|Sourcebook of Alternative Technologies for Freshwater Augmentation in some Asian Countries (UNEP-IETC, 1998)|
|Part B - Technology profiles|
|1. Water conservation technologies|
In South India, coconut pick-ups is a name popularly used for weirs constructed exclusively to provide water to coconut gardens. These weirs or pick-ups are small structures built across the seasonal or perennial streams to slow the flow of water at an appropriate location. This results in surface water storage, groundwater recharge, reduction of soil erosion and availability of water for other purposes. The bunds that form the puck-ips are constructed of locally available materials such as stones, boulders or mud turfed with grass. The bunds are usually built within the water course almost to the height of the surrounding ground level, depending upon the width and steepness of the stream. When stream flows occur, the coconut plantation, situated within the floodplain on either side of the water course, is temporarily flooded. The water impounded by the structures recedes within 3 to 4 days, with the excess water frequently diverted into a tank or cistern. Sometimes there will be several coconut pick-ups within a catchment, and several tanks which may flow from one tank to the other.
Extent of Use
This technology has been used in many places in South India.
Operation and Maintenance
The pick-up is constructed by the farmers and hence both operation and maintenance is the responsibility of the user. The principle maintenance requirement is keeping the pick-up sealed to prevent loss due to leakage.
Level of Involvement
Usually, the pick-ups are managed by the users who build them. Repair and maintenance are also carried out by the user. Government may be involved in the funding of the pick-ups, and in the initial permitting of the project site. This function is commonly performed by the local self-governing body that functions as a farmers/users association and manage their activities.
Construction of a typical coconut pick-up for an area of 10 ha in India would cost about $2 000.
Effectiveness of the Technology
The technology is successful in providing adequate water to many coconut farmers for agricultural purposes.
The technology is suitable for use in tropical areas with moderately rolling topography and small streams.
The use of pick-ups encourages groundwater recharge by promoting infiltration and vertical percolation. This recharge helps to sustain yields to percolation tanks and tube wells supplying open tanks. The recharge of open wells is almost immediate, even at a distance of up to 0.5 km depending on soil structure and gradients.
Ponds created by the pick-ups can serve also as a drinking water source for livestock from up to 10 villages.
Further, the floodwaters deposit a few millimetres of silt behind the pick-up structure and enrich the soils of the floodplains behind the pick-up with nutrients associated with materials like manure, leaves and other terrestrial debris carried in the runoff flows. These minerals and nutrients enrich the soil particularly during the monsoon season without the use of fertilizer supplements.
The presence of the temporary ponds behind the pick-ups can promote mosquito growth and exacerbate human health risks.
Being a traditional technology, the use of pick-ups is culturally acceptable. Some religious functions are held in the pick-up areas.
Further Development of the Technology
More realistic predictions of sustainable water yields will be needed to design cost effective and adequately-sized bunds.
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