Microcomputers and programmable calculators provide several features for today's irrigation engineers and technicians. The discharge per unit width of the field is substantially reduced and topographical variations can be more severe. The advance phase refers to that length of time as water is applied to the top end of the field and flows or advances over the field length. A basin is typically square in shape but exists in all sorts of irregular and rectangular configurations. Depletion is the interval between cut off and the appearance of the first bare soil under the water. to surface irrigation The perimeter dykes need to be well maintained to eliminate breaching and waste, and must be higher for basins than other surface irrigation methods. Of course it is always possible to encounter a heavy rainfall or mistake the cut-off time thereby having too much water in the basin. Chapter 4 Surface Irrigation Part 623 NationalEngineeringHandbook (210–VI–NEH, September 2012) 4–v Figures Figure 4–1 Layout and function of irrigation system components 4–2 Figure 4–2 Basic phases of a surface irrigation event 4–3 Figure 4–3 Typical basin irrigation system in the Western United States 4… The higher inflow reaches the end of the field sooner but it increases both the duration and the magnitude of the runoff. The effectiveness of existing practices or proposed ones can be predicted, even to the extent that control systems operating, sensing and adjusting on a real-time basis are possible. Thus, surface irrigation may appear in several configurations and operate under several regimes. 2.4.2 Water infiltrates through the wetted perimeter and spreads vertically and horizontally to refill the soil reservoir. 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. How large are the fields? Water is applied to the top end of each furrow and flows down the field under the influence of gravity. Surface irrigation is an irrigation type where gravity force is used to distribute water over the soil surface. 2.1.1 Definition. The wetting and drying cycles reduce infiltration rates resulting in faster advance rates and higher uniformity[3] than continuous flow. The most common piped method of furrow irrigation uses plastic or aluminium gated pipe like that shown in Figure 14. The conveyance itself can be an earthen ditch or lateral, a buried pipe, or a lined ditch. 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. 2.1 Introduction Each should be standardized for mass production and fabrication in the field by farmers and technicians. This results in poor uniformity with high application at the top end with lower application at the bottom end. simplicity with which different phases of the irrigation could be described. 1967). Two typical examples are shown in Figure 3, which illustrate the most common basin irrigation concept: water is added to the basin through a gap in the perimeter dyke or adjacent ditch. The recession phase describes the time period while the water front is retreating towards the downstream end of the field. The designs of these structures have been standardized since they are small in size and capacity. Traditionally, the design and operation of surface irrigation systems are based on experience as well as on historically successful designs. Surface irrigation is where water is applied and distributed over the soil surface by gravity. Probably the most interesting evolution in surface irrigation so far as this guide is concerned is the development and application of microcomputers and programmable calculators to the design and operation of surface irrigation systems. Surface Irrigation is an unchanged process and it is older than its recognition. Some irrigation water is supplied in piped delivery systems and some directly pumped from groundwater. 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. One can find optimal designs and management practices for a multitude of conditions because designs historically requiring days of effort are now made in seconds. Typical irrigated basins (from Walker and Skogerboe, 1987). When the water is shut off, it recedes from the upper end to the lower end. However, surface irrigation has limitations because it increases the chance of human contact with the effluent. It either drains from the surface (runoff) or infiltrates into the soil. Surface irrigation systems have two principal sources of inefficiency, deep percolation and surface runoff or tailwater The remedies are competitive. Likewise, in the irrigation of paddy rice, an irrigation very often adds to the ponded water in the basin so there is neither advance nor recession - only wetting or ponding phase and part of the depletion phase. A surface irrigation event composes of the four phases outlined below (Walker, 1989) and illustrated graphically in Figure 2. For design and evaluation purposes, these guidelines will note elements of the conveyance and distribution system, especially those near the field such as flow measurement and control, but will leave detailed treatment to other technical sources. On-farm water management structures (from Skogerboe Surface irrigation comes in three major types; level basin, furrow and border strip. These are generally situations where the value of the crop is very small or the field is used for grazing or recreation purposes. Most surface irrigation systems derive their water supplies from canal systems operated by public or semi-public irrigation departments, districts, or companies. Surface Irrigation is a kind of irrigation where gravity works its best. The aim of modern surface irrigation management is to minimize the risk of these potential adverse impacts. Recession begins at that point and continues until the surface is drained. 2.1 Introduction 2.2.4 Uncontrolled flooding. Water may be supplied using gated pipe, siphon and head ditch, or bankless systems. In this guide, surface methods are classified by the slope, the size and shape of the field, the end conditions, and how water flows into and over the field. Water is applied to individual borders from small hand-dug checks from the field head ditch. Time is cumulative since the beginning of the irrigation, distance is referenced to the point water enters the field. If a field is level in all directions, is encompassed by a dyke to prevent runoff, and provides an undirected flow of water onto the field, it is herein called a basin. 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. Figure 12 shows a system in which siphon tubes are used as a means of serving each furrow. During advance, the water moves down the channel. Automation is easily applied. In the late 1970s, a high-speed microcomputer technology began to emerge that could solve the basic equations describing the overland flow of water quickly and inexpensively. While surface irrigation can be practiced effectively using the correct management under the right conditions, it is often associated with a number of issues undermining productivity and environmental sustainability:[6]. In furrow systems, the volume of water in the furrow is very often a small part of the total supply for the field and it drains rapidly. Phase 2, then the irrigation water will flow out of the land. Here, we will not detail out sub surface irrigation methods. Discussion 1 DISCUSSION OF SURFACE IRRIGATION IN IRAQ 1. As water is applied to the top end of the field it will flow or advance over the field length. Furrows are often employed in basins and borders to reduce the effects of topographical variation and crusting. It is useful to note here that in observing surface irrigation one may not always observe a ponding, depletion or recession phase. Reclamation of salt-affected soils is easily accomplished with basin irrigation and provision for drainage of surface runoff is unnecessary. There are three options available to solve this problem, at least partially: (1) dyke the downstream end to prevent runoff as in basin irrigation; (2) reduce the inflow discharge to a rate more closely approximating the cumulative infiltration along the field following the advance phase, a practice termed 'cutback'; or (3) select a discharge which minimizes the sum of deep percolation and tailwater losses, i.e., optimize the field inflow regime. What is surface irrigation in Iraq like today? et al., 1971). It may be furrowed or corrugated, have raised beds for the benefit of certain crops, but as long as the inflow is undirected and uncontrolled into these field modifications, it remains a basin. Each bay is irrigated in turn using a combination of drainage water from the previous bay and continuing inflow from the supply channel. The process of surface irrigation can be described using four phases. 1.6–1.8). These are: 1) The water supply subsystem 2) The water delivery subsystem 3) The water use subsystem Similarly, the irrigation works themselves are better constructed because of the application of high technology equipment. Furrows provide better on-farm water management flexibility under many surface irrigation conditions. There are few crops and soils not amenable to basin irrigation, but it is generally favoured by moderate to slow intake soils, deep-rooted and closely spaced crops. 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. Figure 8. This chapter uses volume balance methods to design surface irrigation systems. Today in the graduate and undergraduate study of surface irrigation engineering, microcomputer and programmable calculator utilization is, or should be, common practice. The field is divided into a number of bays or strips, each bay is separated by raised earth check banks (borders). In this configuration, the head ditch is divided into a series of level bays which are differentiated by a small change in elevation. Soils can be efficiently irrigated which have moderately low to moderately high intake rates but, as with basins, should not form dense crusts unless provisions are made to furrow or construct raised borders for the crops. 1.2. Surface irrigation is often referred to as flood irrigation, implying that the water distribution is uncontrolled and therefore, inherently inefficient. In Surface Irrigation, water is applied and distributed over the soil surface by the help of gravity. 6.3 SURFACE IRRIGATION METHODS .- - A brief about surface and subsurface irrigation method is given in Unit 1. 2.2.2 Border irrigation Figure 1. In surface irrigation events, there are four phases i.e. Furrow irrigation is particularly suited to broad-acre row crops such as cotton, maize and sugar cane. Surface irrigation is the introduction and distribution of water in a field by the gravity flow of water over the soil surface. This has been compounded by the fact that a single method is often referred to with different names. Time-space trajectory of water during a surface irrigation showing its advance, wetting, depletion and recession phases. Figure 5. Slip-form concrete lining in the USA. Figure 5 shows two typical furrow irrigated conditions. (210–VI–NEH, draft April 2006) Part 623 National Engineering Handbook Chapter 4 Surface Irrigation The U.S. Department of Agriculture (USDA) prohibits discrimination in all it As the inf… The crop is planted on the ridge between furrows which may contain a single row of plants or several rows in the case of a bed type system. Surface irrigation has evolved into an extensive array of configurations that can broadly be classified as: • basin irrigation • border irrigation • furrow irrigation • wild flooding The distinction between the various classifications is often subjective. The process of surface irrigation can be said to include four phases: advance phase; storage phase; depletion phase; and recession phase. PHASES OF IRRIGATION: The logistics of irrigation water It includes all operations since irrigation water enters in our farm to the output of the nutrient solution by the emitter: 2.1.- Treatment: Depending on the physical and chemical nature of the water it is necessary to design a specific treatment for this search. 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. This has tended to make surface irrigation analysis and design appear disjointed. Consequently, some means of emergency surface drainage is good design practice. The advance phase refers to that length of time as water is applied to the top end of the field and flows or advances over the field length. Figure 7. One of the innovations in surface irrigation, the In reality, some of the irrigation practices grouped under this name involve a significant degree of management (for example surge irrigation). 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. 3. Surface irrigation events have 3 phases: advance, storage, and recession. If there is long duration between two rotations, there is likelihood of water stress resulting in wilting point during the recession stage. Typical turnout from a canal or lateral (from walker end Skogerboe, 1987). Irrigation scheduling is a theme covered separately by several publications such as the FAO Irrigation and Drainage Paper 24 (Rev) by Doorenbos and Pruitt (FAO, 1977). For the purposes of describing the hydraulics of the surface flows, the drainage period is segregated into the depletion phase (vertical recession) and the recession phase (horizontal recession). They allow a much more comprehensive treatment of the vital hydraulic processes occurring both on the surface and beneath it. 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). Surface irrigation systems are supported by a number of on- and off-farm structures which control and manage the flow and its energy. How much groundwater pumping is used? 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. Border strip, otherwise known as border check or bay irrigation could be considered as a hybrid of level basin and furrow irrigation. Although surface irrigation is thousands of years old, the most significant advances have been made within the last decade. 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. To minimize deep percolation the advance phase should be completed as quickly as possible so that the intake opportunity time over the field will be uniform and then cut the inflow off when enough water has been added to refill the root zone. Thus, the system operates by moving the check-dam from bay to bay along the upper end of the field. The recession phase 4 1.3. The movement of soil water curve . 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. 2.4 Surface irrigation 2.3.2 Wastewater recovery [5] The effectiveness of surge irrigation is soil type dependent; for example, many clay soils experience a rapid sealing behaviour under continuous flow and therefore surge irrigation offers little benefit.[1]. Many basins are so small that precision equipment cannot work effectively. The surface irrigation system is one component of a much larger network of facilities diverting and delivering water to farmlands. Surge Irrigation is a variant of furrow irrigation where the water supply is pulsed on and off in planned time periods (e.g. Land preparation is largely a land grading problem which will be discussed in Section 5. Surface Irrigation Process. 2.4.3 Field distribution A volume balance approach to determine the parameters of the Kostiakov or modified Kostiakov infiltration equations in border and furrow irrigation is presented. 2.2.1 Basin irrigation 1984; Walker & Skogerboe 1987; Alazba 1999). Surface irrigation (Figure 12.1) of secondary treated and disinfected effluent is permitted in NSW. 2.2.3 Furrow irrigation Head ditch outlets for borders and basins (after Kraatz and Mahajan, FAO, 1975). Flooding • Definition/Description • Advantages – – • Disadvantages – – Graded borders • Covers entire surface • Used for close-growing crops • Slopes: 0.5% - 4% – What is wrong with a steeper slope? The precision of the field topography is also critical, but the extended lengths permit better levelling through the use of farm machinery. In the developed and industrialized countries, land holdings have become as much as 10-20 times as large, and the number of farm families has dropped sharply. Most of these farmers own and operate farms of 1-10 hectares, irrigate with 20-40 litres per second and rely on either small mechanized equipment or animal-powered farming implements. irrigation, 2.3 Requirements for optimal Advantages of Surface Irrigation . While these systems represent significant percentages in some areas, they will not be discussed in detail in this paper. The process of surface irrigation can be described using four phases. The process of surface irrigation can be described using four phases. Surface irrigation methods include furrow, border, and basin irrigation (Figs. 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