Evaluation of the Water Delivery Performance of the Menemen Left Bank Irrigation System Using Variables Measured On-Site

This study determines the water delivery performance at secondary and tertiary canal level of the Menemen Left Bank Irrigation system, an open canal irrigation system located in Turkey, for the irrigation seasons of the years 2005–2007. At secondary canal level, water supply ratio was used, and at tertiary level, the indicators of adequacy, efficiency, dependability, and equity were used. In calculating these indicators in this study, the amounts of water diverted to the canals, efficiency of water conveyance, and of water application were measured. Of these indicators, the water supply ratio was determined for the secondary canal, and the other indicators were determined for a total of six selected tertiary canals at the head, middle, and lower end of the secondary. At secondary level, the water supply ratios obtained to total irrigation water requirements for the months of July and August, when requirement for irrigation water is at a maximum, was determined to be less than one, while the water supply ratios obtained to net irrigation water requirement was found to be more than one. With regard to water delivery performance at tertiary level, adequacy, efficiency, dependability, and equity were found to be poor for each of the three years of the study, with efficiency rising to “fair” level only in 2005. In order to raise the water delivery performance of the system, it is necessary to reduce water conveyance losses to increase the water application efficiency, to prepare water distribution plans which take in tertiary canals, and to measure and monitor the water diverted to the canals.     

Field Verification of Two-Dimensional Surface Irrigation Model

A two-dimensional (2D) model of unsteady shallow-water flow in surface irrigation was developed to evaluate the influence of field-grading precision on surface irrigation performance. This paper presents field data for verification of this 2D model. No attempt was made here to evaluate irrigation performance. Verification of such models relies on independent estimates of parameters for infiltration and roughness. To accomplish this, water surface elevations were measured at 26 points within a 3 ha level basin. A double-bubbler system was used to obtain relative water depths. Field surveys were used to convert these to water surface elevations and field water depths, from which surface water volumes over time were computed. The infiltration function was determined by matching inflow minus surface volume over time with computed subsurface volume. A value of Manning n (0.05) was found for which advance and water depth hydrographs were both well predicted with the 2D model. Differences in advance for a plane versus undulating field surface were minor, except near the end of advance.     

General Irrigation Planning Performance of Water User Associations in the Gediz Basin in Turkey

In this study, an evaluation has been made of the realization level of the planned targets in irrigation planning for all of the 13 water user associations (WUAs) of the Gediz Basin. This evaluation was made according to six performance indicators: level of realization of irrigation ratios, level of realization of crop pattern, dependability, adequacy, efficiency, and equity for the years 1999–2002. Seven associations were successful in irrigation ratio realization, and four were successful in crop pattern. Failure of other WUAs can be reduced by collecting farmers’ declarations and evaluating them with greater care and sensitivity. Water delivery in the general irrigation plan was found to be poor with regard to dependability and equity, and good with regard to the indicators of adequacy (except in the year 2001) and efficiency. In order to improve dependability, the period when water is diverted from the source and the period when water is needed must coincide completely. In order to improve equity, delivery of water to WUAs must be carried out taking account of water requirements predicted in the general irrigation plan. When these two indicators are improved, adequacy and efficiency will improve also.     

Assessing Sensitivity Factors of Irrigation Delivery Structures

The flow behavior along an open-channel irrigation network can be assessed by determining the sensitivity of the irrigation structures. The importance of governing factors of the sensitivity and proportionality indicators is analyzed using a theoretical approach as well as practical results from historical data on a gated system in Sri Lanka and a gated and structured system in Pakistan. The influence of the discharge on the sensitivity indicator varies with the type of flow (overshot-undershot). For a common offtake (e.g., an orifice followed by a crest), sensitivity is at its peak at maximum discharge. The available head through the structure appears to be the most influential factor for sensitivity; the greater the head, the lower the sensitivity is. The submergence of the flow downstream of the structure is a reducing factor of the sensitivity that is important to consider for sensitive structures. Different methods for assessing the governing factors of sensitivity are discussed and illustrated using case studies. It is recommended that the sensitivity indicator be determined for the full supply depth in the parent canal and the maximum discharge through the offtake.     

SIMGRO, a GIS-Supported Regional Hydrologic Model in Irrigated Areas: Case Study in Mendoza, Argentina

The SIMGRO hydrologic simulation model was extended to include irrigation practice. It could then be used to evaluate the effect of hydrologic changes in an irrigated area in the province of Mendoza, Argentina where, given an average annual rainfall of approximately 200?mm, irrigation is crucial for agriculture. A storage dam was recently constructed in the Mendoza River to control the fluctuating river flow and to guarantee that the demand for water is met throughout the year. The dam will impact on parts of the irrigation system where groundwater levels are already high and salinization occurs. To evaluate these changes and possible mitigation measures, two performance indicators that consider groundwater and surface water were used: Relative evapotranspiration and the depleted fraction. Scenario runs revealed that the irrigation water losses from the canals affect the groundwater levels in the downstream part of the irrigated area; an increase in salinity was also revealed.     

Assessing Pressure Changes in an On-Demand Water Distribution System on Drip Irrigation Performance—Case Study in Italy

The hydrant pressure head in an on-demand water distribution system can be subject to high fluctuation depending on the discharge flowing inside the pipes, with consequent impacts on the performance of on-farm irrigation systems. In this work, an Italian water distribution system was analyzed using the AKLA model at upstream discharges of 1,200 and 600?L?s?1 to estimate the range of hydrant pressure variation. A computer model was developed, calibrated, and used to evaluate the performance of a drip irrigation system by relating the on-farm network with the hydrant characteristic curve at a certain operating status. The flow regulator within the hydrant played an important role in stabilizing the performance of the network at hydrant pressures higher than 27 m. At lower hydrant pressures, to apply the same amount of water, irrigation time must be extended by 17 and 95% for pressure heads of 20 and 12 m, respectively. These approaches described have great utility to ensure adequate irrigation management when water is delivered by pressurized on-demand systems.     

Sprinkler Head Maintenance Effects on Water Application Uniformity

The effects of wear on the ability of hand-move and side-roll sprinkler irrigation systems to maintain the designed water application rate and uniformity are of concern with regards to crop performance, water use efficiency, and environmental impact. Six hand-move and six side-roll sprinkler irrigation systems used under commercial crop production in Lane County, Oreg., were evaluated for equipment wear and performance. Individual sprinkler nozzle size and discharge rates were measured for each system and used in a computer model to estimate field application rate and uniformity. New nozzles were installed on six systems to compare potential application rate and uniformity with existing performance. Despite reducing the coefficient of variation in discharge between sprinklers from 10 to 2%, little increase in water application uniformity was attained. A 13% decrease in mean water application rate was documented after nozzle replacement. Ignored overapplication due to worn or mismatched nozzles results in overirrigation in both rate and total amount, which gives rise to the potential for increased surface redistribution and deep percolation, resulting in water and nutrient losses.     

Measuring On-Farm Irrigation Efficiency with Chloride Tracing under Deficit Irrigation

Water is a limited resource in agricultural production in arid climates. Under such conditions, high irrigation efficiency can be obtained either through implementation of efficient irrigation systems such as drip or sprinkler systems or through the age-old practice of deficit irrigation with gravity systems. The method used to increase irrigation efficiency is often dictated by economic and/or social factors. In either case, the effectiveness of water management at the farm level needs to be evaluated by measuring irrigation efficiency. The objective of this study was to evaluate the irrigation efficiencies for three crops in Southern New Mexico using the chloride technique. The chloride technique is a simple method in which the natural chloride in the irrigation water is used as a tracer to estimate the leaching fraction and the irrigation efficiency at the farm level. Soil samples were collected from various fields in 15 cm increments to a depth of 180 cm at the end of the irrigation season. The samples were analyzed for moisture and chloride content. In addition to the chloride technique, on-farm irrigation efficiencies were measured using applied water, yield, and water production functions. Water production functions and yields were used to estimate total evapotranspiration while flow measurements were used to calculate the amount of applied water. The results showed that high irrigation efficiency can be accomplished using deficit irrigation. Irrigation efficiency values ranged from 83 to 98%. Irrigation efficiencies using the chloride technique were compared with efficiencies estimated from direct flow measurements. The differences between the two methods ranged from 2 to 11.4%. The results showed that even though the chloride technique is subject to sampling errors and simplified theoretical assumptions, it can be used to estimate on-farm irrigation efficiency with considerable accuracy.     

Numerical Modeling of Basin Irrigation with an Upwind Scheme

In recent years, upwind techniques have been successfully applied in hydrology to simulate two-dimensional free surface flows. Basin irrigation is a surface irrigation system characterized by its potential to use water very efficiently. In basin irrigation, the field is leveled to zero slope and flooded from a point source. The quality of land leveling has been shown to influence irrigation performance drastically. Recently, two-dimensional numerical models have been developed as tools to design and manage basin irrigation systems. In this work, a finite volume-based upwind scheme is used to build a simulation model considering differences in bottom level. The discretization is made on triangular or quadrilateral unstructured grids and the source terms of the equations are given a special treatment. The model is applied to the simulation of two field experiments. Simulation results resulted in a clear improvement over previous simulation efforts and in a close agreement with experimental data. The proposed model has proved its ability to simulate overland flow in the presence of undulated bottom elevations, inflow hydrographs, and colliding fronts.     

Quantifying Management of Irrigation and Drainage Systems

To evaluate the performance of irrigation systems, different indicators have been used by researchers. In this study some of the water management problems of three different irrigation systems in Iran are presented. In addition, the water delivery performance of the Doroodzan Irrigation and Drainage Network in southern Iran is evaluated in detail. The analyses included wet and dry seasons and were based on the indicators of overall project water delivery efficiency (ep) and the monthly water requirement of crops. The distribution and conveyance of water in the Doroodzan Irrigation Network was unreliable in both seasons. With an overall project efficiency of around 46%, about 20% of the total delivered water was distributed unreliably. Water distribution equity along tertiaries was also found to be poor. A contributing factor could be the poor operation and maintenance of gates.     

Fertigation in Furrows and Level Furrow Systems. II: Field Experiments, Model Calibration, and Practical Applications

Furrow fertigation can be an interesting practice when compared to traditional overland fertilizer application. In the first paper of this series, a model for furrow fertigation was presented. The simulation model combined overland water flow (Saint-Venant equations), solute transport (advection-dispersion), and infiltration. Particular attention was paid to the treatment of junctions present in level furrow systems. In this paper, the proposed model is validated using five furrow fertigation evaluations differing in irrigation discharge, fertilizer application timing, and furrow geometry. Model parameters for infiltration and roughness were estimated using error minimization techniques. The error norm was based on observed and simulated values of advance time, flow depth, and fertilizer concentration. Model parameters could be adequately predicted from just one discharge experiment, although the use of more experiments resulted in decreased error. The validated model was applied to the simulation of a level furrow system from the literature. The model adequately reproduced irrigation advance and flow depth. Fertigation events differing in application timing were simulated to identify conditions leading to adequate fertilizer uniformity.     

Simulation Model for Level Furrows. I: Analysis of Field Experiments

The level-furrow irrigation system consists of furrowing a level basin. In level furrows, irrigation proceeds just like in level basins: the field is flooded from one point and water spreads to irrigate each furrow. Several writers have reported that this irrigation system has the potential to conserve water as compared to level-basin irrigation. However, no comparative studies on the performance of both irrigation systems are available, and the simulation of level furrows has not been attempted. In this work, two field experiments are reported. Both of them were performed in the same soil and in the same conditions. In the first experiment, infiltration was estimated for a series of furrow irrigation discharges and for a level basin. In the second experiment, a level furrow irrigation event was evaluated. A simulated level basin irrigation event in the level furrow experimental field required six times more time and water to complete advance. Infiltration equations including the irrigation discharge or the wetted perimeter as independent variables were proposed for the experimental furrow conditions. Application of a furrow simulation model to the level–furrow experiment resulted in an underestimation of the time of advance. To overcome this problem, a simulation model for level furrows was developed and is presented in a companion paper. The reported field experiments were used to validate the model, which was applied (in a companion paper) to explore adequate conditions for level furrow irrigation performance.     

Impact of Irrigation Management Transfer on Land and Water Productivity and Water Supply in the Gediz Basin, Turkey

In the 1990s, Turkey started a fast transfer program in which a large proportion of government-managed irrigation systems were put into the hands of Water Users’ Associations (WUAs) in a very short space of time. One of the first systems to be handed over was the Gediz Basin. This study aims to set out the effects of the transfer of irrigation management in this basin on water and land productivity and water supply. For this purpose, the indicators of productivity and water supply proposed by the International Water Management Institute have been used to show changes between the pretransfer, transfer, and post-transfer periods. WUA averages for the post-transfer period calculated from the results ranged $2,076–$2,898?ha?1 for output per command area, $2,747–$4,585?ha?1 for output per irrigated area, $0.26–$0.68?m?3 for output per irrigation supply, $0.30–$0.63?m?3 for output per unit water consumed, 0.88–1.49 for relative water supply, and 0.99–1.99 for relative irrigation supply. During the period evaluated by the study, there was a decline in water supply indicators, as against a steady increase in the productivity of water and land use. The basic reason for this decrease in supply is the long-lasting and ongoing drought in the region.     

Sensor-Based Automation of Irrigation on Bermudagrass during Dry Weather Conditions

Overirrigation of lawns with limited resources of potable water has increasingly become an issue for the state of Florida. A previous study showed that soil moisture sensors systems (SMSs) could lead to irrigation water savings during relatively wet/normal weather conditions. This research, as a follow-up comparison, was conducted under dry weather conditions. The first objective was to statistically evaluate the water savings potential of different commercially available SMSs during the first half of 2006. In the second half, the objectives were to quantify irrigation water use and to evaluate turfgrass quality differences among: (1) a time-based irrigation schedule system with and without a rain sensor; (2) time-based schedules compared to SMS-based systems; and (3) SMS-based systems under different irrigation frequencies. The experimental area was located in Gainesville, Fla. and consisted of common bermudagrass [Cynodon dactylon (L.) Pers.] plots. Four commercially available SMSs (brands Acclima, Rain Bird, Irrometer, and Water Watcher) were used to bypass scheduled irrigation cycles when the soil water content at the 7- to 10-cm depth was above field capacity. Time-based treatments with and without rain sensor feedback were set up as comparisons for irrigation depth applied, and a nonirrigated treatment for turf quality comparison purposes was implemented. Due to the dry weather conditions and/or infrequent rain events during the experiment, the nonirrigated plots (as well as a broken SMS treatment) resulted in turfgrass quality below the minimum acceptable level. The rest of the treatments had at least minimum acceptable turf quality. The treatment with rain sensor resulted in 13 to 24% less water applied than without the rain sensor treatment. Most SMS-based treatments resulted in significant irrigation water savings compared to the treatment without rain sensor, which ranged from 16 to 54% in the first half, and from 28 to 83% in the second half of 2006, for three of four SMS brands tested.     

Monitoring and Evaluation Scheme using the Multiple-Criteria-Decision-Making Technique: Application to Irrigation Projects

The application of monitoring and evaluation (M&E) systems to assess agricultural projects has received some attention in recent years. These systems provide valuable information for managers and decision makers by analyzing the implementation process, the progress of trends, and the long-term and short-term effectiveness of these projects. An algorithm is developed to monitor and evaluate drip and pressure irrigation projects in Iran. Different indicators are identified and the framework of an integrated evaluation system is demonstrated using an analytical hierarchy process for multiple-criteria-decision making. There is much subjective information that is quantified and normalized in order to remove any bias in evaluators’ assessment of qualitative measures or sensitivity to linguistic expressions. The application of this system to rank projects in different regions (zones) in Iran is also presented in this paper. The results have shown the significant value of such systems in providing information and input for different decision-making levels.     

Optimum Design and Management of Pressurized Branched Irrigation Networks

The scarcity of water resources is the driving force behind modernizing irrigation systems in order to guarantee equal rights to all beneficiaries and to save water. Traditional distribution systems have the common shortcoming that water must be distributed through some rotational criteria. This type of distribution is necessary to spread the benefits of scarce resources. Irrigation systems based on on-demand delivery scheduling offer flexibility to farmers and greater potential profit than other types of irrigation schedules. However, in this type of irrigation system, the network design has to be adequate for delivering the demand during the peak period whilst satisfying minimum pressure constraints along with minimum and maximum velocity constraints at the farm delivery points (hydrants) and in the pipes, respectively. In this paper, optimum design and management of pressurized irrigation systems are considered to be based on rotation and on-demand delivery scheduling using a genetic algorithm. Comparison is made between the two scheduling techniques by application to two real irrigation systems. Performance criteria are formulated for the optimum design of a new irrigation system and better management of an existing irrigation system. The design and management problems are highly constrained optimization problems. Special operators are developed for handling the large number of constraints in the representation and fitness evaluation stages of the genetic algorithm. The performance of the developed genetic algorithm is assessed in comparison to traditional optimization techniques. It is shown that the methodology developed performs better than the linear programming method and that solutions generated by the modified genetic algorithm show an improvement in capital cost. The method is also shown to perform better in satisfying the constraints. Comparison between on-demand and rotation delivery scheduling shows that a greater than 50% saving can be achieved in total cost at the cost of reducing flexibility in the irrigation time. Finally, it is shown that minimizing standard deviation of flow in pipes does not result in the best distribution, and therefore minimum cost, neither for systems with uniform flows or those with large variations in discharge at hydrants.     

Farmers’ Adaptation and Regional Land-Use Changes in Irrigation Systems under Fluctuating Water Supply, South India

In closing river basins where nearly all available water is committed to existing uses, downstream irrigation projects are expected to experience water shortages more frequently. Understanding the scope for resilience and adaptation of large surface irrigation systems is vital to the development of management strategies designed to mitigate the impact of river basin closure on food production and the livelihoods of farmers. A multilevel analysis (farm-level surveys and regional assessment through remote-sensing techniques and statistics) of the dynamics of irrigation and land use in the Nagarjuna Sagar project (South India) in times of changing water availability (2000–2006) highlights that during low-flow years, there is large-scale adoption of rainfed or supplementary irrigated crops that have lower land productivity but higher water productivity, and that a large fraction of land is fallowed. Cropping pattern changes during the drought reveal short-term coping strategies rather than long-term evolutions: after the shock, farmers reverted to their usual cropping patterns during years with adequate canal supplies. For the sequence of water supply fluctuations observed from 2000 to 2006, the Nagarjuna Sagar irrigation system shows a high level of sensitivity to short-term perturbations, but long-term resilience if flows recover. Management strategies accounting for local-level adaptability will be necessary to mitigate the impacts of low-flow years but there is scope for improvement of the performance of the system.     

Water Reuse in Sequential Basin Irrigation

Level basins, when properly designed and managed, often attain very high irrigation efficiencies. Problems can arise when the infiltrated depth exceeds the soil water holding capacity or when the crops are sensitive to waterlogging. Both cases could benefit from allowing part of the applied water to run off the basin. This water can be reused for on-farm irrigation of the subsequent basin. Such a setup will be referred to as the “runoff rescue” (RR) system. In this work, an RR system composed of five adjacent terraced basins is described and evaluated. The basins were connected by outflow points located at the upstream and downstream ends of the fields. To provide terms for comparison, the performance resulting from conventional irrigation (without RR) of each basin was estimated using a simulation model. The RR system showed reductions of 14, 16, and 24% in irrigation time, infiltrated depth, and recession time, respectively. The average increments for distribution uniformity and application efficiency were 2 and 9%, respectively.     

Operational Sensitivity of Irrigation Structures

The adjustment of structures along irrigation free-surface systems aims to achieve, or maintain, a targeted status of the canal network. The interaction between structures and reaches is an important aspect of canal control and the process of the operation itself can generate perturbations. These perturbations depend on the frequency and mode of operation as well as the sensitivity to the setting of the structures. Highly sensitive structures generate relatively large changes in their outputs for small input changes. Therefore, highly sensitive structures should be operated with more precision than others to minimize deviations between the actual and targeted states. Knowing which are the sensitive structures along a canal and how to operate them is essential for a cost-effective operational procedure. This paper presents a set of sensitivity indicators that enable the identification of sensitive structures and an assessment of their operational tolerance.     

Using HYDRUS-2D Simulation Model to Evaluate Wetted Soil Volume in Subsurface Drip Irrigation Systems

Drip irrigation is considered one of the most efficient irrigation systems. Alternatively to the traditional drip irrigation systems, laterals can be installed below the soil surface. Realizing the subsurface drip irrigation (SDI), which recently has been increasing in use as a consequence of advances in plastics technology, making SDI equipment more affordable and long lasting. Due to its potential high efficiency SDI may produce benefits, especially in places where water is a limited source. As the use of SDI is relatively new, a better understanding of the infiltration process around a buried point source can contribute to increased water use efficiency and consequently the success of drip irrigation system. In addition, proper design and management of such a system needs the judicious combination of drip spacing, discharge rates, irrigation duration and time interval between consecutive irrigations. To this aim, numerical models can represent a powerful tool to analyze the evolution of the wetting pattern during the distribution and redistribution processes, in order to explore SDI management strategies, to set up the duration of irrigation, and finally to optimize water use efficiency. In the paper the suitability of the HYDRUS-2D simulation model is verified, at the scale of a single emitter, on the basis of experimental observations, with the aim to assess the axis-symmetrical infiltration process consequent to subsurface drip irrigation. The model was then applied in order to evaluate the main dimensions of the wetted soil volume surrounding the emitter during irrigation as a function of time and initial soil water content. The investigation, carried out in a sandy-loam soil, showed the suitability of the model to well simulate infiltration processes around an emitter during irrigation. Model application allowed also, for the examined soil, to evaluate the emitter spacing accounting for the maximum soil depth to irrigate.