Irrigation Engineering CE-404 (3+0) - WEC CIVILIANS

Irrigation Engineering CE-404 (3+0) - WEC CIVILIANS

Irrigation Engineering CE-404 (3+0) Course Instructor Engr. Afzal Ahmed MSc Water Resource & Irrigation Engineering UET Taxila BSc Civil Engineering UET Taxila Course Contents Water Resources:

Planning and development of water resources projects. Domestic, Industrial, Agricultural and other water usages, Water resources in Pakistan. Irrigation: Definition and types of irrigation. Merits and demerits of irrigation, Indus Basin Irrigation System (IBIS). Canal Irrigation: Elementary concept about canal head works, selection of their site and layout, weirs and barrages, various components and functions. Measures adopted to control silt entry into canals, silt ejectors and excluders. Design of weirs on permeable foundations, sheet piles and cut off walls. Design of irrigation channels, Kennedys and

Laceys Theories. Rational methods for design of irrigation channels. Comparison of various methods. Computer Aided design of irrigation channels. Barrages and Headworks: Canal head regulators, falls, flumes, canal outlets. Cross drainage works: types and functions. Canal lining: advantages and types. Maintenance of irrigation canals.Monitoring of flows-telemetry system. Irrigated Agriculture: Soil-water-plant relationship. Water requirements of

crops, duty of irrigation water. Delta of crops, consumptive use, estimation of consumptive use, methods used for assessment of irrigation water. Irrigation methods and practices. Irrigation scheduling. Management of irrigation systems, participatory irrigation management. Water logging and salinity:

Causes and effects of water logging, reclamation of water logged soils. Drains and tube wells. Causes and effects of salinity and alkalinity of lands in Pakistan. Reclamation methods. Drainage network in irrigated areas. Drainage: Definition, Land reclamation, Surface Drainage, Subsurface Drainage, Estimation of discharge capacity of Cross-drainage structures, Disposal of drainage effluents.

Text Book Linslay, R.K. and Joseph, B.F. Water Resources Engineering, McGraw Hill. Reference Books 1. Linslay, R.K. and Joseph, B.F. Water Resources Engineering, McGraw Hill. 2. Siddiqui, Iqtidar H., Irrigation and Drainage Engineering, Oxford University Press 3. Iqbal Ahmed, Irrigation Engineering and

Hydraulic Structures Chapter No 01 Water Resources Introduction Utilisation of available water of a region for use of a community has perhaps been practiced from the dawn of civilization. In fact, the Harappa and Mohenjodaro excavations have also shown scientific developments of water utilization and

disposal systems. They even developed an efficient system of irrigation using several large canals. It has also been discovered that the Harappan civilization made good use of groundwater by digging a large number of wells. Of other places around the world, the earliest dams to retain water in large quantities were constructed in Jawa (Jordan) at about 3000 BC and in Wadi Garawi (Egypt) at about 2660 BC. The Roman engineers had built log water conveyance systems,

many of which can still be seen today, Qanats or underground canals that tap an alluvial fan on mountain slopes and carry it over large distances, were one of the most ingenious of ancient hydrotechnical inventions, which originated in Armenia around 1000BC and were found in India since 300 BC. Log water conveyance system Although many such developments had taken

place in the field of water resources in earlier days they were mostly for satisfying drinking water and irrigation requirements. Modern day projects require a scientific planning strategy due to: 1. Gradual decrease of per capita available water on this planet and especially in our country. 2. Water being used for many purposes and the demands vary in time and space. Water availability in a region like county or state or watershed is not equally distributed.

The supply of water may be from rain, surface water bodies and ground water. Water resources project planning The goals of water resources project planning may be by the use of constructed facilities, or structural measures, or by management and legal techniques that do not require constructed facilities. The latter are called non-structural measures and may include rules to limit or control water and land use which complement or substitute for constructed facilities.

A project may consist of one or more structural or non-structural resources. Water resources planning techniques are used to determine what measures should be employed to meet water needs and to take advantage of opportunities for water resources development, and also to preserve and enhance natural water resources and related land resources. The scientific and technological development has been evident during the twentieth century in major

fields of engineering. But since water resources have been practiced for many centuries, the development in this field may not have been as spectacular as, say, for computer sciences. However, with the rapid development of substantial computational power resulting reduced computation cost, the planning strategies have seen new directions in the last century which utilises the best of the computer resources. Further, economic

considerations used to be the guiding constraint for planning a water resources project. But during the last couple of decades of the twentieth century there has been a growing awareness for environmental sustainability. And now, environmental constrains find a significant place in the water resources project (or for that matter any developmental project) planning besides the usual economic and social constraints.

Priorities for water resources planning Water resource projects are constructed to develop or manage the available water resources for different purposes. The water allocation priorities for planning and operation of water resource systems should broadly be as follows: 1. Domestic consumption includes water requirements primarily for drinking, cooking, bathing, washing of clothes and utensils and

flushing of toilets. 2. Irrigation Water required for growing crops in a systematic and scientific manner in areas even with deficit rainfall. 3. Hydropower This is the generation of electricity by harnessing the power of flowing water. 4. Ecology / environment restoration Water required for maintaining the environmental health of a region. 5. Industries

The industries require water for various purposes and that by thermal power stations is quite high. 6. Navigation Navigation possibility in rivers may be enhanced by increasing the flow, thereby increasing the depth of water required to allow larger vessels to pass. Basin wise water resource project development The total land area that contributes water to a river is called a Watershed, also called differently as the

Catchment, River basin, Drainage Basin, or simply a Basin. The image of a basin is shown in Figure 1. Fig. 1 Watershed A watershed may also be defined as a geographic area that drains to a common point, which makes it an attractive planning unit for technical efforts to conserve soil and maximize the utilization of surface and subsurface water for crop production. Thus, it is generally considered that water resources development and management schemes

should be planned for a hydrological unit such as a Drainage Basin as a whole or for a Sub-Basin, multisectorially, taking into account surface and ground water for sustainable use incorporating quantity and quality aspects as well as environmental considerations. Let us look into the concept of watershed or basin- wise project development in some detail. The objective is to meet the demands of water within the Basin with the available water therein, which could be surface water, in the form of rivers, lakes, etc. or as groundwater.

Tools for water resources planning and management The policy makers responsible for making comprehensive decisions of water resources planning for particular units of land, preferably a basin, are faced with various parameters, some of which are discussed in the following sections. 1. Supply of water: a.

Water available in the unit i. Rain falling within the region. This may be utilized directly before it reaches the ground, for example, the roof top rain water harvesting schemes in water scarce areas. ii. Surface water bodies. These static (lakes and ponds) and flowing (streams and rivers), water bodies may be utilized for satisfying the demand of the unit, for example by constructing dams across rivers. iii. Ground water reservoirs. The water stored in soil and pores of

fractured bed rock may be extracted to meet the demand, for example wells or tube wells. b. Water transferred in and out of the unit If the planning is for a watershed or basin, then generally the water available within the basin is to be used unless there is inter basin water transfer. If however, the unit is a political entity, like a nation or a state, then definitely there shall be inflow or outflow of water especially that of flowing surface water. Riparian rights have to be honored and extraction of more water by the upland unit may result in severe tension. c. Regeneration of water within the unit Brackish water may be converted with appropriate technology to

supply sweet water for drinking and has been tried in many extreme water scarce areas. Waste water of households may be recycled, again with appropriate technology, to supply water suitable for purposes like irrigation. 2. Demand of water: a. Domestic water requirement for urban population This is usually done through an organized municipal water distribution network. This water is generally required for drinking, cooking, bathing and sanitary purposes etc, for the urban areas.

b. Domestic and livestock water requirement for rural population This may be done through individual effort of the users by tapping a local available source or through co-operative efforts c. Irrigation water requirement of cropped fields Irrigation may be done through individual effort of the farmers or through group cooperation between farmers, like Farmers Cooperatives. The demands have to be estimated based on the cropping pattern, which may vary over the land unit due to various factors like; farmers choice, soil type, climate, etc. Actually, the

term Irrigation Water Demand denotes the total quantity and the way in which a crop requires water, from the time it is sown to the time it is harvested. c. Industrial water needs This depends on the type of industry, its magnitude and the quantity of water required per unit of production. Structural tools for water resource development This section discusses the common structural options available to the Water Resources Engineer to develop the

water potential of the region to its best possible extent. Dams These are detention structures for storing water of streams and rivers. The water stored in the reservoir created behind the dam may be used gradually, depending on demand. Barrages These are diversion structures which help to divert a portion of the stream and river for meeting demands for irrigation or hydropower. They also help to increase the level of the water slightly which may be advantageous from the point of view of increasing navigability or to provide a pond from where water may be drawn to meet domestic or industrial water demand.

Canals/Tunnels These are conveyance structures for transporting water over long distances for irrigation or hydropower. These structural options are used to utilise surface water to its maximum possible extent. Other structures for utilising ground water include rainwater detentions tanks, wells and tube wells. Another option that is important for any water resource project is Watershed Management practices. Through these measures, the water falling within the catchment area is not allowed to move quickly to drain into the rivers and streams. This helps the rain water to saturate the soil

and increase the ground water reserve. Moreover, these measures reduce the amount of erosion taking place on the hill slopes and thus helps in increasing the effective lives of reservoirs which otherwise would have been silted up quickly due to the deposition of the eroded materials. Management tools for water resource planning The following management strategies are important for water resources planning: Water related allocation/re-allocation agreements between planning units sharing common water resource. Subsidies on water use

Planning of releases from reservoirs over time Planning of withdrawal of ground water with time. Planning of cropping patterns of agricultural fields to optimize the water availability from rain and irrigation (using surface and/or ground water sources) as a function of time Creating public awareness to reduce wastage of water, especially filtered drinking water and to inculcate the habit of recycling waste water for purposes like gardening. Tasks for planning a water resources project The important tasks for preparing a planning report of a water

resources project would include the following: Analysis of basic data like maps, remote sensing images, geological data, hydrologic data, and requirement of water use data, etc. Selection of alternative sites based on economic aspects

generally, but keeping in mind environmental degradation aspects. Studies for dam, reservoir, diversion structure, conveyance structure, etc. Studies for local protective works levees, riverbank revetment, etc. Formulation of optimal combination of structural and non-structural components (for projects with flood control component). Economic and financial analyses, taking into account environmental degradation, if any, as a cost.

Environmental and sociological impact assessment. Punjab The public irrigation infrastructure in the Punjab consists of 13 barrages 2 siphons across major rivers 12 link canals and 23 major canal systems over an aggregate length of 34,500 km. The whole irrigation infrastructure lies within the Indus Basin System. It serves an area of 8.58 million hectares. In addition, there are 135 surface drainage systems including over 670 drains, with an aggregate length of

about 6,600 km, which drain an area of about 5.79 million hectares, within the 23 canal commands. Sindh 14 publicly owned irrigation systems, which receive water from three barrages across the River Indus. These systems, with an aggregate length of 18,000 km of canals, serve an area of about 5.38 million hectares. There are 13 existing surface drainage systems in Sindh, which serve a total area of over 3.5 million hectares and have an aggregate length of about 4,800

km. KPK 5 publicly owned irrigation systems in the Indus Basin, which serve a total area of 0.34 million hectares. These systems receive water from two headworks across River Swat and Warsak Dam. In addition, there are six other canal systems, which serve a total of 0.13 million hectares of land. Also has over 200 canals called `civil canals`, which are

community or privately owned. These irrigate an aggregate area of 0.83 million hectares. There are four surface drainage systems in KPK comprising of 456 drains. These serve a total area of 0.37 million hectares. Balochistan Balochistan has two canal systems, which receive water from the Indus Basin System through Guddu Barrage and Sukkur Barrage, located in Sindh. These canal systems serve a total area of 0.33 million

hectares. One of these, the Pat Feeder Canal System, has been improved recently. In addition, there are 431 independent publicly owned small irrigation schemes, which serve 0.14 million hectares. There are a few privately owned small irrigation schemes too. Groundwater usage for irrigation An estimated 41.6 MAF of groundwater is pumped annually in Pakistan.

According to a study, more than 90% of the extracted groundwater is used for irrigation purposes. Groundwater reservoirs are recharged from the rivers as well as the seepage losses from the canals, watercourses, farm channels and the fields.

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