1. Introduction

Spate irrigation is an old system of agriculture practised in the foothill plains. The system has exclusivity as the area faces the two extremes: the drought in the dry season and huge floods in the wet seasons. There are a number of countries in the world where the spate irrigation is practised; the more obvious are Eretria, Ethiopia, Iran, Pakistan and Yemen [1]. The more extensive spate irrigation system is practised in Pakistan. In Pakistan the system extends near the Sulaiman ranges in the western part of the country.

Floods considered as catastrophe are a colossal opportunity for the spate irrigation farmers. The farmers of the area wait till the monsoon and spring floods. The livelihood of the farming community depends on these floods as a source of irrigation and also drinking water. The floods once received bring fortune to the farmers. Spate irrigation in different parts of the world is defined by different people, as discharged flood from mountainous watershed that flows through different channels in agriculture fields [2], whereas others termed spate irrigation

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 on the floods and may range from 1 to 50 mm year [8]. Figure 1 shows the schematic diagram of spate irrigation.

problems related to tractors' build structures are that they are not as strong as those constructed by bulldozers and worn away by the great magnitude of floods. Also the mechanized agriculture is useful in leveling the land and pulverizing the soils. As each year the floods bring enormous amount of silt, and the farmers capturing huge floods also add massive amount of silt which imbalances the field. Tillage has great influence on the chemical, physical and biological characteristics of soil, and it subsequently results in better plant growth and yield [9]. Also for sustainable

Spate irrigation is an old system being practised in various parts of the world; the

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

Globally the spate irrigation is practised in different continents including South

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

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

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

, while in middle and downstream, it

, respectively. Regarding the physical-chemical

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

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 early civilizations, due to the economic development.

each year the areas under spate irrigation change.

deposited in the range of 8.3–31.6 mm year<sup>1</sup>

was 6.0–18.0 and 5.2–8.6 mm year<sup>1</sup>

after the harvest [15].

103

produce from a soil, it is important to use the tillage optimally [10].

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

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

2. Historical background of the spate irrigation system

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 methods of construction, the Patidari system was ended.

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

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

problems related to tractors' build structures are that they are not as strong as those constructed by bulldozers and worn away by the great magnitude of floods. Also the mechanized agriculture is useful in leveling the land and pulverizing the soils. As each year the floods bring enormous amount of silt, and the farmers capturing huge floods also add massive amount of silt which imbalances the field. Tillage has great influence on the chemical, physical and biological characteristics of soil, and it subsequently results in better plant growth and yield [9]. Also for sustainable produce from a soil, it is important to use the tillage optimally [10].
