Modern analysis of surface irrigation systems with WinSRFR

WinSRFR is a new generation of software for analyzing surface irrigation systems. Founded on an unsteady flow hydraulic model, the software integrates event analysis, design, and operational analysis functionalities, in addition to simulation. This paper provides an overview of functionalities, interface, and architectural elements of the software, and discusses technical enhancements in version 2.1, released in late 2007, and version 3.1, scheduled for release in 2009.     

Comparative analysis of main on-farm irrigation systems in Portugal

Traditional irrigation systems still cover a large area of irrigated lands in Portugal. The needs for competitiveness leads to the gradual abandon of traditional systems, resulting in social and economic impacts. Pressurised on-farm irrigation systems provide labour savings but imply important investments. Surface irrigation does not require expensive equipment and is low energy and low labour consuming, if modern systems are implemented. Flexible-pipe, gated-pipe, surge-flow valve and cablegation are the main equipment issues available to Portuguese farmers for modern surface irrigation practice. Conditions for application of these systems have been studied relative to different soil and topographic conditions. Plane land, either horizontal or sloped and undulated fields can be irrigated by surface systems, if a convenient design is accomplished. The adequacy of the irrigation systems has been evaluated and a cost-benefit study was carried out. A case study of a situation with undulated land, representative of South Portugal, is presented in this paper, comparing surface irrigation issues and a sprinkler system. Conclusions show a particular economic interest on adopting surge-valve, gated-pipe and cablegation.     

An analysis of the appropriateness of wind and other energy systems for irrigation water pumping in India

This study attempts to quantify a figure of merit (appropriateness) for various options of energy technologies feasible for a prespecified task. Within the framework of rural energy development, various attributes are identified, relatively weighted and quantified for a group of energy technologies including renewable energy sources. Based on the data for Indian conditions, it is found that windmills designed to respond to low wind speeds of the order of 12 km/h and very carefully optimised for cost reduction are likely to be most appropriate within the group of alternatives considered in this study. This conclusion, however, holds only for irrigation from shallow wells (10–15 m deep) in small farms (size 1–2 ha).     

An economic perspective on the potential gains from improvements in irrigation water management

In recent years, several researchers have introduced new terms describing irrigation efficiency to enhance the information available when evaluating water policy alternatives. Some of the definitions expand the physical boundary considered when evaluating water use, while others account for the changes in water quality that occur as drainage water is reused in an irrigated area. While the concepts of basin, global, and effective efficiency have enhanced our understanding of water use in agriculture, public officials may derive incorrect policy implications when reviewing empirical estimates of those measures, particularly if information describing the economic impacts of water use and allocation decisions is not available. For example, some authors suggest that when estimates of basin-wide efficiency approach 100%, there is little opportunity to save water by improving water management and achieving higher levels of classical, farm-level efficiencies in upstream portions of an irrigated region. However, there may be significant opportunities to increase the net values generated with limited water resources by improving the distribution of water among farmers and reducing the negative, off-farm effects of irrigation and drainage activities. Economic analysis is helpful in identifying those opportunities and in designing policies that encourage farmers and water agency personnel to improve water management practices in ways that enhance social net benefits.     

Flow path and hydraulic analysis for on-farm pressurized irrigation systems

A model was developed to analyze the steady-state hydraulics of branching pipe networks as found in on-farm pressurized irrigation systems with multiple outlets at sprinklers or emitters. The model uses a new methodology to identify all flow paths based on a shortest-path algorithm. It also uses elevation and hydraulic parameters to determine which outlets are flowing and which (if any) are not. An iterative solution approach results in the calculated flow rates and pressures at all nodes in the network with a single source node, which can have a fixed head (reservoir) or a pump. The methodology provides a guaranteed steady-state hydraulic solution for the network, regardless of the available pressure, pipe layout and characteristics, or field topography.     

Technical and economic considerations in the design of closed conduit irrigation systems: A case study

Closed conduit irrigation systems are designed to respond to moisture requirements and permit water application at different required rates. The formulation of these requirements allows the engineer to select one of the many possibilities of the water system layouts. However, the requirement that the cost of the system for a given set of operational conditions should be minimal is not always included in the design because of the difficulties in selecting the most economic layout among the many alternatives.The main parameters characterizing pipe irrigation systems are presented and discussed. A trade-off among the irrigation system components for various layouts is presented in a case study and discussed, emphasizing the complexity of the decision-making procedure.     

An heuristic algorithm for short term irrigation scheduling using hosereel-raingun systems

Growers who irrigate need to answer three questions throughout the growing season — (i) when should each field be irrigated; (ii) how much water should be applied; and (iii) which field should be irrigated first. An heuristic solution procedure has been developed to produce realistic irrigation schedules, within a practical time, for growers using hosereel-raingun irrigators. The financial implications of the irrigation schedules are analysed over a short term period (typically 7 days). The constraints are limited availability of equipment, labour and/or water. Use of the model is illustrated with a common situation faced by a U.K. grower.     

An economic analysis of conversion from border-check to centre pivot irrigation on dairy farms in the Murray Dairy Region,Australia

The dairy industry in the Murray Dairy Region, Australia, is reliant on irrigation, as evapotranspiration greatly exceeds rainfall during the main growing season. Border-check irrigation is the predominant method of irrigation used in the region, but centre pivot irrigation has emerged as a potential alternative in response to the increasing scarcity and value of irrigation water. This paper presents an economic evaluation of conversion from border-check to centre pivot irrigation for dairy pasture production in the Murray Dairy Region. The evaluation was based on a hypothetical farm with available land to expand the area of irrigated pasture production to utilise water saving generated by converting from border-check to centre pivot irrigation. Income and cost related to the conversion were identified. A pre-tax discounted cash flow analysis was performed. Under the assumption that the conversion resulted in 20% less water use and 10% more pasture production per hectare, an investment in the conversion of border-check to centre pivot irrigation would produce a net present value of $218,200 and a benefit cost ratio of 1.36 at a discount rate of 10%, and an internal rate of return of 23.1%.     

Performance analysis of pressurized irrigation systems operating on-demand using flow-driven simulation models

On-demand pressurized irrigation systems are designed to deliver water with the flow rate and pressure required by the farm irrigation systems, sprinkling or micro-irrigation, and respecting the time, duration and frequency decided by the farmers. Due to the variation in farm demand along the season and the day, a large spatial and temporal variability of flow regimes occurs in these systems, which may affect the performance of the farm systems and the yields of the irrigated crops. Therefore, there is a need to analyse those systems to identify and solve performance problems. In this research, two simulation models for the analysis of irrigation systems operating on-demand, ICARE and AKLA, are used and compared to assess the hydraulic performance of the irrigation network of the Lucefecit Irrigation System, in Southern Portugal. ICARE assesses the global performance of the irrigation system through the indexed characteristic curves, while AKLA provides for the identification of the relative pressure deficit and reliability at every hydrant. Both models adopt a flow-driven analysis approach, performing the analysis for multiple flow regimes. To support the hydraulic characterization of the system and for calibration of the steady-state hydraulic model, field measurements were performed at selected nodes of the network, including four hydrants. The analysis with ICARE does not provide for a sufficient identification of problems. In fact, poor performance is indicated when a few hydrants operate below the minimum pressure set at design. Differently, the analysis with AKLA, applied at the hydrant level, shows that the performance of the Lucefecit system is generally acceptable. AKLA identifies which hydrants operate below the required pressure and, therefore, allows to support any eventual related improvement. Results show that the performance of the system highly improved when changing the piezometric elevation from 260 to 265 m a.s.l. However, this improvement is not sufficient because three hydrants still have high relative pressure deficit and low reliability. Solutions for those hydrants require increasing diameters of network pipes supplying them.     

Sensitivity analysis of optimal operation of irrigation supply systems with water quality considerations

A model for optimal operation of water supply/irrigation systems of various water quality sources, with treatment plants, multiple water quality conservative factors, and dilution junctions is presented. The objective function includes water cost at the sources, water conveyance costs which account for the hydraulics of the network indirectly, water treatment cost, and yield reduction costs of irrigated crops due to irrigation with poor quality water. The model can be used for systems with supply by canals as well as pipes, which serve both drinking water demands of urban/rural consumers and field irrigation requirements. The general nonlinear optimization problem has been simplified by decomposing it to a problem with linear constraints and nonlinear objective function. This problem is solved using the projected gradient method. The method is demonstrated for a regional water supply system in southern Israel that contains 39 pipes, 37 nodes, 11 sources, 10 agricultural consumers, and 4 domestic consumers. The optimal operation solution is described by discharge and salinity values for all pipes of the network. Sensitivity of the optimal solution to changes in the parameters is examined. The solution was found to be sensitive to the upper limit on drinking water quality, with total cost being reduced by 5% as the upper limit increases from 260 to 600 mg Cl l^–1. The effect of income from unit crop yield is more pronounced. An increase of income by a factor of 20 results in an increase of the total cost by a factor of 3, thus encouraging more use of fresh water as long as the marginal cost of water supply is smaller than the marginal decrease in yield loss. The effect of conveyance cost becomes more pronounced as its cost increases. An increase by a factor of 100 results in an increase of the total cost by about 14%. The network studied has a long pipe that connects two distinct parts of the network and permits the supply of fresh water from one part to the other. Increasing the maximum permitted discharge in this pipe from 0 to 200 m³ h^–1 reduces the total cost by 11%. Increasing the maximum discharge at one of the sources from 90 to 300 m³ h^–1 reduces the total cost by about 8%.     

An economic evaluation of native pasture systems in south-eastern New South Wales

The economic productivity of native pasture systems on the New South Wales tablelands has undergone significant change over the past 40 years. The continued modification by landholders of native pastures with fertilisers and introduced species has been an important contributing factor. Using the economic methods of productivity analysis and linear programming, this paper investigates the extent of native pasture productivity change and the relative economic returns to four general native pasture systems. The results quantify declining productivity trends in native pastures overall, but also establish that the native pasture type systems based on high-quality indigenous species can yield good economic returns under sound management. Some implications of these results for research into and the promotion of native pasture systems are discussed.     

Egg production on cooperative farms: An economic analysis

This paper examines the economics of egg production of forty co-operative farms in South-Western Nigeria. In the paper, cost functions are analysed by the use of ordinary least squares and weighted least squares. The impact of different factors of production on revenues was computed by fitting a production function that related total revenue to inputs.Results of the analysis indicated that productive inputs appeared to be combined in fixed proportions over all sizes of co-operative farms. Feed was found to account for over two-thirds of the costs on co-operative farms.     

Sprinkler selection for line-source irrigation systems

Summary Line-source sprinkler irrigation systems have been widely used in plant water relations studies, but lack guidelines for selection of appropriate sprinklers for specific applications. The objective of this study was to systematically evaluate different sprinkler types for potential application in a special line-source sprinkler system for a specific plot size. During its course, a general procedure was developed that can be used to analyze can-catch data from tests on single sprinklers run at different combinations of pressures and nozzle heights. This allows the water application gradient away from the sprinkler to the determined and provides data for selecting the best spacing and sprinkler pattern for maximum uniformity in a line-source application.     

Using drainage systems for supplementary irrigation

The use of drainage systems for supplementary irrigation is widespread in The Netherlands. One of the operating policies is to raise the surface water level during the growing season in order to reduce drainage (water conservation) or to create subsurface irrigation. This type of operation is based on practical experience, which can be far from optimal.To obtain better founded operational water management rules a total soil water/surface water model was built. In a case study the effects of using the drainage system in a dual-purpose manner on the arable crop production were simulated with the model. Also, the operational rules for managing this type of dual-purpose drainage systems were derived.The average annual simulated increase in crop transpiration due to water conservation and water supply for subsurface irrigation are 6.0 and 5.4 mm.y^–1, respectively. This is equivalent with 520 × 10³ and 460 × 10³ Dfl.y^–1 for the pilot region (2 Dfl 1 US $). The corresponding investments and operational costs are 600 × 10³ Dfl and 9 × 10³ Dfl.y^–1 for water conservation and 3200 × 10³ Dfl and 128 × 10³ Dfl.y^–1 for subsurface irrigation. Hence, water conservation is economically very profitable, whereas subsurface irrigation is less attractive.Comparing the management according to the model with current practice in a water-board during 1983 and 1986 learned that benefits can increase with some 50 and 500 Dfl per ha per year, respectively.     

Yield and economic return of vegetable crops under variable irrigation

 Field experiments were conducted for 2 years (1997 and 1998) on sandy loam soil in northwestern Botswana to study the effect of five levels of pan evaporation replenishment (20, 40, 60, 80 and 100%) on marketable yield, yield components, irrigation production efficiency and economic return of winter broccoli, carrot, rape and cabbage under a drip irrigation method. The highest mean marketable yield (2 years) of broccoli (19.1 t/ha), carrot (58.9 and 32.9 t/ha), rape (61.8 t/ha) and cabbage (97.2 t/ha) was recorded at 80% of pan evaporation replenishment. The irrigation production efficiency of broccoli (5.9 kg/m³), rape (14.6 kg/m³) and cabbage (23.6 kg/m³) was maximum at 80, 20 and 60% of pan evaporation replenishment respectively. Irrigation replenishment up to 80% of pan evaporation loss did not influence the irrigation production efficiency for total and root yield of carrot. The results revealed that a further increase in irrigation amount resulting from 100% of pan evaporation replenishment did not increase the marketable yield of crops but reduced the irrigation production efficiency significantly. The seasonal water applied and marketable yield of broccoli, carrot, rape and cabbage showed quadratic relationships (R ² = 0.85–0.98), which can be used for allocating irrigation water within and between the crops. The net return increased with the increase in pan evaporation replenishment. The results revealed that the rape crop is the most remunerative, followed by cabbage, broccoli and carrot. Received: 2 November 1998     

Risk analysis and economic viability of water harvesting for supplemental irrigation in semi-arid Burkina Faso and Kenya

Food insecurity affects a large portion of the population in sub-Saharan Africa (SSA). To meet future food requirements current rainfed farming systems need to upgrade yield output. One way is to improve water and fertiliser management in crop production. But adaptation among farmers will depend on perceived risk reduction of harvest failure as well as economic benefit for the household. Here, we present risk analysis and economical benefit estimates of a water harvesting (WH) system for supplemental irrigation (SI). Focus of the analysis is on reducing investment risk to improve self-sufficiency in staple food production. The analysis is based on data from two on-farm experimental sites with SI for cereals in currently practised smallholder farming system in semi-arid Burkina Faso and Kenya, respectively. The WH system enables for both SI of staple crop (sorghum and maize) and a fully irrigated off-season cash crop (tomatoes). Different investment scenarios are presented in a matrix of four reservoir sealants combined with three labour opportunity costs. It is shown that the WH system is labour intensive but risk-reducing investment at the two locations. The current cultivation practices do not attain food self-sufficiency in farm households. WH with SI resulted in a net profit of 151–626 USD year⁻¹ ha⁻¹ for the Burkina case and 109–477 USD year⁻¹ ha⁻¹ for the Kenya case depending on labour opportunity cost, compared to −83 to 15 USD year⁻¹ ha⁻¹ for the Burkina case and 40–130 USD year⁻¹ ha⁻¹ for the Kenyan case for current farming practices. Opportunity cost represents 0–66% of the investment cost in an SI system depending on type of sealant. The most economical strategy under local labour conditions was obtained using thin plastic sheeting as reservoir sealant. This resulted in a net profit of 390 and 73 USD year⁻¹ ha⁻¹ for the Burkina Faso and Kenyan respective site after household consumption was deducted. The analysis suggests a strong mutual dependence between investment in WH for SI and input of fertiliser. The WH system is only economically viable if combined with improved soil fertility management, but the investment in fertiliser inputs may only be viable in the long term when combined with SI.     

Water uses and productivity of irrigation systems

Reducing overall water diversions for agriculture, while maintaining or increasing production to keep up with increasing world population, has been and will continue to be a challenge. Yet there is not good agreement regarding the programs needed to improve the productivity of agricultural water use, nor what increases are feasible. It is recognized that field irrigation is inherently nonuniform. So also is the distribution of water to users and water delivery service nonuniform. Here, we suggest that crop-scale irrigation uniformity can be examined at a project scale by understanding how field, farm and project irrigation systems contribute to nonuniformity. We also discuss the interrelation between project scale uniformity and the relative irrigation water supply, and their combined impact on project productivity. We provide an example which relates internal measures of project performance (e.g., water distribution operations) and external measures of project performance (e.g., project-wise water productivity).     

A review of methods for evaluating the economic efficiency of irrigation

This paper reviews methods for evaluating irrigation efficiency. Static production function models which do not consider the timing of water applications are contrasted with dynamic crop models and methods for optimizing the timing of irrigation. Methods for considering irrigator risk preferences in evaluating irrigation strategies are covered. Different approaches to the problem of allocating a limited amount of water optimally among competing crops and/or competing units of the same crop are examined. Methods of determining the value of information as a way of improving irrigation efficiency are dealt with also.The paper points out advantages of the economic approach. These advantages include the fact that the methods deal with the dynamic, uncertain environment in which irrigation occurs. Also, the methods recognize the importance of managers' goals such as profit maximization and risk minimization as well as the impact of limited information on the attainment of these goals. The paper draws conclusions on ways in which the methods could be improved.