2.4.2 How much groundwater pumping is used? Level basin irrigation has historically been used in small areas having level surfaces that are surrounded by earth banks. Typical irrigation system components (redrafted from USDA-SCS, 1967). It is widely utilised and therefore a well-known system, which can be operated without any high-tech applications. A very large number of causes of poor surface irrigation performance have been outlined in the technical literature. Large difference in water that crops require and the flow irrigation system actually delivers results in low field water application efficiency. Consequently, some means of emergency surface drainage is good design practice. As water is applied to the top end of the field it will flow or advance over the field length. Issues associated with surface irrigation. and reuse, 2.4.2 Basin irrigation has a number of limitations, two of which, already mentioned, are associated with soil crusting and crops that cannot accommodate inundation. These systems are commonly used in Australia where rice and wheat are grown in rotation.[2]. Border strip, otherwise known as border check or bay irrigation could be considered as a hybrid of level basin and furrow irrigation. 18 - 34 . The attention here then is focused on inflow regulation and tailwater control. There are many cases where croplands are irrigated without regard to efficiency or uniformity. It is useful to note here that in observing surface irrigation one may not always observe a ponding, depletion or recession phase. Basins can be served with less command area and field watercourses than can border and furrow systems because their level nature allows water applications from anywhere along the basin perimeter. simplicity with which different phases of the irrigation could be described. However, this practice increases the tailwater problem because the flow at the downstream end must be maintained until a sufficient depth has infiltrated. 2.4.3 Field distribution Each should be standardized for mass production and fabrication in the field by farmers and technicians. After the water reaches the end of the field it will either run-off or start to pond. Water may be supplied using gated pipe, siphon and head ditch, or bankless systems. When the inflow stream is introduced by the upstream end of the plane, water advances with a sharply defined wetting front down the slope toward the downstream end in what is referred to here as the advance phase of the irrigation flow process. 4. The storage or ponding phase 3 1.2.3. Discussion 1 DISCUSSION OF SURFACE IRRIGATION IN IRAQ 1. Water infiltrates through the wetted perimeter and spreads vertically and horizontally to refill the soil reservoir. The second phase of surface irrigation … DESIGN OF SURFACE IRRIGATION, LECTURE SUPPORTING MATERIALS 2 purpose of the physical system is to supply water to an area for crop production. Basin irrigation is the most common form of surface irrigation, particularly in regions with layouts of small fields. Figure 1. Reuse systems have not been widely employed historically because water and energy have been inexpensive. Typical bay dimensions are between 10-70m wide and 100-700m long. One common use of this technique includes the irrigation of pasture for dairy production. Although surface irrigation is thousands of years old, the most significant advances have been made within the last decade. It is possible to improve the performance of most surface . The structural elements of a surface system perform several important functions which include: (1) turning the flow to a field on and off; (2) conveying and distributing the flow among fields; (3) water measurement, sediment and debris removal, water level stabilization; and (4) distribution of water onto the field. Many basins are so small that precision equipment cannot work effectively. Figure 6. Estimation of the infiltration rate using the infiltrometer method 5 1.3.2. 2.1 Introduction In basins, for example, the post-cut off period may only involve a depletion phase as the water infiltrates vertically over the entire field. The classification of surface methods is perhaps somewhat arbitrary in technical literature. There are three types of Surface Irrigation: Level Basin Irrigation, furrow irrigation, and Border Strip Irrigation. As the inf… Surface Irrigation is an unchanged process and it is older than its recognition. Conveyance, distribution and management structures and reuse. It is also practiced in various horticultural industries such as citrus, stone fruit and tomatoes. In Surface Irrigation, water is applied and distributed over the soil surface by the help of gravity. However, surface irrigation has limitations because it increases the chance of human contact with the effluent. There is substantial field evidence that surface irrigation systems can apply water to croplands uniformly and efficiently, but it is the general observation that most such systems operate well below their potential. A volume balance approach to determine the parameters of the Kostiakov or modified Kostiakov infiltration equations in border and furrow irrigation is presented. Microcomputers and programmable calculators provide several features for today's irrigation engineers and technicians. 1984; Walker & Skogerboe 1987; Alazba 1999). Basins and borders usually receive water through buried pipes serving one or more gated risers within each basin or border. Pipe materials are usually plastic, steel, concrete, clay, or asbestos cement, or they may be as simple as a wooden or bamboo construction. The discharge per unit width of the field is substantially reduced and topographical variations can be more severe. After the water reaches the field ready to be irrigated, it is distributed onto the field by a variety of means, both simple and elaborately constructed. Then the irrigation water either runs off the field or begins to pond on its surface. Before selecting surface irrigation over other types of irrigations, one must investigate the advantages and disadvantages of surface irrigation. These may include: (1) an accumulation of salinity between furrows; (2) an increased level of tailwater losses; (3) the difficulty of moving farm equipment across the furrows; (4) the added expense and time to make extra tillage practice (furrow construction); (5) an increase in the erosive potential of the flow; (6) a higher commitment of labour to operate efficiently; and (7) generally furrow systems are more difficult to automate, particularly with regard to regulating an equal discharge in each furrow. The term 'surface irrigation' refers to a broad class of irrigation methods in which water is distributed over the field by overland flow. Lining materials include slip-form cast-in-place, or prefabricated concrete (Figure 9), shotcrete or gunite, asphalt, surface and buried plastic or rubber membranes, and compacted earth. Needs Assessment --1. The Physical systems of Surface irrigation systems as a whole consist of four subsystems. In surface irrigation events, there are four phases i.e. Typical irrigated basins (from Walker and Skogerboe, 1987). However, in looking for a root cause, one most often retreats to the fact that infiltration changes a great deal from irrigation to irrigation, from soil to soil, and is neither predictable nor effectively manageable. The higher inflow reaches the end of the field sooner but it increases both the duration and the magnitude of the runoff. The time and space references shown in Figure 1 are relatively standard. Surface irrigation is the oldest yet still the most common form of irrigation throughout the world although it traditionally suffers from many problems such as low efficiency and low uniformity. The WinSRFR program, Furrow irrigation is particularly suited to broad-acre row crops such as cotton, maize and sugar cane. 2.4.1 Diversion structures Surface irrigation is an irrigation type where gravity force is used to distribute water over the soil surface. Followings are the surface irrigation advantages. The incidence of surface irrigation process consists of four phases, as illustrated in Figure 7 below. When an irrigation project has been designed for either small basins or furrows and borders, the capacity of control and outlet structures may not be large enough to improve basins. As water is applied to the top end of the field it will flow or advance over the field length. During advance, the water moves down the channel. Surface irrigation is mainly divided in basin, border, and furrow systems. Surface irrigation is the introduction and distribution of water in a field by the gravity flow of water over the soil surface. Surface irrigation involves movement of water as shallow flow over planes or in channels. Border irrigation can be viewed as an extension of basin irrigation to sloping, long rectangular or contoured field shapes, with free draining conditions at the lower end. Surface irrigation events have 3 phases: advance, storage, and recession. The advance phase 3 1.2.2. Very large mechanized farming equipment has replaced animal-powered planting, cultivating and harvesting operations. to surface irrigation Surface irrigation systems are best suited to soil with low to moderate infiltration capacities and land with relatively uniform terrain and slope less than 2 to 3 percent (Booher, 1974). The period of time between the end of the advance phase and the shut-off of the inflow is termed the wetting, ponding or storage phase. Drain back level basins (DBLB) or contour basins are a variant of basin irrigation where the field is divided into a number of terraced rectangular bays which are graded level or have no significant slope. … 2.3.1 Inlet discharge control Historically, the elements of an irrigation system have not functioned well as a system and the result has too often been very low project irrigation efficiencies. on for 1 hour off for 1½ hour). Diversion structures perform several tasks including (1) on-off water control which allows the supply agency to allocate its supply and protects the fields below the diversion from untimely flooding; (2) regulation and stabilization of the discharge to the requirements of field channels and watercourse distribution systems; (3) measurement of flow at the turnout in order to establish and protect water entitlements; and (4) protection of downstream structures by controlling sediments and debris as well as dissipating excess kinetic energy in the flow. The general surface irrigation process includes four phases: advance, storage, depletion, and recession (Holzapfel et al. The water can take a considerable period of time to reach the other end, meaning water has been infiltrating for a longer period of time at the top end of the field. The water is applied to the top end of the bay, which is usually constructed to facilitate free-flowing conditions at the downstream end. 2.3 Requirements The depletion phase is that short period of time after cut-off when the length of the field is still submerged. The soil acts as the growing medium in which water is stored and the conveyance medium over which water flows as it spreads and infiltrates. The bays are typically longer and narrower compared to basin irrigation and are orientated to align lengthwise with the slope of the field. Surface irrigation systems have two principal sources of inefficiency, deep percolation and surface runoff or tailwater The remedies are competitive. Figure 3. Two very recent additions to the efforts to control surface irrigation systems more effectively are the 'Surge Flow' system (Figure 6) developed at Utah State University, USA and the 'Cablegation' system developed at the US Department of Agriculture's Snake River Water Conservation Research Center in Kimberly, Idaho, USA. The tailwater deep percolation trade-off can also be solved by collecting and recycling the runoff to improve surface irrigation performance. The conveyance itself can be an earthen ditch or lateral, a buried pipe, or a lined ditch. [1] This is also a method of surface irrigation. The approach requires measured data from the advance phase, the postadvance (wetting) phase, or both, resulting in three different procedures to characterize infiltration. Figure 11. 2.4 Surface irrigation The gated pipe may be connected to the main water supply via a piped distribution network with a riser assembly like the one shown in Figure 13, directly to a canal turnout, or through an open channel to a piped transition. Infiltration and contact time 4 1.3.1. In those cases where high levels of uniformity and efficiency are being achieved, irrigators utilize one or more of the following practices: (1) precise and careful field preparation; (2) irrigation scheduling; (3) regulation of inflow discharges; and (4) tailwater runoff restrictions, reduction, or reuse. In most cases the performance of furrow irrigation can be improved through increasing the speed at which water moves along the field (the advance rate). A flow is introduced at one edge of the field and covers the field gradually. 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