Watercourse Improvement

Tertiary level irrigation system in the Punjab comprises of more than 58,500 watercourses. It has been established that a significant portion of irrigation water (about 40%) is lost in these century old community watercourses because of their poor maintenance and aging.

Causes of Water Losses

The main sources of these losses are seepage, spillage, and side leakage from the watercourses, resulting from following factors:

  • Irregular profile and zigzag alignment of banks with many points of weakness

  • Variable cross section of water channels

  • Silt deposition causing restrictions in flow and overtopping

  • Trees, shrubs, and vegetation growing in watercourses

  • Damage caused by rodents and farm animals

  • Frequent bank cutting and plugging for water abstraction


Un-Improved Watercourses

Process of Watercourse Improvement

The watercourse improvement / renovation consists of complete demolishing of community channel and its rebuilding/re-aligning according to the engineering design to increase conveyance efficiency by reducing seepage, evaporation, and operational losses. Parts of reconstructed channel are lined and necessary water control structures are installed to improve conveyance of the canal and tubewell water. The standard "Pucca" lining carried out under previous and ongoing OFWM programs is a rectangular shaped channel using double-brick masonry walls (23 cm) and a brick masonry bed (7 cm) plastered inside and on top of the walls. This design has proved to be durable and easy to install. Other types of lining e.g. pre-fabricated concrete (pre-cast parabolic lining), pipe, plastic etc. have also been considered keeping in view the farmers’ choice, field conditions, and cost effectiveness. Currently the lining with precast concrete parabolic segments (PCPS) is being practiced under all development projects.

 

Installation of Nakkas

Precast "nakkas" are installed at all authorized places to reduce channel deterioration, seepage loss, to improve water control, and considerably reduce drudgery in irrigation operation. Under normal conditions, where the land is fairly leveled and belongs to one or two farmers only, the standard practice of providing one nakka (turnout and check) for every 25 acres is quite satisfactory. Extra provision of nakkas are, however, made where the land has been subjected to fragmentation because of uneven topography repeated division of ownership, social problems etc. Moreover, culverts are constructed at major crossings as well as a limited number of checks/drop structures, animal wallows/buffalo baths, and laundry sites are provided as required. The construction of washing places and lining of reaches through villages give additional public health benefits.

Selection Criteria

Currently, the following criteria are adopted to improve watercourses:

  • Watercourse that have not been previously improved/lined beyond 50% of total length

  • The farmers are willing to form a water users association (WUA) and agree with the cost sharing arrangements

  • The shareholders agree to re‑construct katcha portion of the watercourse prior to commencement of lining work

  • Sections of watercourse to be lined:

    • Head reaches having maximum usage and flows

    • Elevated sections susceptible to leakage, over topping, and spillage

    • Portion of watercourse crossing / passing through / along villages/roads

    • Sections having sandy/porous soils

Cost Sharing Arrangements

The government provides entire cost of construction materials besides providing technical guidance while the beneficiary farmers contribute entire labour costs for improvement of unimproved watercourses as well as completion of improvement works on partially improved watercourses. Farmers contribute entire labour costs for:

  • Demolishing and reconstruction of katcha watercourse

  • Excavation for the portion to be lined

  • Back earth filling of structures and lined section

  • Masons and unskilled labour for all civil works

Impact

  • 229 Acre Feet Annual Water Saving in Regular Watercourse
  • 164 Acre Feet Annual Water Saving in Additional Watercourse
  • 55 Acre Feet Annual Water Saving in Irrigation Scheme
  • 9% Increase in Cropping Intensity
  • 31% Crop Yield Enhancement
  • Reduced Theft and Amicable Dispute Resolution
  • Improved Equity
  • Annual production gain of PKR 3 million per watercourse
  • EIRR : 42%