Equal water sharing in scarcity conditions: the case of the Chaisombat Muang Fai Irrigation System in Thailand

With increasing water conflicts arising from competing demands and global climate changes, it has become paramount to understand how the available water resources can be judiciously utilized for sustaining life. This article extends the previous studies on equal water sharing in water-abundant conditions to water-scarce conditions. On the basis of a case study of the self-managed Chaisombat Muang Fai irrigation group in Chiang Rai Province of northern Thailand, the article analyzes the factors that helped the group in successfully sharing water equally when they faced dry-season water scarcity caused by the competing demands of upstream irrigation systems. Interview data on Muang Fai development and management obtained from all levels of Muang Fai managers and field observations reveal three major success factors. First, Muang Fai managers across all levels recognized that water scarcity is a common problem and that, in their capacity as delegates accountable to all members, they must decide how intense competition for water and extensive crop failure can be prevented. Second, the Muang Fai organization provided a large number of farmers of diverse backgrounds with two-way communication and resilient implementation mechanisms for reaching a mutual agreement and synchronically adapting to a new water environment. Third, the group was ready to constantly update and employ socio-technical information to maximize the total benefit, so that all members obtain a proportionately larger share. These results reveal that in addition to social organization and traditional practices related to the normal condition, in the scarcity condition, it is essential to understand the “common” nature of the problem and acquire skills in extracting, updating, communicating, and using socio-technical information for decision making on equal water sharing. Therefore, these capacities should be built, or knowledge on building them should at least be developed, before the water scarcity problem worsens.     

Transferring water from irrigation to higher valued uses: a case study of the Zhanghe irrigation system in China

The Zhanghe irrigation system (ZIS) is located in the Yangtze River Basin approximately 200 km west of Wuhan in Hubei Province. The reservoir was designed for multiple uses—irrigation, flood control, domestic water supply, industrial use, aquaculture, and hydropower. Over a period of more than 30 years a steadily increasing amount of water has been transferred from irrigation to other uses. Activities on the part of government, irrigation system managers, and farmers made this transfer possible with only modest decline in rice production. Most important factor was the steady increase in rice yields. The water pricing system provided an incentive for ZIS to reduce irrigation releases. With the steady decline in releases, farmers were forced to find ways to save water. Farmers improved existing ponds and built new ones to store water (improved infrastructure). Access to pond water on demand facilitated the adoption of alternate wetting and drying (technology) particularly in dry years. The establishment of volumetric pricing (price policy) and water user associations (institutions) may also have provided incentives for adoption of AWD, but more research is needed to establish their impact. These activities taken together can be seen as potentially complementary measures. Farmers received no direct compensation for the transfer of water, but recently farm taxes have been reduced or altogether abolished. Further reduction in water releases from the ZIS reservoir could adversely affect rice production in normal or dry years.     

Delivery management water requirement for irrigation ditches associated with large-sized paddy plots in Korea

Delivery management water requirement (DMWR) is the use of bypass water in paddy field irrigation to help maintain desired water levels in irrigation canals and to distribute water to paddy plots in a uniform manner. Diverted irrigation water (DIW), DMWR, and the DMWR/DIW ratio were investigated for concrete lined irrigation ditches with large-sized paddy plots (100 m×100 m) during irrigation periods (May to mid-September). DIW and DMWR were measured at 5- to 10-day intervals at the inlets and outlets of irrigation ditches on stable water supply days. The mean DMWR/DIW ratios in irrigation ditches L₁ and L₂ over 3 years were 36 and 34%, respectively. The mean DMWR/DIW ratios displayed month-to-month and year-to-year variation. The monthly mean DMWR/DIW ratios were highest (55 and 71%) in June and lowest (<20%) in August and September. The annual mean DMWR/DIW ratios during a dry year markedly decreased to 11%, compared with 42% in other years. The decrease was due to the small DIW and farmers water management to maximize capture of limited irrigation water during the drought. The DMWRs in May and June were significantly (p<0.01) correlated with the DIWs, indicating that high DMWR in May and June are attributed to excessive DIW.     

More Rice,Less Water—Integrated Approaches for Increasing Water Productivity in Irrigated Rice-Based Systems in Asia

Abstract

The water crisis is threatening the sustainability of the irrigated rice system and food security in Asia. Our challenge is to develop novel technologies and production systems that allow rice production to be maintained or increased in the face of declining water availability. This paper introduces principles that govern technologies and systems for reducing water inputs and increasing water productivity, and assesses the opportunities of such technologies and systems at spatial scale levels from plant to field, to irrigation system, and to agro-ecological zones. We concluded that, while increasing the productivity of irrigated rice with transpired water may require breakthroughs in breeding, many technologies can reduce water inputs at the field level and increase field-level water productivity with respect to irrigation and total water inputs. Most of them, however, come at the cost of decreased yield. More rice with less water can only be achieved when water management is integrated with (i) germplasm selection and other crop and resource management practices to increase yield, and (ii) system-level management such that the water saved at the field level is used more effectively to irrigate previously un-irrigated or low-productivity lands. The amount of water that can be saved at the system level could be far less than assumed from computations of field-level water savings because there is already a high degree of recycling and conjunctive use of water in many rice areas. The impact of reducing water inputs for rice production on weeds, nutrients, sustainability, and environmental services of rice ecosystems warrants further investigation.     

灌溉策略对冬小麦水分利用和生长的影响

为探究不同灌溉策略下冬小麦水分利用和生长的情况,在总灌溉量相同的前提下设置拔节水+开花水单次参比蒸散30%灌溉(W1)、拔节水+开花水单次参比蒸散60%灌溉(W2)和拔节水+开花水大水漫灌(W3)3种灌溉策略,利用称重式蒸渗仪和diviner 2000研究了不同灌溉策略下冬小麦的耗水动态、蒸散特征和水分利用效率。结果表明,大水漫灌处理(W3)下冬小麦主要利用上层(0～50 cm)土壤水分,而低速率灌溉(W2和W1)处理增强了植株根系对深层(70～100 cm)土壤水分的吸收;同时,低速率灌溉可以降低蒸散速率,W3、W2和W1的日蒸散速率最大值在拔节水灌溉期间分别为13.20、10.82和10.58 mm·d^-1,在开花水灌溉期间分别为15.10、10.57和9.10 mm·d^-1,其中低速率灌溉主要降低了单日蒸散的午间高峰值,减少了无效耗水。大水漫灌处理不利于生长后期株高的增加,而低速率灌溉不仅有利于株高的形成,也有利于叶片维持较高水平且稳定的SPAD值,保证了籽粒灌浆,使得W2处理的穗粒数和千粒重较W3处理分别提高7.25%和3.93%。综合来看,低速率灌溉策略通过低量持续的供水改变了冬小麦植株根系对土壤水利用的层次,减少无效水蒸散,维持叶片稳定的光合能力,提高了产量和水分利用效率。     

Successful factors and activation theory/concept of water users’ organizations - based on the MWMS project in Thailand

This paper analyzes successful factors and develops theory/concept for the activation of the Water Users’ Organizations (WUOs) in the Modernization of Water Management System (MWMS) project in Thailand. The main successful factors are as follows: (1) improvement of irrigation facilities with the farmers’ participation; (2) providing an opportunity for discussions with farmers to enable the adjustment of water allocation through the establishment of an Integrated Water Users’ Group (IWUG) in the early stages of the project; (3) holding monthly meetings of the IWUG; (4) developing, operating, and monitoring the water allocation plan in cooperation with both farmers and government officials. That is to say, initiation of the facilities’ improvement and the establishment of the WUOs were performed concurrently. Moreover, the farmers participated from the beginning of the planning stage to the management stage. The MWMS project contributed to create a system that farmers can acquire and use irrigation water with reliability. Through this system, farmers could have ownership in their facilities, and then they participated in the operation and maintenance spontaneously. The most important thing is to give priority to a joint study process between the farmers and government officials for producing mutual understanding and building a good confidential relationship.     

Assessment and water saving issues for Ningxia paddies,upper Yellow River Basin

In the Hetao Irrigation Districts of the Ningxia autonomous region, Upper Yellow River Basin, the continuous deep flooding irrigation method is used for the rice paddies. The field irrigation water use during the rice-growing season is two to three times higher than in other regions of North China where water-saving practices have been introduced. This paper, based on the data measured in experimental rice fields and sub-branch canal systems, presents main results concerning crop evapotranspiration, percolation and irrigation requirements for deep and shallow water irrigation. Causes for water waste relate to both the lack of regulation in supply and distribution canals and to the poor management of paddy fields. The potential for water saving is discussed using water balance data. Improved irrigation techniques and water management strategies, including the shallow water irrigation method, are suggested considering the expected impacts and benefits. Replacing the current continuous deep flooding with the shallow-ponded water irrigation method may reduce the growing season irrigation water use from 1,405 to 820 mm in average, with a likely increase in yields of 450 kg/ha. Water productivity would then increase from 0.49 to 1.03 kg/m³. Adopting improved canal management and modernization of regulation and control structures may lead to decreasing the gross irrigation demand from the present 3,100 mm to about 1,280 mm, which would highly benefit the environmental conditions in the area.     

Farm level practices and water productivity in Zhanghe Irrigation System

China, the biggest rice-producing country in the world, has put considerable effort into finding ways to conserve water in rice cultivation. One very promising practice, intermittent submerged irrigation (ISI) was reported to be applied on farmers fields over a large area in the Zhanghe irrigation system (ZIS), which serves about 160,000 ha of irrigated land, which is intensively cultivated with rice. To better understand the actual farmer practices, the degree to which farmers adopt ISI, the resulting water productivity, and implications for farm and system water management, a water accounting methodology developed by IWMI was applied at farm and a larger meso scale. Two areas were observed: Tuanlin, where ISI was reported to be widespread (with ISI), and Wenjiaxiang, where farmers were reportedly not adopting ISI (without ISI). The field water level measurements demonstrate that farmers at the with ISI site follow a practice similar to the theoretical ISI techniques by letting ponding levels drop to the soil surface several times during the cropping season. At the without site, farmers keep higher water levels ponded, and do not let water levels drop to the soil surface as often as the with site. A major determinant of practice is ease of access to water. At the with site, farmers have access to a variety of sources such as ponds and drains. At the without site, access to water was primarily from canal water, without the degree of flexibility as areas that had a water source near the field. The process fraction of gross inflow at field scale (rice evapotranspiration divided by irrigation plus rain) ranged between 0.66 and 0.93, remarkably high values showing how effective farmers are in converting water sources to productive evapotranspiration. The on-farm water accounting results show that with ISI, the average values of irrigation water applied over two years 1999–2000 are 22% less than without ISI, and the yields approximately the same. The resulting water productivity values per unit of irrigation water (WP_irrigation) are 20% higher under ISI practices, but per unit of evapotranspiration water productivity results are similar. The meso site study yielded surprising insights into overall water management in the area. In the years 1999 and 2000, at the meso sites, the irrigation duty in Tuanlin (with ISI) was 29% and 21% less than in Wenjiaxiang (without ISI), respectively, resulting in WP_irrigation values of 24% and 26% higher at Tuanlin than Wenjiaxiang. But values of process fraction of gross inflow were considerably reduced at the meso scale ranging between 0.12 and 0.29, with considerable drainage outflow observed. Different land uses, trees, roads, villages, and ponds, begin to play an important role in overall water resource management at this scale. Drainage water from fields plus runoff served as supplies to ponds within the meso area as well as downstream reservoirs. Ponds play a very important role as an additional source of water, and in fact facilitate the uptake of ISI practices. This demonstrates that there are multiple strategies at play influencing water savings and productivity beyond ISI in the management of water within the area.     

Appropriation of Río San Juan water by Monterrey City, Mexico: implications for agriculture and basin water sharing

Monterrey metropolitan area’s growth has resulted in water transfers from the Río San Juan basin with significant impacts for downstream water users, especially farmers in the Bajo Río San Juan (BRSJ) irrigation district. El Cuchillo dam is the centerpiece of the basin’s water management infrastructure and has become the flashpoint of a multi-faceted water dispute between the states of Nuevo León and Tamaulipas as well as between urban and agricultural water interests in the basin. Subsequent to El Cuchillo’s implementation in 1994, the BRSJ irrigation district has been modifying its irrigation operations to adjust to the new water availability scenario. Compensation arrangements for farmers have been established, including crop loss payments on the order of US$ 100 per hectare un-irrigable due to the diversion of water to Monterrey plus 60% of the water diverted to be returned to farmers as treated effluent via the Ayancual Creek and Pesquería River, a process with its own water competition and environmental implications. The Mexican irrigation sector will continue to face intense competition for water given: (a) low water productivity in agriculture leading decision-makers to allocate water to higher productivity uses particularly in cities, (b) priority accorded to the domestic use component of municipal water supply, and in the BRSJ case, (c) Mexico’s national interests in meeting its water sharing obligations with the United States.     

Comparative analysis of management of three water users’ organizations: successful cases in the Chao Phraya Delta, Thailand

A good water users’ organization (WUO) is a significant factor in the practical success of an irrigation project. The major duties of WUOs are to operate and maintain their irrigation facilities and to perform the financial and organizational management. This paper analyzes the history and present situation of three WUOs in the Chao Phraya Delta, Thailand which have been awarded for their successful activities: namely, two pilot integrated water user groups (IWUGs) and one pilot water users’ association. The results of a field survey and questionnaire revealed the users’ past experience, methods of irrigation management, and social mobilization efforts. The main results of our analysis are as follows: (1) among the three WUOs, only the IWUG Sao Hi Unity Agriculture Irrigation (IWUG SHUAI) can be regarded as a successful case in terms of long-term management, (2) as a pumping irrigation project, the IWUG SHUAI entails an upfront electricity cost, which gives farmers added impetus to organize a management system and budget, and to learn from past failures, and (3) in contrast, the member farmers in the gravity irrigation projects lack the impetus to realize the necessity of a common management budget, a situation which can be improved only by the education of the leaders and clear explanation to the member farmers.     

An institutional case study of Japanese Water Users Association: towards successful participatory irrigation management

This paper examines irrigation management conduct within the Japanese Water Users Association (WUA), namely the Land Improvement District (LID). LID is regarded as a successful case of participatory irrigation management (PIM), in which there are few conflicts over water between farmers so that it attains high social cost performance. However, the management system of LID still remains obscure. We throw light on this system assuming the existence of "the rule of fairness". Farmers operate the irrigation facilities in a self-serving way and have their own rule of fairness, such as upstream superiority, based on the long-term experiences of irrigation systems. We defined this rule of fairness as made up of two components: one is "fairness of outcome" and the other is "fairness of procedure". Finally, we discovered that the approach of LID staff is the essential factor to satisfying the farmers' criteria of fairness and maintaining peace; LID staff place importance on farmers' customary rules, taking care to remain neutral in arbitrating quarrels between farmers and trying to ensure organizational transparency to farmers. This can be also a good lesson for future PIM projects.     

Evaluation of the management practice for controlling herbicide runoff from paddy fields using intermittent and spillover-irrigation schemes

Two water management practices, an intermittent irrigation scheme using automatic irrigation system (AI) and a spillover-irrigation scheme (SI), were compared for the fate and transport of commonly used herbicides, mefenacet (MF) and bensulfuron-methyl (BSM) in experimental paddy plots. Maximum mefenacet concentrations in paddy water were 660 and 540 μg L⁻¹ for AI and SI plot, respectively. The corresponding values for bensulfuron-methyl were 46.0 and 42.0 μg L⁻¹. Dissipation of the herbicides in paddy water appeared to follow the first-order kinetics with half-lives (DT₅₀) of 1.9–4.5 days and DT₉₀ (90% mass dissipation) of 7.8–11.3 days. The AI plot had no surface drainage, hence no herbicide was lost through paddy-water discharge. However, SI plot lost about 38 and 49% of applied mefenacet and bensulfuron-methyl, respectively. The intermittent irrigation scheme using automatic irrigation system with a high drainage gate was recommended to be a best management practice for controlling the herbicide losses from paddy fields. The paddy field managed by spillover-irrigation scheme may cause significant water and herbicide losses depending on the volume of irrigation and precipitation. The water holding period after herbicide application was suggested to be at least 10 days according to the DT₉₀ index.     

High-yield irrigated maize in the Western U.S. Corn Belt: II. Irrigation management and crop water productivity

Appropriate benchmarks for water productivity (WP), defined here as the amount of grain yield produced per unit of water supply, are needed to help identify and diagnose inefficiencies in crop production and water management in irrigated systems. Such analysis is lacking for maize in the Western U.S. Corn Belt where irrigated production represents 58% of total maize output. The objective of this paper was to quantify WP and identify opportunities to increase it in irrigated maize systems of central Nebraska. In the present study, a benchmark for maize WP was (i) developed from relationships between simulated yield and seasonal water supply (stored soil water and sowing-to-maturity rainfall plus irrigation) documented in a previous study; (ii) validated against actual data from crops grown with good management over a wide range of environments and water supply regimes (n = 123); and (iii) used to evaluate WP of farmer's fields in central Nebraska using a 3-y database (2005–2007) that included field-specific values for yield and applied irrigation (n = 777). The database was also used to quantify applied irrigation, irrigation water-use efficiency (IWUE; amount of yield produced per unit of applied irrigation), and the impact of agronomic practices on both parameters. Opportunities to improve irrigation management were evaluated using a maize simulation model in combination with actual weather records and detailed data on soil properties and crop management collected from a subset of fields (n = 123). The linear function derived from the relationship between simulated grain yield and seasonal water supply, namely the mean WP function (slope = 19.3 kg ha⁻¹ mm⁻¹; x-intercept = 100 mm), proved to be a robust benchmark for maize WP when compared with actual yield and water supply data. Average farmer's WP in central Nebraska was ∼73% of the WP derived from the slope of the mean WP function. A substantial number of fields (55% of total) had water supply in excess of that required to achieve yield potential (900 mm). Pivot irrigation (instead of surface irrigation) and conservation tillage in fields under soybean–maize rotation had the greatest IWUE and yield. Applied irrigation was 41 and 20% less under pivot and conservation tillage than under surface irrigation and conventional tillage, respectively. Simulation analysis showed that up to 32% of the annual water volume allocated to irrigated maize in the region could be saved with little yield penalty, by switching current surface systems to pivot, improving irrigation schedules to be more synchronous with crop water requirements and, as a fine-tune option, adopting limited irrigation.     

A combined technique of floodplain storage and reservoir irrigation for paddy rice cultivation

This paper introduces an irrigation system developed in the floodplain of a lake and studies the water management technique of the irrigation system by estimating the total water balance of the whole system. The system is characterized by a reservoir combined with a dike system in the floodplain of the Tonle Sap Great Lake and an irrigation system. Two main models are used for calculating the total water balance. The first model is the water balance of the reservoir. The inputs to the model are water level of the reservoir, precipitation, lake evaporation, infiltration, and area–volume curve of the reservoir. The outputs are inflow and outflow of the reservoir. The supply from the reservoir to paddy fields is computed from the outflow. The second model is the water balance of paddy fields, based on which the water requirement in paddy fields is derived. The reference evapotranspiration needed to calculate the water requirement is simulated for monthly time series using the FAO Penman–Monteith model. Since there is no drainage network in the irrigation system, surface drainage and runoff are not included in the calculation of the water balance, and seepage is considered negligible in the flat floodplain area. The evapotranspiration, rice variety, soil type and irrigated area are used to simulate water consumption in paddy fields. Finally, the two models are connected to produce the total water balance from the reservoir to paddy fields. The total outflow from the reservoir is estimated and the total water consumption for dry season cultivation is also determined. Finally, the efficiency of the whole system is examined.     

Analysis of return flows in a tank cascade system in Sri Lanka

In Sri Lanka, irrigation reservoirs (tanks) are usually connected sequentially and form cascades along the landscape. A study was carried out in the Anuradhapura District in the dry zone of Sri Lanka to understand the role of return flows in such tank cascade systems. The water balance of a tank cascade system was estimated using hydrological data collected over a one-year period. The system was extended about 25 km along a river composed of three small reservoirs having the command area of 31, 55, and 55 ha, respectively. In this system, about 46% of seepage water from tanks entered the paddy fields of the command area. The crop consumed part of the water and the rest returned to the downstream tank through the drainage canals. Percolation loss in the command areas was low (3.6 mm/day) since a considerable portion of the percolation returned to the downstream tank. These results showed that return flows, which are generally disregarded in the water budget, contributed considerably to the water supply of the tank cascade system.     

Characteristics of paddy irrigation in Taiwan

Paddy and water environment are closely related to each other in Asia. Developing agriculture by way of construction of farmland irrigation works has long been the principal objective of policies in Taiwan. Owing to significant temporal and spatial difference in rainfalls, natural river runoff has hardly corresponded with irrigation requirements. The cultivation of rice paddies and upland crops are practiced according to the state of the water sources, and cultivation patterns and irrigation systems are framed by placing the same importance on the role of irrigation and drainage management. In this article, the characteristics of paddy irrigation in Taiwan, distinguishable from the western arid farming, have been categorized and will be reviewed in terms of irrigation development, agricultural water utilization, equitable distribution management, farmland consolidation, and the Irrigation Association with its role as that of a public juridical body.Dr. Tsai is the Chief of Irrigation and Engineering Division, Council of Agriculture (COA), Executive Yuan, Taiwan, R.O.C, and also serves as the president of the Chinese Society of Agricultural Engineers (CSAE), the Vice-President of the International Society of Paddy and Water Environment Engineering, the vice-president of International Commission on Irrigation and Drainage (ICID) Chinese Taipei Committee, Managing Supervisor of Chinese Water Resources Management Society. He has an M.Sc. diploma in agricultural engineering from the National Taiwan University and in 1990 he received his Ph.D. degree in natural science and technology from Okayama University, Japan.     

Water transfer from agriculture to urban domestic users: a case study of the Tone River Basin, Japan

Agricultural water reorganization measures (AWRM) is an approach that has been adopted in Japan for more than 30 years to capture excess water from agriculture for other uses by relying on the modernization of existing irrigation infrastructures. This paper reviews the history and processes of four such permanent water transfers by AWRM in the Tone River Basin, specifically those conducted in the Saitama Prefecture, Japan. The benefit of AWRM for the agricultural sector is the lowering of rehabilitation costs by sharing part of it with the city sector. AWRM does not require saving water at the on-farm level. Instead, the labor requirement of farmers is reduced by the rehabilitation and installation of pipelines. The benefit to the city is the lower cost, when compared with costs for the development of new water resources, and the relatively short duration of the project, which are important factors in an environment of the rapid increase in domestic water demand.

New performance indicators for rice-based irrigation systems

Various indicators are used for evaluating the performance of different aspects of an irrigation system. This study proposes rice relative water supply (RRWS) and cumulative rice relative water supply (CRRWS) indicators to characterize the irrigation water delivery performance as the season advances in rice irrigation systems. These indicators were determined from field tests and evaluated. Traditionally, some standing water depth is kept in the field throughout the irrigation season. Some water is continuously delivered to maintain the standing water depth in the field due to the difference between the maximum standing water depth (WSmax _j ) and the present standing water depth (WS _j ). The widely used relative water supply (RWS) concept is found to incorrectly characterize an oversupply condition on irrigation deliveries for not considering the additional water supply to maintain standing water. Consequently, the cumulative relative water supply (CRWS) gives a wrong scenario in characterizing irrigation delivery performance throughout the season. The RRWS, on the other hand, distinctly characterizes the oversupply and undersupply condition on irrigation delivery as the season advances. A value of 1.0 for RRWS indicates an irrigation delivery that perfectly matches with the field water demand. Both in the main and off-season, RWS remains higher than RRWS during depletion periods (WS _j −WS _j ). On the other hand, the values of RWS and CRWS were higher than RRWS and CRRWS during 3rd to 6th weeks in the main season; and 3rd to 7th weeks in the off-season. The proposed indicators were found to be useful to enhance the decision-making and operational strategy for delivering the right amount of water to the fields for the upcoming period.     

浅谈水田灌溉示范区节水措施

八五三农场选择水库、泵站、井灌三种不同类型灌区作为水田节水示范区,在控水灌溉、运行管理、优化配置、渠系配套、农业综合、水情自动化等方面采取了相应的措施,降低了灌水定额,提高了灌溉水利用率。