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.     

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.     

Fit for purpose: taking integrated water resource management back to basics

Integrated Water Resource Development and Management (IWRM) was the paradigm recommended for water resource management at the UN Conference on Environment and Development (UNCED) in Rio de Janeiro in 1992. Subsequently, however, “development” disappeared from the IWRM lexicon and the Dublin Principles, a preconference lobbying product, were widely promoted instead. A review of case studies suggests that the normative approach of Dublin has constrained infrastructure investments in developing countries, often ignoring the context within which water resources are managed. As a result, its positive outcomes have been limited. Meanwhile, in countries following the Rio approach, water management has made significant contributions to broad development objectives. It is suggested that a return to the UNCED agreement is needed to address effectively the challenges to water management posed by economic transformation, population growth and climate change.     

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.     

Economic analysis of water harvesting in a mountainous watershed in India

Water management is an essential feature of any project related with overall development of agriculture. The Soan river catchment in the northwest Himalayas, is fed only by rainwater. Hence, a strategy of rainfed agriculture needs to be developed through water conservation and storage techniques. The Soan is an important river from a soil erosion and water management point of view and detailed economic analysis is needed for any proposal to be implemented in the field. The present study was undertaken to propose an economic analysis of water harvesting structures for the Soan catchment. The purpose of the investigation is to control erosion and conserve water to meet the requirements of supplemental and pre-sowing irrigation for major cereal crops in the area and to maximise agricultural productivity. Benefit/cost ratios ranging from 0.41 to 1.33 are obtained for water harvesting structures of different sizes with estimated life of 25 and 40 years respectively, by taking into account different crop return from maize and wheat.     

Reducing poverty in sub-Saharan Africa through investments in water and other priorities

Water resources are essential to human development processes and to achieve the Millennium Development Goals that seek, inter alia, to eradicate extreme poverty and hunger, achieve universal literacy, and ensure environmental sustainability. Expanding irrigation is essential to increase agricultural production, which is needed to achieve economic development and attain food security in much of sub-Saharan Africa. Water resources and irrigated agriculture are not developed to their full potential. Currently less than 4% of renewable water resources in Africa are withdrawn for agriculture. Barriers include the lack of financial and human resources to build irrigation and related rural infrastructure and acquire agricultural technology, and inadequate access to markets. This constrains progress towards poverty reduction. We examine the linkages between agricultural water, education, markets and rural poverty through a review of published studies. We argue that, linking agricultural water, education, and market interventions, which are so often implemented separately, would generate more effective poverty reduction and hunger eradication programs. Investments in agricultural water management and complementary rural infrastructure and related policies are the pathways to break the poverty trap in smallholder African agriculture.     

A comparative analysis of rainfed and irrigated agricultural production in Ethiopia

Ethiopia’s economy is dependent on agriculture which contributes more than 50% to GDP, about 60% to foreign exchange earning and provides livelihood to more than 85% of the population. Ethiopia has a large potential of water resources that could be developed for irrigation. Despite the large water resources, Ethiopia continues to receive food aid to about 10% of the population who are at risk annually, out of a total of more than 67 million. The government of Ethiopia is committed to solving this paradox through an agricultural led development program that includes irrigation development as one of the strategies. This paper compares rainfed and irrigated agricultural production in Ethiopia. Using the stochastic production frontier approach, the study concludes that irrigation development in Ethiopia is a viable development strategy but attention needs to be paid to improving the technology available to farmers under both rainfed and irrigated production.     

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.     

Urban growth, wastewater production and use in irrigated agriculture: a comparative study of Accra, Addis Ababa and Hyderabad

The relationships between urban development, water resources management and wastewater use for irrigation have been studied in the cities of Accra in Ghana, Addis Ababa in Ethiopia and Hyderabad in India. Large volumes of water are extracted from water sources often increasingly far away from the city, while investments in wastewater management are often lagging behind. The resulting environmental degradation within and downstream of cities has multiple consequences for public health, in particular through the use of untreated wastewater in irrigated agriculture. Despite significant efforts to increase wastewater treatment, options for safeguarding public health via conventional wastewater treatment alone remain limited to smaller inner-urban watersheds. The new WHO guidelines for wastewater irrigation recognize this situation and emphasize the potential of post- or non-treatment options. Controlling potential health risks will allow urban water managers in all three cities to build on the benefits from the already existing (but largely informal) wastewater reuse, those being the contribution to food security and reduction of fresh water demands.     

Estimating the potential of rainfed agriculture in India: Prospects for water productivity improvements

A detailed district and agro-ecoregional level study comprising the 604 districts of India was undertaken to (i) identify dominant rainfed districts for major rainfed crops, (ii) make a crop-specific assessment of the surplus runoff water available for water harvesting and the irrigable area, (iii) estimate the efficiency of regional rain water use and incremental production due to supplementary irrigation for different crops, and (iv) conduct a preliminary economic analysis of water harvesting/supplemental irrigation to realize the potential of rainfed agriculture. A climatic water balance analysis of 225 dominant rainfed districts provided information on the possible surplus runoff during the year and the cropping season. On a potential (excluding very arid and wet areas) rainfed cropped area of 28.5 million ha, a surplus rainfall of 114 billion m³ (Bm³) was available for harvesting. A part of this amount of water is adequate to provide one turn of supplementary irrigation of 100 mm depth to 20.65 Mha during drought years and 25.08 Mha during normal years. Water used in supplemental irrigation had the highest marginal productivity and increase in rainfed production above 12% was achievable even under traditional practices. Under improved management, an average increase of 50% in total production can be achieved with a single supplemental irrigation. Water harvesting and supplemental irrigation are economically viable at the national level. Net benefits improved by about threefold for rice, fourfold for pulses and sixfold for oilseeds. Droughts have very mild impacts on productivity when farmers are equipped with supplemental irrigation.     

Pathways to breaking the poverty trap in Ethiopia: Investments in agricultural water, education, and markets

Investments in agricultural water management should complement or strengthen the livelihood and coping systems of the rural poor, and should thus be instrumental for breaking the poverty trap in Ethiopia. Underdeveloped water resources constrain progress towards poverty reduction. We examine linkages and complementarities between agricultural water, education, markets and rural poverty through an empirical study using household level data from selected villages in southern Ethiopia. We show that investments in irrigation can contribute to poverty reduction, but the poverty reducing impacts of irrigation water are greater when human capital and rural markets are well developed. The size of landholding, access to irrigation water, on-farm land and water conservation practices, literacy of the household head, and years of education of adults are all significant determinants of household welfare, and thus potential pathways for reducing poverty. Expansion of cultivated land, particularly irrigated land, universal literacy, and an extra school year for adults all reduce poverty, but reductions in poverty are greater when irrigation is combined with universal literacy. These findings call for simultaneous investments in agricultural water, education, markets and related policy support measures for reducing poverty in smallholder agriculture in Ethiopia.     

Increasing water productivity with improved N fertilizer management

There is continuing debate about the role of water productivity and the potential to increase it in response to significantly increased water demand to meet the future needs for food—estimated to be roughly double that of today by 2050. The debate centers round the relative potential benefits of enhancing rainfed agriculture, improving irrigation and expanding areas of both. All expansion and intensification options will require significantly more water to be used, often in places where the ecosystem impacts of agriculture are already severe. Improvement in water productivity can result from improving the provision and management of the other factor inputs of crop production. There is considerable debate on the ability of other inputs—typically nitrogen—to substitute for water. This paper describes a set of simulations undertaken with well calibrated maize (Zea mays L.) crop model in Decision Support System for Agro-technology Transfer (DSSAT). The simulations investigate the response to nitrogen under rainfed conditions in Florida, and show that neither the transpiration ratio nor the harvest index are constant in practice, and that fertilizer use can enhance water productivity, even in quite high yield conditions and that the transpiration ratio can be increased by N fertilizer application at low levels of crop water use.     

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 water management in water-starved countries: challenges and opportunities

Agriculture commands more water than any other activity on this planet. Although the total amount of water made available by the hydrologic cycle is enough to provide the world’s current population with adequate freshwater, most of this water is concentrated in specific regions, leaving other areas water-deficient. Because of the uneven distribution of water resources and population densities worldwide, water demands already exceed supplies in nearly 80 countries with more than 40% population of the world. Consequent to future population increase in these countries, supplies of good-quality irrigation water will further decrease due to increased municipal–industrial–agricultural competition. These facts reveal that the time has come for the sustainable management of available water resources based on global, regional, and site-specific strategic options: (1) understanding the concept of ‘virtual water’ and potential use of this water as a global solution to regional deficits, i.e. the water-short countries may import a portion of food crops or other commodities that require more water and export those that need less water in production; (2) improvement in current efficiencies of agricultural water use and conservation, both in the rain-fed and irrigated agriculture, i.e. to produce more with the existing resources with minimum deterioration of land and water resources; (3) use of efficient, economic, and environmentally acceptable methods for the amelioration of polluted waters and degraded soils, and (4) re-use of saline and/or sodic drainage waters via cyclic, blended, or sequential strategies for crop production systems, wherever possible and practical. We believe that these strategies will serve as the four pillars of integrated agricultural water management and their suitable combinations will be the key to future agricultural and economic growth and social wealth, particularly in regions that are deficient in freshwater supplies and are expected to become more deficient in future.     

Good governance and IWRM—a legal perspective

Developing a methodology for the measurement of governance in the context of water management requires a clear understanding of what is meant by (good) governance, and what is meant by IWRM—terms which are often, but incorrectly, used almost interchangeably. This paper sets out the foundations developed for the STRIVER project upon which an assessment of governance could be made. It identifies the key principles of good governance as being accountability, participation and transparency, and seeks to elucidate the relationship between good governance and IWRM, especially in relation to the specific role of law. The paper concludes that while the two are not mutually exclusive, the access points between them appear to concentrate around issues relating to equity, the protection of “silent” interests and the importance of governance in facilitating feedback mechanisms.     

陕西省低碳农业发展改革路径

陕西作为西部农业大省,农业发展存在着资源消耗高、环境污染重、农业竞争力弱化的不足。发展低碳农业具有提升陕西省的农业竞争力、推进农业转型升级和增加农民收入的重要作用。从政府治理层面入手,加强政府治理体系的顶层设计,建立强有力的统筹协调机构;提升政府的监管水平,实现对于低碳农业全方位和全过程监督管理;推进政府治理的科学化水平,提升政府决策质量;提升政府的公共服务水平;构建政府治理的责任制陕西省推动低碳农业发展的有力切入点。      

Participatory water management at the main canal: A case from South Ferghana canal in Uzbekistan

After the independence of Central Asian countries, many international projects have been launched to promote water users’ inclusion into the water management at different levels. The aim of such projects is to achieve sustainable water management through inclusion of interests of different groups on day-to-day water management. Although IWRM in Central Asia has been already promoted for a decade, there are only a few examples of the implementation in real life situations.The Integrated Water Resources Management in Ferghana Valley (IWRM FV) is a pilot project on implementing integrated water resources management elements at the main canal levels and below. The experience gained from IWRM FV project and lessons learnt could be useful for the national and international organizations for their future work on IWRM implementation at the different regions of Central Asia.IWRM FV project has been active since 2001 in the Ferghana Valley, one of the largest irrigated areas of Central Asia. The project has promoted and implemented participatory irrigation management for three pilot canals. This paper presents the process of implementation and some preliminary outcomes of the IWRM VF project.     

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.     

发展节水灌溉是调整治水思路的重要实践

水资源分配不均，工程供水不足，输配水及管理中的浪费造成了农业灌溉水源的供需矛盾。推广节水灌溉技术是湖南农业可持续发展的必由之路。近几年来节水灌溉工程的建设，充分显示了质量效益性农业的巨大威力。加强领导，调整思路，深化改革是节水灌溉事业发展的有力措施。     

Irrigation management for groundwater quality protection

Deep percolation flow below agricultural and can transport nitrate and pesticide residues to underlying groundwater. Irrigated agriculture in dry climates can also contaminate groundwater with salt from irrigation water and with trace elements such as selenium leached from the vadose zone. Groundwater contamination by agricultural chemicals can be minimized by using best management practices (BMPs) for crop production (including low-input sustainable agriculture or other source control) and for irrigation. Irrigation systems should be designed and managed for zero or minimum deep percolation during the growing seasons to keep fertilizer and pesticides in the root zone as long as possible. At other times, irrigation efficiencies can be lower to produce enough deep percolation water for leaching salts out of the root zone. Because of spatial variability and preferential flow, however, some deep percolation and movement of chemicals may still occur, even if the irrigation efficiency is 100%. BMPs should be developed to minimize such deep percolation flow.