Bunds are among the most common techniques used in agriculture to collect surface run-off, increase water infiltration and prevent soil erosion. Their principle is comparably simple: by building bunds along the contour lines, water runoff is slowed down, which leads to increased water infiltration and enhanced soil moisture. Using different designs, bunds are applicable to even and uneven grounds (with a gentle slope of up to 5 per cent). Bunds are usually constructed either with soil or stones.
Being one of the most often used precipitation harvesting methods in agriculture, the main purpose of bunds is to slow down and filter runoff water from rainfall and hence reduce soil degradation. As the water flow is decelerated, higher amounts can infiltrate in the soil, leading to increased soil moisture (see also conservation of soil moisture). Furthermore, water is spread more evenly, which can prevent gully formation. Bunds are basically the opposite of field trenches, where slots and trenches are excavated to stop, store and infiltrate floodwater and surface run-off.
Contour bunds can either be made of stones or soil (sometimes in variation with crop remains). They are constructed along a contour in order to best slow the water flowing down the slope, which increases the green water pool of the soil and prevents erosion. There should always be several bunds next to each other, whereas the distance between them depends on the slope and the soil type of the field: the steeper the ground, the closer the bunds. Contour bunds can be used for both yearly field crops as well as the planting of trees. Their use is widespread throughout Africa. In northwestern Somalia, contour bunds have reportedly increased yields of sorghum by up to 80% (MALESU et al. 2007; OUESSAR et al. 2012).
A special and well-known type of contour bunds is terracing contour bunds, often used for the production of rice. In comparison to normal contour bunds, terraces even out the slope of the ground and therefore make the paddies plain.
Due to their half-moon design, semi-circular bunds are well suited for planting individual trees. In opposition to contour bunds, each bund has to be made singularly by hand, making them much more time consuming in their implementation. As a plus factor, semi-circular bunds can also be applied to steeper fields.
It is important to choose the right measures for semi-circular bunds, as the amount of collected water depends on both its height and the position of its tips. A further factor for the appropriate size of bunds is the selected crop (see also crop selection): bigger bunds are needed for fruit trees, which require a radius and height of at least 0.6m. Furthermore, it is also important to leave free spaces between the bunds in order to enable excess water to run off.
Advantages / Disadvantages
Contour bunds (contour ridges)
Applied to sloping, but even terrain in order to catch runoff water.
Not suitable for uneven terrain.
These bunds are also possible to apply on uneven ground.
Can be constructed on any slope, from almost flat terrain up to steep slopes.
Implementation is more time consuming, as construction cannot be mechanised.
Adapted from RUFFINO (2009)
The costs for the implementation of bunds depend strongly on the choice of design. For contour bunds, working time of approximately 32 person days is estimated per hectare. If machinery can be used, the time required reduces, but the costs may rise due to higher investments (only possible for contour bunds, as semi-circular bunds cannot be made mechanically). For stone bunds, increased costs may apply where stones are rare.
The effectiveness of contour bunds may be enhanced by placing planting pits between the bunds and/or constructing upward ties. The ties are meant to create micro-catchments along the bund and can be built manually or with the help of special machines. If there is excess rainfall, it may be helpful to build cut-off drains in order to let surplus water run off (OUESSAR et al. 2012).
The required maintenance of bunds depends on the type of construction: constructions made of stones are very resistant to erosion and therefore only need limited on-going repair (ADB 2008). Earthen ridges on the other hand need to be rebuilt to their original height after each season (ANSCHUETZ et al. 2003). To limit maintenance to a minimum, it is important that the primary construction is done carefully and solidly. Grass growing on bunds can further enhance stability as its roots fix the soil. It should therefore not be removed.
If built thoroughly, bunds are a reliable tool for water harvesting.
Self-help compatibility is high due to their simple construction and maintenance.
Contour bunds may be enhanced with the construction of planting pits and/or upwards facing ties. Maintenance is limited for bunds made of stones. More reconstruction is needed for earthen bunds, as they are less robust.
Bunds have a high reliability if construction and maintenance are done correctly.
Simple and comparably cheap. Prevents erosion.
Bunds are generally applied to sloping fields in order to reduce water runoff and erosion and may also be functional for severely degraded soils (RUFFINO 2009). Contour bunds can only be constructed on even ground, whereas semi-circular bunds can also be applied to uneven terrain.
Design and construction are easy and can be done without much specialised knowledge. Stone bunds are generally more resistant and need less maintenance. But building stone bunds can be expensive if stone resources are limited. It is therefore advisable to build earthen bunds in such areas.
ADB (Editor) (2008): Rainwater Harvesting Handbook. Assessment of Best Practices and Experience in Water Harvesting. Tunis-Belvedere, Tunisia: African Development Bank (ADB). URL [Accessed: 08.08.2012].
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MALESU, M.M. (Editor); ODUOR, A.R. (Editor); ODHIAMBO, O.J. (Editor) (2007): Green Water Management Handbook. Rainwater Harvesting for Agricultural Production and Ecological Sustainability. Nairobi: The World Agroforestry Centre. URL [Accessed: 09.05.2012]. PDF
OUESSAR, M.; HESSEL, R.; SGHAIER, M.; RITSEMA, C. (2012): Water Harvesting Potential for Africa. An Assessment of Costs and Impacts. Tunisia: Water Harvesting for Rainfed Africa (WAHARA). URL [Accessed: 13.08.2012].
RUFFINO, L. (2009): Water Conservation Technical Briefs. Rain Water Harvesting & Artificial Recharge to Groundwater. Brussels: SAI Platform. URL [Accessed: 13.08.2012].
WILDCHINA (Editor) (2012): Cross Border Journey. Trip Notes from Vietnam and China. URL [Accessed: 07.11.2012].
IBRAIMO, N.; MUNGUAMBE, P. (2007): Rainwater Harvesting Technologies for Small Scale Rainfed Agriculture in Arid and Semi-arid Areas. Maputo: University Eduardo Mondlane. URL [Accessed: 08.08.2012]. PDF
This paper is a review of simple water harvesting techniques, which have been tested and found useful in arid and semi-arid regions, and which might be suitable for use in other areas. The paper also tries to show some successful cases of application of water harvesting techniques in African countries, which have increased the overall productivity of smallholder farms and hence improved farmers’ livelihood.
This newsletter includes a short overview on different internal catchment practices in rainwater harvesting. The portrayed techniques include: earthen bunds, pitting and meskat-type system.
OWEIS, T.; HACHUM, A. (2009): Water Harvesting for Improved Rainfed Agriculture in the Dry Environments. In: WANI, S. (Editor); ROCKSTROEM, J. (Editor); OWEIS, T. (Editor) (2009): Rainfed Agriculture. Unlocking the Potential. Oxfordshire, 164. URL [Accessed: 26.11.2012]. PDF
NYSSEN, J.; POESEN, J.; GEBREMICHAEL, D.; VANCAMPENHOUT, K.; D’AES, M.; YIHDEGO, G.; GOVERS, G; LEIRS, H.; MOEYERSONS, J.; NAUDTS, J.; HAREGEWEYN, N.; HAILE, M.; DECKERS, J. (2007): Interdisciplinary On-site Evaluation of Stone Bunds to Control Soil Erosion on Cropland in Northern Ethiopia. In: Soil & Tillage Research 94, 151-163. URL [Accessed: 28.08.2012]. PDF
An evaluation on the positive effects of stone bunds with regard to technical, ecological, economical and social factors. The conclusions are drawn from a case study in Northern Ethiopia.
WOLKA, K.; MOGES, A.; YIMER, F. (2011): Effects of Level Soil Bunds and Stone Bunds on Soil Properties and its Implications for Crop Production. The Case of Bokole Watershed, Dawuro Zone, Southern Ethiopia. In: Agricultural Science 2, 357-363. URL [Accessed: 28.08.2012]. PDF
This study analysed the effects of level soil bunds and stone bunds on selected soil properties, when compared with non-terraced cropland in the Bokole watershed, Southern Ethiopia. The comparison was done with regard to stored soil organic carbon, nitrogen, phosphorus, potassium, pH-level, and the cation exchange level.
HATIBU, N.; MAHOO, H.F. (2000): Rainwater Harvesting for Natural Resources Management; A planning Guide for Tanzania . Stockholm: Sida's Regional Land Management Unit. URL [Accessed: 29.02.2012]. PDF
A planning handbook that provides planners with practical tips on how rainwater harvesting can form an integrated part of district development efforts. The book also gives practical guidelines in the planning steps required to incorporate rainwater harvesting in development plans, and shows how to implement them in the farmers’ context.
http://www.wahara.eu/ [Accessed: 13.08.2012]
This website delivers information on WAHARA, a project aiming at increasing the potential of water harvesting by closing knowledge gaps through research. It focuses on four African countries with different rainfall conditions: Ethiopia, Zambia, Burkina Faso and Tunisia.
http://www.rainwaterharvesting.org/ [Accessed: 29.08.2012]
This site contains short introductions to different rainwater harvesting systems applicable to dry lands.