Regulation of irrigation canals

This article suggests and defines a characterisation of irrigation canal regulation methods, based on four criteria: considered variables (controlled, measured, and control action variables), logic of control, design method (structure and technique) and field implementation (configuration and device). Depending on the chosen criterion and partition rule, different classifications can be built from this characterisation. In conclusion, a structured characterisation table of the main published canal regulation methods is presented.Abbreviations ASCE American Society of Civil Engineers - CACG Compagnie d'Aménagement des Coteaux de Gascogne - CARA Compagnie d'Aménagement Rural d'Aquitaine - CARDD Canal Automation for Rapid Demand Deliveries - CEMAGREF Centre National du Machinisme Agricole, du Génie Rural, des Eaux et des Forêts - CNABRL Compagnie Nationale d'Aménagement du Bas — Rhône Languedoc - ELFLO Electronic Filter and Level Offset - FB Feedback or closed — loop control - FB _dn Feedback or closed-loop downstream control - FB _mi Feedback or closed-loop mixed control - FB _up Feedback or closed-loop upstream control - FF Feedforward or open-loop control - GPC Generalised Predictive Control - LQR Linear Quadratic Regulator - MIMO Multiple Inputs, Multiple Outputs - nI mO n Inputs, m Outputs - P Perturbation - P Estimation of perturbations - PID Proportional, Integral, Derivative Controller - PIR Contrôleur Proportionnel, Intégral, Retard (PI Delay controller) - Q Discharge in the canal - Q _dn Downstream discharge in the canal - Q _in Intermediate discharge in the canal - Q _up Upstream discharge in the canal - SCP Société du Canal de Provence - SISO Single Input, Single Output - U Control action variable - V Volume in a canal pool - V Elementary control action variable - w Regulator gate opening - Y Controlled variable - Y _c Target controlled variable - y Water elevation - y _dn Downstream water elevation of the pool (therefore upstream of a regulator) - y _in Intermediate water elevation in the pool - y _up Upstream water elevation of the pool (therefore downstream of a regulator) - Z Measured variable     

Soil-cement tiles for lining irrigation canals

Laboratory flume test was conducted to investigate the effect of flowing water an soil-cement canal tiles. For this purpose, soil-cement tiles were constructed from different soils at various cement contents. A flume, 3 metre long and 100 mm wide, was lined with the tiles and the lined bed was subjected to flow velocities of around 2 m/s for a period of 7 days. The tiles made from coarse-textured soil (sandy loam and silt loam) aggregates of 5 mm and from fine textured soil (clay loam) aggregates of 2 mm size were found to be intact and smooth even when constructed at a cement contents lower than that needed to meet the durability requirements.Attempts were also made to measure seepage losses of soil-cement tile linings. A channel section of approximately 1 metre length with a side slope of 1:1 was constructed in the laboratory with the tiles and seepage losses measured by the ponding method were found to be in the range of 0.00123–0.00343 m³/m²/day.The results clearly suggest that soil-cement tiles (irrespective of type of soil) made with 2 mm or less size of soil aggregates are erosion resistant and due to very little or negligible rates of seepage losses, the soil-cement tile lining of irrigation canals is expected to be very promising especially in the areas where irrigation water is costly.     

Analytical formulae for the response time of irrigation canals

Two analytical methods are discussed to determine the response time of an open canal system after a change in flow rate. The first method of canal routing is a simple method and is used to determine the filling time of short canal reaches. The prediction error increases for longer canal reaches as a result of neglecting the non-uniform flow conditions. The second method to determine the response time after a change in flow rate, the diffusion approximation, is a more accurate method and valid for canal reaches of any length.     

Regime behavior for alluvial stable Egyptian canals

The design of stable alluvial canals in Egypt is based on regime formulas. These formulas are valid for conditions prevailing before the construction of the High Aswan Dam (HAD), in which the solid suspension was more than 3500 p.p.m. As the regime of Egyptian canals has changed after the construction of HAD (Suspension solid became less than 100 p.p.m.), the design adopted by old regime equations is not satisfactory and a new design concept for the new regime is necessary.In 1982, investigations were carried out in Egypt based on field study on a group of stable alluvial irrigation channels and other collected data from Irrigation Districts and others, from which a series of design formulas for stable canals has been deduced.In this paper a continuation of regime studies have been emphasized by analyzing currently the available field data measurements on thirty alluvial stable channels in Egypt. A more useful relationships have been achieved which may give an approach for a better solution in the scope of stable canal design in Egypt.An investigation of regime theory verifies that the regime formulas of Egyptian Canals are only valid for the limited range of conditions upon which they are based.     

Evaluation of the sand-trap structures of the Wonji-Shoa sugar estate irrigation scheme, Ethiopia

A study was undertaken to evaluate the performance of sand-traps at Wonji-Shoa Sugar Estate, Ethiopia. Inflow and outflow samples from the sand-traps and deposited sediment samples from the sand-traps, main canal, and reservoirs were taken. The samples were analyzed for sediment concentration and particle size distribution. During the study period, the sand-traps were performing satisfactorily in removing a good portion of suspended sediment (as high as 63% in case of sand-trap A and 54% in case of sand-trap B) in the week after flushing and they were performing poor (as low as −40% in case of sand-trap A and 6% in case of sand-trap B) when the sand-trap was running without flushing for about two months. Sediment particle size analyses of the samples indicated that the sand-traps retained almost all the sand fractions (90–95%) greater than 0.15 mm. Fifty to sixty percent of the sediment particles passing the sand-traps into the main canal was smaller than 0.002 mm. Sieve analyses of the bed materials taken from the sand-traps showed that particles up to medium gravel size (6.3–13.2mm) were entering the sand-traps and almost all were trapped. This result shows that performance of the sand-traps under the existing sediment load of Awash River was found to be satisfactory. However, it was observed that performance level of the sand-traps was very much dependent on the flushing interval of deposited sediment.     

Using a hydraulic model to prioritize secondary canal maintenance inputs: results from Punjab,Pakistan

A computer-based hydraulic model,RAJBAH, was used to assess the utility of such models to assist and support canal system managers in planning and targeting maintenance activities on secondary canals. The work was conducted on Lagar distributary, a secondary channel off-taking from Upper Gugera Branch canal, Lower Chenab Canal system, Punjab, Pakistan. Measured discharges of off-takes and water levels along the distributary for premaintenance and post-maintenance periods were obtained. These data were used to assess the impact of actual maintenance inputs at specific locations identified in a model application in 1989. The predicted results of the model were satisfactorily close to conditions measured in the field. The study confirmed that suitably calibrated hydraulic simulation models can be effectively used in a decision support planning capacity to target and prioritize maintenance inputs for secondary canals in the irrigation systems of Pakistan's Punjab.     

Satellite remote sensing in irrigation

Data on flows in irrigation and drainage canals and data on climate, crops, and cropped areas are essential for the management of irrigation systems. Only part of these data can be collected with satellite remote sensing (SRS). This paper discusses the possibilities for the practical use of SRS data in the management of irrigation systems. Satellite remote sensing images are more useful for intra- and inter-seasonal monitoring, with a time horizon of months or years, than for use in day-to-day management of irrigation schemes: either the operation of the system cannot be changed quickly, or the operation would require a more frequent input of SRS data than is at present feasible.     

涌泉根灌技术研究与应用

提出了一种新型涌泉根灌灌水方法,研究设计了一种灌水器,实现了直接将灌溉水输送到植物根系部位的研究目标,研制的涌泉根灌灌水器流态指数小于0.5,属紊流范畴.为了测得不同节水灌溉方式的应用效果,在陕北山地5年生枣树实施了管灌、滴灌和涌泉根灌等工程38.67hm^2,对3种不同灌水方法的经济效益作了分析.结果表明,与不灌溉相比,管灌、滴灌和涌泉根灌的净增收入分别为4707.70,8446.00和10926.00元/hm^2;管灌、滴灌和涌泉根灌每方灌溉水产值分别为1.90,11.30和14.60元/m3.涌泉根灌与滴灌相比,年成本降低2030元/hm^2,净收入增加2480元/hm^2,每方灌溉水产值提高3.30元/m3;涌泉根灌与管灌相比,年成本降低743.30元/hm^2,净收入增加6218.30元/hm^2,每方灌溉水产值提高12.70元/m3.不同节水灌溉方式均使得枣园净收入大幅度提高,尤其是涌泉根灌方式,净增值率高达235.0%.建议在山地经济林果中大面积推广应用涌泉根灌技术.     

变量技术在精准灌溉上的应用

本文通过对精准灌溉系统基本概念的论述,提出变量技术是精准灌溉的技术关键。阐述了变量技术与设备在圆形和平移式喷灌机上的应用,并指出在应用中应注意的问题。     

Innovations in irrigation management and development in Hunan province

Mass movement labor was an important contributor to irrigation system construction in China during the seventies, making up a third or more of system costs. Total per-ha system costs are roughly consistent with those in other Asian countries when contributed labor is valued at estimated farm wage rates, but less than average if zero labor opportunity cost is assumed.Innovative practices are being employed in managing and supporting irrigation system operations in Western Hunan Province. Many are ones which have been advocated repeatedly elsewhere but infrequently applied. These include the volumetric wholesaling of water to distribution organizations, farmer water charges with both fixed and volumetric components, financially autonomous irrigation management agencies, and delegation of water distribution and fee-collection responsibility to village-based organizations. Heavy emphasis currently rests on financial self-reliance of schemes as denoted by the slogan, let water support water. This has led to a proliferation of secondary income-generating enterprises associated with irrigation system management, as well as strenuous efforts to collect irrigation fees. Often the secondary enterprises generate a larger share of total income than does the irrigation service itself.Fee levels for rice generally fall into the $12 to $20 ha/yr range, intermediate to those prevailing in Pakistan at $8.50/ha for two crops of rice and the Philippines at $45/ha for double cropped rice. Collection of fees is typically handled by the village. Charges are usually levied on an area basis but one large system employed a more complicated system which had both fixed and variable components. Water allocation at lower system levels is also delegated to the village in many cases, with the state serving as a wholesale provider of water.Abbreviations and units ha-m hectare-meter - jin unit of weight equal to 0.5 kg - kw kilowatt - mu unit of land area equal to 1/15 ha - Rmb Renmimbi (Yuan) equal to US$ 0.27 officially in September 1988 and about half of that unofficially - RMD Reservoir Management Division - WCB Water Conservancy Bureau - WMD Water Management Department     

Yield measures of irrigation performance in Pakistan

Customary evaluations of irrigation performance based upon crop yield per unit area do not reflect an adequate assessment of performance in water scarce environments such as Pakistan. Yield per unit water is a complementary and sometimes more appropriate measure. This note illustrates the different evaluations based upon yields of irrigated wheat and rice in Pakistan.     

Community managed irrigation in Eastern Nepal

This paper examines several farmer managed irrigation schemes in the eastern hills of Nepal. The development and management structure of these is considered in order to identify characteristics of successful schemes which could be used in planning future projects.     

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.     

Carbon retention in the soil-plant system under different irrigation regimes

Carbon (C) sequestration through irrigation management is a potential strategy to reduce C emissions from agriculture. Two experiments (Exps. I and II) were conducted to investigate the effects of different irrigation strategies on C retention in the soil-plant system in order to evaluate their environmental impacts. Tomato plants (Lycopersicon esculentum L., var. Cedrico) were grown in split-root pots in a climate-controlled glasshouse and were subjected to full irrigation (FI), deficit irrigation (DI) and alternate partial root-zone irrigation (PRI) at early fruiting stage. In Exp. I, each plant received 2.0 g chemical nitrogen (N), while in Exp. II, 1.6 g chemical N and maize residue containing 0.4 g organic N were applied into the pot. The results showed that, in both experiments, the concentration and the amount of total C in the soil were lower in FI and PRI as compared to DI, presumably due to a greater microbial activity in the two treatments; particularly the PRI induced drying and wetting cycles of the soils may cause an increase of microbial activities and respiration rate, which could lead to more C losses from the soil. However, in both experiments the total C concentration in the PRI plants was the highest as compared with the FI and DI plants, and this was seemingly due to improved plant N nutrition under the PRI treatment. Consequently, the total amount of C retained in the soil-plant system was highest in the FI and was similar, but lower, for the PRI and DI. The different N input in the two experiments might have affected the C retention in the soil and in the plant biomass. Nevertheless, with a same degree of water saving, PRI was superior to DI in terms of enhancing C concentration in the plant biomass, which might have contributed to a better fruit quality in tomatoes as reported by [Zegbe et al., 2004] and [Zegbe et al., 2006].     

Drip irrigation water and salt flow model for table grapes in Coachella Valley,California

Unlike annual crops where reclamation leaching of salts can be readily conducted between cropping, leaching of salts in permanent crops that are drip irrigated pose challenges. A need exists to formulate and test a management-type of salinity model for drip irrigation of table grapes. The model reported herein predicts the distribution of salts along the vine row and between the rows during the growing season, as affected by reactivity of salts of the applied irrigation water as well as rate and duration of drip application. The calibrated model reproduced the initial field salinity profiles after repeated irrigation cycles by adjusting only the routing factor α which is the ratio of horizontal to vertical water flow. After eight cycles the profiles stabilized and the calibrated horizontal to vertical flow routing ratio was 0.6. There is remarkable agreement between measured and simulated salinity. Corresponding soil moisture profiles show the expected high water content with depth at the emitter, the decrease in surface water content with radial distance and the increase with depth, at the distal end of the wedge. Although the model is location specific it can be applied knowing soil, initial and boundary conditions, as well as irrigation application quantity and quality and as such can be applied location by location in order to assess flow and quality of deep percolation recharging the groundwater system. With this capacity the model can predict soil water quantity and quality outcomes for possible land and water management scenarios.     

Farmers’ scheduling patterns in on-demand pressurized irrigation

Irrigation scheduling results from the irrigator's integration of meteorological, environmental and crop information. In this paper, the irrigation scheduling patterns of a group of irrigators in the Candasnos Water Users Association (WUA), located in north-eastern Spain, were analysed. Scheduling sprinkler and drip irrigation in this WUA shows additional complications due to the sharing of a collective pressurized irrigation network and to the need to file water orders two days in advance of its foreseen use. The database created by a remote surveillance and control system was mined to obtain the time evolution of hydrant operation time during the 2004–2008 irrigation seasons. Records were selected for clearly identified crops and irrigation systems, and for verified water allocations. Hydrant operation showed a relationship with meteorology (precipitation, wind speed, relative humidity and air temperature), although this relationship was often not evident when hydrants were individually analysed. Statistical analyses were run to classify irrigator's scheduling practices, leading to the establishment of ten different groups. The adopted classification criteria included the average number of weekly irrigations, the SD of the number of weekly irrigations and the modal range of the irrigation starting time. The irrigation pattern was determined by the irrigator (56%), the irrigation system (33%), and the crop (11%). Only in a fraction of the cases (22%) the time change in the scheduling pattern responded to a clear time trend; in 39% of the cases, changes in time appeared random. Further, 45% of the irrigators used the same irrigation pattern in at least half of their hydrant-years, independently of the crop. Only 14% of the irrigators applied different irrigation scheduling patterns to different crops. Our results suggest that irrigators do not find value or do not have the capacity to develop irrigation patterns more consistent and adapted to the local environment, the crops and the irrigation systems.     

Optimal Maintenance in Irrigation

This article asks and addresses thequestion ``what is `optimal' maintenance inirrigation.' It examines alternativedefinitions of irrigation maintenance andexplores pathways of system deteriorationunder alternative input levels. It thendefines maintenance as a service, where thefunctions of arranging, providing, payingfor, and using the service are considered,and discusses the arrangements andrelationships necessary to provide thisservice. Key to this approach is theconcept of maintaining a specified level ofservice – a concept drawn from the assetmanagement approach to systems maintenance. A contingency matrix is developed whichdefines basic maintenance strategies underdifferent levels of cost and risk. Thepaper concludes that optimality ofirrigation system maintenance is somethingwhich cannot be defined on technicalgrounds, or economic ones, or even oninstitutional grounds alone. Rather it mustbe defined as a process operating within aset of framework conditions and technical,economic and institutional constraints.     

三江平原粉质粘性土工程地质特性探讨

三江平原地形平坦,农田水利工程众多,构成各级排干的边坡主要由粉质粘性土组成。由于粉质粘性土粉粒含量高,具有膨胀性,孔、裂隙发育,凝聚力小,在干湿和强烈冻融作用下,易发生变形、破坏。为此,详细阐述了粉质粘性土的工程地质特性,为采取防治措施提供了可靠的依据。     

Changes in hydraulic performance and comparative costs of lining and desilting of secondary canals in Punjab,Pakistan

Observations on the hydraulic changes of lining of secondary canals in Punjab, Pakistan show that performance improvement objectives are not always achieved. If lining is justified on the basis of water savings through reduced seepage losses, then tail end areas should receive improved water deliveries. Observations in two distributary canals following lining do not demonstrate significant improvements in tail end conditions. Justification of lining on the basis of more stable water conditions is also hard to identify; reduction in the variability of discharges was not observed.Financial analysis of a recent canal lining experience in Punjab indicates that water savings would have to be unrealistically high, and sustained for long periods, if the initial capital cost is to be repaid through improved water conveyance efficiency. Furthermore, the hydraulic improvements achieved through alternative interventions appear to strengthen the argument that lining can be justified only under special conditions, rather than adopted as a wholesale approach to solving water distribution problems. Whatever the intervention, management control must be strengthened; lining is not a substitute for effective canal operational and maintenance inputs.