Pakistan is one of the water-deficient countries of the world where provision of water for drinking and agrarian purposes has alarmingly decreased in recent years. On the other hand, Pakistan has already utilized major part of its conventional water resources and this situation necessitates the need to look for other available sources of water to meet the rising water needs.
One of the cheap sources of water comes in the shape of hill torrents in hilly regions of Pakistan. Studies revealed that hill torrents encompass about 65 percent area of the total agricultural area of the country. Flood flows of hill torrents offer great prospects to meet the growing demand of water for agriculture and the same could also be utilized for drinking purposes. About 200 hill torrents, of which 13 are major, originate from Suleiman Range and flows through Dera Ghazi Khan and Rajanpur districts towards the River Indus in Punjab. The catchment area of these hill torrents is 7453 square miles which is sufficiently big to benefit a large number of people. This area is extended over a length of 360 KM (200 miles) from Ramak to Kashmore; while in width, it varies from 25 KM to 40 KM. The area between the foot hills of Suleiman Range, from Ramak to Kashmore and Chashma Right Bank Canal System and D.G. Khan Canal System is locally known as “pachad area” (Piedmont area). Flood water emanating from the hill torrents is used for irrigation purposes in the pachad area, through a network of diversion and dispersion structures. However, there is a dire need to develop a series of well-designed structures to optimally utilize this gratis gift of nature.
During the rainy seasons, these hill torrents cause flash floods of shorter duration and higher magnitude. Flood-flows move with high velocity in steep direction and often cause great destruction to life and property. The banks and bed of the channels are also eroded due to steep gradients. The flood-water brings high silt content in the plain areas and thus precludes flood management by diversion & dispersion structures. The silting and scouring phenomena are largely responsible for frequent changes in flow regime and shifting of flow paths of hill torrents.
As the floods in hill torrent areas are unpredictable and of erratic nature, therefore, these pose challenges to the flood planners for
their economic management. The farmers in pachad and sub-mountainous areas utilize low flows of hill torrents by construction of small earthen bunds, called “Gandas.” It’s also observed that high-flows breach earthen diversion bunds and move towards Chashma Right Bank Canal (CRBC), Kacchi Canal and D.G. Khan Canal System. Unprecedented intensity of rainfall in catchment area of hill torrents namely Vidore, Sori Lund, Kaha and Chachar has generated very high floods in D.G. Khan Division. Cumulative effect of hill torrents called Vidore and Sori Lund on 09-09-2012 was 230,000 Cusecs and that of Kaha & Chachar was 180,000 Cusecs on September 10, 2012. This mighty attack of torrents massively devastated the canal system in the districts of D.G. Khan and Rajanpur. The long duration of peak of hill torrent Vidore was 8 hours and the velocity was 100,000 Cusecs. Similarly, peak duration of Sori Lund was 4 hour and the velocity was recorded as 70,000 Cusecs which further aggravated the intensity of floods, resulting in colossal damages to the irrigation network structure and agricultures lands in the area.
Unfortunately, incomplete hill torrent crossings, cuts and openings in the right bank of under construction Kacchi Canal further aggravated the flood situation. Due to the ill-planning, natural routes of hill torrents have been mostly obstructed by the newly built road networks, canals and mushrooming of katchi-abadies. Similarly, the capacity of culverts/bridges of roads was found inadequate to drain-out the flood water well in time. It was also observed that non-existence of flood carrying channels in both the districts caused delay in drainage of flood water to the river. For drainage of torrents’ flood water of low to moderate intensity surface runoff is disbursed and / or utilized in the fan area of the stream torrent; however, high intensity runoff often reaches to canal command areas and become cause of large scale devastations.
Taking cognizant of the situation, Punjab irrigation & power department constituted a high-powered technical committee of agri. and water experts to suggest comprehensive measures to mitigate the effects of the torrent floods. In this context, the technical committee recommended certain actions to carry out review of previous studies, impact evaluation and continuity of Hill Torrent Development Projects to make this nature’s fury a boon for the local farmers. The need for sustained early weather forecasting system, ensured financial resources, redesigning of flood embankments (right bank of Kacchi, D.G. Khan and Dajal Canals) and improved drainage of torrential flood water was also emphasized.
Towards this end, both short term and long term plans have been identified by the irrigation & power department. The short term plans such as desilting and strengthening of banks of existing seepage drains, identification and removal of obstructions in the route of flood water after canal crossing have been implemented. The medium to long term plans include enhancing the capacity of existing seepage drains by remodeling, providing flood carrying channels from hill torrent crossing to river Indus in D.G. Khan district and providing flood carrying channels and surface water drains in Rajanpur district. Punjab I&P department started work on different developmental projects costing Rs. 5.3 billion for hill torrents’ management. Rs.1.6 billion has been approved for Kohra, Dahwa and Sanghar torrents. Similarly, Rs.717 million is provided for Kohra; while another amount of Rs. 3 billion is allocated for the management of hill torrents in Sorilund, Chahar, Vidore and Mithawan in D.G. Khan.
It’s expected that after the completion of these developmental schemes, thousands of acres of barren land will be utilized for cultivation with the available water of hill torrents; and it would be helpful in increasing productivity in hilly areas which are facing socio-economic poverty due to lack of resources and support by the government.
