|Related Agroforestry Livelihood (IIRR, 1992, 30 p.)|
|Small water-impounding technologies|
Earth or mixed-material dam -- a structure composed of readily available materials (such as rocks, boulders, logs and earth) and is used to store water for watering and other similar purposes. The structure is usually applied in live or intermittent creeks or streams with up to three meters width and not prone to flash flooding.
Earth or mixed-material dam
1. Earth dam - a structure composed mainly of compacted soil with a base of at least one meter thickness arranged in a pyramidal fashion. It usually has an opening near the base (through a bamboo tube) and at the top (small opening lower in height than the dam) to control the water flow.
To make reservoir area more impermeable to minimize seepage of water, the following should be conducted: a) scrape the bed of rocks until reaching the clay surface; b) line the bed with at least 20 cm thick of fresh leaves, grasses and fine organic matters; c) cover the organic materials with soil of at least 20 cm thick and compact it eliminating air spaces; and, d) allow the organic matter to rot, thus forming a sticky and impermeable layer.
2. Earth and stone dam - a structure composed of compacted earth (soil) and a core of boulders and rocks. The dimension is more or less similar with the earth dam.
Earth and stone dam
3. Earth, Rock, Log Dam - a structure composed of compacted soil rocks and log (wooden) materials. The core is mainly composed of boulders and rocks with interspaces filled up with clay materials. Compacted earth materials cover the core and the logs are arranged either in horizontal or vertical fashion with clay materials as the outer covering.
4. Bamboo and earth dam - a structure mainly composed of bamboo poles and crushed bamboo and earth materials. Two lines of bamboo poles and crushed bamboo culms are constructed at 0.25 m distance between lines. The distance between bamboo poles in a line is approximately one meter. The interspaces between the lines are filled up with rocks mixed with clay. The outer covering is composed of compacted earth.
Bamboo and earth dam
For further storage efficiency of the above mentioned dams, the surface of the structure should be lined with two inches of clay materials. Planting of grasses, such as bermuda grass, can also be done to strengthen the outer surface of the dam.
Bamboo and earth dam lined with two inches of clay materials