2. Historical background of the spate irrigation system

Spate irrigation is an old system being practised in various parts of the world; the most prominent countries where the system is prevailing are Eretria, Ethiopia, Pakistan, Yemen, etc. The historical perspectives and the archeological evidences show that this system may have started 2000 years ago in the Arabian Peninsula and it covered most of the Yemen area [11]. The agriculture practices and the techniques involved in spate irrigation were spread in the Muslim world through the trade and development of the countries. In Eretria the system was introduced in its eastern part by the onset of the migrants from Yemen some centuries ago [12]. The system also prevails in other parts of African countries since 100 of years. The countries include Alegria, Ethiopia, Morocco, Sudan and Tunisia [13].

The torrential floods and spate irrigation in western Pakistan are also very old, and it goes back to 330 BC [14]. The spate irrigation was an important fragment of the early civilizations, due to the economic development.

Globally the spate irrigation is practised in different continents including South and Central Asia, Middle East, North and West Africa and Latin America. It is difficult to make an accurate estimate of the land under spate irrigation, because each year the areas under spate irrigation change.

In Eritrea the spate irrigation is carried out in Sheeb area [15]. The crops are grown without the use of fertilizers as the silt brings nutrients to the field and also increases the surface level. The investigation on quantity of silt deposited and its influence on the properties of soil revealed that in the upper stream the silt was deposited in the range of 8.3–31.6 mm year<sup>1</sup> , while in middle and downstream, it was 6.0–18.0 and 5.2–8.6 mm year<sup>1</sup> , respectively. Regarding the physical-chemical characteristics of soil, it was found that siltation brings plant nutrients, but it can be further increased by the application of manures and incorporation of plant residues after the harvest [15].

Spate irrigation is a source of living to huge number of poor people. It is estimated that approximately 13 million people are directly or indirectly linked to spate irrigation around the world. This system is practised in 20 countries in different continents of the world [16]. Spate irrigation is a very old system but the work done in this area is very little. The system has achieved some attention in the last few decades as some of the organizations have intervened into the area and carried out some interventions. In Pakistan the major issue in negligence of the area was its infrastructure; in the last few years, some of the areas have been linked to the city by the construction of roads which increased the mobility of the people. The farmers are now installing tube wells through solar system, using improved varieties of crops (wheat and gram), applying tillage operations periodically, etc. [17]. In other parts of the world, the spate farmers have carried out studies on efficiency of flood water, its diversion and distribution. It has been emphasized in the publication that distribution and diversion efficiency may be achieved by proper management practices. The effectiveness of modernized package in three major countries

as flood water that flows in the torrent beds and stream from the hilly watershed and spread in cultivable fields used for growing the crops [3]. Also some of the researchers have defined spate irrigation as "Diversion and distribution of torrential floods as source of irrigation for raising the crops [4]. Locally in Pakistan the system is called as Rodh Kohi, derived from two Persian words Rodh which means riverine and Koh which means hilly. So in this system the rainfall received in the mountains is captured as floods in the plains. The riverine helps in the flow of water and brings it into the field. The field of spate irrigation is different from the normal field as they are larger in area and are surrounded by big embankments of 4–5 ft for retaining the water. The water once captured is allowed to infiltrate in the field till it reached the field capacity. It requires almost 2 months for infiltration of water into deep layers of soil and is used by the growing crop for the entire season. Spate irrigation is a natural system having great potential for organic cropping. As the crop are grown without the use of chemical fertilizes, herbicides and pesticides, the flood brings lots of sediments which have the natural fertility. The floods with huge magnitude usually make their way to the river, while the average and small floods are stored in the fields. The coarse size particles usually settle in the riverine and canals. While the fine silt and clay make its way to the field and build a layer of sediment greater than 50 mm per year [5, 6, 7], others have reported that it depends

Irrigation - Water Productivity and Operation, Sustainability and Climate Change

on the floods and may range from 1 to 50 mm year [8]. Figure 1 shows the

The occupation of most of the dwellers in spate is crop farming and rearing of livestock; the farmers had the informal water user association which was previously known as the Patidari system, which is comprised of a Patidar, Mosair (front runner) and labourer. The main role was to labour in the watershed to divert the water by constructing stone bunds. But after the introduction of the mechanical

In spate irrigation after introduction of mechanization, the distribution of irri-

gation water and the amount of water used for agriculture have changed. The government intervention for construction of earthen bund by bulldozers provided by the Agriculture Engineering Department in Southern Khyber Pakhtunkhwa was a big assistance for the people of spate and was a step towards equal distribution, but as the agriculture engineering department was closed, the people have problems in timely construction of check dams. Now the farmers' association at village levels is involved to construct the check dam locally called as Gandi and also the other communal structures related to the spate water distribution by the tractors. But the

Schematic diagram of flood. From the mountains to the fields (courtesy Mr. Nabeel Rizwan).

schematic diagram of spate irrigation.

Figure 1.

102

methods of construction, the Patidari system was ended.

practising spate was studied for 5 years, and it has been concluded that the spate farmers should use less number of irrigations, restrict the embankment length to less than 1 m, control overstretching the area under command, obey the rules for water right distribution to allow water to the downstream and enhance the water holding capacity of soil by conservation practices as mulch, tillage, crop residue management, etc. [16].

In Pakistan a very extensive area is under spate irrigation system (Figure 2). It spreads adjacently to the western mountain ranges. It starts from the southern part of Khyber Pakhtunkhwa including the Dera Ismail Khan and Tank district. In Balochistan province it is mostly practised in Sibi, Kachhi, Loralai, Gwadar, Awaran, Pishin, Turbat, Killa Saifullah, Dera Bugti, Lasbela, Panjgur, Mastung and Khuzdar districts. In Punjab it is mainly practised in Dera Ghazi Khan and Rajanpur districts and Larkana, Malir and Dadu districts in Sindh province (Table 1). In Pakistan the hydrological system is not only found in the northern region, but the western mountain regions also have the potential of 18.68 million acre feet (MAF) of water which flows to the plains through torrential floods [18]. It is found in various other countries. In this irrigation system, the floods after the rainy monsoon season in the catchment flow down as fast moving water in channels and reach the foothill plains. This water is used for growing crops after construction of big embanked field. The torrential floods are unpredictable both in magnitude and flowing velocity, due to which it possesses greater energy and thus creates problems for the farmers. The rainfall in the plains is very low (less than 250 mm year<sup>1</sup> ), but the floods bring greater amount of water to plains. Irrigation used for agriculture purpose may be attained through rainfall and floods. As the region is resource poor and lacks modern techniques, so this result is wastage of huge quantity of water. Sometimes the situation gets even poorer as timely check dams are not constructed so the water cannot be diverted to the fields. Government and non-government organizations have intervened in the area for construction of local structure for management of floods, but still there is a huge work needed for the spate irrigation area.

Ref. [19] reported that there is an inadequate data available of the spate irrigation area of Pakistan to develop a proper strategy for water management. Hence, the baseline data is very vital for the sustainable development of the spate-irrigated region. To develop and plan for the future of the system depend on the availability of data or information and also proper assessment of the water resources. The changing climatic pattern has made the assessment of the available water resources

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

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

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

more important.

Province Number of

Khyber Pakhtunkhwa

Table 1.

torrents

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

Province wise area under spate irrigation in Pakistan.

Potential area (million hectare)

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

Federal — 0.271 — —

Punjab 17 0.571 2.24 0.319 Balochistan 17 4.680 5.81 0.841 Sindh — 0.551 6.99 1.000 Pakistan 59 6.935 19.97 2.868 Sources: Agriculture Census of Pakistan, Census Organization of Pakistan, 2003; NESPAK, 1998.

Population dependent (million)

25 0.862 4.91 0.708

Approximate households (million)

standing field crops.

105

3. Problem and solution of spate irrigation

their potential solution have been illustrated in Table 2.

Figure 2. Map of spate-irrigated area of Pakistan.

Province Number of torrents Potential area (million hectare) Population dependent (million) Approximate households (million) Federal — 0.271 — — Khyber Pakhtunkhwa 25 0.862 4.91 0.708 Punjab 17 0.571 2.24 0.319 Balochistan 17 4.680 5.81 0.841 Sindh — 0.551 6.99 1.000 Pakistan 59 6.935 19.97 2.868

Spate Irrigation: Impact of Climate Change with Specific Reference to Pakistan DOI: http://dx.doi.org/10.5772/intechopen.85889

Sources: Agriculture Census of Pakistan, Census Organization of Pakistan, 2003; NESPAK, 1998.

#### Table 1.

practising spate was studied for 5 years, and it has been concluded that the spate farmers should use less number of irrigations, restrict the embankment length to less than 1 m, control overstretching the area under command, obey the rules for water right distribution to allow water to the downstream and enhance the water holding capacity of soil by conservation practices as mulch, tillage, crop residue

Irrigation - Water Productivity and Operation, Sustainability and Climate Change

In Pakistan a very extensive area is under spate irrigation system (Figure 2). It spreads adjacently to the western mountain ranges. It starts from the southern part of Khyber Pakhtunkhwa including the Dera Ismail Khan and Tank district. In Balochistan province it is mostly practised in Sibi, Kachhi, Loralai, Gwadar, Awaran, Pishin, Turbat, Killa Saifullah, Dera Bugti, Lasbela, Panjgur, Mastung and Khuzdar districts. In Punjab it is mainly practised in Dera Ghazi Khan and Rajanpur districts and Larkana, Malir and Dadu districts in Sindh province (Table 1). In Pakistan the hydrological system is not only found in the northern region, but the western mountain regions also have the potential of 18.68 million acre feet (MAF) of water which flows to the plains through torrential floods [18]. It is found in various other countries. In this irrigation system, the floods after the rainy

monsoon season in the catchment flow down as fast moving water in channels and reach the foothill plains. This water is used for growing crops after construction of big embanked field. The torrential floods are unpredictable both in magnitude and flowing velocity, due to which it possesses greater energy and thus creates problems for the farmers. The rainfall in the plains is very low (less than

used for agriculture purpose may be attained through rainfall and floods. As the region is resource poor and lacks modern techniques, so this result is wastage of huge quantity of water. Sometimes the situation gets even poorer as timely check dams are not constructed so the water cannot be diverted to the fields. Government and non-government organizations have intervened in the area for construction of local structure for management of floods, but still there is a huge work needed for

), but the floods bring greater amount of water to plains. Irrigation

management, etc. [16].

250 mm year<sup>1</sup>

Figure 2.

104

Map of spate-irrigated area of Pakistan.

the spate irrigation area.

Province wise area under spate irrigation in Pakistan.

Ref. [19] reported that there is an inadequate data available of the spate irrigation area of Pakistan to develop a proper strategy for water management. Hence, the baseline data is very vital for the sustainable development of the spate-irrigated region. To develop and plan for the future of the system depend on the availability of data or information and also proper assessment of the water resources. The changing climatic pattern has made the assessment of the available water resources more important.
