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Precast Ferro Cement Channel Sections as an Alternative for Channel Lining in Private Sector Irrigation of Bangladesh

A. A. Hassan
Agricultural Engineering Division Bangladesh Institute of Nuclear Agriculture, P. O. Box 4, Mymensingh-2200, Bangladesh.

M. H. Ali
Bangladesh Institute of Nuclear Agriculture, P. O. Box 4, Mymensingh-2200, Bangladesh.

A. A. Sarkar
Bangladesh Institute of Nuclear Agriculture, P. O. Box 4, Mymensingh-2200, Bangladesh.

M. N. Karim
Bangladesh Institute of Nuclear Agriculture, P. O. Box 4, Mymensingh-2200, Bangladesh.

Abstract/ Executive Summary:

Private sector irrigation covers about 90% of irrigated land ill Bangladesh. Most of the channels of the irrigated area are earthen. The present estimated average cultivable command area of a deep tubewell (56 litre per see i.e. 2 cusec capacity) is 20 ha and a shallow tubewell (15 litre per see i.e. 0.25 cusec capacity) is 4 ha, which should be about 40 ha and 8 ha, respectively. Low command area is mainly due to high conveyance loss which is about 35-50% in earthen channel. The water distribution systems are not normally lined as the farmers cannot afford because of high investment cost. As an alternative, precast ferrocement channel sections were constructed and tested at micro level to evaluate the technical and economic feasibility for improving water conveyance efficiency in irrigation schemes. The cost of precast ferrocement channel sections were found to be low (US $ 9.5 per meter) compared to the cost of brick lined channel sections (US $ 20.0 per meter). Cost estimates were made on the basis of direct costs incurred during the research work. Water conveyance efficiency in ferrocenient channel sections was found to be 96 percent. Thus, the result revealed that the precast ferrocement channel sections were more economic and technically suitable for reducing water loss in conveyance system.

Keywords: Precast ferrocement channel sections, Cultivable command area, Economic feasibility, Improving water conveyance efficiency

Location: Bangladesh Institute of Nuclear Agriculture, P. O. Box 4, Mymensingh-2200, Bangladesh.

Start Date: 01-06-1994

End Date: 30-06-2004

Program Area: Crop-Soil-Water Management

Commodity: Command area development

Objectives:

Recognizing the merit of lining and high investment cost of brick lining, an attempt has been made to construct precast ferrocement channels and estimate the cost of construction. After construction of ferrocement channels and field installation, the field evaluations were made to have comparative assessment of different types of channel lining like rectangular brick-lined channel and precast ferrocement channels of semi-circular and rectangular X-sections compared to earthen channel to be used in private sector irrigation.

Methodology:

The best hydraulic channel section is defined as the cross section which will convey maximum water with minimum wetted perimeter or area, for a given shape. Depending on this concept, two types of precast ferrocement sections, semi circular and rectangular, were designed and constructed for a deep tubewell of 60 lires/sec capacity. Ferrocement channel sections were constructed with coarse sand, fine sand, cement and brick dust mixed in the ratio of 1:1:1:1, respectively. A single layer of the wire mesh net having one ern spacing and M. S. rod of 3.17 mm diameter was also used in constructing the channel sections. After construction of the ferrocernent sections, the compressive strength was measured at 7 days interval up to 28 days of curing. Length and width of the channel determine the actual length occupied by the channel. Besides that each type of channel needs extra side bund for support of the channel. Bund widths are different for different construction materials and shape of section. Cracks, rate holes and weed growth in the channel were observed after field installation of different channels through direct observation. This was observed in terms of conveyance or seepage loss, cracks and weed growth in different types of channel sections in different years after completion of the construction work. Maintenance work to different types of channel sections can also be considered as an indicator of durability which was also recorded. Seepage loss was measured by ponding method.During data analysis, corrections were applied to the primary data regarding evaporation and rainfall. The cost of construction of the channel was calculated from the amount of different materials used for construction and the market price during the project work. Conveyance losses in three different types of channels were measured by inflow-outflow method. Fixed cross-sections of certain lengths were selected in different channels to measure discharge at the sections using standard float. Correction factor of 0.8 was applied to convert float velocity to average velocity of the stream, The flow rate was then calculated through multiplication of the average velocity (measured velocity x correction co-efficient, 0.8) by the average cross sectional area.

Source of Information: Bangladesh J. Agri. Engg. 17 (l&2): 19-30; 2006

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Installation of precast ferrocement channel sections as lining material in private sector irrigation system would obviously improve the water distribution system and increase the command area per unit of water.

Knowledge Management: Journal