWAYS FOR DIRECTING WATER TO PONDS WATER MANAGEMENT
CLIMATE CHANGE ADAPTATION AND RESILIENT FOOD SYSTEMS ISSUE
How to overcome water loss through evaporation and runoff and also mitigate the effects of insufficient and erratic rainfall
ESSENTIAL TECHNICAL INFORMATION
Earthen bunds are one of the options for overcoming the above issues
1.1. What are earthen bunds?
Earthen bunds are essentially an external catchment, long slope technique of water harvesting. Typically, a u-shaped structure of earthen bunds which farmers build on their cultivated lands to harvest runoff from adjacent upslope catchments, this technique usually collects rainwater and, sometimes, floodwaters (Figure 1).
Figure 5: Typical element of the teras water harvesting structure (van Dijk, 1995).
1. Base contour bund
2. Outer collection arm
3. Inner collection arm
4. Shallow channel
5. Basin 6. Cultivated area
7. External catchment
8. Internal catchment
9. ‘Mother’ (main structure)
1.2. Effectiveness of the Technology
The technique allows the production of a crop of millet or sorghum. Based on data from Sudan, yields may reach 750 kg/ha in a good year. Quick maturing sorghum or millet should be planted immediately after the water from a storm has subsided. This crop grows and matures in about 80 days.
1.3. Environmental Benefits
Use of this technology reduces land degradation and improves water infiltration.
This technology is appropriate for areas of the sorghum-based farming system where the foothills reinforce high intensity and short duration rainfall, with 150 to 400 mm rainfall, annually.
The technology is entirely farmer managed and, therefore, not subject to the organizational problems of other soil and water conservation techniques. Socio economic surveys have indicated that application of soil and water conservation practices contributed about an additional 75% to the total household crop production income in the 1980s and 1990s.
The lack of a spillway can result in breached bunds.