3. Problem and solution of spate irrigation

The area under spate irrigation has many problems and faces the two extreme conditions, i.e. drought and floods. In Pakistan the vast area under spate irrigation is Dera Ismail Khan (D. I. Khan) and Dera Ghazi Khan (D. G. Khan) districts, the southern-most district of Khyber Pakhtunkhwa and Punjab provinces, respectively. It is adjacent to the Sulaiman ranges, the western mountain range. There are five watersheds in the Sulaiman ranges adjacent to the D. I. Khan district, which are locally called as Zam. These zams are Tank, Gomal, Sheikh Haider and Chodhwan. In districts of DI Khan and Tank, there are 27% of the total land mass (0.687 mha) under spate irrigation system only in Khyber Pakhtunkhwa, while the rest is under canal irrigation, tube well and rainfed. There is a vast network of the small and large canal known as Rodhs in these two districts (Figure 3). There are a number of problems faced by the spate farmers in this area [20]. Some of the problems and their potential solution have been illustrated in Table 2.

Different researchers have reported various problems of spate irrigation; flash floods brought by the torrents are of high peak but very short duration [21]. The velocity of the flood water is high due to steep gradient and greater masses, and it results in damaging the infrastructure, irrigation channel and also the standing crop [22]. The basic constraint of the torrents' flow is the conservation or management of the flood being received [23]. In D. G. Khan district of Punjab, the spate irrigation system is satisfactorily functioning for longer time, but due to continuous siltation brought by the floods, the riverine or channel has become uneven and has affected the distribution of water and has created serious management problems [24]. The capacity of the water channel has reduced due to siltation in the channels, and this has created overspill of flood water and has caused damage to the embankments and standing field crops.

Ref. [25] stated that spate irrigation using the flood water for irrigation is the cheapest technique as compared with the other methods. They have investigated

cost of production, greater capital for irrigation, own labour (family) and least rainfall may take the option of spate irrigation. Also they reported that crop choice is not affected by the market. Most of the spate farmers grow cereals and pulses as their own food security. The probability of the modern techniques in the spate irrigation may increase by spending less money on cost of production, availability of

Spate Irrigation: Impact of Climate Change with Specific Reference to Pakistan

This anomalous behaviour of water opens new windows for searching water resources. We receive water either from rainfall or from floods. Both resources are the outcomes of recycling. When climate temperatures slightly rise, it causes glaciers to melt which changes the ice into water. But this change in climate is controlled and bearable. In summer when temperatures are expected to become the highest, it then dismays the environment and brings floods. On having such situations, it becomes necessary to channelize this flood into irrigation water that can be termed as water harvest. In spate areas the inhabitant or farmers receive these floods as blessing of God, and in urban area it is not more than a menace.

In spate-irrigated areas, poverty commands and people are very hard to live. They are dependent of agriculture profession as main and sole profession. Soil is hard and barren, and water table is very low and neither so link nor black top road to link between farms to market. Although the area is responsive to many crops like wheat, gram, millet, Sorghum, guar, melon, Brassica and onion, they prefer to grow wheat and gram as second choice. An irony is that farmer cannot decide, only flood decides which crop should be sown and when to sow that crop. In Pakistan, after 2010 floods, the climate sway has been observed by the scientific community. This flood was prominent for its severity; 2010 floods are notable for their severity [26]. Projections related to the impacts of climate change warn that developing countries will be the greatest victims of climate change. The Global Climate Risk Index has rated Pakistan as the seventh most vulnerable country to be affected by climate change [27]. Imbalance environment (climate change) and over- and underwatering have depicted the significant changes amongst the common strata/people.

Unusual floods in terms of time and magnitude have greatly influenced the prevailing climate and also disturbed the seasonal monsoon route. Such alteration has also made upset the rainfall schedule due to which crops are being grown either early or delayed to their actual time. Thus it can be said that farmers'sowing trend has been shifted due to changed rainfall docket. An interesting thing which has been observed in locality amongst the farmer is adoption of the people according to changed climate as well as water mood/temper. That is why they apply indigenous knowledge which they have perceived from remote ancestors for the purpose of biological control, moisture conservation from the flood water, fencing the flood, diverting flood route, converting flood water into irrigation water and handling noxious weeds and baneful pests. This native cognition also covers the cultivation method, crop choice, quality seed grading, seed storage, livestock health and crop

care and their safety from diseases, pest identification and eradication.

The farmers in spate are growing different crops as source of fodder, fibre and food for earning their livelihood. The farmers in the spate-irrigated area are subsistent and wait throughout the year for harvesting water and growing crops. During the dry season, they have to migrate to the canal-irrigated area to earn their living.

4.1 Crops

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water resources, variation and climatic factor.

DOI: http://dx.doi.org/10.5772/intechopen.85889

4. Water-agriculture balance in spate irrigation

#### Figure 3.

The extensive system of spate irrigation of Dera Ismail Khan.

