The need to reduce water losses due to canal infiltration and associated land salinization is common throughout the country, at all levels of the water management system, from long distribution lines to individual farms. But the cost and effort required for lining over 40,000 km of supply and drainage canals is enormous.
In accordance with the second component of the joint UNDP/GEF project “Energy efficiency and renewable energy for sustainable management of water resources of Turkmenistan” that presupposes increased investment in improvement of water infrastructure in order to reduce water losses, save energy and reduce land degradation, it was decided to focus on demonstration, testing with the subsequent introduction of production processes necessary for manufacturing canal lining materials using local raw materials.
The greatest potential for the project in terms of speedy, reasonable and large-scale outcomes on canal lining is with the domestic production that has untapped opportunities for upgrading materials, productivity as well as efficiency gains.
The main project partner, the State Committee for Water Economy of Turkmenistan, currently operates a plant in Bezmein, which produces mainly reinforced concrete pipes and canal slabs. UNDP and the State Committee for Water Economy of Turkmenistan (SCWET) have identified a priority area where production at the plant can be efficiently expanded, redirected and made more efficient and cost effective. One lining option that has been empirically tested is the lining of the canal with a 0.5 mm high density polyethylene (HDPE) membrane protected by a 5 cm layer of sand and a layer of hexagonal concrete slabs. The main function of an intermediate sand layer is to protect the membrane from being punctured by hexagonal plates during installation. The advantage of this option is the lower consumption of raw material in the production of the HDPE membrane, and that it can be produced locally in a short time.
On the research site of 145 hectares, a demonstration section of a canal in an earthen bed had been lined by means of covering with an anti-seepage polyethylene film and hexagonal concrete slabs.
|Figure 1 The design of hexagonal slabs||Figure 2 Lining of the irrigation canal with a film with a protective layer of hexagonal slabs|
|Figures 3-4 Finished irrigation canal, lined with polyethylene film with a protective layer of hexagonal slabs|
1. Extrusion Line to produce High-Density Polyethylene (HDPE) geomembrane
As part of the project, UNDP purchased and installed an extrusion line to produce HDPE membrane at the Bezmein enterprise of construction products of PA Ahalsuwhojalyk of the State Committee for Water Economy. After delivery and installation of the necessary equipment, the Supplier conducted a three-day training for the operators and maintenance personnel of the end-user on the operation, diagnostics, maintenance and minor repairs of the extrusion line and on the production of high-density polyethylene film. During the training, the operation of the equipment was demonstrated, including the production of a trial batch of a polyethylene membrane in the amount of 500 kg. Also, within the framework of the release of a trial batch of products as a part of commissioning process, the best type of local raw materials for the production of geomembranes was determined through testing.
|Figures 5-6 Extrusion line for the production of impervious polymer coatings installed at the SCWE plant for the production of construction materials in Bezmein|
In addition to the production line, laboratory equipment for measuring and controlling the quality of products has been supplied, as well as welding equipment for gluing finished polyethylene film into large assembly rolls (depending on the size of the channels).
Furthermore, a granulator is installed for processing waste residues. This device can produce polypropylene granules from its own production residues, as well as from secondary raw materials. Using this device allows enjoying the environmental and economic benefits of plastic waste disposal.
In addition, the Supplier provided two copies of the operating instructions of the extrusion line in Russian.
Recently, the title for the asset has been transferred officially to the end user. During an upcoming operation of the equipment by the end user, raw materials to produce HDPE membranes will be purchased from a polymer plant located in Kiyanly (Balkan region), commissioned in October 2018.
Technical parameters of the HDPE membrane:
1. Raw material to be used: granular polyethylene (HDPE - LDPE) or similar recycled materials;
2. Productivity: 100 - 200 kg/h;
3. Size of the product (membrane): width from 2000 mm, thickness 0.5mm +/- 10%.
Summing up, it is worth noting the fact that within 15 years of operation lifetime, the equipment will be able to produce a quantity of HDPE film to allow lining 1950 km. of canals and is expected to lead to energy savings of 80,940.6 GJ. and a reduction in greenhouse gas emissions of 13,899 tCO2.
2. Forms for casting hexagonal concrete slabs
To date, within the framework of the project, 1200 pieces of rubber precast hexagonal slabs - used in the manufacture of hexagonal concrete slabs to protect the polyethylene film from mechanical damage when lining irrigation canals with an anti-filtration coating - have also been purchased and transferred to the Buzmein plant of construction materials. It is worth noting that with this number of precast hexagonal slabs, it is estimated that approximately 250 m2 of finished concrete slabs can be produced during one working day (8 hours).
A comparative analysis of monitoring water losses from a canal section lined with an anti-seepage coating in a natural earthen bed on medium loamy soils showed that hourly water losses in a lined canal account to 4 litres, which provides a canal efficiency of 0.99 (losses occur mainly due to evaporation with water surface), and in the earthen bed channel the hourly water loss is 205 litres.
Theoretically, reducing water losses from canals and improving drainage in irrigated areas can bring the following benefits:
• Increasing irrigated area due to the saved volumes of water;
• Reducing the volume of removed drainage;
• Lowering groundwater levels and improving conditions for growing crops and increasing yields.