Tertiary Canals Research Articles

Critical and Normal Depths in Semielliptical Channels

AbstractNormal and critical epths are important parameters in the design, operation, and maintenance of open channels. Semielliptical, prefabricated channels are widely used as tertiary canals in irrigation networks. In semielliptical channels, the governing equations are highly nonlinear in the normal and critical flow depths; thus, the solution of the implicit equations involves numerical methods. The main challenge with semielliptical sections is the calculation of the wetted perimeter. The wetted perimeter of semielliptical sections can be expressed in terms of incomplete elliptic integrals of the second kind. The elliptic integrals can be computed simply using commercial mathematical software, but most engineers who use a simple tool such as Microsoft Excel need a simple yet accurate expression for computing the wetted perimeter. Because elliptic integrals cannot be directly computed using Excel, a simple and accurate expression with maximum error less than 0.07% (near exact solution) is proposed for...

Improving Irrigation Water Delivery Performance of a Large-Scale Rice Irrigation Scheme

AbstractThe availability of irrigation water and its equitable allocation in a large-scale rice irrigation scheme of Malaysia have been modeled. The model reliably estimates available water for irrigation at the intake of the main canal and simulates the recommended irrigation deliveries for 120 tertiary canals. Different water allocation and management scenarios were evaluated based on the sensitivity of the growth stages of rice to water, varying field-water demand, and perceived water shortages. The model provides a quantitative assessment not only of water allocation for irrigation but also of day-to-day or periodic irrigation delivery performances for a large-scale rice irrigation system. It provides 86% adequacy and 87% equity of irrigation delivery in the main season (August–December). The corresponding performance indicators provided by the model are 74 and 89% in the off-season (February–June). The dependability of water supply is higher in the off-season than in the main season, while the relati...

LONG‐TERM EFFECTIVENESS OF LINING TERTIARY CANALS IN THE INDUS BASIN OF PAKISTAN

ABSTRACTThis study was conducted to determine the effectiveness of lining tertiary canals with respect to their lining age. Twenty partially lined canals (1–25 years of lining age) were randomly selected and these were classified into five age groups with a class interval of 5 years. The flow rate of each selected channel was measured at the head and tail of the lined sections, and in the unlined sections at a distance equal to the length of the lined sections. The conveyance losses varied from 0.76 to 1.31 l s‐1 per 100 m length. The lowest losses were observed in the newly lined canals (1– 5 years old) while the highest losses were observed in the case of group IV, having a lining age of between 16 and 20 years. The conveyance losses were reduced by 47 and 30% respectively in groups I and V. Thus, these results clearly demonstrate that the effectiveness of lining decreases with its age. A significant amount of water is saved by the newly lined canals; however, this benefit decreases as the lining become older. Copyright © 2013 John Wiley & Sons, Ltd.

Assessment of irrigation practices at the tertiary canal level in an improved system—a case study of Wasat area, the Nile Delta

Egypt faces great challenges due to its limited water resources by enforcement policies to improve the performance of the existing delivery system and its development. The improvement of irrigation systems in the Nile Delta is one of the most important attempts in Egypt to implement more effective irrigation technologies. This study was carried out to evaluate improved tertiary canal level and farmers’ practices by comparing with other unimproved systems to understand the farmers’ practices in their farms after modifying the existing irrigation system. This study area applied to the Wasat command area’s most commonly used to the cultivation of a paddy field in Egypt, which contributes 40 % of production. The overall results indicate that the water-use application at the improved system level improved. This was due to the role of water user association in the successful management and operation of the water-supply system on the private level of water distribution network. So, water users’ association has the positive effect on managing of the improved tertiary canal. Although, there are main problems of water delivery in the irrigation networks that was a water shortage in the main canal owing to its location at the tail of the feeder canal system in the Nile Delta, and other reasons include the absence of crop production planning by farmers, especially rice farmers in summer, and the greater demand of some fields than supply.

Patterns of variability in large-scale irrigation schemes in Mauritania

Large-scale irrigation schemes have not yielded the expected outcomes in Sub-Saharan Africa. In Mauritania, average land productivity of rice schemes lies between 3 and 3.5tha−1 and irrigated land has progressively being abandoned. At the same time, there is new international attention towards interventions in large-scale irrigation in the Sahel. Spatial and temporal variability of production are main causes of low productivity of large-scale irrigation schemes in Mauritania and threats to their sustainability. The present paper focuses on the performance of three representative large-scale schemes located along the River Senegal by analysing intra-scheme variability with respect to yield and irrigation intensity using field observations and satellite images. A sample of tertiary canals was selected in each irrigation scheme for weekly surveys of irrigation processes and maintenance. Yield measurement, irrigation (II) and harvest intensity (HI), indicators of irrigation adequacy (IIA) and drainage adequacy (IDA) constituted the basis of this analysis. Semi-structured interviews with the different actors at the various management levels (farmers; cooperatives; union of cooperatives; state irrigation agency; and the private service provider managing the water delivery in one of the schemes) were held in order to gain information on irrigation and drainage infrastructure, organisation and management of the schemes, financial aspects and irrigated surface. Within each irrigation scheme, a great variability was detected with respect to irrigation intensity and yield. Irrigation intensity could vary as much as from 0 to 1 whilst yield could range from 0.4 to 7tha−1 in a single scheme.The analysis of water distribution patterns at scheme level indicated that variability in irrigation supplies and drainage were main sources of variability of yields and irrigation intensity. Physical, technical, and organisational factors underlie non-uniform water distribution patterns. The understanding of the origins of patterns of variability is a first step towards a more realistic assessment of schemes’ sustainability and contribution to food security.

Usefulness of Empirical Equations in Assessing Canal Losses through Seepage in Concrete-Lined Canal

AbstractThe correct estimation of conveyance water losses from an irrigation system is vital for the proper management for the system. Seepage is the most dominant process by which water is lost in the canal. Thus, for the effective operational planning and management of an irrigation system, a dependable forecasting of the seepage is very important. Seepage rates are obtainable either by direct measurement or by estimation. This study investigated the usefulness of the equations of Moritz and Davis-Wilson in estimating the seepage losses of concrete-lined canals. Seepage losses of the concrete-lined trapezoid canals of the Menemen irrigation system at the end of the Gediz basin were measured by the inflow-outflow method and the results were compared with the estimates of seepage losses given by the use of these two equations. Average seepage losses were measured as 107.6 l s-1 km-1 for the main canal, 32.1 l s-1 100 m-1 for the secondary canals, and 11.7 l s-1 100 m-1 for the tertiary canals. Stand...

Determination of water conveyance loss in the ahmetli regulator irrigation system in the lower Gediz Basin Turkey

AbstractDetermining the water conveyance loss in large‐scale irrigation systems is important not only from the points of view of irrigation programming and optimum allocation of deficit resources but also for the sustainable operation of the system. The aim of this investigation is to determine the conveyance losses of the concrete‐lined main secondary and tertiary canals in the Right Bank Irrigation System of the Ahmetli Regulator in the Gediz Basin Turkey. The investigation was carried out according to the inflow–outflow method. Average conveyance losses of the main (0.067 l s−1 m−2) secondary (0.119 l s−1 m−2) and tertiary canals (0.030 l s−1 m−2) were found to be higher than either the average conveyance loss of Turkey or the seepage standard of the Bureau of Reclamation. It may be suggested that associations responsible for maintenance repair and operation of the system can be supported financially to reduce conveyance loss. Apart from this application of new technologies with lower cost to the systems will reduce conveyance losses. In addition the participation of farmers in the maintenance of the network will ensure that the system is used more rationally. In this way most of the operational problems of the system can be solved. Copyright © 2010 John Wiley & Sons Ltd.

Local Irrigation Management Institutions Mediate Changes Driven by External Policy and Market Pressures in Nepal and Thailand

This article assesses the role of local institutions in managing irrigation water use. Fifty irrigation systems in each country were studied in Nepal and Thailand to compare the influence of local institutions on performance of irrigation systems amid changes in external policy and market pressures. Nepal's new irrigation policy after the re-instatement of multiparty democracy in 1990 emphasized participatory irrigation management transferring the management responsibility from state authorities to water users. The water user associations of traditional farmer-managed irrigation systems were formally recognized by requiring registration with related state authorities. In Thailand also government policies encouraged people's participation in irrigation management. Today water users are directly involved in management of even some large irrigation systems at the level of tertiary canals. Traditional communal irrigation systems in northern Thailand received support for system infrastructure improvement but have faced increased interference from government. In Thailand market development supported diversification in farming practices resulting in increased areas under high water-demanding commercial crops in the dry season. In contrast, the command areas of most irrigation systems in Nepal include cereal-based subsistence farming with only one-third having commercial farming. Cropping intensities are higher in Nepal than in Thailand reflecting, in part, differences in availability of land and management. In both countries local institutions play an important role in maintaining the performance of irrigation systems as external drivers and local contexts change. Local institutions have provided alternative options for irrigation water use by mediating external pressures.

Estimating the effectiveness of a rotational irrigation delivery system: A case study from Pakistan

AbstractIn this study, basic principles of the rotational irrigation water delivery system of Pakistan (i.e. the warabandi) and the performance of the warabandi system under current socio‐economic conditions have been investigated from a farmers' survey completed from 154 farmers located on five watercourses of the lower Indus River Basin. It is shown that irrigation water allocation based on very limited criteria does not give much incentive to the farmers for improving agricultural income. Also, the survey results suggest that the productivity of limited irrigation water could not be maximized under the warabandi system. We have therefore suggested the basic principles of the warabandi system should be revised by making them suitable for the current socio‐economic conditions. We propose that the existence or non‐existence of fresh groundwater resources along with other critical variables should be taken into consideration when making canal water allocation decisions. A framework to allow distribution equity and efficiency in water allocations – such as considering the gross area of a tertiary canal, sensitivity of crop growth stage to water shortage, crop value, bias of allocation towards most water use efficient areas, the potential losses from water deficiency, etc. – should be developed as a tool to improve water productivity for Pakistan and for individual farmers. The contribution of groundwater in the farmers' income from agriculture and the economic value of irrigation water have also been estimated. Copyright © 2009 John Wiley & Sons, Ltd.

PEMODELAN FLUKTUASI MUKA AIR TANAH UNTUK MENDUKUNG PENGELOLAAN AIR PADA PERTANIAN LAHAN RAWA PASANG SURUT TIPE A/B

The objectives of this research are to develop a model of water table fluctuation on tidal lowland area of A/B type. The results of the research are expected to support of the agricultural development on tidal lowland area, especially on water management, because the water management play an important role in the agricultural on tidal lowland area. The water table on tidal lowland area fluctuates according to space and time. The water table controls at a certain depth can support the plant growth and the pyrite oxidation restraint. The model of water table fluctuation which is developed in this research based on the ellipse concept. The research was conducted on the reclamation area of tidal lowland at the fourth tertiary block in P8-12S Delta Telang I, Banyuasin district, South Sumatra province. The simulations of model show good result of estimating the depth of water table on tidal lowland area of A/B type. The proportion of variation the depth of water table which can be explained by model that is 89,6% up to 95,5% with standard error of the estimate is 0,021-0,035 meters. The parameter of the water level in the tertiary canals has high sensitivity to the model.

GIS-Integrated Rice Irrigation Management Information System for a River-Fed Scheme

The Tanjung Karang Irrigation Scheme is one of the large rice granaries in Malaysia. Irrigation management for rice irrigation is difficult because of different planting schedules, variability in soil and crop conditions and unreliable intake of water in the main canal due to the absence of storage reservoir and their uneven distribution to tertiary canals. In view of this concern, the scheme needs the daily estimation of the available water for irrigation and its equitable allocation among tertiary canals to cater trade-offs in water use for the scheme. Easy access of these spatially and temporally distributed data helps to make management system simpler. A GIS-integrated tool known as RIMIS was developed for equitable irrigation supply to tertiary canals and the characterization of their irrigation delivery performance as the season advances. RIMIS dynamically links a field irrigation demand prediction model for the area irrigated by a canal network in GIS. The system can correctly simulate and evaluate recommended irrigation supplies among tertiary canals that match the available discharge at the system head with the crop water demand for the actual field conditions. The user-interface was developed using ArcObjects and Visual Basic for Application (VBA) programming languages in ArcGIS software. RIMIS can give information on the uniformity of water distribution and the shortfall or excess and what decisions to adopt for the next day. It ensures equal sharing of water for the tail-end users. The system helps to keep input and output databases always updated with respect to the real field conditions. The results are displayed on the computer screen together with colour-coded maps, graphs and tables in a comprehensible form. This will help irrigation managers to enhance decision-making in the management and operation of the irrigation system. The development of the overall system and procedures is illustrated with data from a study area.

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 r...

Influence of lateral canal water depth on offtake and cross‐regulator discharge

AbstractMonitoring and effective operation of control structures are of importance in a modern irrigation system. Previously developed sensitivity indicators can be useful tools for better management of irrigation systems. The influence of lateral canal water depth on the offtaking and ongoing discharges were simulated and evaluated using a simple model in the Doroodzan irrigation system in south‐western Iran. Results confirmed the influence of water level changes in the lateral irrigation canal on offtake and cross‐regulator discharge. Results obtained also led us to introduce and evaluate two other sensitivity indicators: offtake sensitivity to downstream water depth, and check sensitivity to tertiary canal water depth.Application of the sensitivity indicators in the Doroodzan irrigation system showed the usefulness of developed sensitivity indicators. The average sensitivity indicators varied from 1.10 to 0.44 (m−1) for offtakes and 0.58 to 0.03 (m−1) for cross‐regulators. Copyright © 2008 John Wiley & Sons, Ltd.

Groundwater and soil salinity variations in a canal command area in Pakistan

AbstractThis three‐year study was undertaken to investigate the groundwater and soil salinity variation in a canal‐irrigated area. Water and soil samples were collected along 54 tertiary canals located on six secondary canals (two each at head, middle and tail end) of a main canal. Data of crop yield and income of the farmers were also collected. The results show that electrical conductivity (EC) of groundwater increased from head to lower reaches along all the irrigation channels, i.e. main, the secondary and the tertiary canals. Similarly, the soil water ECe also increased with increased distance from the head of the irrigation system. Reduced canal water supply at lower reaches of the irrigation system forced the downstream water users to pump more groundwater, thereby increasing their irrigation cost. The deteriorating groundwater quality further adds misery to the downstream farmers by degrading productivity of their lands caused by excessive use of saline groundwater. Location of the water users along the canal irrigation system had an impact on their crop yield as well as income and these parameters decreased with increased distance from the head of the irrigation channels. For example, the net income of the tail‐end farmers varied from 43% to 59% of the head‐end farmers. Copyright © 2008 John Wiley & Sons, Ltd.

Water Productivity in a Rigid Irrigation Delivery System

The rotational irrigation water delivery (warabandi) system practiced in the Indus river basin of Pakistan has continued for 100 years. Irrigation water allocated to the farmers under the warabandi system is proportional to farm size and is fixed. This rigid allocation system has been partly justified by its contribution to social equity though this may have been at the cost of economic gains. In order to assess the operation of warabandi’s basic rules, a farmers’ survey was completed from 124 farmers located on five watercourses. A questionnaire was administered to each farmer and farm management data were gathered. As fresh water resources are under stress and becoming scarce their efficient use in all applications should be assured in water allocations. It is shown from the survey results that water allocation based on very limited criteria does not maximize the socio-economic benefits gained from the use of scarce water. Thus, it is suggested that the existence or non-existence of fresh groundwater resources along with other critical variables should be taken into consideration when making canal water allocation decisions. Missed water deliveries due to failure of the canal system appear to be the largest cause of losses. Water charges need to be increased to fund large improvements in canal maintenance programs. It is pointed out that a framework should be developed as a tool to improve water productivity for Pakistan. This should include: consideration of the gross area of a tertiary canal, sensitivity of crop growth stage to water shortage, crop value, bias of allocation towards most water use efficient areas and water use efficient crops, the potential losses from water deficiency.

Linking Performance and Collective Action—the Case of the Office du Niger Irrigation Scheme in Mali

Increasing irrigation efficiency in irrigation schemes has always been high on the agenda of policy makers. Despite quite some ‘social’ experiments, whereby large portions of management were carried over to the farmer level, results often remained disappointing. This paper explores why this came about for a case study in the Office du Niger irrigation scheme in Mali. Since Irrigation Management Transfer, farmers are responsible for the tertiary level, but collective action for water management remains below expectations. This paper applies an analytical framework based on the conceptual model developed by van Noordwijk et al. (Conserv Ecol 5:21, 2002) and proceeding in two steps. Firstly, an interview-based stakeholder analysis assesses the objectives and mental models of farmers and the central management regarding water management. It appears from the interviews that the central management wants to increase irrigation efficiency through fully-fledged collective action, whereas farmers value the latter only when it favours easy irrigation. Secondly, the relation between collective action and performance was tested through a field study on a sample of 36 tertiary blocks. Results indicate that only collective action at the inlet of the tertiary canal, currently implemented on less than a third of the tertiary blocks, increases irrigation efficiency (with 14%). Collective action for water allocation is implemented within almost three quarters of tertiary blocks and effectively reduces irrigation problems. However, if they lack the necessary social capital, not all farmers can establish collective action when needed. Based on this analysis, the paper proposes a mix of incentives and measures to resolve the conflict between farmers and the central management to their mutual benefit.

Evaluation of Irrigation Canal Maintenance according to Roughness and Active Canal Capacity Values

This work assesses the state of maintenance of the concrete-lined trapezoidal canals of the Menemen irrigation system at the end of the Lower Gediz Basin according to the values of roughness (n) and active canal capacity (ACC). The study was carried out on two main canals, five secondary canals, and 12 tertiary canals at 45 measurement points. Average values of n and ACC were found to be 0.023 and 69%, respectively, for the main canals, 0.018 and 93%, respectively, for the secondary canals, and 0.023 and 81%, respectively, for the tertiary canals. The fact that values of n for the selected canals were higher than projected values and higher than the limit values, which would indicate adequate maintenance, and that the related ACC values were low, indicates that maintenance is insufficient in these canals. In order for maintenance work to be carried out more effectively, it may be suggested that new techniques should be applied for canal linings, which are economical and longer lasting, that farmers who be...

WaDI (water delivery for irrigation): A simulation tool to address strategic interaction of water demand and supply in irrigation schemes

The WaDI (water delivery for irrigation) model deals with the relations between the collective water supply and the demand within irrigated schemes. It is based on a separate modelling of the water supply and demand, including (i) a simplified representation of the hydraulic structure, characteristics and organizational parameters of the scheme, (ii) an assessment of the water demand of farms based on their total irrigated area, cropping pattern and irrigation practices, (iii) a farm typology, (iv) a confrontation between water demand and supply at each node of the scheme from pumping plants to tertiary canals, and (v) calculation of response factors between supply and demand during the peak demand period. “What-if” scenarios are simulated in order to enhance the stakeholders’ capacity to plan strategic decisions such as water delivery allocation rules or infrastructure investments. WaDI was implemented on two Brazilian schemes. It allowed broadening the stakeholders’ limited representation of collective water supply and demand into a more comprehensive understanding of these relations. The approach however showed some limits, along with the difficulty of assessing the real impact on the stakeholders’ capacity for strategic planning.

Spatial productivity along a canal irrigation system in Pakistan

AbstractThis study was undertaken to investigate the impact of location on productivity of the farmers along an irrigation network in Pakistan. Data were collected from 54 tertiary canals situated along six secondary canals: two each at the head, middle and tail end of the main canal. Results revealed that location of the farms has a significant impact on farmers' productivity on different reaches along all the irrigation channels, i.e. the main canal, the secondary and the tertiary canals. The productivity of the tail‐reach farmers varies from one‐third to one‐half of their head‐ reach counterparts. The overall finding of this study is that location of the water users along the canal irrigation system has a significant impact on their income as well as productivity, and these parameters decrease with increase in distance from the head of the irrigation canals. The reduced canal water supply at the lower reaches of the irrigation system forced these water users to pump more groundwater, resulting in a many times increase in their irrigation costs. Additionally, groundwater quality deteriorates all along the irrigation channels (i.e. along the main canal, the secondary and tertiary canals), compounding the misery of the downstream farmers by degrading productivity of their lands because of increased soil salinity. Copyright © 2007 John Wiley & Sons, Ltd.

Estimation of disaggregated canal water deliveries in Pakistan using geomatics

Lack of accurate information on water distribution within an irrigation system is a major roadblock for effective management of scarce water resources. Numerical techniques to estimate canal water distribution require large amounts of data with respect to hydraulic parameters and operation of the hydraulic structures; such data are absent in large irrigation systems. In this study, six quantitative geomatic models, with varying complexity and physical representation, were formulated. They all use high-spatial resolution Landsat-7 images and a canal network stored in a GIS. The models require only the flow rates at the head of the distribution system to calculate downstream water distribution. Results were compared with discharge measurements for three tertiary canals (watercourses) within two selected secondary canals (distributaries), Gajiana and Ghour Dour, in Rechna Doab, Pakistan. The model that computed canal water distribution using the shape of the irrigated area was the most accurate at the watercourse scale. The overall deviation was 28% and the standard deviation of differences between modelled and measured flow was 10%. The model that relates canal water distribution directly to normalized difference vegetation index (NDVI) has the lowest accuracy with a 32% absolute deviation and 16% standard deviation. We conclude that geo-information techniques can be used to compute water distribution in large irrigation systems with a minimum of field data if an appropriate geomatic model is selected.