Irrigation and Drainage

  • Areas of Expertise
  • Project - Pehur High Level Canal
  • Project - Merowe Irrigation Project (Sudan)
  • Project - Irrigation Rehabilitation (Pakistan)
  • Project - Precast Parabolic Canal
  • Project - The Yeleru Left Bank Canal
  • Project - Irrigation Rehabilitation (Albania)
  • Example Structure - Cross Regulator
  • Installation - Semi-Closed Pipeline Network
  • Land Drainage in Argyll
  • Project - Irrigation Rehabilitation (Armenia)
  • Irrigation Engineering Portfolio
  • Areas of Expertise


    Pehur High Level Canal

    The Pehur High Level Canal, North-West Frontier Province, Pakistan. This is thought to be the world’s largest true parabolic canal, designed by Adrian Laycock.

    The parabolic profile of concrete lining is superior to the normally-used trapezoidal section and imparts great strength and resistance to cracking from slumping, settlement or soil movement. It is also easy to construct using a rotating striker tube.

    This canal is 26 km long with a capacity of 30 m3/sec. It is designed for downstream control with self-regulating gates,- the first canal in Pakistan to be automated in this way.

    Adrian Laycock was Chief Design Engineer for Lahmeyer International on this project.


    Above: The main earthworks are done by machine.

    Above: The screed bars are cast at 6 metre
    intervals using a special formwork to accurately level and form the parabolic profile.

    Above: Final trimming is done between screed bars, and a layer of blinding concrete fills in any overbreak.

    Above and Left: Concrete is poured and placed using a Bunyan striker tube.

    This is a steel tube which rotates against its direction of travel, compacting and spreading the concrete as it goes. It is commonly used for laying flat slabs, but was originally conceived for laying trapezoidal canal lining in California.

    The parabolic shape is especially suited to this form of construction.

    Why parabolic?

    Most canals are built to a trapezoidal profile. Parabolics offer several advantages:

    Strength. The shell shape offers great structural strength with no points of weakness such as occur in a trapezoidal profile.

    Ease of construction. No problems of slumping or tension cracking during concrete placement that occur near the base of a trapezoidal slope. The actual gradient of the lower profile is much flatter than for a trapezoidal.

    Cost. Volume of concrete and excavation can be reduced over an equivalent trapezoidal profile.

    Speed. This method of construction is fast. Slipforming can also be used, although the machinery is expensive.

    Beauty. It is a rare thing for engineers to combine functionality with beauty, but here it is.

    Installation of downstream control gates

    The self-regulating float-controlled gates are designed to automatically regulate the downstream water level to a predetermined level. With downstream control, flexibility of supply on the main canal system is guaranteed. Response time of the 100 mile-long canal system is cut from days to hours, and wastage of water and power generation at Tarbela Dam can be reduced.

    Above: Orifice type gate at the outlet of Kundal Siphon. The siphon will carry 30 cubic metres/second over a length of 1.8 km, controlled by two of these float-operated gates.

    Above: Kundal Siphon outlet structure.

    Above: A cross regulator on Maira branch Canal under construction.

    Above: Installing the self-regulating gates.

    Above: Interior of the completed regulator structure.

    Above: Upstream view of the completed cross regulator.

    Above: Howell Bunger valves discharging water from Tarbela Dam into the head of the Pehur High Level Canal, January 2003

    Above: The Pehur High Level Canal during commissioning trials, March 2003

    Commissioning the Pehur High Level Canal, October 2003

    Above: Adjusting downstream control gates on the Pehur Canal.

    Above: Adjusting downstream control gates on the Pehur Canal

    Above: Gandaf Tunnel Outlet into the head of Pehur high level canal. Howell-Bunger valves.

    Above: Free discharge valves in operation

    Above: Free discharge valves in operation.

    Above: A flow division structure on a minor canal.

    Above: A labyrinth escape weir on the main canal.

    Merowe Irrigation Project, Sudan

    This massive project is now undergoing detailed design. A dam on the Nile is already under construction at the 4th cataract. The irrigable area will extend for 400 kilometres downstream. Adrian Laycock is irrigation design consultant to Lahmeyer International. The irrigation system will include pumping and parabolic gravity canals, and automatic pipeline distribution systems. The terrain is extremely hostile and requires some careful engineering. Existing projects in the area have been affected by salinity, moving sand dunes, waterlogging and dispersive silts which have severe constraints on canal design and operation.



    Irrigation Rehabilitation (Pakistan)

    A proportional division structure on the Swabi SCARP irrigation rehabilitation project, Pakistan. A design introduced by Adrian Laycock as a means of passive automation for this century-old project of 100,000 hectares.

    Precast Parabolic Canal

    Small precast parabolic canal. Adrian Laycock has introduced these in Indonesia, India and Pakistan, where they have proved a runaway success in rehabilitation of watercourses. They are made of high strength unreinforced concrete and can be fabricated under controlled conditions in small casting yards, providing basic principles of quality control are followed. They have the triple advantages of being cheap, long-lasting and hydraulically efficient.

    The Yeleru Left Bank Canal

    The Yeleru Left Bank Canal carries water 150 km to the new industrial town of Vishakapatnam in Andra Pradesh, India. The canal leaks badly and is severely affected by instability of its side slopes which are in deep cut for much of its length. Adrian Laycock is consultant to Lahmeyer International in formulating engineering rehabilitation works, including bentonite grouting of canal banks, slope stabilisation, canal lining and desilting.


    Irrigation Rehabilitation (Albania)

    Albania - rehabilitation of irrigation schemes.

    Top right - A pump station near Vlore.

    Below left - Saline land near Vlore.

    Below right - Rehabilitation of irrigation schemes amidst the Fier oilfield.

    Radial-Gated Cross Regulator

    Radial-gated cross regulator on the Machai Branch Canal, Pakistan, designed by Adrian Laycock. Elliptical transitions are used to good effect.

    Semi-closed Pipeline Network

    Installing a low-pressure semi-closed pipeline network, Pakistan. The design principles of this demand-scheduled irrigation system are quite different from those normally used. The tail-end problem is eliminated, and farmers are able to take water at any time to suit themselves or their crop, without being restricted to a tightly-regimented supply schedule.

    This is a new concept for Pakistan and represents a major shift from traditional irrigation principles. The design procedures were developed by Adrian Laycock, based on the philosophies of Professor John L Merriam. Pressure control is achieved through float-operated Harris Valves.

    Land Drainage in Argyll

    This work became necessary after the installation of a sewer pipeline caused damage to an existing underground field drainage system. A field is being re-drained using gravel and geotextile filters.


    Irrigation Rehabilitation (Armenia)

    Adrian Laycock was technical auditor for a USA-financed rehabilitation project.


    Irrigation Engineering Portfolio

    Adrian Laycock Ltd was established in 1982 and has been active in irrigation development in the following countries :

    ALBANIAFeasibility studies for rehabilitation of irrigation schemes up to 9,000 hectares.
    ARMENIARehabilitation of Irrigation schemes, large weirs and pump stations.
    AFGHANISTANDesign of river training and erosion control works
    BRUNEIDesign of urban drainage and river control
    BURMAFeasibility studies for small-scale irrigation
    ETHIOPIADesign and field investigations for a sugar estate
    GREECEEnvironmental rehabilitation of Lake Koronia
    INDIARehabilitation of Yeleru Left Bank Canal, Andra Pradesh
    INDIARehabilitation of small irrigation projects, Karnataka
    INDONESIADesign and implementation of sugar estates
    INDONESIARehabilitation of conjunctive use irrigation schemes
    KAZAKSTANAppraisal mission for Aral sea environmental rehabilitation
    KIRGISTANAppraisal mission for Aral sea environmental rehabilitation
    NIGERIADesign of irrigation projects and earth dams
    PAKISTANDesign of Pehur High Level Canal
    PAKISTANRehabilitation of Swabi SCARP Irrigation Project
    SRI LANKAWater Management studies, Victoria Project, Mahaweli System
    SUDANEstablishment of training programme for irrigation staff on the Gezira Project
    SUDANFeasibility and detailed design for Merowe Irrigation Project
    SYRIAFeasibility study for El Ghab Project
    TANZANIAFeasibility Study, Stieglers Gorge Project
    UZBEKISTANAppraisal mission for Aral Sea environmental rehabilitation
    ZAMBIARehabilitation of coffee estates

    The company was set up to work on the interface between civil engineering and other disciplines such as agriculture, ecology, the environment, sociology, management, economics, soil conservation, which come together in most irrigation projects and often give rise to conflicting solutions for development.

    Operating from its base in Scotland, Adrian Laycock Ltd is a small scale organisation which maintains close working links with independent specialist consultants in related fields. Much of its work is in providing specialist expertise to larger international consultants.

    © Adrian Laycock Ltd 2000. Fair use and distribution of this material is encouraged provided proper citation is given.