Performance assessment of irrigation water management in old lands of the Nile delta of Egypt

This paper provides the methodology and results of a cross-scale diagnostic performance assessment program of the irrigation water management in the old lands of the Nile Delta of Egypt. The analysis was done at three levels; main canal level, branch canals level and on-farm level of the Meet Yazid command (82,740 ha) for the year 2008?C2009 to highlight areas for improvement. At the main canal level the annual average percentage of irrigation water returning to drains and groundwater was 53% of the total water supplied. Since Meet Yazid lies at tail end of the delta, and there is groundwater salinity, opportunities for reuse are increasingly limited moving north to Lake Burullus. This would indicate opportunities for real water savings. The results of monthly relative water supply of the main canal indicated mismatch between demand and supply especially during the winter months, and when supply is low farmers do reuse drainage or groundwater. Also, the assessment of the three branch canals showed non-uniformity of water distribution and mismatch between demand and supply even when comparing improved and non-improved canals. At the on-farm level in paddy fields, the amount of irrigation flows to drains and saline sinks varied from 0.46 to 0.71 of inflow. In spite of these values of non-uniformity and low depleted fraction, the relative evapotranspiration (ratio of actual to potential) evaporation was uniformly high, indicating most crops of most farmers were not water stressed, which is also confirmed by the high yield values. The average values of productivity per unit water depleted by ET_act were 1.04 and 1.05 kg/m³ for rice and wheat fields, respectively, with yields of rice and wheat at 8 and 6 t per ha respectively. On farm and tertiary improvements alone will not yield real water savings, as excess water in the main canal and drains will continue to flow out of the system. Rather the focus should first be on supplies to the main canal, accompanied by more precise on farm and water delivery practices at branch and tertiary levels, and ensuring that environmental flows are met. There is an added advantage of focusing on this tail end region of Egypt that this response would lessen vulnerability to reuse of polluted and saline water.     

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.     

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)     

复式断面渠道渠系水利用系数测算方法研究

【目的】研究采用复式断面渠道的灌区渠系水利用系数更精确地测算方法。【方法】采用动水测定法测定了渠道各断面水力要素,之后通过修订后的戴维斯-威尔逊公式和考斯加科夫渠道渗漏经验公式求得研究区域复式断面渠道渠系水利用系数,对比分析了各渠道水损失以及渠系水损失量。【结果】动水测定法更适合不断流复式断面渠道水力要素的测算;采用标准梯形断面渠道衬砌的方式渠道损失最小;考斯加科夫渠道渗漏经验公式求得灌区渠系水利用系数为0.75,而戴维斯-威尔逊公式求得灌区渠系水利用系数为0.82,更加接近实际值0.86,精确度提高了9.5%。【结论】由于占地、开挖等影响因素,灌区渠系衬砌后多形成复式断面渠道,灌区渠道衬砌优先采用标准梯形断面衬砌方式。对于这类渠系工程,动水测定方法明显优于典型渠道测量方法,戴维斯-威尔逊公式也更适用于复式断面渠道的渠系水利用系数的测定。     

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.     

Simulation of automatic control of an irrigation canal

Improved water management and efficient investment in the modernization of irrigation schemes are essential measures in many countries to satisfy the increasing demand for water. Automatic control of the main canals is one method for increasing the efficiency and flexibility of irrigation systems. In 2005, one canal in the irrigation scheme ‘Sector B-XII del Bajo Guadalquivir’ was monitored. This canal is representative of irrigation schemes in Southern Spain; it is divided into four pools and supplies an area of 5154 ha. Ultrasonic sensors and pressure transducers were used to record the gate opening and water levels at the upstream and downstream ends of each canal pool. Using the recorded data and the SIC (Simulation of Irrigation Canals) hydraulic model, two canal control options (local upstream control and distant downstream control) were evaluated using a PI (Proportional-Integral) control algorithm. First, the SIC model was calibrated and validated under steady-state conditions. Then the proportional and integral gains of the PI algorithm were calibrated. The controllers were tested using theoretical demand changes (constant outflow followed by a sudden demand increase or decrease) and real demand changes generated on the basis of a spatially distributed crop water balance that included a number of sources of variability (random and not random) in the determination of field irrigation timing and depth. The results obtained show that only the distant downstream controller was able to adjust quickly and automatically the canal dynamics to the varying water demands; it achieved this efficiently and with few spills at the canal tail, even when there were sudden and significant flow variations.     

灌区渠道防渗工程规划研究

针对渠道防渗中的一般问题 ,从不同层面上研究了进行规划的一些技术问题。包括渠道衬砌功能定位和灌区防渗的总体规划 ,并重点研究了井渠结合灌区的防渗效果分析 ;结合防渗效果和投资效益 ,研究了渠道防渗的优先级别选择和布局 ;根据渠道防渗将使水力要素发生显著变化 ,破坏原渠系的水位衔接 ,提出缩窄底宽、改变坡降和改变边坡的改造方案 ,通过图表 ,分析各种方案的技术可行范围。     

刚性衬砌渠道受冻胀时衬砌层受力的试验研究

为了研究刚性衬砌道受冻胀时衬砌层的受力状况，通过模型模拟试验研究，找出了刚性砌渠道受冻胀时边坡衬砌层（板）的受力情况与其下渠床上含水量渠道横断面高度分布之间的内在规律，为寒区刚性衬砌渠道如何采取防洪胀措施提供了科学依据。     

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.     

Groundwater modelling to assess the effect of interceptor drainage and lining

Recharge to the aquifer through seepage from irrigation canals is often quoted as one of the main causes for waterlogging in Pakistan. In the design of drainage systems to control this waterlogging, rules-of-thumb are often used to quantify the seepage from canals. This paper presents the option to use a groundwater model for a more detailed assessment. Groundwater models may assist in evaluating the effect of recharge reducing measures such as interceptor drains along irrigation canals and lining. These measures are commonly aimed at reducing the drainage requirement of adjacent agricultural lands. In this paper an example is given of the application of a numerical groundwater model, aimed at assessing the effect of interceptor drainage and canal lining in the Fordwah Eastern Sadiqia project, being a typical and well-monitored location in Pakistan. The paper also presents references to other conditions. The model was used to obtain a better insight in the key hydraulic parameters, such as the infiltration resistance of the bed and slopes of irrigation canals, the drain entry resistance of interceptor drains and the hydraulic conductivity of soil layers. The model was applied to assess the effectiveness and efficiency of interceptor drains under various conditions. The results of the study show that the net percentage of intercepted seepage is too low to have a significant effect on the drainage requirement of the adjacent agricultural lands. Besides, the operation of the system, with pumping required, is often an added headache for the institution responsible for operation of the system. The marginal effect of interceptor drains and lining on the drainage requirement of adjacent agricultural land does not always justify the large investments involved. It can be concluded that:

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.     

Impacts of concrete lining of irrigation canals on availability of water for domestic use in southern Sri Lanka

Irrigation schemes have contributed to the availability of water not only for agriculture but also for domestic use by rural households. In the Uda Walawe irrigation scheme in southern Sri Lanka, irrigation canals are being lined with concrete to save water, meant to enable extension of the irrigated area. The effects of lining on the availability of water for multiple uses were investigated by field measurements of water levels and by an inventory of the perceptions of changed water availability by the population through focus group discussions. From the measurements it was determined that canal seepage provides an important contribution to groundwater recharge. It was estimated that after concrete lining the annual groundwater recharge in the irrigated areas will be reduced by approximately 50%. This saves a substantial amount of water that can be used to extend the irrigation area so more people can benefit from the available irrigation water. However, in the currently irrigated areas lining will have negative impacts by lowering groundwater levels due to a reduction in seepage from canals. This seepage contributes to the recharge of shallow wells used by the population to obtain water for drinking and cooking. The perception of the population was that enough water remains for domestic use. Other changes, such as reduced yields from home gardens were considered to be more important. Despite these negative impacts the expected positive impacts in the extension area justify, from a social equity point of view, concrete lining as a measure to redistribute the available water over the Uda Walawe area.     

Application of a hydraulic model for testing management decisions at distributary level

Summary This study was conducted on the Lagar Distributary of Gugera Branch of Lower Chenab Canal, Punjab, Pakistan. A computer model MISTRAL was adopted for evaluating management options. The study showed that the model can be used as a decision support tool for prioritizing management options. The model suggests that under current physical conditions of this distributary the combination of rotation between the distributaries and along the distributary canals can improve the equity of water discharge. For example, in case of Lagar Distributary the discharge of tail outlets can be increased threefold by introducing rotation between the tail of the distributary and an offtaking minor canal. A small decrease in the discharge of the minor would result from adopting this option. A combination of rotations between this and neighboring distributaries and along the Lagar itself can increase the discharge of tail outlets up to seven times. The results of the model indicate that operational changes can improve the discharge of tail outlets to some extent, but the improvement of physical conditions of the distributary is needed to achieve equity conditions, as specified in the design.     

Optimum decisions for lining irrigation canal distribution networks

A new approach to arriving at an optimum decision for lining irrigation canal distribution networks is given. The method proposed ensures optimal allocation of limited funds for lining sub-minor canals of the distribution network. The optimum length of lining of sub-minor canals for maximum benefits can be determined when only limited funds are available.     

Delivery system performance case study: Wellton-Mohawk irrigation and drainage district,USA

An irrigation district in southwestern Arizona was studied to assess the performance of its water delivery system. Data were obtained through monitoring of lateral canals, examining water order reports and bills, and conducting a diagnostic analysis of the water delivery and on-farm irrigation systems through interviews. A number of differences between official andde facto district operating policies were found. These policies had changed over the years and provided far more flexibility and better service than provided by the original official policy. The canal system, which was designed to be operated under upstream control, was found to be operated under a complex mixture of manual upstream and downstream control that resembled dynamic regulation. Farmers made official (recorded) water orders only about half the time. Deliveries usually occurred within one day of the ordered date, as per district policy, with more late deliveries at the tail end of the system during peak water use periods. On average, the district delivered the rate and duration ordered, but average flow rates for individual deliveries were not accurately estimated due to fluctuating flows. The two biggest shortfalls observed were the lack of water measurement records at intermediate points in the system and lack of thorough water accounting. These shortfalls appeared to have had only a minor effect on overall district objectives.     

高寒地区灌溉渠系的防冻胀设计

西藏那曲地区气候高寒,渠道冻胀破坏严重。通过才曲塘人工草场灌溉渠系的修建,分析了引起该区渠道冻胀的气候、地质等主要因素,提出了新建渠道时规划和设计方面的防冻胀措施。规划中要依据地质条件选择透水性较强的砂砾石地段,依据地下水条件选择地下水位埋藏较深的地段,依据地形地貌条件选择地形较高的脊梁地带或尽量采用填方渠道规划渠系。设计中对于挖方渠道,采用适变断面、换填、设置排水、保温和架空衬砌等措施,以适应和回避冻胀;对于填方渠道,采用架空渠槽或道渣石垫层明设的措施,以消减或消除冻胀。这些措施对高寒高海拔地区渠道建设具有一定的指导意义。     

Study of feasibility of night-closure of irrigation canals for water saving

The feasibility of closing distributary canals at night was investigated in a recently modernized surface irrigation system in Pakistan, the Upper Swat-Pehur High Level Canal system. Increased water supply, greater delivery capacity and the introduction of downstream control potentially allow more flexible service. In the command area of Maira branch of this system, farmers are anyway abandoning night-time irrigation, as they can meet their needs from improved supply during the day. They practice night irrigation only during the times of peak crop water demand. The rotational delivery system, known as warabandi in the sub-continent and Dauran in Arabian countries, has even broken down in the day in some parts of the command area. This is believed to be typical of systems with more than adequate water supply.A simulation study was undertaken using the CanalMan software developed by Biological & Irrigation Department, Utah State University, Utah Logan, USA. Primary data collected in one distributary canal and the two minors connected to it was utilized for simulations. The feasibility of night-time closure depends on the speed of filling and emptying the canal each day, and the time required to meet full irrigation demand during the day. The results show that where canal lengths are less than 5 km, in this system, there is good potential to make savings, which can be realized at system level through reduced demand on supplemental supplies from Tarbela Dam.     

梯形防渗渠道塑膜铺衬机的试验

借助均匀设计理论和软件对防渗渠道塑膜铺衬机进行了试验研究。提出了渠道塑膜铺衬效果的评价方法,分析了机器前进速度、展膜刷后倾角、展膜刷高度对铺膜效果的影响规律,并对设计参数进行了优化,证明主动同步放膜、展膜刷随动展膜的铺膜机构适于渠道空间铺膜作业。     

宁夏支渠结构现状及衬砌破坏成因

针对宁夏支渠衬砌运行中出现冻胀破坏严重现象，通过对灌区现有支渠的梯形断面、U形断面、弧底梯形断面、弧形坡角梯形断面和梯形混合断面（衬砌板＋砌石护脚）5种衬砌结构型式进行调查，阐述了各种衬砌结构的破坏状况、破坏原因和影响因素，着重从渠道结构、断面型式、流量、走向、挖填方、地下水位、施工工艺等方面进行分析，通过引用大量的调查资料分析说明各种衬砌结构的优缺点，提出结构优化的建议，这将对宁夏支渠的节水改造，防治渠道冻胀破坏，延长渠道使用寿命等方面起到积极的作用。     

The adoption of improved irrigation technology and management practices—A study of two irrigation districts in Alberta, Canada

Irrigation is by far the largest consumer of water in Alberta. The government is therefore dependent on this sector to achieve water savings for reallocating water to other sectors. Hence, a major objective of a recent government strategy is to see an increase in water efficiency and productivity of 30%. A survey of two irrigation districts was undertaken to determine the measures irrigators have taken and plan to take in the future to improve irrigation technologies and management practices to enhance water use efficiency and which factors facilitate or impede the adoption of such measures. As anticipated, the adoption rate varied between the two districts as a result of differences in production characteristics. The major drivers of adoption were to ensure security of water supply during drought, to increase quantity and quality of crops, and to save cost, while the major impediments were financial constraints and physical farm conditions. It seems that most feasible technological improvements have been implemented and considerable financial improvements or subsidies will be necessary to encourage a significant increase in adoption. There seems to be considerable scope for improvement through the adoption of better management practices. Considering that farmers in the two irrigation districts also have modest plans to adopt improved management practices, promotion and education campaigns that encourage new practices that involve minimal cash outlays might yield the greatest water savings in the future.