The policy relevance of virtual water can be enhanced by considering comparative advantages

The virtual water metaphor was created originally to gain the attention of public officials responsible for choosing policies that influence the use of water resources in arid regions. Over time, the metaphor has been used in both empirical and conceptual settings, primarily to describe the water used to produce crop and livestock products that are traded in international markets. Several authors have described how water-short countries can enhance their food security by importing water-intensive food crops. Some authors have noted similarities between the virtual water metaphor and the economic theory of comparative advantage. The virtual water metaphor addresses resource endowments, but it does not address production technologies or opportunity costs. Hence, the metaphor is not analogous to the concept of comparative advantage. The metaphor can be helpful in motivating public officials to consider policies that will encourage improvements in the use of scarce resources, but comparative advantages must be evaluated to determine optimal production and trading strategies. The theory of comparative advantage is explained and demonstrated in several scenarios that depict differences in resource endowments and production technologies. Optimal strategies are not always consistent with expectations based only on resource endowments. Policy discussions regarding water resources can be enhanced by considering comparative advantages when evaluating opportunities to import or export agricultural products.     

A robust modeling approach for regional water management under multiple uncertainties

In regional water management systems, various uncertainties may be derived from random feature of resource conditions and natural processes, errors in estimated modeling parameters, as well as imprecision or fuzziness human-induced. This leads to difficulties in formulating and solving the resulting regional water management problems. In this study, a robust multistage interval-stochastic programming (RISP) method is developed for dealing with vague and random information in regional water management systems. The decision variables are useful for justifying and/or adjusting the decision schemes for agricultural activities through the incorporation of their implicit knowledge on regional water management. Different policies for agricultural water supply have been analyzed. The results can help to identify desired water-allocation schemes for agricultural sustainable development that the prerequisite water demand for supporting crops’ survival can be guaranteed when the water resource is scarce.     

Economic and agronomic strategies to achieve sustainable irrigation

The achievement of sustainable irrigation in arid regions requires greater attention to waterlogging, salinization, and degradation of ground and surface waters, which are among the problems that continue to threaten productivity and degrade environmental quality. We consider sustainability to be achieved when irrigation and drainage are conducted on-farm, and within irrigation districts, in a manner that does not degrade the quality of land, water, and other natural resources, either on-farm or throughout an irrigated region. Sustainability may also be described as maintaining the productive resources required for irrigation, so that future generations may have the same opportunity to use those resources as we do. Given the increasing importance of irrigated land for food production, the time has come when it is vital to intercept, reuse, and isolate drainage waters within the regions in which they are generated. Adoption of this strategy can be enhanced by policies that require farmers, and irrigation districts, to consider the off-farm impacts of irrigation and drainage. Such policies include linking water rights with salt rights to require the monitoring and management of both irrigation water and the salt loads in drainage waters. We review the knowledge gained since the early 1970s regarding the economic and agronomic aspects of irrigation and drainage, with a focus on drainage water reduction and sequential reuse of drainage water on salt-tolerant crops. Economic incentives that motivate farm-level and district-level improvements in water management are also reviewed. We conclude that adequate knowledge exists for implementing strategies that focus on water use and salt disposal within irrigated regions, and we recommend policies that will motivate improvements in productivity and enhance the likelihood of achieving sustainability.     

Measuring and enhancing the value of agricultural water in irrigated river basins

This paper provides an overview of the issues in and approaches to measuring and enhancing the value of agricultural water in large irrigated river basins. It develops a framework and a set of indicators for valuing agricultural water by looking into various dimensions and underlying key factors that influence the value of water at micro, meso and macro levels. The indicators are applied to recent, primary- and secondary-level empirical data from the Indus basin Irrigation system of Pakistan. In addition, the paper compiles recent estimates of the value of agricultural water from 40 settings in 23 countries. Finally, the paper outlines measures for enhancing the value of agricultural water. The paper makes four main points: (1) The popular productivity indicators based on crop output do not capture the full range of benefits and costs associated with agricultural water use. (2) The value of agricultural water may not be as low as it is generally perceived or estimated when all major uses and direct and indirect benefits of water at various levels are properly accounted for. (3) The value of water varies across time and space, and the value to stakeholders at various scales (farmer, system manager, basin planner and national policy maker) could be quite different. For example, the estimate of agricultural water value in the upper Indus basin in Pakistan varies from US$0.04/m³ at the farm scale to US$0.22/m³ at the national scale. The farm-scale value is more relevant, e.g., for agricultural water charging policies, but for water-sector investments and allocation decisions, the national-scale value is important. The decision-making processes related to water sector investments, allocations, management, and charging/cost recovery schemes could be potentially misguided if key dimensions of water value that are related to water availability and use, benefits/costs, and temporal and spatial aspects are not properly accounted for in valuation. (4) Efforts should be directed not only at increasing the productivity of water in terms of mass of output per unit of water, but also the overall benefits or value of water at various levels for larger growth and poverty alleviation impacts, considering the sustainability of the systems.

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Agricultural water management and poverty linkages

Water is critically important to the livelihoods of more than 1 billion people living on less than $1 a day, particularly for the 850 million rural poor primarily engaged in agriculture. In many developing countries, water is a major factor constraining agricultural output, and income of the world's rural poor. Improved agricultural water management can contribute to poverty reduction through several pathways. First, access to reliable water improves production and productivity, enhances employment opportunities and stabilizes income and consumption. Secondly, it encourages the utilization of other yield-enhancing inputs and allows diversification into high-value products, enhances nonfarm outputs and employment, and fulfils multiple needs of households. Third, it may contribute either negatively or positively to nutritional status, health, societal equity and environment. The net impact of agricultural water management interventions on poverty may depend individually and/or synergistically on the working of these pathways. Improved access to water is essential, but not sufficient for sustained poverty reduction. Investments are needed in agricultural science and technology, policies and institutions, economic reform, addressing global agricultural trade inequities, etc. But how best to match the agricultural water management technologies, institutions and policies to the needs of the heterogeneous poor living in diverse agro-ecological settings remains unclear. This article provides a menu of promising pathways through which agricultural water management can contribute to sustained poverty reduction.     

Water harvesting and supplemental irrigation for improved water productivity of dry farming systems in West Asia and North Africa

In the dry areas, water, not land, is the most limiting resource for improved agricultural production. Maximizing water productivity, and not yield per unit of land, is therefore a better strategy for dry farming systems. Under such conditions, more efficient water management techniques must be adopted. Supplemental irrigation (SI) is a highly efficient practice with great potential for increasing agricultural production and improving livelihoods in the dry rainfed areas. In the drier environments, most of the rainwater is lost by evaporation; therefore the rainwater productivity is extremely low. Water harvesting can improve agriculture by directing and concentrating rainwater through runoff to the plants and other beneficial uses. It was found that over 50% of lost water can be recovered at a very little cost. However, socioeconomic and environmental benefits of this practice are far more important than increasing agricultural water productivity. This paper highlights the major research findings regarding improving water productivity in the dry rainfed region of West Asia and North Africa. It shows that substantial and sustainable improvements in water productivity can only be achieved through integrated farm resources management. On-farm water-productive techniques if coupled with improved irrigation management options, better crop selection and appropriate cultural practices, improved genetic make-up, and timely socioeconomic interventions will help to achieve this objective. Conventional water management guidelines should be revised to ensure maximum water productivity instead of land productivity.     

Spatial and temporal trends of water productivity in the lower Mekong River Basin

We estimate the physical and economic water productivities of rice and upland crops grown in the Lower Mekong River Basin and we examine their spatial and temporal trends. We discuss the constraints to low productivity, suggest measures for improvement and show the future productivity requirements for food security for increased population. Both the physical and economic water productivities of rice are higher in Vietnam, moderate in Laos, and lower in Thailand and Cambodia. In contrast, the physical water productivities of upland crops such as sugarcane and maize are highest in Thailand. The economic water productivity of upland crops is higher in Laos followed by Vietnam, Cambodia and Thailand, and is much higher than that of rice. However, the economic productivity of all crops is dominated by the productivity of rice, particularly lowland rainfed rice, which is the dominant crop in the Lower Basin. The intra-regional variation (among the provinces within a country) of productivity is not substantial. There is an increasing trend of both physical and economic water productivity in all four riparian countries; however, the increase is more prominent in Laos and Vietnam. The economic productivity of upland crops is much higher than that of rice and therefore cultivation of more upland crops can significantly increase farm-level incomes, with positive impacts on reducing poverty. Increasing upland crops areas is unlikely to have any impact on the food security of the basin. The current rate of increase of both production and productivity of rice is considerably greater than the rate required to feed the expected extra population by 2050, suggesting that food security is not threatened by the population increase. There appears to be considerable scope to increase productivity and maintain the export potential of the basin.     

基于混合DEA的临沂市农业土地利用效率研究

本文采用BCC模型和Malmquist指数方法,对临沂市2017-2020年的农业土地利用效率进行静态、动态分析。研究结果表明,临沂市整体农业土地利用效率水平在0.969左右,制约农业土地利用效率的关键是规模效率较低,大部分县级区域存在不同程度的规模效率和纯技术效率的提升空间,且在农业要素投入过程中存在一定程度的冗余和浪费。临沂市农业土地利用的全要素生产率呈上升趋势,并且存在明显的波动,技术进步率对于全要素生产率贡献较大,发展状态良好。临沂市各县级区域应因地制宜的调整农业政策,加大农业科技的投入,推行土地流转,优化资源投入结构。     

基于评价的水资源优化模型适用性比较

为了比较不同目标的水资源优化配置模型在黑河中游的适用性,在充分考虑地表径流随机性的基础上,分别构建以灌区农业水生产力最大、农业灌溉损失最小、净经济效益最大为目标函数的灌区水资源优化配置模型,并引入多指标综合评价法以及熵权法对3个优化模型的配置结果进行综合效应评价．评价结果显示,基于黑河中游水资源利用现状,以灌区农业水生产力最大为目标函数的模型,更适合现阶段黑河中游灌区水资源配置要求．使用灌溉水生产力最大为目标函数的优化模型对有限水资源进行优化后的配水方案整体用水比现状水平年减少了334×108 m3,灌溉水生产力增加了0453 kg／m3,用水成本比实际减少了421×107元．评价结果验证了水资源优化配置模型方案评价的可行性．     

Planning and management modeling for treated wastewater usage

Due to urban growth, some agricultural lands have been replaced by residential, municipal, and industrial areas. In some cases the remaining agricultural land will not have enough water because of transfers from agriculture to M&I (municipal and industrial) users. Therefore, in many places, especially in arid and semi-arid regions, the use of treated wastewater as a reliable source of irrigation water has already been, or will be, considered in the future. Due to its unique characteristics, this new resource has many challenges that cannot be ignored, such as health issues, water quality, and long- and short-term effects on soils and crops. The study described herein considered the development of a new GIS-based model for planning and managing the reuse of treated wastewater for the irrigation of agricultural and green lands, considering various factors such as population and urban growth. The model is composed of several different modules, including an urban growth model. These modules are designed to help in the decision-making process for allocations of water resources to agricultural areas, considering factors such as crop types, crop pattern, water salinity, soil characteristics, pumping and conveyance costs, and also by comparing different management scenarios. Appropriate crops that can be grown with a specific water salinity and soil characteristics, proper water resources for each farm (according to pumping and conveyance costs, and analysis of water demand, and water supply) can be determined through the application of this model. The model can also rank agricultural areas and open spaces in and near an urban area according to their suitability for irrigated agriculture.     

Livestock water productivity in mixed crop–livestock farming systems of the Blue Nile basin: Assessing variability and prospects for improvement

Water scarcity is a major factor limiting food production. Improving Livestock Water Productivity (LWP) is one of the approaches to address those problems. LWP is defined as the ratio of livestock’s beneficial outputs and services to water depleted in their production. Increasing LWP can help achieve more production per unit of water depleted. In this study we assess the spatial variability of LWP in three farming systems (rice-based, millet-based and barley-based) of the Gumera watershed in the highlands of the Blue Nile basin, Ethiopia. We collected data on land use, livestock management and climatic variables using focused group discussions, field observation and secondary data. We estimated the water depleted by evapotranspiration (ET) and beneficial animal products and services and then calculated LWP. Our results suggest that LWP is comparable with crop water productivity at watershed scales. Variability of LWP across farming systems of the Gumera watershed was apparent and this can be explained by farmers’ livelihood strategies and prevailing biophysical conditions. In view of the results there are opportunities to improve LWP: improved feed sourcing, enhancing livestock productivity and multiple livestock use strategies can help make animal production more water productive. Attempts to improve agricultural water productivity, at system scale, must recognize differences among systems and optimize resources use by system components.     

机械化地块整治是丘陵山区实现现代化农业的重要举措

随着时代的发展,农业发展趋于现代化,其突出表现为“资源利用率”、“劳动生产率”、“土地产出率”不断提高。文章首先分析丘陵山区农业现代化进程缓慢的原因,随后提出几点推动丘陵山区农业现代化进程的措施,以期为更好整治土地、推动丘陵山区农业现代化做出贡献。     

On the estimation of on-farm benefits of agricultural research

The on-farm benefits of agricultural research or extension often depend in complex ways on the way that the new technology or information affects the farming system. The existence of farming system-wide impacts of research and extension is highlighted as a critical but neglected issue in economic evaluations of agricultural research. The issue is neglected in the available texts on agricultural research evaluation and in most applied evaluations. Given the difficulty and complexity of accurate benefit estimation, we see a renewed role for farm-level economic models (such as whole-farm linear programming models) in this area. The benefits of undertaking a more sophisticated and detailed analysis to estimate research benefits include not just greater accuracy but also greater credibility with researchers and greater relevance through representing factors which they perceive to be important. The paper discusses how, if such respect is engendered, a formal research evaluation can yield additional benefits by improving the design of research.     

亚热带丘岗山区雨水资源开发利用

以亚热带丘岗山区的典型区域——衡阳盆地为研究对象，分析了其雨水资源利用的必要性、可行性。提出了衡阳盆地雨水资源化的初步设想：一是强化雨水就地利用，构建衡阳经济社会发展的生态屏障；二是积极推广庭院雨水集蓄，发展庭院经济；三是适当发展雨水集蓄小型灌溉工程，提高农业生产的水分保证率。     

Modeling wheat yield and crop water productivity in Iran: Implications of agricultural water management for wheat production

In most parts of Iran, water scarcity has been intensifying and posing a threat to the sustainability of agricultural production. Wheat is the dominant crop and the largest irrigation water user in Iran; hence, understanding of the crop yield-water relations in wheat across the country is essential for a sustainable production. Based on a previously calibrated hydrologic model, we modeled irrigated and rainfed wheat yield (Y) and consumptive water use (ET) with uncertainty analysis at a subbasin level in Iran. Simulated Y and ET were used to calculate crop water productivity (CWP). The model was then used to analyze the impact of several stated policies to improve the agricultural system in Iran. These included: increasing the quantity of cereal production through more efficient use of land and water resources, improving activities related to soil moisture conservation and retention, and optimizing fertilizer application. Our analysis of the ratio of water use to internal renewable water resources revealed that 23 out of 30 provinces were using more than 40% of their water resources for agriculture. Twelve provinces reached a ratio of 100% and even greater, indicating severe water scarcity and groundwater resource depletion. An analysis of Y-CWP relationship showed that one unit increase in rainfed wheat yield resulted in a lesser additional water requirement than irrigated wheat, leading to a larger improvement in CWP. The inference is that a better water management in rainfed wheat, where yield is currently small, will lead to a larger marginal return in the consumed water. An assessment of improvement in soil available water capacity (AWC) showed that 18 out of 30 provinces are more certain to save water while increasing AWC through proper soil management practices. As wheat self-sufficiency is a desired national objective, we estimated the water requirement of the year 2020 (keeping all factors except population constant) to fulfill the wheat demand. The results showed that 88% of the additional wheat production would need to be produced in the water scarce provinces. Therefore, a strategic planning in the national agricultural production and food trade to ensure sustainable water use is needed. This study lays the basis for a systematic analysis of the potentials for improving regional and national water use efficiency. The methodology used in this research, could be applied to other water scarce countries for policy impact analysis and the adoption of a sustainable agricultural strategy.     

Agricultural land use and flood risk management: Engaging with stakeholders in North Yorkshire

Recent changes in agricultural and flood defence policies create new opportunities for involving rural land use, in particular agriculture, in flood risk management. This paper presents the results of a case study on land management and flooding in the Laver and Skell catchments in North Yorkshire. The perceptions of local stakeholders were explored through interviews with farmers and discussions among stakeholders that were held, supported by the Floods and Agriculture Risk Matrix (FARM) tool, during a stakeholder workshop. These stakeholder perceptions are reviewed against scientific evidence. Temporary storage of runoff water on farmland was found to have potential to mitigate flooding, but the participating stakeholders thought that this was beyond farmers’ responsibility of good farming practice. During the stakeholder workshop, it was therefore agreed among all participants that targeting funding is needed, as well as stakeholder engagement and demonstration farms, in order to successfully involve farmers in flood risk management.     

Production policies for pastoralists: The Borana case

The design of improved technology or production policies depends upon evaluation of alternative options in terms of their efficiency.Measurement of the efficiency of a pastoral livestock system may be based on the food energy output per livestock unit, while rangeland carrying capacity is assessed in terms of livestock units per square kilometre. On this basis we conclude that, for the Sidamo Borana and probably other pastoral societies: (i) rangeland carrying capacity is limited by the existing density of dry-season waterpoints rather than the primary productivity of the rangeland, with the implication that research in hydrology and design of water supplies may be more beneficial than studies aimed at increasing primary productivity of the rangeland; (ii) that pastoralists have a comparative advantage in milk production and, up to a point, human consumption is a more efficient use of milk than feeding it to calves; (iii) the trade of livestock products for grain is essential for survival.     

FSWM: A hybrid fuzzy-stochastic water-management model for agricultural sustainability under uncertainty

A hybrid fuzzy-stochastic water-management (FSWM) model is developed for agricultural sustainability under uncertainty, based on advancement of a multistage fuzzy-stochastic quadratic programming (MFSQP) approach. In MFSQP, uncertainties presented in terms of fuzziness and randomness can be incorporated within a multilayer scenario tree, such that revised decisions are permitted in each time period based on the realized values of the uncertain events. Moreover, fuzzy quadratic terms are used in the objective function to minimize the variation of satisfaction degrees among the constraints; it allows an increased flexibility in controlling the system risk in the optimization process. Results of the case study indicate that useful solutions for the planning of agricultural water management have been obtained. In the FSWM model, a number of policies for agricultural water supply are conducted. The results obtained can help decision makers to identify desired water-allocation schemes for agricultural sustainability under uncertainty, particularly when limited water resources are available for multiple competing users.     

Changes in system performance in two Chinese irrigation systems as a result of organizational reforms

Drawing on a study of two irrigation systems in Hebei Province, this paper documents the impacts of rural economic and organization reforms on irrigation system performance. In the two systems, prior to development of irrigation, farmers consumed all their grain within the household. However, at present both districts are selling grain, with annual output of 11.9 tons/hectare in Bayi and 8.5 tons/hectare in Nanyao. However, due to the use of groundwater in Bayi, output per unit of water is 1.5 kg/m3 in Bayi and 1.3 kg/m3 in Nanyao. In Bayi, farmers have augmented declining surface water supplies with groundwater and purchased water – using funds from sideline enterprises – and have increased output. In contrast, in Nanyao both income and grain output increases have reached a plateau. Nanyao, with its weak resource base, will probably need to develop additional income sources to be able to improve water management in order to reach the next plateau of productivity.     

Modified rice cultivation in Tamil Nadu,India: Yield gains and farmers’ (lack of) acceptance

The looming water crisis and water-intensive nature of rice cultivation are driving the search for alternative management methods to increase water productivity in rice cultivation. Experiments were conducted under on-station and on-farm conditions to compare rice production using modified methods of irrigation, planting, weeding and nutrient management with conventional methods of cultivation. Farm surveys were used to evaluate adoption of modified rice cultivation method. On-station experiments showed that, a combination of water-saving irrigation, young seedling or direct seeding, mechanical weeding and green manure application increased the rice water productivity though the largest yields were obtained for a combination of conventional irrigation, young seedling or direct seeding, mechanical weeding and green manure application. On-farm experiments demonstrated a yield advantage of 1.5 t ha⁻¹ for the modified method over conventional method. We found, however, that yield advantages were not the sole factor driving adoption. Associated changes required in management, including the increased labour demand for modified planting, unwillingness of agricultural labourers to change practices, difficulties with modified nursery preparation and the need to replace cheaper women’s labour for hand weeding with more costly men’s labour for mechanical weeding, all reduced the chance of adopting the modified rice cultivation method. Risks associated with water-saving irrigation, such as uncertainty about the timing and amount of water release for irrigation affect adoption adversely as well. There was no incentive for farmers to adopt water-saving irrigation as water from reservoirs and electricity for pumping well-water are both free of charge. To date farmers continue to experiment with the modified cultivation method on a small part of their farms, but are unlikely to adopt the modified method on a large-scale unless policies governing water management are changed.