Equity of water distribution along secondary canals in Punjab,Pakistan

Equity in the distribution of irrigation water has long been an operational objective for the management of the large canal systems in the north and west of the Indian subcontinent. How well that operational objective continues to be met is the central concern of the research reported in this paper. Detailed studies of canal operations were conducted on three distributaries in the Lower Chenab Canal system in Punjab Province, Pakistan. Mananwala and Lagar Distributaries off-take in the head reach of the Gugera Branch Canal and Pir Mahal Distributary is at the very tail of this Branch. Flow conditions for these distributaries and of selected outlets served by each were measured daily throughout 1988, and data were converted to discharges. These field observations show that discharge variation at the head of distributaries greatly exceeds the original design criteria. The data also indicate that two design assumptions for outlets are no longer valid: continuous full supply water level in the distributary and outlet modular flow conditions. Field measurements confirm that the distribution of surface water among the outlets of all three distributaries is substantially inequitable. Outlets in the channels' head reaches commonly draw 3 to 6 times greater share of total supplies than do tail outlets. Although all three selected distributaries are perennial canals, some outlets remained dry for up to 90% of the total operational days in a year. Finally, evaluation of field data also shows that better operational procedures at the distributary level can substantially improve water supply conditions in the tail reaches.     

Using a hydro-dynamic flow model to plan maintenance activities and improve irrigation water distribution: application to the Fordwah distributary in Punjab, Pakistan

In secondary canals in Pakistans Punjab, the waterdistribution depends on the hydraulic characteristicsof channels, cross-structures and tertiary outlets.Maintenance of channels and structures plays a crucialrole in upholding equitable distribution of water tothe tertiary units. In the past, maintenance has beenundertaken by irrigation managers based on experienceand observations. In the present study a hydro-dynamicmodel (SIC – Simulation of Irrigation Canals) is usedto assess a priori the impact of maintenance measureson water distribution. Maintenance measures can thusbe selected that remove existing bottlenecks in thewater distribution in the most cost-effective way. The methodology is applied to a secondary canal insouth-east Punjab. The simulation results show thatthe main cause of present inequity in waterdistribution are deviations in dimensions of tertiaryoutlets, which, if restored, would make the mosteffective contribution to improve the waterdistribution. Maintenance of the channel is necessaryif its capacity diminishes.     

Water distribution on a large distributary,Tungabhadra, India

Results are presented of field research on water distribution in the command area, covering 18,200 ha, of a secondary irrigation canal in the Tungabhadra Left Bank Scheme, Karnataka State, India.The official objective of the Scheme and the resulting implications for the water distribution are discussed first. An explanation of the planning and operation of the water distribution follows.The results are based on analyses of the water flows taken from the D36 secondary canal and distributed along the canal to the pipe outlets (inlet structures to the tertiary units), and of the canal section rotation practised along the canal. The analyses concentrate on three dimensions of the water supply:The design flows, according to the official Scheme objectives and criteria;The targets, as set by the system operators before every season;The actual distribution procedures and flows, as observed during the operation.The analyses, supported by flow measurement data, illustrate that the water distribution is not based on consistent and clear criteria and procedures, but that it is the outcome of varying compromises, decided upon pragmatically by the field staff, to bridge the gap between the farmers' demands and the upstream constraints to water availability. This paper explains the widespread phenomenon of head reaches taking too much water, leaving little or nothing for the tail end of the canal.     

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.     

Linking water market functioning, access to water resources and farm production strategies: example from Pakistan

As a response to inadequacy in canal water supplies, farmers in Pakistan have invested in private tubewells to control irrigation water resources. Also, they participate in surface water and groundwater markets that take place within tertiary units of the irrigation system.The present paper describes the functioning and organization of these water markets, using information collected in sample watercourses of the Fordwah Branch irrigation system, South-Punjab, Pakistan. The variability in type and intensity of water markets is investigated with regard to access to water resources and farm production strategies and constraints.     

Comparing water management in rice-wheat production systems in Haryana, India and Punjab, Pakistan

The intensive irrigated rice-wheat systems in the northwest Indo-Gangetic Plains of South Asia are built on a long tradition of canal irrigation and the more recent advent of tubewells. Findings from farm surveys are used to examine water management and water productivity in the rice-wheat belt of India's Haryana State and Pakistan's Punjab province. Attributes of the irrigation sources help explain the widespread interest in groundwater use and the relative demise of canal water use. In each area groundwater now is the main irrigation source, used either solely or in conjunction with surface water. The ownership of tubewells is near universal among the surveyed farms, whereas conjunctive water use is more widespread during the monsoon season, among better endowed farmers and in the Pakistan Punjab. In Pakistan Punjab farmers primarily rely on diesel powered tubewells whereas Haryana farmers mainly use relatively cheaper electric power. Water productivity indicators for rice are markedly lower than those for wheat—largely reflecting significantly higher water inputs in paddy cultivation—but also vary between the study areas and by the prevailing water use, reflecting the limited incentives for farmers to use water wisely. A combination of technological, land use and market based approaches is likely to be most effective in achieving sustainable water management in these intensive cereal systems.     

Spreadsheets for water management — a case study from the Brantas Delta,East Java

The use of commercially available spreadsheet programs for scheduling of water supplies for large scale irrigation networks is a relatively new phenomenom. The paper describes the development and application of such a program for a 30 000 ha irrigation scheme in the Brantas Delta, East Java. The program has been in use for day-to-day scheduling of main system supplies since April 1986, during which time refinements and adjustments have been necessary to formulate a working package. The paper draws conclusions regarding the value of the program for improving water management.     

Conjunctive use of canal and groundwater in Punjab,Pakistan: management and policy options

Data from 41 watercourses commands in Pakistan show that, as expected, farmers in head end reaches of canals receive more canal water than those in tail end reaches. Contrary to conventional wisdom, however, these head end farmers also use more groundwater than those at the tail end. Overall, groundwater plays a more important role in irrigation than surface water, ranging from 65% dependence on pumped water in head end areas to over 90% in tail end areas. This means that groundwater is no longer supplemental to canal water, but is an integral part of the irrigated agricultural environment. However, the cropping choices of farmers appear to reflect the amount of good quality canal water they receive: head end farmers are able to grow more high value basmati rice in the summer and more vegetables in the winter, leaving tail enders to rely on less valuable crops such as fodder and wheat.Tail end areas are not only deprived of their fair share of surface water: they have to pump proportionately more groundwater which shows decreasing quality towards the tail. Typically, head end areas have groundwater with EC values of less than 1.0 dS/m, rising to over 2.0 dS/m in tail end areas. When the quality of both surface and groundwater used by farmers is examined, only the top 40% of the distributary gets water of adequate quality, the next 40% get below average quality, while the tail 20% of farmers irrigate with water that is classified as saline.Because of higher dependence on more expensive groundwater tail enders use less water per unit area, thereby reducing the leaching requirement. The result is a clear increase in soil salinity from head to tail along distributary canals, and there is some evidence of land abandonment in tail end watercourses due to excess salinity.The implications of these results are far reaching. Government policy includes plans to divert significant quantities of fresh canal water to areas underlain by saline groundwater on the basis that farmers already have adapted to pumping fresh groundwater. The results reported suggest that if this policy were implemented, there is a risk that over-dependence on fresh groundwater could lead to an intensification of the rate of soil salinization and deterioration of quality in areas currently classified as fresh groundwater zones.At present, the location and utilization of privately owned shallow tubewells is not monitored, and thus it is not possible for government agencies to determine just how much water of different qualities is being used. Further, canal water deliveries, public deep well monitoring, watercourse monitoring programs, soil salinity measurements, and agricultural performance monitoring are all scattered among different agencies and organizations, making the task of effective conjunctive management of surface and groundwater even more difficult.Conventional wisdom: Groundwater in Pakistan ... where it exists within the canal system ... is used to supplement surface water supplies to meet peaks in demand. (WAPDA, 1990)     

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.     

A new approach to water management of tropical peatlands: a case study from Malaysia

The use of peatlands in the humid tropics requires drainage to remove excess rainfall. The design principles for the drainage systems currently being implemented on peatlands are the same as for mineral soils. The objective of such systems is the timely removal of excess rainfall by surface runoff. For peatlands, with their different soil-hydraulic characteristics, these systems have resulted in poor watertable control and high rates of irreversible subsidence. Concerns about this rate of subsidence and the level of sustainability of the present land use have prompted a study to develop a new water management system. This new system includes a shift from a drainage system that focuses on discharge of excess water towards a system that combines drainage and water conservation. In the new two-step design, the drain spacing and corresponding drain discharges are obtained with a steady-state approach. These outputs are used to calculate the capacity of the drains, including control structures, using an unsteady-state approach. The new system results in a shallower but more narrowly spaced drainage system and maintains a more constant but relatively high watertable and reduces subsidence. It should be remembered however, that even with the improved water management, subsidence cannot be arrested; it is the price one has to pay for the use of tropical peatlands.     

Performance assessment of irrigation water management of heterogeneous irrigation schemes: 2. A case study

The non-uniformity of soils, weather, fields, cropping pattern and canal systems in most surface irrigation schemes makes irrigation water management complex, but optimum performance is important particularly in irrigation schemes with limited water supply. This paper focuses on the performance of irrigation water management during the area and water allocation with a case study of an irrigation scheme in the semi-arid region of India. Often the irrigation managers or authorities of these heterogeneous irrigation schemes also need to deal with different allocation rules. The allocation plans and the corresponding water delivery schedules during the allocation process were estimated with the help of a simulation–optimisation model for different allocation rules based on cropping distributions (free and fixed), water distributions (free and fixed-area proportionate), irrigation depth (full, fixed depth and variable depth irrigation) and irrigation interval (from 14 to 35 days). The performance measures of productivity (in terms of net benefits and area irrigated), equity (in water distribution), adequacy and excess were assessed for these different allocation plans and schedules. These were further compared with the performance measures of the existing rule (fixed depth irrigation at a fixed interval). The analysis revealed that these performance measures are in some cases complimentary and in other cases conflicting with each other. Therefore, it would be appropriate for the irrigation managers to understand fully the nature of the variation in performance measures for different allocation rules prior to deciding the allocation plans for the irrigation scheme.     

Effects of construction defects on hydraulic performance of Kalpani distributary, NWFP, Pakistan

The hydraulic performance of canals designed to deliver water by proportional allocation is highly dependent on the accuracy of construction of water division structures. If construction is inaccurate then inequity of water delivery is built into the system from the onset. A survey of hydraulic performance of Kalpnai distributary in NWFP Pakistan immediately after construction showed that the canal could only deliver 90% of designed discharge due to deficiencies in construction of two siphons, and that the tail end of the canal only received 70% of designed discharge. When operated at 70% of design discharge tail end reaches received 50% of designed discharge. Measurements of outlet structures showed that 57% of structures were built as intended and had not been damaged. All orifice outlets delivered more than 115% of design discharge and on average delivered 40% more than intended. Only 20% of open flumes were within 10% of design width, while 58% were more than 30% wider. As a result of these construction defects many watercourses were able to obtain much higher discharges than intended. The lack of control gates means there is no managerial remedy to redress the existing inequity. The only solution is to reconstruct a high proportion of outlet structures. Potential causes of poor construction are many, including lack of involvement of the agency responsible for subsequent operation, lack of dialogue with water users, and lack of accountability built into the project framework.     

The use of measured water flows in furrow irrigation management — a case study in Swaziland

The use of measured water in controlling flows for the irrigation of sugarcane was found to be vital for the rehabilitation and management of surface irrigation on a 5000 ha sugarcane project. Methods of water delivery, measurement and control at Inyoni Yami Swaziland Irrigation Scheme (IYSIS) are described. Improvements to the irrigation, using existing methods of water measurement, were carried out over a period of four years. The lessons gained in this programme of improvements confirmed the benefits of using modulus gates which allow a constant, measured, discharge of water.     

Estimation of a network irrigation efficiency to cope with reduced water supply

The overall irrigation efficiency, e_p, for the irrigationnetworks in the Thessaloniki plain, in Northern Greece, wasestimated from historical data, spanning eight years. Irrigationnetworks differ regarding the method of water delivery and themethod of field application. Overall irrigation efficiency is theparameter which helps to adjust water supply to meet the actualcrop water requirements. A method is introduced which calculatesnetworks e_p using spatially distributed data. Efficiencyvalues for all systems were calculated using the proposed method.Seasonally averaged e_p values for eight years for 32(surface and sprinkler) irrigation networks ranged from 0.38 to0.81. Analysis of the time series e_p values can identifyoperational factors that might affect network e_p. Sprinklerand surface network irrigation efficiencies did not show anysignificant difference.     

The financial viability of irrigation management companies: A case study of Cu Chi irrigation system,Vietnam

A crucial, yet little understood, element in the economic studies of irrigation is the role played by companies who manage the supply of water. Many of these companies are publicly managed as they have the potential to act as monopolists. Possibly as a consequence of their ownership structure, analysts have questioned the economic viability and management of these firms. The case is made that many of these companies do not run profitably, that they rely on government subsidies to survive, that they do not spend enough on maintenance and that they run down their capital base. The purpose in this paper is to specify the measures that allow analysts to examine the financial viability of a publicly owned irrigation management companies and to apply these to a scheme in Vietnam. Of concern and contention in any irrigation scheme is the price that a company should charge for water in order to recover costs in the short-run. It was found that the company under investigation could not operate without subsidies and did run down their assets. It was found that a great disparity exists between what the consumers were charged for water and what the company received for supplying it. To ensure the sustainability of the Irrigation Management Companies in long term, they may have to increase the water fee by 3.75 times the current rate set by the provincial government (US$ 20 per ha).     

Modernization of irrigation systems: A case of research,oriented to improve management

In recent years, the traditional concept of an irrigation project has been changing. From just a physical structure for the storage, conveyance and distribution of water, it is now being regarded as a more complex system, including farmers' participation. This implies an improved management in all phases, from reservoir operation to farm management, and therefore the change from simple operation and maintenance to operation, maintenance and management.To face this new challenge, existing projects must be modernized. The Sorraia Irrigation Project is one of those projects. In this paper major problems are identified and it is showed how research (namely through modelling) can be oriented towards an improved management, regarding the conveyance and distribution systems as well as the on-farm systems.Finally it becomes evident that beyond the technical problems to be solved, the involvement and participation of farmers must be improved at all levels of management. Hence, there is also a need for implementing programs on education, training and extension.     

Drainage water salinity of tubewells and pipe drains:: A case study from Pakistan

Drainage water salinity data from 71 public deep tubewells and 79 pipe drainage units near Faisalabad, Pakistan, were studied. Drainage water salinity of the tubewells and the pipe drains remained approximately constant with time. This was attributed to the deep, highly conductive, unconfined aquifer underlying the area, which facilitates lateral groundwater inflow into the drained areas. Tubewells alongside surface drains showed average electrical conductivity, sodium adsorption ratio, and residual sodium carbonate values of 3.2 dS m⁻¹, 17.2 (meq l⁻¹)^0.5, and 6.4 meq l⁻¹, respectively. For pipe drains, which are situated in areas with comparable conditions, the corresponding values were 2.5 dS m⁻¹, 12.2 (meq l⁻¹)^0.5, and 3.7 meq l⁻¹, respectively. Tubewells have an inferior drainage water quality because they attract water from greater depths, where the water is more saline.     

Performance of agency-managed and farmer-managed irrigation systems: A comparative case study at Chitwan, Nepal

Management reforms are considered one of the best alternatives in increasing efficiency of the irrigation systems. Transfer of day-to-day operation and maintenance to farmers is not a new concept. However due to lags, even now it is a hot issue in developing countries and Nepal is not an exception. In this context of growing argument about the transfer of management of public irrigation systems to the Water Users' Group, this paper examines the comparative performance of farmer-managed and agency-managed irrigation systems. Khageri Irrigation System in the Chitwan district of Nepal was taken as the study site where complete management transfer has been done in 1996. The situations before and after complete transfer were compared. Intensive case studies of the selected farmers showed that equity in distribution of water and leakage had significantly improved after management transfer. Logit analysis revealed that age and education level of the household head, distance from main canal, leakage of the canal and equity in distribution are significantly related to the satisfaction level of the beneficiary farmers from FMIS compared to AMIS. However, landholding size of the respondent farmer has no significant effect. Similarly results from t-test revealed that rice productivity and overall profits from agriculture has also increased significantly due to irrigation management transfer.     

Managing the water balance of The Fayoum Depression,Egypt

A study of the water balances of The Fayoum irrigated lands and Lake Qarun was made to investigate the management of the irrigation system and the efficiency of irrigation water use. The two water balances are strongly interrelated. The drainage flow to Lake Qarun and the water level of the Lake are in delicate balance. A rise in Lake level causes the inundation of adjacent land. Management of The Fayoum water balance assumes control over irrigation water flows, but this control has technical and organizational limitations. Also discussed is the influence of irrigation practices in The Fayoum on the water balance (e.g., the autumn flushing of fields and farmers' preference for not irrigating at night in winter). Notwithstanding a high overall efficiency, irrigation efficiency during the winter is low. The reasons for this are given, together with the constraints against improving system management. Improved uniformity of the division and application of irrigation water will enable a better technical control of flows and will result in better water management in The Fayoum. Abbreviations: FID — Fayoum Irrigation Department, 1 feddan (fe) — 0.4 ha, 1 mcm — 1 million cubic metres: an average annual flow of 3.17 m³/s gives 100 mcm, m³/fe.year — supplied volume (m³) per surface area (fe) per year: 1000 m³/fe.year equals 240 mm/year, MSL — Mean Sea Level     

压力对低压喷头水量分布模型影响的试验研究

为研究喷头压力对水量分布模型的影响,以低压喷头为例,对其进行水力性能试验.通过计算矩形组合下不同压力的喷灌组合均匀系数C_u和组合分布均匀系数D_u,探索喷头压力对水量分布模型的影响.结果表明:对于低压喷头,喷灌强度随压力增大先逐渐增大,达到一定值后基本保持不变.在距喷头不同距离时,不同压力下的喷灌强度变化情况不同.在低压范围内,压力对喷灌组合均匀系数和组合分布均匀系数的影响较明显.在100~200 kPa范围下,C_u和D_u均随着压力的增大而增大.在200~300 kPa范围下,C_u与D_u均变化不大.最终提出二者的函数关系式,为多因素下水量分布模型的建立提供理论依据.