ISLAMABAD, Aug 26: The Punjab government has prepared the concept design of a medium-sized concrete gravity dam and reservoir on the Dotal Kas stream near Fatehjang to provide irrigation water to the drought-vulnerable agricultural land and potable water to the residents.

A request has been sent to the Asian Development Bank (ADB) for funding of the project, says a document prepared by Punjab irrigation and power department.

The Small Dams Organisation (SDO) will implement the project.

The dam will be 20 metres at bottom of the valley with an elevation of 377 metres above sea level and about 115 metres at the top of the valley cut.

The spillways will be placed on top of the dam as an integrated structure. For flood control, a gated ogee (S-shaped) spillway with chute and an energy dissipating stilling basin has been proposed. The spillway is designed to discharge 1,330 cubic metres of water per second.

The remaining flow will be discharged through low level outlets that can also be used as sluices for flushing sediment from the reservoir.

The reservoir will be quite narrow and will be approximately 4.6 km long. It will impound an area of 1.7 square-kilometers and have a maximum gross capacity of 18.1 million cubic metres (MCM).

The dam is expected to provide 11,000 MCM water for irrigation purposes in the targeted areas of 2,024 hectares every year.

During the implementation of the project, potable water supplies for local communities around the dam will also be developed. Water demand for domestic use is a very small percentage of the requirements for irrigation and has been included in the overall irrigation water demand.

A concept design for the canal and irrigation system has also been prepared. Irrigation water needs to be lifted from the level of the dam to a distribution tank from where it is initially fed by gravity flow to an area of about 930 hectares. This will be developed as command areas for three villages - Makial, Sapial and Rattarian.

The main canal will be divided into two and the remaining irrigation water will be carried along a 13 km branch that will allow the development of another 1,094 hectares of irrigated land.

Due to the terrain, the canals will require siphons to cross some depressions and the irrigated areas will be scattered and located in several villages. A small micro-hydropower plant will be installed to provide power for pumping water up to the distribution tank.