Aflaj irrigation and on-farm water management in northern Oman

This paper reports on results from a case study on water management within a traditional, falaj irrigation system in northern Oman. In the planning and design of regional irrigation development programs, generalized assumptions are frequently made as to the efficiency of traditional surface irrigation systems. Although qualitative accounts abound, very little quantitative research has been conducted on on-farm water management within falaj systems. Daily irrigation applications and crop water use was monitored during an 11-month period among 6 farm holdings at Falaj Hageer in Wilayat Al-Awabi. Contrary to the frequent assumptions that all surface irrigation systems incur unnecessarily high water losses, on-farm ratios of crop water demand to irrigation supply were found to be relatively high. Based on actual crop water use, irrigation demand/supply ratios among monitored farms varied from 0.60 to 0.98, with a mean of 0.79. Examination of the soil moisture budget indicates that during most irrigations of wheat (cultivated in the low evapotranspiration months of October–March) sufficient water is applied for the shallow root zone to attain field capacity. With the exception of temporary periods of high falaj delivery flows or periods of rainfall, field capacity is usually not attained during irrigations within the more extensive root zones of date palm farms. The data presented in this paper should provide a better understanding of water use performance by farmers within traditional falaj systems. Moreover, these data should also serve to facilitate more effective development planning for irrigation water conservation programs in the region.     

Review of irrigation system performance with respect to initial objectives

This paper presents the results of assessment studies of the performance of gravity irrigation projects, in six countries in different climate and social environments, with respect to their original objectives in terms of water availability, water use efficiencies, equity of water distribution, cropping intensity and crop yields, and project economic rates of return.An important lesson is the need for more realistic assumptions in the adoption of design standards, especially irrigation efficiency which affect the cropping intensity, the overall productivity of the project and its economic viability. This comparative method of performance assessment applied to a variety of projects has also provided some useful insights into the relative value of the different approaches to design of gravity irrigation systems.The views expressed in this paper are those of the author and are not presented as official views of the World Bank.     

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.     

Building a climate resilient farm: A risk based approach for understanding water, energy and emissions in irrigated agriculture

The links between water application, energy consumption and emissions are complex in irrigated agriculture. There is a need to ensure that water and energy use is closely considered in future industry planning and development to provide practical options for adaptation and to build resilience at the farm level. There is currently limited data available regarding the uncertainty and sensitivity associated with water application and energy consumption in irrigated crop production in Australia. This paper examines water application and energy consumption relationships for different irrigation systems, and the ways in which the uncertainty of different parameters impacts on these relationships and associated emissions for actual farms. This analysis was undertaken by examining the current water and energy patterns of crop production at actual farms in two irrigated areas of Australia (one using surface water and the other groundwater), and then modelling the risk/uncertainty and sensitivity associated with the link between water and energy consumption at the farm scale. Results showed that conversions from gravity to pressurised irrigation methods reduced water application, but there was a simultaneous increase in energy consumption in surface irrigation areas. In groundwater irrigated areas, the opposite is true; the use of pressurised irrigation methods can reduce water application and energy consumption by enhancing water use efficiency. Risk and uncertainty analysis quantified the range of water and energy use that might be expected for a given irrigation method for each farm. Sensitivity analysis revealed the contribution of climatic (evapotranspiration and rainfall) and technical factors (irrigation system efficiency, pump efficiency, suction and discharge head) impacting the uncertainty and the model output and water-energy system performance in general. Flood irrigation systems were generally associated with greater uncertainty than pressurised systems. To enhance resilience at the farm level, the optimum situation envisaged an irrigation system that minimises water and energy consumption and greenhouse gas emissions. Where surface water is used, well designed and managed flood irrigation systems will minimise the operating energy and carbon equivalent emissions. Where groundwater is the dominant use, the optimum system is a well designed and managed pressurised system operating at the lowest discharge pressure possible that will still allow for efficient irrigation. The findings might be useful for farm level risk mitigation strategies in surface and groundwater systems, and for aiding adaptation to climate change.     

Performance based irrigation planning under water shortage

A linear programming (LP) based optimization model and a simulation model are developed and applied in a typical diversion type irrigation system for land and water allocation during the dry season. Optimum cropping patterns for different management strategies are obtained by the LP model for different irrigation efficiencies and water availability scenarios. The simulation model yields the risk-related irrigation system performance measures (i.e. reliability, resiliency and vulnerability) for the management policies defined by the optimization model. The alternative strategies are evaluated in terms of all performance criteria (i.e. net economic benefit, equity and reliability) simultaneously through a trade-off analysis using a multi-criteria decision making method (compromise programming). For the case study of the Kankai irrigation system in Nepal, with equal preference to the objectives, a management strategy with equal share of water among the project subareas appears to be the most satisfactory alternative under water shortage conditions. The existing water allocation policy is not economically efficient. Deficit irrigation in Early paddy appears attractive under favorable hydrologic scenario, particularly if accompanied by measures to improve existing irrigation system efficiency.     

Validation of a methodology for grouping intakes of pressurized irrigation networks into sectors to minimize energy consumption

A methodology to optimise the amount of energy consumed in pressurized irrigation systems was presented by Jimenez-Bello et al. (2010a). These authors proposed grouping pressurized irrigation network intakes, each of the water turnouts resulting from a shared hydrant, into sectors via a genetic algorithm. In the present research, the methodology was applied and validated in a water users association. Several energy efficiency indicators were calculated and compared during five consecutive seasons (2006–2010). The first two seasons, when the methodology was not employed, were used as reference for the results obtained from 2008 onwards, when the methodology was applied to the management of irrigation network. Results obtained in seasons 2008–2010 showed that the average energy savings were 16% in comparisons to the 2006 season. However, it should be noted that the potential, theoretical savings, could have been as high as 22.3% if the modelled grouping networks would have been accurately followed. There was in fact some discrepancy between the theoretical model outputs and the final groupings due to some intake restrictions. In addition, during the irrigation campaigns, the number of irrigation intakes that operated within each sector was not always equal to the modelled sectoring, a fact that reduced the overall water users association energy efficiency. This occurred particularly during rainy periods, when some users deliberately decided to close their manual irrigation intakes valves. Overall, results showed the potential of the validated methodology for optimising energy use. However, the final overall system efficiency might depend on specific constraints that need to be taken into account when attempting to use model output predictions.     

Irrigation reliability and the productivity of water: A proposed methodology using evapotranspiration mapping

Irrigation is the dominant user of water worldwide, but provision of potable water and water for industry are higher priorities and give higher social and economic returns. Irrigation will continue to lose water to competing sectors and the productivity of irrigation systems (since food demand continues to grow) remains a central issue in water management. Performance assessment of irrigation has traditionally been difficult when based on field measurements of flows, deliveries and depths over large areas. Furthermore, performance measures have shifted from narrow engineering indicators to broader productivity issues of production achieved per unit of water consumed. Remote sensing, applied to the estimation of evapotranspiration (ET) over large areas, provides analysts of irrigation systems with extraordinary new tools for the objective assessment of consumption and production – constituting a quantum leap in the assessment of irrigation system performance. Awareness and utilisation of these tools is spreading, but important areas remain to be “converted” from traditional approaches that rely on an array of estimated parameters. The next challenge for remote sensing will be to map the frontier between the reliability of the irrigation service and the productivity achieved. Reliability provides the inducement for farmers to invest in higher productivity – to the benefit of themselves and society – and understanding better how the individual maximises profits within an uncertain irrigation environment can provide important guidance to managers and system designers.     

Effects of alternative water distribution rules on irrigation system performance: a simulation analysis

Based on a simulation model reflecting physical and economic conditions typically found in rice irrigation systems in Asia, the irrigation performance implications of alternative water distribution rules for dry season irrigation are evaluated under varying degrees of water shortage. The rules examined reflect differing water distribution strategies designed either to maximize conveyance efficiency, economic efficiency, or equity; or to achieve a balance between efficiency and equity objectives. Irrigation performance is evaluated using several efficiency measures reflecting the physical, agronomic and economic productivity of water, and one measure of equity. Economic efficiency and equity among farmers within the portion of the irrigation system that is on in any given season are shown to be complementary, and not competing objectives. Economic efficiency and equity among all farmers within the command area of the irrigation system are largely complementary strategies at the lower levels of water shortage, but with increasing shortage, significant tradeoffs develop between these objectives. An operational rule for water distribution under a goal of maximizing economic efficiency is developed, and the data requirements for its implementation are shown to be modest. Under the model's assumed conditions of dry season rice production dependent solely on surface irrigation for water, the distribution strategy designed to maximize conveyance efficiency results in only modestly lower levels of economic efficiency and equity than could be achieved by the strategy designed to maximize economic efficiency.     

On-farm performance evaluation of improved traditional small-scale irrigation practices: A case study from Dire Dawa area, Ethiopia

Field evaluation of surface irrigation systems play a fundamental role to determine the efficiency of the system as it is being used and to identify management practices and system configurations that can be implemented to improve the irrigation efficiency. This study evaluated the performance of an ‘improved’ traditional small-scale irrigation practice at Adada, a representative small-scale irrigation practice in Dire Dawa Administrative Council, Eastern Ethiopia. In order to determine numerical values of performance measures, certain parameters were measured/observed before, during and after an irrigation event while farmers are performing their normal irrigation practice. These parameters include: irrigated crop, irrigation method, stream size, cutoff time, soil moisture deficiency, and field size, shape and spacing. The results showed that the irrigation water applied to a farmer's plot during an irrigation event/turn was generally higher than the required depth to be applied per event. Since the irrigation method used was end-dyked, the major cause of water loss was due to deep percolation. The deep percolation loss was 32% in sorghum, 57% in maize, and 70% in tomato and potato fields. The type of irrigation system used, the ridged irrigation practice and the poor irrigation scheduling in the study sites were the main problems identified in the management and operations of the schemes. The following corrective measures are recommended to improve the system: (1) farmers should regulate the depth of irrigation water they apply according to the type of crop and its growth stage, change the field irrigation system and/or configuration especially for shallow rooted row crops, to furrow system, (2) guidance and support to farmers in developing and introduction of appropriate irrigation scheduling, and (3) future development interventions towards improvement of traditional irrigation practices should also focus in improving the on farm irrigation systems in addition to improving physical infrastructure of the scheme.     

Irrigation evaluation based on performance analysis and water accounting at the Bear River Irrigation Project (U.S.A.)

The purpose of this work is to contribute to the development of a combined approach to evaluate irrigated areas based on: (1) irrigation performance analysis intended to assess the productive impacts of irrigation practices and infrastructures, and (2) water accounting focused on the hydrological impacts of water use. Ador-Simulation, a combined model that simulates irrigation, water delivery, and crop growth and production was applied in a surface irrigated area (1213 ha) located in the Bear River Irrigation Project, Utah, U.S.A.. A soil survey, a campaign of on-farm irrigation evaluations and an analysis of the database from the Bear River Canal Company and other resources were performed in order to obtain the data required to simulate the water flows of the study area in 2008. Net land productivity (581 US$ ha⁻¹) was 20% lower than the potential value, whereas on-farm irrigation efficiency (IE) averaged only 60%. According to the water accounting, water use amounted to 14.24 Mm³, 86% of which was consumed through evapotranspiration or otherwise non-recoverable. Gross water productivity over depleted water reached 0.132 US$ m⁻³. In addition, two strategies for increasing farm productivity were analyzed. These strategies intended to improve water management and infrastructures raised on-farm IE to 90% reducing the gap between current and potential productivities by about 50%. Water diverted to the project was reduced by 2.64 Mm³. An analysis based on IE could lead to think that this volume would be saved. However, the water accounting showed that actually only 0.91 Mm³ would be available for alternative uses. These results provide insights to support the decision-making processes of farmers, water user associations, river basin authorities and policy makers. Water accounting overcomes the limitations and hydrological misunderstandings of traditional analysis based on irrigation efficiency to assess irrigated areas in the context of water scarcity and competitive agricultural markets.     

山东禹城引黄灌区非充分灌溉配水模型

为了制定有多种作物且灌溉水源为动态变化的灌区的配水计划，提出了由充分灌溉和非充分灌溉2级模型组成的配水模型。其中非充分灌溉配水模型包括优化模型和模拟模型2部分，优化模型的方案具有较好的经济效益，而模拟模型的方案便于实施。模型中联合运用引黄水和地下水，可减少因黄河缺水对农业造成的重大损失。在此基础上编制的山东禹城灌溉配水管理决策支持系统界面友好，实用性强，基本上可灌溉灌区的管理需要。     

Modelling water control needs for diversified cropping

The background and concepts of water control for crop diversification in rice-based irrigation systems are discussed. Water control is described in terms of the irrigation event volumes and intervals between irrigation events. The development of the WACCROD model to simulate these water control parameters under selected agroclimatic conditions is described. The simulation model can recommend irrigation event volumes and intervals for various dry season cropping patterns in rice-based irrigation systems. Also, the application of the model to a general situation at field level of a ‘typical’ rice based irrigation system is reported.     

内蒙河套灌区建立回归水灌溉系统可行性分析

通过详实可靠的资料及多种因素分析 ,对河套灌区建立回归水灌溉系统的可行性进行了论证     

Water and salt balance in an irrigated area of the Ebro River Basin (Spain)

Summary Water balance components (effective precipitation, diverted water, actual evapotranspiration and irrigation return flow) and salt balance components (TDS of precipitation, diverted water and irrigation return flow, and sources/sinks in the soil profile) of the Violada irrigation district (3,913 ha) located in the Ebro river basin were measured for the 1982 and 1983 hydrological years. The irrigation district discharges annually 73,000 t of salt into its receiving river. The gypsiferous character of the soils gives a saturated gypsum character to the leachate resulting in a fairly constant TDS of the irrigation return flow (coefficient of variation of 12% for the 1982 hydrological year). The salt load of this area is 18.8 t/ha due to the gypsum content of the soils and improper water management. This results in a mean annual irrigation application efficiency (JAE), calculated as the average actual evapotranspiration/diverted irrigation water ratio, of 0.67 for the 2 years studied. On-farm irrigation system evaluation tests were performed in order to evaluate uniformity of water application and irrigation requirements of the main crops. The results indicate that JAE can be improved by means of better irrigation water management (especially irrigation scheduling) and proper land levelling of the fields.Formerly Instituto Nacional de Investigaciones Agrarias, CRIDA-03     

Prediction of irrigation return flows through a hierarchical modeling approach

The quantity of water available for irrigation is getting scarce in many countries and it assumes great importance for assured crop production, especially in view of the erratic behavior of the monsoon. Thus, there is a pressing need to improve the water efficiency of irrigation systems. One-way of improving the efficiency of the irrigation system is reusing the return flow from the irrigation system. This task requires quantification of return flow, which still remains as a grey area in irrigation water management. The estimation of return flow from the irrigation system is usually obtained using thumb rules depending upon the site-specific conditions like command area conditions and soil properties. In this paper, a hierarchical modeling technique, namely, regression tree is developed for return flow estimation. Regression tree is built through binary recursive partitioning. The effective rainfall, inflow, consumptive water demand, and percolation loss are taken as predictor variables and return flow is treated as the target variable. The applicability of the hierarchical model is demonstrated through a case study of Periyar-Vaigai Irrigation System in Tamil Nadu, India. The model performance shows a good match between the simulated and the field measured return flow values. Results of statistical analysis indicated that the correlation coefficients are high for both single as well as double crop seasons.     

Water use estimates for various rice production systems in Mississippi and Arkansas

Rice irrigation-water use was estimated in Mississippi (MS) and Arkansas (AR) in 2003 and 2004. Irrigation inputs were compared on naturally sloping (i.e. contour-levee system) and mechanically graded fields. In MS, rice production consumed, on average, 895 mm water, but irrigation inputs were greatly affected by production system. Contour-levee systems accounted for 35% of the production area and consumed 1,034 mm irrigation. Fields mechanically graded to a consistent slope of approximately 0.1% (i.e. straight-levee systems) consumed 856 mm irrigation and accounted for 60% of the production area. Fields devoid of slope (i.e. zero-grade system) accounted for 5% of the production area and consumed 382 mm irrigation. In AR, contour-levee rice production consumed 789 mm compared to 653 mm with a straight-levee system. Using low pressure, thin wall (9–10 mil) disposable irrigation tubing to deliver water to each paddy independently reduced irrigation inputs by 28% in MS and 11% in AR when compared to a single-point (levee-gate) distribution system.     

Landscape irrigation scheduling efficiency and adequacy by various control technologies

Automated residential irrigation systems tend to result in higher water use than non-automated systems. Increasing the scheduling efficiency of an automated irrigation system provides the opportunity to conserve water resources while maintaining good landscape quality. Control technologies available for reducing over-irrigation include evapotranspiration (ET) based controllers, soil moisture sensor (SMS) controllers, and rain sensors (RS). The purpose of this research was to evaluate the capability of these control technologies to schedule irrigation compared to a soil water balance model based on the Irrigation Association (IA) Smart Water Application Technologies (SWAT) testing protocol. Irrigation adequacy and scheduling efficiency were calculated in 30-day running totals to determine the amount of over- or under-irrigation for each control technology based on the IA SWAT testing protocol. A time-based treatment with irrigation 2 days/week and no rain sensor (NRS) was established as a comparison. In general, the irrigation adequacy ratings (measure of under-irrigation) for the treatments were higher during the fall months of testing than the spring months due to lower ET resulting in lower irrigation demand. Scheduling efficiency values (measure of over-irrigation) decreased for all treatments when rainfall increased. During the rainy period of this testing, total rainfall was almost double reference evapotranspiration (ET_o) while in the remaining three testing periods the opposite was true. The 30-day irrigation adequacy values, considering all treatments, varied during the testing periods by 0-68 percentile points. Looking at only one 30-day testing period, as is done in the IA SWAT testing protocol, will not fully capture the performance of an irrigation controller. Scheduling efficiency alone was not a good indicator of controller performance. The amount of water applied and the timing of application were both important to maintaining acceptable turfgrass quality and receiving good irrigation adequacy and scheduling efficiency scores.     

Can irrigation be sustainable?

Globally, about 10 Mha of agricultural land is lost annually due to salinisation, of which about 1.5 Mha is in irrigated areas. While some climate and management aspects are common to semi-arid regions, the detailed mechanisms and options to secure ecological sustainability and economic viability may vary considerably from case to case. This paper applies a whole of system-water balance to compare irrigation in three semi-arid regions suffering from similar sustainability issues: Rechna Doab (RD), Pakistan; the Liuyuankou irrigation system (LIS), China; and Murrumbidgee irrigation area (MIA), Australia. Soil salinity, lack of adequate water resources and groundwater management are major issues in these areas. The MIA and LIS irrigation systems also suffer from soil salinity and low water-use efficiency issues. These similarities occur in spite of very different climatic and underlying hydrogeological conditions. The key data used to compare these different regions are climate and soils, available water resources and their use, as well as components of the water balance. In addition, the history of water resource development in these areas is examined to understand how salinity problems emerge in semi-arid regions and the consequences for production. Based on the efficiency parameters and the definitions of sustainability, approaches are explored to solve common environmental problems while maintaining economic viability and environmental sustainability for irrigation systems.     

A simulation study of comparison of the evaluation procedures for three irrigation methods

Standard evaluation procedures, based on field measurements and statistical, hydraulic models, have been developed for assessing irrigation systems performance. However, given the diverse nature of the irrigation methods, it is not possible to use a unique evaluation procedure. Ideally, variables would be measured at every point throughout the field under study, but that is clearly impractical. Instead, measurements are taken of selected samples, or irrigation models are used to predict field-wide distributions of the variables. In this paper, irrigation models for trickle, sprinkler and furrow irrigation are used to assess how well the irrigation performance indicators generated by standard procedures match those generated by whole-field simulations. Six performance indicators were used: distribution uniformity, uniformity coefficient of Christiansen, application efficiency, deep percolation ratio, tail water ratio and requirement efficiency. The analysis was applied to systems typical of cotton crops in Southern Spain. The results show that the procedure used to determine performance indicators in trickle irrigation provides good estimates of the whole field performance. The procedure used in sprinkler irrigation is also acceptable, but yields variable results. Finally, the standard procedure used for furrow irrigation produces biased, highly variable results and overestimates distribution uniformity.