On an average 9% of the irrigated area of Pakistan is under the system of hill torrents. Though there is a potential of increasing the area under spate irrigation up to 34%.
Floods are often considered as havoc. However, the other side of coin has seldom been accounted for in a positive context. Rain water from dry mountains can be a potential source for irrigating low lying fields, and getting a reasonable crop production.
Floods in plains through rise in level of river flow and floods originating from mountainous areas (Hill torrents / Rod Kohi) differ from each other. The floods from rivers builds gradually, has a long lasting impact and recedes even more slowly.
On the other hand, hill torrents from mountains are transient (usually up to 10 hours) and appear shortly after rains. Speed of water flow is very high as compared to floods of rivers in plains.
What is spate irrigation?
The irrigation technique that diverts flood water from dry mountainous area by gravity through regulatory structures for crop cultivation in low lying farmland is referred to as spate irrigation. This irrigation system is a distinct feature of arid and semi-arid regions bordered by highlands.
There are two systems of management in hill torrent areas:
- Upland rod kohi areas. Here check dams are built to create obstacles in the movement of speedy water. It aids in reducing losses to soil erosion. Contouring, terracing is practiced and mini dams are also constructed. Medium reservoirs can also be built where feasible.
- Lowland rod kohi areas: In such areas regulatory structures, diversion bunds, headworks, field inlets and field outlets can be constructed. For smooth flow of water and to avoid erosion, water can be conveyed through an array of channels like stone masonry lined channels, closed channels, parabolic lined channels, plastic sheet lined channels and open channels etc. A well planned channelization of the water from river bed at the take-off point will make the most use of the area with better coverage and spread of water with effective groundwater recharge.
On an average, currently 9% of the irrigated area of Pakistan is under the system of hill torrents. Though there is a potential of increasing the area under spate irrigation up to 34%. About 1.4 to 2.34 million hectare area is under spate irrigated agriculture. Nevertheless, the potential area is approximately 7 million hectares.
Following three aspects must be inculcated to harvest the benefits from hill torrents
- Building regulatory structures
- Canal maintenance and repair system
- Management of commanded area of the hill torrents
Essential aspects to harness hill torrents
Building dams, mini dams, headworks, regulatory structures etc. is the major responsibility of engineering authorities whereas command area management is a diverse subject involving multiple stakeholders. The bund repair and maintenance in such areas is of utmost importance.
In some areas, there is penalty on farmers who do not take care of repairing and maintaining bunds on annual and sometime on seasonal basis. Moisture conservation can be enhanced by ploughing, surface mulching, strip cropping, and growing cover crops like legumes etc.
Pakistan has the largest area in the world under spate irrigation with maximum area being in Balochistan. In Punjab, this sort of irrigation is practiced in districts of Dera Ghazi Khan and Rajanpur and parts of Mianwali. There are 13 major hill torrents besides many minor torrents locally called “chur”.
In Khyber Pakhtunkhwa spate irrigation is practiced in Dera Ismail Khan and parts of Lakki Marwat and Kohat. In Sindh, it is mostly practiced in the northwestern Kirthar range along Dadu, Jamshoro and reaching up to part of Karachi district. There are 25 hill torrent systems in Sindh. Balochistan has 44% area of the country by geography.
However, only 13% area of Balochistan is irrigated. There are 19 major spate irrigation systems in Balochistan.
Government through irrigation department has established hand pumps for drinking water in some villages but still in many areas the human and animals drink water from the ponds or from water collected in depressions made by soil transportation and erosion.
Water rights are not followed in their true essence in most of the spate irrigated areas. If in dry years, a small volume of water is received through rainfall, the farmers at upstream have the rights to use it. But as a malpractice, influential people and those at upstream divert the water flow during wet years to their lands which results in non-availability or very limited water availability to farmers at tail of the command area.
Traditionally, at field level, tactical breaching of field bunds is done for field to field irrigation. However, it damages the bunds sometimes besides several other adverse ecological and social impacts.
On field management include selection of suitable crop and cultivars which require less water till maturity and can withstand dry spells and hot weather in summer. Sorghum and millets can be successfully grown and seeds of these crops are threshed at harvest for future use while their stalks can be dried for hay to feed livestock.
Mulching, tillage, strip cropping, using leguminous crops in the cropping system improves soil conditions and soil moisture holding capacity. Millet, cluster bean and mungbean is used in different areas in summer. In winter season chickpea, rapeseeds, mustards and wheat are mostly grown in different areas.
Dug well irrigation is also in practice in some areas like Mithawan hill torrent command area. As the farmers do not use external inputs in subsistence farming; therefore, the returns from the field crops are also marginal.
- There is a need to build a database of spate irrigation in the country. Currently, there is very little academic research regarding key aspects of spate irrigation. Wherever feasible, spate irrigation should be augmented with judicious groundwater use.
- Improvement in indigenous vegetables, trees and fodder should be included in research program for improving the intended benefits. In most of the areas as the produce from the fields are obtained without using any chemical, there is a huge potential for developing commodity specific organic markets.
- Thal and Cholsitan Development Authorities, rod kohi development authorities on at least province level should be initially established having experts from disciplines of agriculture, livestock, health, forestry and education etc. There should be concrete efforts for promoting the focus on fodder, pulses, oilseeds and wheat etc. using available water supply.
- Research should be focused on breeding crop cultivars that can extract water from deeper soil depths.
Creating awareness and coordination among all the society groups is need of the time. On farm water management through active involvement of irrigation, engineering, conservation, agriculture and extension departments etc. can bring a significant change.
- Research should also be focused on developing drought tolerant fruit plants like Beri and Dates. There is potential of planting more forest trees in spate irrigated areas. This will also reduce the soil erosion and avoid negative consequences of climate change besides other benefits.
- Low cost drinking water technologies for humans and livestock consumption should be taken into account on priority basis. As the area is drought prone with water scarcity, hence growing crops through high efficiency irrigation systems like drip irrigation can bring fruitful results where applicable.
- Engineering and agricultural faculties of universities should incorporate spate irrigation curriculum for capacity building and preparing scientific brains in future perspective. It is of utmost importance to include spate irrigated area into national development plan.
An integrated approach unveiling all these aspects will definitely promise uplift in the socio-economic lives of poorest of the poor farmers in country.
This article is jointly written by Dr. Khuram Mubeen and Dr. Amar Matloob from Department of Agronomy, Muhammad Nawaz Shareef University of Agriculture, Multan. Corresponding author can be reached at firstname.lastname@example.org