India

To measure how fast water percolates into the soil, you need to measure the time it takes for a specific amount of water to soak into a specific area of soil. The easiest way to do this is to get a length of cylindrical pipe that is sharp enough to push (or hammer) into the soil at one end. Mark it with two lines – one is the line to which you insert it into the soil, and the other is the line to which you fill the water.

You can measure slope by making use of gravity. Find a protractor for measuring angles. Attach a straw across the straight edge of the protractor.

The ideal farm pond should be dug into the ground in a naturally low-lying area. Some of the soil that is removed can be used to construct an earthen berm around the pond, which should be planted with trees and grasses for stability. The shade and wind protection provided by the raised mound and vegetation will reduce evaporative losses.

Where conditions are favorable, it is better to recharge the groundwater than to create surface ponds for storage. This approach minimizes evaporative losses, and often improves water quality. Recharge structures can be anything from a small pit simply dug into the soil, to a borewell converted for recharge. Recharge structures are useful in sloping landscapes where the water would not otherwise have time to sink into the ground before running off.

Where possible, it is much more cost effective to restore existing tanks, than to build new tanks. Restoration can involve silt removal to increase the storage capacity of the tank and reduce evaporative loss. The silt can be used to restore the earthen bund, and any remaining silt can be applied to nearby farmland. The outflow structure can also be improved.

If the intention is to develop a tank by holding back a large amount of water, then the dam must be carefully designed (with the assistance of experienced local people or engineers).

In addition to controlling gully erosion, check dams also serve to slow the movement of water, allowing increased percolation into the soil. Just above a check dam is a good place to put in a percolation structure. Silt that builds up behind the dam creates good farmland, which can be planted after the rains while it retains moisture. The following series of pictures show one farmer’s success with building a percolation tank just upstream of a series of check-dams.

Over the years, unchecked soil erosion can lead to the formation of deeper and deeper gullies. There are several methods for controlling gully erosion, which can be chosen depending on the materials available.

If it is a small gully, vegetation can be planted in strips across the gully to slow the velocity of water, trap silt, and prevent further erosion.

These techniques are useful to slow runoff and erosion from sloping land, and also to revegetate degraded areas. Areas with high rainfall, steep slopes, and thin soils should use slightly graded bunds / terraces / trenches to allow some drainage.

Bunds have many benefits, including marking the boundaries of farm-holdings, slowing the movement of soil and water, and providing a place for integrating trees into agricultural systems. Here are some tips for using bunds within farmland:

• Cattle should be kept away from the area while establishing saplings, by using livehedge fencing. Cactus, Euphorbia spp, and Agave are useful for a livehedge fence.
• Larger trees can be planted on boundary bunds, and smaller trees which will be harvested more frequently can be planted on internal bunds, which divide one holding into separate sections.