Making the user visible: analysing irrigation practices and farmers’ logic to explain actual drip irrigation performance

The actual performance of drip irrigation (irrigation efficiency, distribution uniformity) in the field is often quite different from that obtained in experimental stations. We developed an approach to explain the actual irrigation performance of drip irrigation systems by linking measured performances to farmers’ irrigation practices, and these practices to the underlying logic of farmers who operate these systems. This approach was applied to 22 farms in Morocco. Four sets of variables helped explain the gap between the actual irrigation performance and the performance obtained in experimental conditions: (1) farmers have agro-economic motivations or want to improve their social status, and for them, irrigation performance is at best an intermediate objective. (2) Irrigation performance is not a static value, but a rapidly evolving process, related to the (perceived) ability of farmers to change irrigation practices and renew irrigation equipment, but also to farmers’ aspirations. (3) The social network of farmers, supporting the introduction and use of drip irrigation, determines how farmers may share experience, information and know-how related to drip irrigation. (4) Today, there is no social pressure to irrigate carefully to save water; only the state explicitly links the use of drip irrigation to saving water. Making the drip user visible in research and policy studies would lead to more realistic assessments of irrigation performance and draw the attention of policy makers to the actual conditions in which drip irrigation is used, and as a consequence help incorporate ‘saving water’ as an objective for drip irrigation users.     

A rational method for assessing irrigation performance at farm level with the aid of fuzzy set theory

Of the various client groups with interests in irrigation system performance, farmers are probably the least often considered. This is, at least in part, attributable to the profound difficulty encountered in attempting to obtain reliable measurements of performance at farm level in most systems. Yet irrigation systems should be seen as a service to farmers, whose perspective on the utility of the supply is an important component of performance monitoring. Direct measurement at field level is generally not feasible and an alternative approach is proposed utilising fuzzy set theory. The procedure can be seen as a rapid appraisal technique which is also applicable to performance assessment in informal farmer-managed systems. The usefulness of the approach lies in its ability to gather data in imprecise linguistic terms from individual farmers and to aggregate them rationally and objectively.     

Cumulative relative water supply: A methodology for assessing irrigation system performance

This paper discusses the usefulness and limitations of using the concept of Relative Water Supply (RWS) for evaluating the performance of irrigation systems, with special reference to systems irrigating rice. It then describes and demonstrates the use of a modification of RWS called Cumulative Relative Water Supply (CRWS), which can be used in conjunction with RWS. The advantage of CRWS is that it provides a measure of the cumulated RWS throughout a season, both in absolute terms at any given time, and in terms of the overall seasonal trend. It allows comparison of performance of an irrigation system or subsystem both to the target, and to other systems or subsystems. It can therefore be used both as an analytical tool by researchers, and as an operational tool by managers. The use of CRWS in conjunction with RWS is illustrated with examples from Sri Lanka.     

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.     

Evaluation of surface irrigation system performance using System Dynamics (SD) approach

Various methods and criteria have been proposed and utilized for the evaluation of irrigation systems performance, which can be used for comparison of design conditions and irrigation systems performance. Surface irrigation systems should be paid more attention among all other irrigation systems due to their operation simplicity and high losses. In the present study, while describing main relationships of irrigation evaluation criteria of application efficiency, water requirement efficiency, Deep Percolation Ratio and Tail Water Ratio, a method based on SD will be introduced. Modeling of this approach has been done using VENSIM-DSS software. Model has been tested in a case study that included the modeling of a furrow in four irrigation status: current situation, full irrigation, deficit irrigation and finally deficit irrigation with optimized irrigation cutoff time and inflow into furrow. The results reveal the high capabilities of SD approach in modeling water resources and irrigation systems. Its user friendly and ability in transferring data to the data bank can introduce this approach and software as an applicable decision support system.     

The downstream externalities of harvesting rainwater in semi-arid watersheds: An Indian case study

Water-related investment projects affect downstream water availability, and therefore should account for these externalities. Few projects do, however, owing to lack of awareness, lack of data and difficulty in linking upstream investments to downstream effects. This article assesses the downstream impacts of rainwater harvesting in a semi-arid basin in Southern India, focusing on the trade-offs that arise when crop water use is re-allocated from a downstream surface water irrigation system to groundwater irrigated agriculture upstream. The results indicate that the downstream impacts are considerable and that net benefits are insufficient to pay back investment costs. Further research is required to reduce the uncertainties in the water balance of irrigation systems at basin level, to account for the inter-annual variability of crop water availability and to elaborate the wider welfare effects.     

A pattern fit coefficient for water application

A new coefficient, the pattern fit coefficient for water application, Pa, is introduced. It expresses the differences between an applied and any predetermined water pattern. The efficiency of many irrigation systems and methods are evaluated by comparing them to a uniform pattern. In several cases, however, strip patterns are more efficient and, therefore, preferred (e.g. small row crops, early growing stages). Fortunately strip patterns can be applied by recently developed irrigation systems such as linear move irrigation machines. The necessity to evaluate these patterns is the reason and the justification for the new coefficient. This paper presents the mathematical background and several uses of Pa as well as its interpretation in terms of availability access and shortage of water within the wetted area of whatever shape.     

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).     

Assessment of water delivery efficiency in irrigation canals using performance indicators

Agricultural water is delivered by open irrigation canals in system of reservoirs with a widespread distribution in South Korea. Traditional irrigation management problems include water distribution systems with less capacity than the peak demand, irregular delivery rates, and low irrigation efficiency and uniformity. It is necessary to strategically compare the estimated irrigation demands with the actual water supplies for decision making in order to maintain the water supply according to the demand. Accurate measurement and monitoring of water distribution systems is essential in order to solve the problems of water efficiency and availability. Auto water level gauges installed at the head and tail sections of each irrigation canal in the Dongjin River were used to measure the discharge during irrigation periods. In this study, we introduced an approach to assess the water delivery performance indicators of the open irrigation canals, which is essential for identifying the key issues for water management improvement. The irrigation efficiencies according to the water delivery performance indicators were measured with an automatic water gauge in the irrigation canals and were calculated from the spatial and temporal distribution of the water supply for the lack of planning in water delivery. The calculated performance indicators are useful to understand the irrigator behavior and general irrigation trends. Analysis of the results yielded insights into possible improvement methods in order to develop water management policies that enable irrigation planners to improve the temporal uniformity and equity in the water distribution.     

Diagnosing irrigation performance and water productivity through satellite remote sensing and secondary data in a large irrigation system of Pakistan

Irrigation policy makers and managers need information on the irrigation performance and productivity of water at various scales to devise appropriate water management strategies, in particular considering dwindling water availability, further threats from climate change, and continually rising population and food demand. In practice it is often difficult to access sufficient water supply and use data to determine crop water consumption and irrigation performance. Energy balance techniques using remote sensing data have been developed by various researchers over the last 20 years, and can be used as a tool to directly estimate actual evapotranspiration, i.e., water consumption. This study demonstrates how remote sensing-based estimates of water consumption and water stress combined with secondary agricultural production data can provide better estimates of irrigation performance, including water productivity, at a variety of scales than alternative options. A principle benefit of the described approach is that it allows identification of areas where agricultural performance is less than potential, thereby providing insights into where and how irrigation systems can be managed to improve overall performance and increase water productivity in a sustainable manner. To demonstrate the advantages, the approach was applied in Rechna Doab irrigation system of Pakistan’s Punjab Province. Remote sensing-based indicators reflecting equity, adequacy, reliability and water productivity were estimated. Inter- and intra-irrigation subdivision level variability in irrigation performance, associated factors and improvement possibilities are discussed.     

Water allocation and management in an emerging spate irrigation system in Makanya catchment, Tanzania

Although spate irrigation systems are risk-prone, they can be an important component for livelihood security in semi-arid areas. Spate uses water (flood water), which upstream users often do not require, as rainfall during these periods is more than sufficient. The use of this flood water for spate irrigation is therefore a good opportunity to convert water with a low opportunity cost to high value water. As more rivers are closing, due to socio-economic and climate changes, spate irrigation may become increasingly relevant in semi-arid areas. Spate irrigation systems pose institutional and technical challenges: collective action is challenged by complex upstream-downstream interactions between users within the system, and the high labour demands for regular reconstruction of temporary diversion weirs and intake structures. This paper describes a spate irrigation system in Makanya village, Tanzania that emerged in response to increased upstream water use. We use three of the four dimensions (hydrological, hydraulic and sociological) of spate irrigation proposed by Van Steenbergen (1997) to assess the Makanya spate irrigation system. The Makanya spate irrigation system has an organisational structure that is similar to the canal irrigation (furrow) committees located upstream, and effectively deals with the institutional demands of managing water in spate irrigation systems. Water allocation is reminiscent to the water sharing arrangements existing in the full irrigation system, which previously was in place at the site and in the high- and midlands of the Makanya catchment and therefore set this system apart from the traditional spate irrigation practice elsewhere. Technically, a major challenge is the reconstruction of the head works after each flood. Another aspect is the changes in the river bed. Flash floods carry sediments that deposit on the fields, raising the elevation of the irrigated land every year and making it increasingly difficult for the river water to enter the plots. Improving system efficiency through modernisation of the diversion and distribution structures in this case is not feasible due to the huge amounts of sediments delivered to the system each year. Instead investments in conjunctive use of groundwater could be the solution because it involves a relatively small intervention, minimises the physical disturbance of the system, and therefore is likely to respect the existing locally developed water management arrangements.     

On trade-offs in low-input agroecosystems

More fundamental knowledge on critical trade-offs is potentially important to improve the performance of low-input agroecosystems. Productivity, stability and sustainability are expressions of performance, and their trade-offs are a cause of scientific debate. Our results show that articulation and storage within the system play an important role in the trade-offs between productivity and stability, and between productivity and sustainability. Both articulation and storage involve complex structures that have a high maintenance cost, and consequently depress the overall ecosystem productivity. However, they are important to smooth the effect of external perturbations. The inverse relationship between productivity and stability and productivity and sustainability cannot be easily reverted unless external inputs are added. But some structural arrangements in the agroecosystem that produce anomalies and deviations from those inverse trends look promising as a means to reconcile opposite effects in a low-input scheme.     

Assessing the performance of participatory irrigation management over time: A case study from Turkey

In many countries today, irrigation systems have been transferred to the water user associations (WUAs). Accordingly, it is believed that the performance of the irrigation systems is dependent on the performance of the WUAs.In this study, the performance of participatory irrigation management (PIM) over time is assessed with regard to the Kestel WUA serving a wide area of Turkey's Aegean coast. Data relating to the WUA is obtained from both the State Hydraulic Works and WUAs’ own records. In addition, two surveys have been carried out with the members of the WUA with an 8-year interval between them. Data have been analyzed within the framework of selected irrigation performance criteria and indicators. The non-parametric Mann-Whitney U test was used to compare the perceptions of the farmers on the WUA at different survey periods. A Logit model was estimated to evaluate the relationship between the irrigation problems and the level of satisfaction from the WUA.The performance of the WUA with the indicators of utility, productivity, sustainability and financial efficiency was found to be positive; while the performance of adequacy was identified as poor. The farmers were generally satisfied of the WUA's operation, with their level of satisfaction improving over time. On the other hand, the farmers were not fully convinced that they had input with the system management. The initial design of the channel system and its maintenance were identified to be the key factors affecting user satisfaction.Overall, the Kestel WUA may be considered a successful example, thus supporting a promising future for PIM. Yet improved control and farmer education is needed for a superior performance of all indicators; and further enhanced farmer participation in management should be achieved in order to raise the level of farmer satisfaction.     

Seasonal on-farm irrigation performance in the Ebro basin (Spain): Crops and irrigation systems

Irrigation performance assessments are required for hydrological planning and as a first step to improve water management. The objective of this work was to assess seasonal on-farm irrigation performance in the Ebro basin of Spain (0.8 million ha of irrigated land). The study was designed to address the differences between crops and irrigation systems using irrigation district data. Information was only available in districts located in large irrigation projects, accounting for 58% of the irrigated area in the basin. A total of 1617 records of plot water application (covering 10,475 ha) were obtained in the basin. Average net irrigation requirements (IR_n) ranged from 2683 m³ ha⁻¹ in regulated deficit irrigation (RDI) vineyards to 9517 m³ ha⁻¹ in rice. Average irrigation water application ranged from 1491 m³ ha⁻¹ in vineyards to 11,404 m³ ha⁻¹ in rice. The annual relative irrigation supply index (ARIS) showed an overall average of 1.08. Variability in ARIS was large, with an overall standard deviation of 0.40. Crop ARIS ranged between 0.46 and 1.30. Regarding irrigation systems, surface, solid-set sprinkler and drip irrigated plots presented average ARIS values of 1.41, 1.16 and 0.65, respectively. Technical and economic water productivities were determined for the main crops and irrigation systems in the Aragón region. Rice and sunflower showed the lowest productivities. Under the local technological and economic constraints, farmers use water cautiously and obtain reasonable (yet very variable) productivities.     

过滤后黄河水对滴灌系统的影响

为探明黄河水经孔径为0.05 mm(300目)过滤器过滤后进行滴灌的可能性,模拟大田滴灌研究了黄河水滴灌条件下4种滴灌带(Nf0.72,Nf1.60,Nf2.20,Dy1.38)不同位置流量变化规律,滴灌系统平均相对流量Q_r与流量变异系数C_v、系统均匀度C_u变化规律及相关关系.结果表明:黄河水对滴头的堵塞早期呈快速发育状态,不同类型引黄滴灌系统平均相对流量随灌水次数的增加呈平缓下降—快速下降—平缓下降的规律,均在相对流量75%附近快速下降;滴头流量变异系数在系统运行初期线性增大,之后平缓变化,且与系统平均相对流量具有很好的线性关系(p<0.001);当系统平均相对流量Q_r大于75%时,滴灌系统克里斯琴森均匀度系数C_u与Ln Q_r呈线性关系(R²=0.790 9),因此,引黄滴灌系统可通过系统平均相对流量Q_r来判断系统均匀度C_u,以方便及时快速了解系统堵塞状况,以便对其运行管理进行决策.     

Higher performance through combined improvements in irrigation methods and scheduling: a discussion

Prior to the discussion on approaches to combine irrigation scheduling and water application practices, several farm irrigation performance indicators are defined and analysed. These indicators concern the uniformity of water distribution along an irrigated field and the efficiency of on-farm water application. Then, the analysis focus is on three main irrigation systems: surface, sprinkler and microirrigation. For each of these systems, the analysis concerns the main characteristics and constraints of the systems, more relevant aspects influencing irrigation performances, and approaches which could lead to a more appropriate coupling of irrigation scheduling and water application methods. Conclusions point out on the need for combined improvements in irrigation scheduling and methods, for expanding field evaluation of irrigation in farmers fields, for improved design of on-farm systems, and for quality control of irrigation equipments and design.     

Management evaluation of Water Users Associations using benchmarking techniques

The development of different tools to evaluate the performance of Water Users Associations (WUAs) is an important practice for improving water and energy management, together with other production costs. One of these tools is the Benchmarking technique, which is based on the comparison between different WUAs to determine the best practices in each of them.In this paper, a Benchmarking process is applied to seven WUAs located in Castilla-La Mancha (Spain) during three irrigation seasons (2006-2008). The performance indicators developed by the International Programme for Technology and Research in Irrigation and Drainage (IPTRID) are used, while new indicators dealing with production and energy are proposed. The goals of this paper are to group WUAs with the same characteristics, using performance and energy indicators, and to reduce the set of indicators using statistical methods. The most important indicators, easy to obtain and yielding result in maximum information are retained for further use.Three proposals reducing the initial number of indicators were proposed, with an aim of being useful for future applications based on characterizing WUAs. Indicators results highlighted that irrigable areas can be grouped based on the application of drip irrigation systems and those with sprinkler irrigation systems. When using groundwater resources, no significant differences were observed for energy consumption between these irrigation systems. This can be explained by the indicator energy load index (ICE, m), which had similar values in all WUAs analyzed. According to annual irrigation water supply per unit irrigated area (V_TSr, m³ ha⁻¹), the highest values (between 5200 m³ ha⁻¹ and 6800 m³ ha⁻¹) were obtained in WUAs with sprinkler irrigation systems, which contained crops characterized by high water requirements, compared to the V_TSr (less than 1800 m³ ha⁻¹) of WUAs with drip irrigation systems, with crops that required less volume of irrigation water. Regarding production efficiency indicators, in drip irrigation systems the high presence of vineyards, almond and olive trees, crops with low water requirements, explained high values of gross margin per unit irrigation delivery (MBVs, € m⁻³)(close to 0.82 € m⁻³) in comparison with sprinkler irrigation systems (close to 0.36 € m⁻³).     

An economic analysis of irrigation systems

Summary An array of irrigation systems are available which can be broadly classified as being gravity flow or pressurized. Pressurized irrigation systems provide better control on the amount of applied water and, in most cases, better irrigation uniformity than gravity flow systems. They also have a higher initial capital cost than gravity flow systems and an analysis is required to determine whether the improved performance of pressurized systems justifies the additional costs. An economic analysis was done on several irrigation systems which included consideration of farm management costs associated with a given irrigation system, shifts in crop yield and drainage volumes associated with the optimal management of each irrigation system, and costs associated with disposal of drainage waters. Cotton was selected as the crop for analysis. Irrigation uniformity is a significant determinant to the results. Although irrigation uniformities can be highly variable based on design, maintenance and management, a typical uniformity for each irrigation system was selected. For the conditions of the analysis, gravity flow systems were calculated to be more profitable than pressurized systems if there was no constraint on the amount of drainage water generated or cost for its disposal. Imposition of costs for drainage water disposal induced a shift whereby pressurized systems became more profitable than gravity flow systems.     

Evaluation of the water cost effect on water resource management:: Application to typical crops in a semiarid region

The greatest water consumption takes place during irrigation of arid and semiarid areas, therefore, water resource management is fundamental for sustainability. For correct management, several tools and decision-making systems are necessary while paying close attention to aspects such as profitability, water cost, etc. Water resources are scarce and some of them are of low quality. This extremely delicate situation occurs in some regions of the world and it explains increasing water cost. In Europe, the policies relating to water use (2000/60/EC) pay particular attention to the need of its protection and conservation. To ensure this, a large number of measures, including the establishment of prices which really correspond to their usage costs, have been set forth. Water subsidies are relatively important in all European countries. In this study, a specific methodology is applied to a Spanish semi-arid region. It is useful and easy to apply, not only by farmers, but also by water managers and politicians in charge of policy. The methodology also helps in the decision-making process about water cost in agriculture. In this area (Hydrogeological System 08.29, Spain), the resources are mainly underground water with a high variable cost and without any direct subsidies. This model allows us to analyse the effect of different water costs and to find the optimum strategy giving the maximum gross margin in line with water cost and its main determining factors (irrigation system, climatic variability, etc.).The methodology is based on the effect of irrigation on crop yield with its production function, integrating the effect of application efficiency. In this way, a relationship between gross margin and gross irrigation depth is obtained. Working with permanent irrigation systems and four crops (barley, garlic, maize and onion), the main conclusion is that the optimum gross irrigation depths are always fewer than those necessary for maximum crop yield and when irrigation depths are fewer water cost increases. Irrigation depths, which maximise the economic efficiency in the use of water (€ m⁻³), are fewer than those which maximise the gross margin; therefore, this aspect must be considered in irrigation scheduling. The results also show important differences among crops, depending on their water requirements and their economic profitability.