Fish pond construction on slope area on clayey subsoil for water harvesting [Lao People's Democratic Republic]

Good Practices

Fish pond construction on slope area on clayey subsoil for water harvesting [Lao People's Democratic Republic]

Definition of the Technology:

The methods for construction of earthen pond on slope area in adjacent to the village where it forms perennial water channels with clay soil which is unsuitable for other agricultural purposes. Therefore, Oxfam encouraged the construction of communal pond to create the interest for many households to build their own ponds.

Description:

With the slope mountainous area, the top soil's soil nutrients and organisms are leached by heavy rain during wet season (July-November). This land was mainly used for Bong tree plantation (Nothaphoebe umbelliflora) and a variety of fruit trees; however, farmers have to wait for many years to be able to get small harvest from these trees. In 2004, an Oxfam Project promoted and encouraged local community to construct a communal mud-pond with a size of 50 x 40 m on steep terrains near the village. The project utilized the water resource potential by digging a pond for the villager's use as year round gravity fed water supply system. The project initially provided fish fingerlings (tilapia, silver barb: scientific name is Barbonymus gonionotus, and grass carp: scientific name is Ctenopharyngodon idella). The village residents realized immediately the significant benefits of the pond. Besides raising fishes in the pond, local people could use water for household gardening and as a source of drinking water for livestock (cow, water buffalo, pig, duck, etc). The pond is easy to manage and maintain whilst it is also more convenient to collect aquatic resources in proximity to the village. Typically, the potential site condition for pond construction is steep mountainous terrain with average slope of 10 -15 degrees. The soil property should be clay or silt clay which can hold the water.
Later after the community pond has been constructed some villagers who had potential land left constructed their individual ponds to improve their own production. This because they have seen the benefit of communal pond which can provide approximately 200 - 300 kg of fish per years. The individual pond construction reduced finally also conflicts caused by different issues of the community pond.
The construction of the pond is not very complicated. First, the water valves from GFS (provided by the Poverty Reduction Fund) turned off the sources water from the upstream area. Bush clearing, tree felling, stump removal and vegetation stockpiling (for burning) was then required on construction areaof the pond The pond size should be designed at a size of approx. 30 x 20m. Next step, the manual excavation works (by using hoes and shovels) should ba undertaken at upper section of the canal. The ground has to be excavated with an average depth between 0.5 – 1m and with the excavated soil pond dyke has to be alligned arround the pond area (square shape). The dykes soil has to be compressed to very compact barriers to prevent water leaking and dyke erosion (even small holes in dyke can rapidly enlarge, leading to the potential future damages and dyke bursting). The pond dyke’s height is 1.2m in hight and 2m wide with dyke slopes from the foot to the edge (where it also provides a walkway for feeding fishes or gardening) is approximately 45%. The design of the thick dyke is to ensure its stability from soil erosion as a result from a certain fish species that pierces the dyke slopes and rapid water flow. If the pond dyke is designed with fewer slopes, it will be susceptible to soil erosion. At least a drainage outlet is required with a P100 pipe for 4m long. The pipe should be installed with 1m height from the pond bottom at the outlet. This pipe will drain water and prevent overflow that may cause damage to the dyke. The pond area later need to be leveled by using hoes and shovels cut the undulating area. Then should be kept the pond bottom dry for at least one week to allow time for pond repair as well as to increase the production of the pond bottom, after that fill the water into the pond by turn on the inlet valves that have been turn off earlier. This pond construction method may require intensive labors and extensive time to complete. Funding for construction tools and construction method are still insufficient. However, this is the effective way to maximize water from perennial stream for integrated management and its benefits are considerable especially for fish consumption in household and selling for generate household income.