Irrigation timeliness indicators and application in smallholder irrigation systems in Zimbabwe

Timing of supply of irrigation water is an important measure of water management performance. Yet despite this widely accepted importance of timeliness, few studies have attempted to quantify this performance indicator. This paper suggests a methodology for quantifying timeliness. The indices thus generated are used to compare the performance of some types of smallholder irrigation schemes in Zimbabwe. Results indicate that applying measures of timeliness helps to assess water management practices across scheme types.The methodology given in this paper differentiates between timely irrigation deliveries which meet Crop Water Requirements (CWR) and surplus water supplies due to poor timeliness which cannot be used by the crop, hence denoting wastage. The timeliness indices provide more information regarding management practices than simple measures of total water applications over a given season.     

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.     

Performance assessment of irrigation water management of heterogeneous irrigation schemes: 1. A framework for evaluation

Studies of the performance assessment of irrigation schemes have gained momentum since the late 1980s due to the common perspective that the resources (land and water) in irrigation schemes are not being managed appropriately. In this paper irrigation water management is considered as one of the activities of the irrigation scheme. Three phases of irrigation water management namely planning, operation and evaluation are identified. A framework for the performance assessment of irrigation water management in heterogeneous irrigation schemes is proposed in this paper, based on earlier studies made in this direction. The paper presents two types of allocative measures (productivity and equity) and five types of scheduling measures (adequacy, reliability, flexibility, sustainability and efficiency), together with the methodologies for estimating these for the scheme as a whole during different phases of irrigation water management.     

Didactic tools for supporting participatory water management in collective irrigation schemes

In many irrigation schemes, Water Users Associations (WUAs) acquired the responsibility for water management after withdrawal of the state. Based on the success of some indigenous irrigation schemes, it was assumed that farmers could easily become managers. As decision-making was the exclusive terrain of the governmental agencies that ran the schemes, farmers never gained the necessary experience with water management. Therefore, training of farmers and WUAs on the principles and processes of water management is essential. This paper demonstrates a practical example of training material on water management that incorporates research results on the process of Irrigation Management Transfer and resulting farmers’ water management for the case of the Office du Niger irrigation scheme. The results of the paper explain how input from research was used in the four steps of the construction of training material. These steps are (1) setting the training agenda, (2) selecting and adapting information to be featured, (3) targeting the audience and (4) designing the actual training material. A first validation of the approach and examples of the actual training material were obtained in a workshop uniting all stakeholders.     

Farmer's perspective on irrigation performance

Of the many client groups with interests in irrigation system performance, farmers are probably the least often considered. This paper attempts to explore the meaning of irrigation performance from their perspective, highlighting at the outset basic difference between this perspective and that of system managers. It then reviews several important concepts underlying a consideration of performance in irrigation systems. The paper then proposes and discusses a set of twelve measures of irrigation service judged to be of interest to farmers. These are adequacy, timeliness, equity, tractability, convenience, predictability, temperature, sediment content, salt content, nutrient content, toxics, and pathogens.     

The evolution of smallholder irrigation policy in Zimbabwe: 1928–1986

Voluntary smallholder irrigation schemes in Zimbabwe were launched in 1913 as a means of famine relief and subsequently to settle black farmers displaced from designated areas for white commercial farmers. In 1928 the colonial government inaugurated a programme to provide services to existing smallholder schemes and to assist in developing new schemes. This process eventually led to the erosion of farmer participation in planning, development and financing of smallholder schemes. Since 1928 the smallholder schemes have been heavily subsidised, a pattern that continues today. Currently about 3.4% of the land under irrigation is farmed by small holders who pay about 11% of the costs of irrigation operation and maintenance; the remaining 89% is subsidised by the government. More smallholder irrigation development is currently being planned. The government has made loan funds available to groups on the basis of financial viability, but to date this fund has not been significantly utilized by smallholders. In essence, smallholder irrigation development is being constrained by problems that have plagued smallholder schemes since 1928.Abbreviations AGRITEX Agricultural Technical and Extension Services - ARDA Agricultural and Rural Development Authority - DERUDE Department of Rural Development - NFIF National Farm Irrigation Fund - Z$ Zimbabwe Dollar     

An evaluation of the performance of six smallholder irrigation schemes in Zimbabwe

Informal and formal survey procedures were used to assess the performance of six smallholder irrigation schemes. The predominant crops grown at the schemes were maize (Zea mays) in summer and beans (Phaseolus vulgaris) in winter. Average crop yields range from 2.7 to 7.4 t/ha for maize and 0.4 to 2.4 t/ha for beans at the lowest and highest yielding schemes respectively. There was also a large gap between the lower and higher producing farmers at each scheme. Only one out of the six schemes realized a profit margin of more than ZWD 223 per month per plotholder (the minimum wage rate for agriculture workers) after operating and maintenance costs (currently met by government) were deducted. Major constraints on the schemes included limited cash for input purchases, unreliable water supplies for winter cropping, limited market outlets and poor roads. Ways of alleviating some of these constraints to improve overall scheme performance are proposed.     

An approach to multi-criterion evaluation of irrigation system performance

Irrigation systems aim to meet multiple objectives and performance must therefore be assessed using quantifiable measures for each. It therefore becomes an extremely difficult task to capture the valuation of all of them simultaneously and to mentally process the trade-offs between them in order to arrive at an overall impression of system performance. There is a need for a methodology which provides a systematic approach to comparing and combining the components of overall performance.Multi-Attribute Utility Theory offers an attractive approach to assessing performance of irrigation systems in the form of a utility function which reflects the strength of preferences and trade-offs between individual performance criteria. The method is described and demonstrated on the basis of a case study of irrigation in Sudan.     

Methodologies for assessing performance of irrigation and drainage management

This paper presents a framework irrigation managers can use in assessing performance of irrigation, and recommends a specific set of indicators for measuring performance that the authors believe are practical, useful, and generally applicable. Although the primary focus is on the management of canal systems for agricultural production, the paper also discusses indicators that can be used for assessing longer term performance, including physical, economic and social sustainability. Finally, the paper highlights the crucial importance of strategic, as well as operational management performance, and the necessity of having an incentive system that encourages managers to improve performance.     

A benefit-cost analysis of smallholder irrigated farms in Zimbabwe

The government of Zimbabwe uses agricultural development as one of the ways to stimulate economic growth. Agriculture in Zimbabwe is characterized by a dual agrarian system comprising the large scale commercial sector and the smallholder communal sector. The communal sector, 47 percent of the country, supports more than 70 percent of the population. One strategy used to improve agricultural performance is the development of agricultural infrastructure. Of the 117, 830 ha developed for irrigation only slightly more than 6 percent is in the communal (smallholder) sector. The smallholder irrigation systems are managed under four different systems, namely the government-managed Agritex, farmer-managed community, the informal bani (dambo) managed by farmers and the ARDA outgrowers managed jointly by a parastatal and farmers. This paper evaluates the benefits and costs associated with these different management systems. Benefit-cost ratios are computed for each system. The bani system achieves higher benefit-cost ratios than the community, which achieves higher ratios than the Agritex management system. This indicates that the government should consider using the community system for developing the potential 93,000 ha of communal smallholder irrigation systems. It should also seriously consider the bani system as an alternative development strategy.     

Effects of alternative water distribution rules on irrigation system performance: a simulation analysis

Based on a simulation model reflecting physical and economic conditions typically found in rice irrigation systems in Asia, the irrigation performance implications of alternative water distribution rules for dry season irrigation are evaluated under varying degrees of water shortage. The rules examined reflect differing water distribution strategies designed either to maximize conveyance efficiency, economic efficiency, or equity; or to achieve a balance between efficiency and equity objectives. Irrigation performance is evaluated using several efficiency measures reflecting the physical, agronomic and economic productivity of water, and one measure of equity. Economic efficiency and equity among farmers within the portion of the irrigation system that is on in any given season are shown to be complementary, and not competing objectives. Economic efficiency and equity among all farmers within the command area of the irrigation system are largely complementary strategies at the lower levels of water shortage, but with increasing shortage, significant tradeoffs develop between these objectives. An operational rule for water distribution under a goal of maximizing economic efficiency is developed, and the data requirements for its implementation are shown to be modest. Under the model's assumed conditions of dry season rice production dependent solely on surface irrigation for water, the distribution strategy designed to maximize conveyance efficiency results in only modestly lower levels of economic efficiency and equity than could be achieved by the strategy designed to maximize economic efficiency.     

Cumulative relative water supply: A methodology for assessing irrigation system performance

This paper discusses the usefulness and limitations of using the concept of Relative Water Supply (RWS) for evaluating the performance of irrigation systems, with special reference to systems irrigating rice. It then describes and demonstrates the use of a modification of RWS called Cumulative Relative Water Supply (CRWS), which can be used in conjunction with RWS. The advantage of CRWS is that it provides a measure of the cumulated RWS throughout a season, both in absolute terms at any given time, and in terms of the overall seasonal trend. It allows comparison of performance of an irrigation system or subsystem both to the target, and to other systems or subsystems. It can therefore be used both as an analytical tool by researchers, and as an operational tool by managers. The use of CRWS in conjunction with RWS is illustrated with examples from Sri Lanka.     

Statistical methods for irrigation system water delivery performance evaluation

There are several different parameters that can be measured and used to describe the performance of water delivery service; flow rate, volume, duration, pressure, and frequency. The proper one(s) to consider depends on the project conditions and objectives. The overall performance of an irrigation water delivery system can be broken down into two components; the delivery schedule and operations. The performance of the delivery schedule can be evaluated by looking at the ratio of intended to required water (volume, rate, duration, etc.) and the performance of operations by the ratio of actual to intended water. The overall performance is expressed by the product of these two ratios; the actual divided by the required water. Statistical relations are provided to express equity, adequacy and reliability from measurement of these ratios.     

Measuring conveyance efficiencies to improve irrigation water management

This paper presents a study of conveyance efficiencies of Canal de Salvaterra, in the Sorraia Irrigation Project, Portugal. The Canal and the Project are briefly described and the water measurement techniques and structures utilized are analysed. Results comprise the main aspects of the inflow-outflow balance with identification of water losses and conveyance efficiencies. Analysing the results showed that irrigation efficiencies are higher during work days and labour hours and lower during weekends and at night. This identified the need to improve operation and management of the irrigation system, adapting inflow to demand according travel time and response time of the conveyance (and distribution) system, of the different main sections of the system.     

Design and management nomograph for furrow irrigation

There exist capabilities for analyzing the behavior of surface flow and the ultimate distribution of infiltrated water in furrow irrigation. The corresponding synthesis, i.e., the selection of appropriate combinations of inflow rates, cutoff times and length of furrow — design and management, currently not so well established, is treated herein. A design-management nomograph is proposed for free draining graded furrows. This is a plot of efficiency, time of cutoff and uniformity coefficient contours each given on a length-flow rate space adjacent to one another, for a furrow with given infiltration characteristics, flow geometry, slope, roughness and required depth of application. The nomograph can be used to determine the combinations of length, time of cutoff and flow rate that would yield in optimum combination of efficiency and uniformity.     

Evaluating factors influencing farmers' satisfaction with their irrigation system

The logit technique is used to analyze the relationship between dichotomous reactions of satisfaction (satisfied/dissatisfied) with the irrigation system and certain independent variables. The result shows that five important variables — water availability on time, fertilizer availability, landholding size, farmers' participation in irrigation activities and location of farmland along the canal — significantly determine satisfaction.     

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.     

基于稳健设计理论的畦灌质量敏感性分析

针对畦灌系统运行管理水平和灌水质量较低的问题,该文应用稳健设计的基本理论,结合地面灌溉SRFR模拟模型,评价了畦田的灌水质量,模拟了单宽流量和入渗参数对灌水质量的影响,分析了灌水质量对各因素的敏感性。结果表明,对某一固定的畦田,单宽流量并非越大越好,单宽流量在4～7 L/(s·m)时,畦灌可以获得较高的灌水效率和灌水均匀度。灌水均匀度对入渗参数的敏感程度要大于灌水效率,灌水质量对入渗指数的敏感性大于入渗系数,增加单宽流量能够降低灌水质量对入渗参数的敏感程度。对灌水质量影响较大的因素依次为单宽流量、入渗指数     

Aflaj irrigation and on-farm water management in northern Oman

This paper reports on results from a case study on water management within a traditional, falaj irrigation system in northern Oman. In the planning and design of regional irrigation development programs, generalized assumptions are frequently made as to the efficiency of traditional surface irrigation systems. Although qualitative accounts abound, very little quantitative research has been conducted on on-farm water management within falaj systems. Daily irrigation applications and crop water use was monitored during an 11-month period among 6 farm holdings at Falaj Hageer in Wilayat Al-Awabi. Contrary to the frequent assumptions that all surface irrigation systems incur unnecessarily high water losses, on-farm ratios of crop water demand to irrigation supply were found to be relatively high. Based on actual crop water use, irrigation demand/supply ratios among monitored farms varied from 0.60 to 0.98, with a mean of 0.79. Examination of the soil moisture budget indicates that during most irrigations of wheat (cultivated in the low evapotranspiration months of October–March) sufficient water is applied for the shallow root zone to attain field capacity. With the exception of temporary periods of high falaj delivery flows or periods of rainfall, field capacity is usually not attained during irrigations within the more extensive root zones of date palm farms. The data presented in this paper should provide a better understanding of water use performance by farmers within traditional falaj systems. Moreover, these data should also serve to facilitate more effective development planning for irrigation water conservation programs in the region.     

Hydraulic-hydrological simulations of canal-command for irrigation water management

A modelling system that combines the hydraulic simulations of the canal and hydrological simulations of the irrigated command is introduced. It uses MIKE 11 and MIKE SHE, two well-established modelling systems, for the hydraulic and hydrological simulations respectively. In addition, it also has an irrigation scheduling module and a crop growth module. The modelling system is applied to the Mahanadi Reservoir Irrigation Scheme, a large irrigation project in Central India. The results show that presently a significant amount of water is wasted in the command during the monsoon season. It is demonstrated that the minimization of this wastage could lead to a substantial crop production in the subsequent dry season. Furthermore, the simulations illustrate the versatility of the modelling system for planning and analysing the various aspects of an irrigation project.