[[Image:Bund.JPG|thumb|right|400px| Inside of a bund wall. Photo courtesy of [http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=0CGsQFjAI&url=http%3A%2F%2Fwww.arcworld.org%2Fdownloads%2Fsmart%2520water%2520harvesting.pdf&ei=NXNzT7CYEIiTiQKdxviYCw&usg=AFQjCNECS9O4gaRRQadp5dd4B5RDPxTwQA&sig2=QwWuUbra7my8Dpq5c_0baw ''Smart Water Harvesting Solutions]]]
Bunds (also called teras) are small barriers to runoff coming from external catchments (and possibly to a field where crops are to be grown). Bunds slow down water sheet flow on the ground surface and encourage infiltration (groundwater recharge) and soil moisture. This plot of There are different types if bunds. A rectangle type, where land is "bunded" on three sides, with the fourth side left open to capture runoff from an elevated areaand a contour type, where bunds are created in rows along the contour of a hillside. The bunds consist of small stone or earthen walls constructed along the contour of a plot of land. Bunds also trap sediment and prevent erosion or land degradation. A small channel on the inside of the bunds is made to let the water run along. Excess water drains along the tips of the outer arms(rectangle type). These spillways may improve the efficiency and reduce maintenance costs of the teras. The base bund can be 50-300 meters long, while the arms are usually 20-100 meters long.
Bund design has to be adjusted according to local conditions. They can vary in design and include non-enclosed systems (e.g. trapezoidal bunds where water escapes around the edges), and enclosed systems (e.g. bunded fields where water enters via a channel and escapes from a spillway in the bund once the field is flooded). In certain site-specific examples, they are used to create small artificial glaciers which helps release melt water slowly, so as to adjust to short sowing seasons.
====Maintenance====
Stone bunds: There is limited, ongoing repair required as the stones are not vulnerable to erosion. However, silting behind the stone bunds requires that the stones to be relaid from time to time. Care must be taken that overtopping of the bunds does not lead to erosion on the downstream face, with subsequent gully formation and undercutting of the bund.
==Costs==
Where stones are in short supply, there are increased costs associated with their acquisition and transport. If bunds are formed in a terrace-like design, the labour required for construction is estimated at 150 to 350 person days/ha for terraces and cut off drains. The cost of these structures is approximately $60-460/ha.
