Water is precious:
In India agriculture contributes 40% to our country’s GNP and gives subsistence to 70% of our population. And yet 1/3 of our total geographical area is drought –prone because we are dependent upon the monsoons which can be erratic. Drought-prone areas have to be provided water not only for human and cattle consumption but also for irrigation. Whereas even after good monsoons water is not available only because of lack of proper management and storage as mentioned in beginning.

Why pond lining?
These reservoirs and ponds are located in a variety of soil types which –exhibit a wide range of seepage characteristics. Because of seepage, the water level of the reservoirs and tanks depletes rapidly.seepage losses not only mean loss of useful water but also lead to other problems such as breach in the embankment, waterlogging and increased salinity in adjacent areas.

With appropriate lining of reservoirs, ponds, canals the seepage loss can be minimized.

Lining film is tough, multilayer, wide width, black, low density polyethylene (LDPE) film by the latest Co-extrusion blown film technique it is available in various widths (4 to 10 metres) and thicknesses (100 to 250 microns).

The Mppls Pond / Canal Lining film has excellent mechanical properties which meets the specifications for LDPE films as per IS:2508-1984. Moreover its multilayer structure significantly improves the film properties like impact strength, tear resistance, flex crack resistance, environmental stress cracking resistance, etc. MPPL s Multilayer Lining film has excellent water barrier properties (practically nil water permeation), very good blend of physical properties such as tensile-impact streanth coupled with good weatherability and chemical resistance properties.

Procedure to construct a Lined Pond:
First of all the pond dimensions (L*B*D, Side Slope) are to be identified and than mark the top level as well as the bottom level length and breadth on the ground clearly. Put pegs at the corners of the pond and tie a rope to demarcate pond dimensions.

Next start digging the pond from the inside rectangle) and dig till desired depth is achived. Excavated soil can be kept near the pond around the demarcated periphery and can be used later after screening as a soil cover. Screening is very important as it will remove big boulders and sharp edged gravel which could damage the plastic film.

Precautions:
Digging along the slope is a tedious task but it must be done meticulously as the durability of the structure depend on it. If desired, a bamboo frame can be used to achieve uniform digging as per the desired slope.

Making the Bamboo Frame:
It can be constructed in a triangular shape of the desired slope e.g. if a slope is n:1 and the desired depth is ‘d’ then the bamboo structure sould be framed as shown in fig. Recommended side slope in case of soil cover (Horizontal : Vertical) is 3.5 : 1 and in case of Brick lining it is 2:1.

Further:
The next comes - Dressing. This is to be done carefully, it includes the removal of all sharp edged objects inside the pond otherwise the Lining film will get punctured.

Toe-wall:
If we are going for soil cover in bed and sides, there is no need for constructing toe-wall. But for a Brick Lining in the side, a toe-wall is essential to support the side bricks. For this a trench 30cms x 30cms minimum is to be dug along the bottom periphery of the pond. This trench is also to be dressed to prevent sharp objects damaging the lining. Once the toe-wall is constructed than the brick lining of the sides should be done from bottom to top.

A small trench (15cms x 15cms) is to be dug around the external periphery of the pond to anchor the plastic film. This trench could be approximately 1 metre away from the external boundaries of the pond. Now the pond is ready for the laying of the film.