Non-conventional water resources and opportunities for water augmentation to achieve food security in water scarce countries

Given current demographic trends and future growth projections, as much as 60% of the global population may suffer water scarcity by the year 2025. The water-use efficiency techniques used with conventional resources have been improved. However, water-scarce countries will have to rely more on the use of non-conventional water resources to partly alleviate water scarcity. Non-conventional water resources are either generated as a product of specialized processes such as desalination or need suitable pre-use treatment and/or appropriate soil–water–crop management strategies when used for irrigation. In water-scarce environments, such water resources are accessed through the desalination of seawater and highly brackish groundwater, the harvesting of rainwater, and the use of marginal-quality water resources for irrigation. The marginal-quality waters used for irrigation consist of wastewater, agricultural drainage water, and groundwater containing different types of salts. In many developing countries, a major part of the wastewater generated by domestic, commercial, and industrial sectors is used for crop production in an untreated or partly treated form. The protection of public health and the environment are the main concerns associated with uncontrolled wastewater irrigation. The use of saline and/or sodic drainage water and groundwater for agriculture is expected to increase. This warrants modifications in the existing soil, irrigation, and crop management practices used, in order to cope with the increases in salinity and sodicity that will occur.     

生态文明视角下日照市农业水资源高效利用

在全球气候变暖和淡水资源短缺背景下,日照市作为滨海城市典型代表,实现农业水资源的高效利用是贯彻生态文明建设、实现可持续发展的必由之路。结合日照市气象、水资源等条件,针对农田水利发展、土地利用等情况,探讨生态文明视角下日照地区实现农田水资源高效利用的思路。研究表明:日照市农业人口、耕地分布表现出地域性差异,旱地面积比例较大,蓄水工程相对缺乏,严重制约着农业发展,影响着生态文明建设。合理有效地进行农田水利工程建设与维护、水土保持工作和节水灌溉技术的引进,可全面促进资源合理利用和农业多功能开发,为滨海地区农业水资源高效利用提供借鉴。      

Investing in water for food, ecosystems, and livelihoods: An overview of the comprehensive assessment of water management in agriculture

The authors of the recently completed Comprehensive Assessment of Water Management in Agriculture (CA) concluded that there are sufficient water resources to produce food for a growing population but that trends in consumption, production and environmental patterns, if continued, will lead to water crises in many parts of the world. Only if we act to improve water use will we meet the acute fresh water challenge. Recent spikes in food prices, partially caused by the increasing demand for agricultural products in non-food uses, underline the urgent need to invest in agricultural production, of which water management is a crucial part. The world experienced similar pressure on per capita food supplies and food prices in the 1960s and 1970s, but the challenges now are different than those we experienced 50 years ago. The world's population is substantially larger, there are many more people living in poverty, and the costs of many agricultural inputs are much higher. The current situation and the long-term outlook require a fresh look at approaches that combine different elements such as the importance of access to water for the poor, providing multiple ecosystem services, rainwater management, adapting irrigation to new needs, enhancing water productivity, and promoting the use of low-quality water in agriculture. This special issue highlights the analysis behind a number of policy options identified by the CA, a five-year multi-disciplinary research program involving 700 scientists. This introductory article sets the background and context of this special issue, introduces the key recommendations from the CA and summarizes the papers in this issue.     

Wastewater production, treatment, and irrigation in Middle East and North Africa

The Middle East and North Africa (MENA) region is the driest region of the world with only 1% of the world’s freshwater resources. The increasing competition for good-quality water has cut into agriculture’s water share but since the use of freshwater for domestic, industrial and municipal activities generates wastewater, the volume of wastewater used in agriculture has increased. About 43% of wastewater generated in the MENA region is treated; a relatively high percentage compared to other developing-country dominated regions. This is because of the perceived importance of wastewater as a water resource and several oil-rich countries with the resources to treat wastewater. The MENA region has an opportunity for beneficial reuse of wastewater but few countries in the region have been able to implement substantial wastewater treatment and reuse programs. The major constraints leading to seemingly slow and uneven reuse of wastewater are: inadequate information on the status of reuse or disposal of wastewater and associated environmental and health impacts; incomplete economic analysis of the wastewater treatment and reuse options, usually restricted to financial feasibility analysis; high costs and low returns of developing wastewater collection networks and wastewater treatment plants; lack of wastewater treatment and reuse cost-recovery mechanisms and lack of commitment to support comprehensive wastewater treatment programs; mismatch between water pricing and regional water scarcity; preference for freshwater over wastewater; and inefficient irrigation and water management schemes undermining the potential of wastewater reuse. However, some countries such as Tunisia, Jordan, and Israel have policies in place that address wastewater treatment through a range of instruments. Policymakers in these countries consider use of treated wastewater to be an essential aspect of strategic water and wastewater planning and management. With flexible policy frameworks addressing rapid demographic changes and increasing water scarcity in the MENA region, water reuse has great potential if integrated with resource planning, environmental management and financing arrangements.     

Managing water in rainfed agriculture—The need for a paradigm shift

Rainfed agriculture plays and will continue to play a dominant role in providing food and livelihoods for an increasing world population. We describe the world's semi-arid and dry sub-humid savannah and steppe regions as global hotspots, in terms of water related constraints to food production, high prevalence of malnourishment and poverty, and rapidly increasing food demands. We argue that major water investments in agriculture are required. In these regions yield gaps are large, not due to lack of water per se, but rather due to inefficient management of water, soils, and crops. An assessment of management options indicates that knowledge exists regarding technologies, management systems, and planning methods. A key strategy is to minimise risk for dry spell induced crop failures, which requires an emphasis on water harvesting systems for supplemental irrigation. Large-scale adoption of water harvesting systems will require a paradigm shift in Integrated Water Resource Management (IWRM), in which rainfall is regarded as the entry point for the governance of freshwater, thus incorporating green water resources (sustaining rainfed agriculture and terrestrial ecosystems) and blue water resources (local runoff). The divide between rainfed and irrigated agriculture needs to be reconsidered in favor of a governance, investment, and management paradigm, which considers all water options in agricultural systems. A new focus is needed on the meso-catchment scale, as opposed to the current focus of IWRM on the basin level and the primary focus of agricultural improvements on the farmer's field. We argue that the catchment scale offers the best opportunities for water investments to build resilience in small-scale agricultural systems and to address trade-offs between water for food and other ecosystem functions and services.     

Evaluation of soil salinity leaching requirement guidelines

Water for irrigation is a major limitation to agricultural production in many parts of the world. Use of waters with elevated levels of salinity is one likely option to meet the supply of increased demands. The sources of these waters include drainage water generated by irrigated agriculture, municipal wastewater, and poor quality groundwater. Soil salinity leaching requirements that were established several decades ago were based on steady-state conditions. Recently transient-state models have been developed that potentially can more correctly predict the dynamics of the chemical-physical-biological interactions in an agricultural system. The University of California Center for Water Resources appointed a workgroup to review the development of steady-state analyses and transient-state models, and to determine whether the current recommended guidelines for leaching requirement based on steady-state analyses need to be revised. The workgroup concludes that the present guidelines overestimate the leaching requirement and the negative consequences of irrigating with saline waters. This error is particularly large at low leaching fractions. This is a fortuitous finding because irrigating to achieve low leaching fractions provides a more efficient use of limited water supplies.     

灌溉农田高效用水研究进展与发展趋势

为提高水资源的利用率,发展高效用水农业首先要发展节水灌溉,在农业水利灌溉领域,通过分析国际先进的节水模式及水资源高效利用技术,评价我国灌溉农业高效用水工程进展。针对我国人口与水、土地等资源的矛盾问题,论述我国水资源现状和农业用水状况以及我国节水灌溉进展,指出我国农业节水灌溉现状和推广中存在问题。提出了加提高节水意识,健全节水法规,发挥政府职能,提高资金投入,不断加强节水灌溉技术创新以及落实管护责任等改进建议,激发节水灌溉工程长效运行等方式以推进我国灌溉农田高效用水发展进程。     

基于SD变化环境下农业水资源供需平衡模拟

为了探讨变化环境对农业水资源供需平衡的影响,运用系统动力学软件Vensim-Dss建立了农业水资源供需平衡的系统动力学模型,综合考虑社会经济发展和气候变化情景,仿真模拟了变化环境下农业供、需水量及缺水量的变化情况.石羊河流域模拟结果表明:未来农业供水量和需水量受气候变化的影响程度不同,但 2033年以后,农业供水量在不同气候变化情景下的变化趋势相同;不同行政区农业水资源系统对气候变化的响应存在明显差异,金昌市A2气候情境缺水率大于B2情景,在2029年、2038年缺水率分别达到32.0%,28.6%, B2情境下,2021年开始出现轻度缺水,中度缺水年仅出现在2023年和2039年,缺水率分别为30.7%,30.5%;武威市A2气候情境下缺水率小于B2情景,仅2038年为中度缺水,缺水率为24.9%,B2气候情景中度缺水年较多,2023年缺水率最大,达到33.2%.研究结果可以对变化环境下区域用水规划和农业发展规划提供指导.     

塔里木河流域基于资源环境水价的农业水价的承受力分析

首先在成本水价基础上,分别构建塔河流域作物和流域基于水资源费的未来农业水价,然后进一步汇总和计算了塔河流域农户对基于资源环境水价的未来农业水价的承受力分析的基本指标;在此基础上,分析了塔河流域农户对基于资源环境水价的未来农业水价的承受力,主要结果表明：除叶尔羌河、和田河流域和干流下游基于资源环境水价的未来流域和作物水价的农户承受力超过适宜经济承受力外,其它源流和干流上中游的农户水价承受力则处于适宜经济承受力范围,未来塔河流域应当实行差别水价政策;干流下游、叶尔羌河流域未来农业水价承受力很低,尤其是流域未来粮食作物水价的承受力很低,必须给予粮食作物农业水价直接补偿。而且,环境水价对农户水价承受力影响较小,能够成为未来流域生态环境保护的主要经济手段。     

Water productivity in rainfed systems: overview of challenges and analysis of opportunities in water scarcity prone savannahs

Addressing the Millennium Development Goals on food and poverty over the coming decade puts enormous pressure on the world’s finite freshwater resources. Without water productivity (WP) gains, the additional freshwater in agriculture will amount to 5,600 km³ year⁻¹ in 2050. This is three times the current global irrigation use. This paper focuses on the underlying processes and future opportunities of WP gains in water scarcity prone and poverty stricken savannah regions of the world. The paper studies the consumptive (green) WP dynamics rainfed farming systems, and shows that the often assumed linear relationship between evapotranspiration (ET) and yield (Y) does not translate into constant WP over a wide range of yields. Similarly, crop transpiration (T) and Y show non-linearity under on-farm and low yield conditions. This non-linearity is validated against several on-farm research experiments in semi-arid rainfed farming systems. With integrated soil and water management, focusing on dry spell mitigation and soil fertility can potentially more than double on-farm yields, while simultaneously improve green (ET) WP and productive green (T) WP. Through the adoption of appropriate soil and water management in semi-arid smallholder farming systems, crop yields improve and result in improved livelihoods and WP gains.     

浅析我国农业节水灌溉技术研究及进展

中国是世界上人均水资源占有量最贫乏的13个国家之一,水是农业的命脉,水资源的严重不足,使我国农业发展面临非常大的挑战。发展节水灌溉技术是我国未来农业发展的一项重大战略决策,也是坚持绿色发展理念的必然选择。为了解我国农业节水灌溉技术现状和研究进展,本文通过综合分析国内外节水灌溉技术现状,梳理我国目前主要的节水灌溉工程技术,总结我国在农业节水灌溉技术现阶段面临的主要问题和未来发展趋势。     

Managing water by managing land: Addressing land degradation to improve water productivity and rural livelihoods

The premise of this paper is that the key to effective water resources management is understanding that the water cycle and land management are inextricably linked: that every land use decision is a water use decision. Gains in agricultural water productivity, therefore, will only be obtained alongside improvements in land use management. Expected increases in food demands by 2050 insist that agricultural production - and agricultural water use - must increase. At the same time, competition for water between agricultural and urban sectors will also increase; and the problem is further compounded by land degradation. A global survey suggests that 40% of agricultural land is already degraded to the point that yields are greatly reduced, and a further 9% is degraded to the point that it cannot be reclaimed for productive use by farm level measures. Soil erosion, nutrient depletion and other forms of land degradation reduce water productivity and affect water availability, quality, and storage. Reversing these trends entails tackling the underlying social, economic, political and institutional drivers of unsustainable land use. This paper is based on a review of global experiences, and its recommendations for improving water management by addressing land degradation include focusing on small scale agriculture; investing in rehabilitating degraded land to increase water productivity; and enhancing the multifunctionality of agricultural landscapes. These options can improve water management and water productivity, while also improving the livelihoods of the rural poor.     

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.     

我国农机信息化技术发展的区域特征分析

当前，我国进入了农机信息化高速发展的时代。不同于世界其他国家，我国由于地形多样化，农机信息化表现出了明显的区域特点。本文针对不同场景农机信息化情况进行分析，并在农机化发展现状的基础上研究其共性特征，对农机信息化未来发展重点方向进行预测。     

Impacts of population growth, economic development, and technical change on global food production and consumption

Over the next decades mankind will demand more food from fewer land and water resources. This study quantifies the food production impacts of four alternative development scenarios from the Millennium Ecosystem Assessment and the Special Report on Emission Scenarios. Partially and jointly considered are land and water supply impacts from population growth, and technical change, as well as forest and agricultural commodity demand shifts from population growth and economic development. The income impacts on food demand are computed with dynamic elasticities. Simulations with a global, partial equilibrium model of the agricultural and forest sectors show that per capita food levels increase in all examined development scenarios with minor impacts on food prices. Global agricultural land increases by up to 14% between 2010 and 2030. Deforestation restrictions strongly impact the price of land and water resources but have little consequences for the global level of food production and food prices. While projected income changes have the highest partial impact on per capita food consumption levels, population growth leads to the highest increase in total food production. The impact of technical change is amplified or mitigated by adaptations of land management intensities.     

基于县域尺度的中国农业水资源利用效率评价

基于县域尺度,选取降水产出率、灌溉水产出率、灌溉指数和总水分生产率4个指标,定量评价了中国不同地区(台湾省除外)的农业水资源利用效率,在此基础上,利用GIS空间分析技术,分析了各个指标的空间区域差异。结果表明,全国平均总水分生产率仅为0.61kg/m3,与发达国家的水生产效率相比,还有很大的潜力空间;黄淮海平原区、四川盆地、长江中下游区的农业水资源利用效率较高;在天然降水和灌溉水资源均较丰富的江南区和华南区,除灌溉指数较高外,其他3个指标都处于中等或中等偏低水平。总水分生产率和降水产出率的低值区空间分布基本一致,主要分布在大小兴安岭区、内蒙古高原区、黄土高原北部、横断山区一线;西北区的灌溉水资源浪费严重,亟待提高。     

Use of saline and non-potable water in the turfgrass industry: Constraints and developments

The need for salt-tolerant turfgrasses is ever-increasing. Rapid urban population growth has put enormous pressures on limited freshwater supplies. Many state and local governments have reacted by placing restrictions on the use of potable water for irrigating turfgrass landscapes, instead requiring use of reclaimed, or other secondary saline water sources. In coastal areas, overpumping, and resultant salt water intrusion of coastal wells used for irrigating turfgrass facilities has widely occurred. The nature and extent of the salinity problem, followed by basic salinity issues and available management choices, will be discussed. Issues facing the turf manager using saline water sources are soil salinization, resulting in direct salt injury to turf, and secondary problems of loss of soil structure ensuing from sodium and bicarbonate effects, resulting in loss of salt leaching potential and soil anaerobiosis. Management choices for the turf manager using saline water are limited. Soil salinity must be maintained below the level deemed detrimental to the turf, by maintaining sufficient leaching. Sodium/bicarbonate affected soils must be managed to maintain sufficient permeability to permit adequate leaching. Finally, salt tolerant turf species/cultivars must be used. Long-term solutions to the salinity problem will require development of improved salt-tolerant turfgrasses. Progress in cultivar development, and future development of potential alternative halophytic turfgrass species will also be discussed.     

Satisfying future water demands for agriculture

The global demand for water in agriculture will increase over time with increasing population, rising incomes, and changes in dietary preferences. Increasing demands for water by industrial and urban users, and water for the environment will intensify competition. At the same time, water scarcity is increasing in several important agricultural areas.We explore several pathways for ensuring that sufficient food is produced in the future, while also protecting the environment and reducing poverty. We examine four sets of scenarios that vary in their focus on investments in rainfed agriculture and irrigation, and the role of international trade in adjusting for national disparities in water endowments. Rainfed agriculture holds considerable potential but requires adequate mechanisms to reduce inherent risks. Irrigation expansion is warranted in places where water infrastructure is underinvested such as sub-Saharan Africa. In South Asia the scope for improving irrigation performance and water productivity is high. International trade can help alleviate water problems in water-scarce areas, subject to economic and political considerations. We examine also a regionally optimized scenario that combines investments in rainfed and irrigated agriculture with strategic trade decisions. Compared to ‘business as usual’, this scenario reduces the amount of additional water required to meet food demands by 2050 by 80%. Some of that water could be made available for the environment and other sectors. We conclude that there are sufficient land and water resources available to satisfy global food demands during the next 50 years, but only if water is managed more effectively in agriculture.     

Irrigation and food security in the 21st century

Global food projections indicate that food prices in the next threedecades will likely be stable or decline, but progress inreducing malnutrition in developing countries will be slow. Smallshortfalls in crop productivity growth would lead to rising foodprices and worsening malnutrition. Increased food production fromirrigation is essential, and will require expansion of irrigatedarea and water supplies, and improved efficiency of use of existingwater supplies. Neither of these growth factors will prove easy, andboth will require complex institutional and policy reforms. Failureto meet food production needs through efficient expansion andintensification of irrigated agriculture would increase pressure onland resources and hasten the process of environmental degradation.Irrigation and water development strategies have been hampered bya lack of understanding of the links between water scarcity, foodproduction, food security, and environmental sustainability.Research to improve this understanding would have high payoffs.     

Enhancing water policy discussions by including analysis of non-water inputs and farm-level constraints

Water resource professionals have many opportunities to contribute to policy discussions regarding agricultural productivity. Often those discussions are focused on increasing the output generated with limited water supplies, such as maximizing the “crop per drop” or improving irrigation efficiencies, either at the field level or throughout a river basin. Policy discussions involving water resources in developing countries can be enhanced by placing greater emphasis on the roles of non-water inputs and resource constraints in farm-level production and marketing decisions. Three categories of policies that lie outside the water resource realm, but have substantial impacts on water use and agricultural productivity, are examined: (1) policies that modify farm-level input and output prices directly; (2) international trade policies; and (3) policies that modify key institutions, such as land tenure and the sources of investment funds.