Figure 2. Contour/Graded Bund System


K


The contour/graded bund system has long been the standard recommended practice in Indian
SWC programs. This picture demonstrates the problem that arises because contour lines (the
heavy black curved line) rarely match boundary lines (the light lines in the grid). The contour
bunds and central waterways tend to cut covers on small fields.

Indigenous SWC structures on small farms of the study regions lie almost uniformly on field
boundaries, which rarely correspond exactly to contours. Indigenous practices vary more widely
than recommended practices, reflecting the diverse conditions under which they have evolved.
Boundary bunds are made either from earth or stone or a combination of both, depending on
relative abundance of these materials. Bunds increase in height and width as slope, rainfall
intensity and erodibility of the soil increase. Often vegetation is preserved or planted on the bunds
to strengthen them and provide fodder and other products.

Methods to dispose of excess runoff are also based on boundary lines. In areas with red soil and
low rainfall, some farmers build small earthen bunds to keep all the moisture on the field. Where
the land is stony, they build stone bunds that retain soil but allow water to filter through. In
medium rainfall zones, especially in black soil areas where waterlogging can be a problem,
farmers build stone waste weirs (drains) to dispose of runoff into the field below theirs. In the
highest rainfall zones, the waste weirs deposit water into boundary waterways, protecting the
lower fields. Sometimes grass strips are planted on the lower end of the field to arrest soil while
allowing to water to drain. These three systems are displayed in Figure 3.


GATEKEEPER SERIES NO. SA34