2005-CE-44WATER RESOURCES AND IRRIGATION ENG CED-401 University College of Engineering and Technology Program: Term Resource Person: Class Day and Time BSC Civil Engineering 7th –Session 2005-09 Prof. Dr Abid Latif Monday (8:30 am to 12:10 pm) ATTENDENCE Attendance at all classes in this course is expected; however, circumstances may arise which make it impossible for you to attend. For example, if you are unable to attend a class due to health-related or other compelling reasons, you are expected to advise your instructor in advance. Under University regulations, your instructor can determine at Water Resources and Irrigation Technology CED--401 Page 1 of 10 2005-CE-44 which point absenteeism has become excessive and thus can prevent you from passing the course. TEXT BOOK 1. Irrigation and Hydraulic Structures. Theory, design and practice BY Iqbal Ali REFERENCE BOOKS 1. Irrigation and water power Engineering BY B.C Tumia 2. Irrigation and Drainage BY R.K Sharma ASSESSMENT The overall assessment of the course will be as follows Sessional Marks: 50 Internal: 30 External: 20 Exam: 75 Distribution of the internal marks is as under Quizzes Design / Lab Internal Viva Class Notes Assignment/Presentation Participation / Attendance Grand Total = 125 05 05 03 02 05 10 Lecture No. 1 Irrigation: The process of artificial application of water to the soil for the growth of agricultural crops is known as irrigation. Introduction about Irrigation: Water Resources and Irrigation Technology CED--401 Page 2 of 10 2005-CE-44 It is practically a science of planning and designing of the water supply system for the agricultural land to protect the corps from bad effects of drought or low rainfall. It includes the construction of weirs or dams, barrages or canal system for the regular supply of water to the cultivable lands. There are three essential requirements of plant growth, 1. Heat 2. Light 3. Moisture In England the one of three essential requirements is available that is moisture, which means irrigation is not required due to sufficient rainfall. But in Pakistan the first two of the three essential requirements of pant growth that is light and heat is present in large amount but the third (moisture) is required due to insufficient rainfall . Hence Irrigation is supplementary to rainfall. When the rainfall is either deficient or comes irregularly or at unseasonable times in Pakistan. Components of the Irrigation System or Irrigation System Network: The main components of an irrigation system are listed below, 1. Dam /Barrage 2. Canal Head regulator 3. Main canal 4. Branch Canal 5. Distributory canal 6. Minor canal 7. Water course (W.C) Water Resources and Irrigation Technology CED--401 Page 3 of 10 2005-CE-44 Phases of Irrigation Engineering: There are four stages of Irrigation Engineering, 1. Storage (Dams, Reservoirs) or Diversion (Barrages) 2. Conveyance of irrigation water (Canals) 3. Distribution (water courses ) and Application (Irrigation methods ) of irrigation 4. Drainage of excessive water through drains Importance of Irrigation: Question: Why irrigation is required? Answer: We know the water requirements for crops vary from place to place depending upon the nature of crops and site. In some areas there is no need of irrigation because the conditions are fulfilled by the natural resources (rainfall etc). Most of the areas of the earth are situated in arid zones (less than 15 '' of mean annual rainfall) and even in humid zones (greater than 30 '' of MARF). The rainfall is not distributed evenly. So it is only possible to use artificial means (supplying channel) to provide water for more cultivation. In Pakistan the annual rainfall ranges from 75 mm to 800 mm. So irrigation becomes a necessity to provide, (i) (ii) (iii) Sufficient amount of water in desirable seasons Period of requirement ( Time when water is required) Desirable amount of water for sufficient type of crops Thus the necessity of irrigation can be summarized in the following four points, 1. Less rainfall (Need fulfill through artificial supply ) Water Resources and Irrigation Technology CED--401 Page 4 of 10 2005-CE-44 2. Non-uniform rainfall (through dam , requirement is fulfilled at the need time crop) 3. Commercial crops with additional water ( more water is required for cash crops e.g. Sugar cane , tobacco, rice ) 4. Controlled water supply (By the construction of proper distribution system the yield of crop may be increased) Necessity of Irrigation: Question: What are the factors which govern the necessity of irrigation? Answer: Throughout the crop period adequate quantities of water is required near the root zone of the plants for their growth. At times during the crop period the rainfall may not be adequate to fulfill the water requirement. The intensity of rainfall is practically uncertain and beyond the control of human power and it may not be well distributed throughout the crop season or the culturable area. So, irrigation becomes absolutely necessary to fulfill the water requirement of crops. The following are the factors which govern the necessity of irrigation, (a)Insufficient Rainfall: When the seasonal rainfall is less than the minimum requirement for the satisfactory growth of crops, the irrigation system is essential. (b)Uneven Distribution of Rainfall: When the rainfall is not evenly distributed during the crop period or throughout thre culture able area the irrigation is extremely necessary. (c)Improvement of Perennial Crops: Some crops like sugarcane, cotton, etc require water throughout the major part of the year. But the rainfall may fulfill the water requirement in rainy season only. So for the remaining part of the year, irrigation becomes necessary. (d)Development of Agriculture in Desert Area: In desert area where the rainfall is very scanty , irrigation is required for the development of agriculture. Merits and demerits of Irrigation: The following are the benefits of Irrigation, Merits of Irrigation 1. Yield of Crops: Water Resources and Irrigation Technology CED--401 Page 5 of 10 2005-CE-44 In the period of low rainfall or drought the yield of crop may be increased by the irrigation system. 2. Protection from famine: The food production of a country can be improved by ensuring the growth of crops by availing the irrigation facilities. This helps a country to prevent famine situation 3. Improvement in cash crops: Irrigation helps to improve the cultivation of cash crops like vegetables, fruits, tobacco, etc. 4. Prosperity of farmers: When the supply of irrigation water is assured , the farmers can grow two or more crops in a year on the same land. Thus the farmers may earn money and improve their living standard. 5. Source of revenue: When, irrigation water is supplied to the cultivators in lieu of some taxes. it helos to earn revenue which may be spent on other development schemes. 6. Hydroelectric Power generation: In some river valley projects, multipurpose reservoirs are formed by constructing high dams where hydroelectric power may be generated along with the irrigation system. 7. Water Supply: The irrigation canals may be the source of water supply for domestic and industrial purposes. Demerits of Irrigation 1. Rising of water table: Due to the excessive of water through the bed and banks of the canals, the water table in the surrounding area may be raised which may constantly saturate the root zone of the crops and the soil may develop alkaline property which is harmful to the crops. 2. Formation of marshy land: Excessive seepage and leakage of water from the irrigation canals may lead to formation of marshy lands along the course of the canals. These marshy lands form the colonies of mosquitoes which may be responsible for diseases. 3. Formation of marshy land: Water Resources and Irrigation Technology CED--401 Page 6 of 10 2005-CE-44 The temperature of the commanded area of an irrigation project may be lowered considerably and the area may become damp. Due to dampness, the people residing around the area may suffer from cold, cough and other such diseases originating from dampness. 4. Loss of valuable lands: Valuable land may get submerged when the storage reservoirs are formed by constructing barrages or dams and it also may be lost, while constructing irrigation canals. Resources of Irrigation: There are three resources of irrigation, 1. Rainfall 2. Surface Water 3. Ground Water 1. Rainfall: Rainfall can directly help irrigation by precipitation occurring over the crop area or indirectly by adding its runoff to the rivers. This runoff is then stored by weir , barrage or dam downstream or it may replenish as an underground reservoir. Direct rainfall is the most helpful for the plant and crop growth if it occurs in proper amount at proper time .But it is unreliable as a source of irrigation water. It varies from year to year and it may fall altogether. It is irregularly distributed throughout the year as well as within the same season. In Pakistan, It occurs particularly in the summer season in the form of high showers resulting in the heavy rainfall. As the temperature is high evaporation rate is also increased. It is a great booster for agriculture. For canal irrigated areas the rains compliment the irrigation water. In Pakistan the mean annual rainfall ranges from 4 to 30 inches in the lower Indus region to the northern foot hills. Only a small proportion of this annual rainfall makes any direct or useful contribution to irrigation water supplies. According to World Bank consultants report the figure ranges from 1 to 17 inches. The rest is either converted to Direct Runoff or becomes a part of the ground water. While a small proportion is lost by evaporation. According to estimation the present direct contribution to the crops is 6 MAF / Annual. 2. Surface Water: Surface water include water diverted from the stream and stored into dams and barrages and then applied to the land through canals or pumped from rivers, lakes and canals . In dry months melting snow adds a great amount of water to the river discharge. Snow remaining on ground provides storage greater than any man made reservoir for 1 foot snow holds 1-4 inches of water. Snowfall usually occurs over many square miles on the mountainous terrain providing a surface reservoir which is then released in the summer months. The most important thing for irrigation engineer is when and how fast this vast quantity is released. In Pakistan, the rivers carry the melting snow and rains from the northern hills to the areas where they can be used for irrigation purpose. Water Resources and Irrigation Technology CED--401 Page 7 of 10 2005-CE-44 River water available in PAKISTAN for irrigation is, Average flow of River Indus = 90 MAF Average flow of River Jehlum = 23 MAF Average flow of River Chenab = 27 MAF Average flow of River Ravi = 3 MAF Average flow of River Sutlej = 2 MAF Total Surface Flow = 145 MAF Total Surface Flow 145 MAF Canal Diversion 105 MAF Wastage to seas 40 MAF Total Water available for field crops 72 MAF 3. Ground Water: Along with the rainfall and surface water the ground water is an important source of irrigation. In Pakistan we have enormous ground water reservoirs. In rainy season, due to rain, most of water seeps into the earth thus raising the water table in ground. This water is then taken out with the help of pumps and tube wells for irrigation Water Resources and Irrigation Technology CED--401 Page 8 of 10 2005-CE-44 purpose. The areas for which there is no access of canals, there we can get water for irrigation from underground sources of water. Ground water can cause water logging sometimes due to rise in water table and this can be avoided by pumping out water from the ground using several techniques i.e. pumps, tube-wells etc. In the underground water, there are less chances of the presence of impurities but it does not contain silt which is helpful for crop production acting as a fertilizing agent. In Pakistan we normally use all three sources of irrigation. But based on quality, sometimes it may be desired to use single source of water or it may be necessary to mix the ground water with the surface water so that the combined salts of both sources mixed in any quantity may not cause any damage to the crops. FLOW CHART OF RAINFALL FROM SOURCE TO FIELD: FLOW CHART OF SURFACE WATER FROM SOURCE TO FIELD: Water Resources and Irrigation Technology CED--401 Page 9 of 10 2005-CE-44 FLOW CHART OF GROUNDWATER FROM SOURCE TO FIELD: Water Resources and Irrigation Technology CED--401 Page 10 of 10