scholarly journals Analysis of virtual water flows associated with the trade of maize in the SADC region: importance of scale

2008 ◽  
Vol 5 (5) ◽  
pp. 2727-2757 ◽  
Author(s):  
J. M. Dabrowski ◽  
E. Masekoameng ◽  
P. J. Ashton
Keyword(s):  
South Africa ◽  
Water Use Efficiency ◽  
Water Content ◽  
Water Use ◽  
Water Scarcity ◽  
Virtual Water ◽  
Blue Water ◽  
Maize Production ◽  
Water Flows ◽  
Use Efficiency

Abstract. The concept of virtual water encourages a country to view agricultural crops in terms of the amount of water required to produce those crops, with a view to implementing trading policies that promote the saving of scarce water resources. Recently, increased attention has focussed on partitioning the virtual water content of crops into green and blue water (derived from rainfall and irrigation, respectively) as the latter has higher opportunity costs associated with its use and therefore impacts directly on scarcity. Maize is the most important crop traded within the SADC region. South Africa is the largest producer and exporter of maize, with the majority of its exports destined for other SADC countries. In comparison to other SADC countries, South Africa produces maize relatively efficiently, with a low virtual water content and a high green (868 m3 tonne−1) to blue (117 m3 tonne−1) water ratio. The blue water content is however higher than for maize produced in all other SADC countries, with the exception of Namibia (211 m3 tonne−1). Current trade patterns therefore result in a net expenditure of blue water (66×106 m3), almost all of which is exported by South Africa (65×106 m3). South Africa is one of the most water scarce countries in the region and analysis of virtual water flows indicates that current SADC maize trading patterns are influenced by national productivity as opposed to water scarcity. The virtual water content of maize was estimated for each of South Africa's nineteen Water Management Area's (WMA) and used as a proxy to represent water use efficiency for maize production. The virtual water content varied widely across all of the WMAs, ranging from 360 m3 tonne-1 in the Ustutu Mhlatuze to 1000 m3 tonne−1 in the Limpopo. A comparison of the virtual water content and production of maize (expressed as a percentage of the total national production) identified those WMAs where maize production is highly water inefficient (e.g. Lower Orange and Limpopo WMAs). Results suggest that, while a national estimate of the virtual water content of a crop may indicate a relatively efficient use of water, an analysis of the virtual water content at smaller scales can reveal inefficient use of water for the same crop. Therefore, analysis of the virtual water content of crops and trading of agricultural products at different spatial scales (i.e. regional, national and WMA) could be an important consideration within the context of water allocation, water use efficiency and alleviation of water scarcity.

scholarly journals Analysis of virtual water flows associated with the trade of maize in the SADC region: importance of scale

2009 ◽  
Vol 13 (10) ◽  
pp. 1967-1977 ◽  
Author(s):  
J. M. Dabrowski ◽  
E. Masekoameng ◽  
P. J. Ashton
Keyword(s):  
South Africa ◽  
Water Use Efficiency ◽  
Water Content ◽  
Water Use ◽  
Water Scarcity ◽  
Virtual Water ◽  
Blue Water ◽  
Maize Production ◽  
Water Flows ◽  
Use Efficiency

Abstract. The concept of virtual water encourages a country to view agricultural crops in terms of the amount of water required to produce those crops, with a view to implementing trading policies that promote the saving of scarce water resources. Recently, increased attention has focussed on partitioning the virtual water content of crops into green and blue water (derived from rainfall and irrigation, respectively) as the latter has higher opportunity costs associated with its use and therefore impacts directly on scarcity. Maize is the most important crop traded within the SADC region. South Africa is the largest producer and exporter of maize, with the majority of its exports destined for other SADC countries. In comparison to other SADC countries, South Africa produces maize relatively efficiently, with a low virtual water content and a high green (868 m3 t−1) to blue (117 m3 t−1) water ratio. The blue water content is however higher than for maize produced in all other SADC countries, with the exception of Namibia (211 m3 t−1). Current trade patterns therefore result in a net expenditure of blue water (66×106 m3), almost all of which is exported by South Africa (65×106 m3). South Africa is one of the most water scarce countries in the region and analysis of virtual water flows indicates that current SADC maize trading patterns are influenced by national productivity as opposed to water scarcity. The virtual water content of maize was estimated for each of South Africa's nineteen Water Management Area's (WMA) and used as a proxy to represent water use efficiency for maize production. The virtual water content varied widely across all of the WMAs, ranging from 360 m3 t−1 in the Ustutu Mhlatuze to 1000 m3 t−1 in the Limpopo. A comparison of the virtual water content and production of maize (expressed as a percentage of the total national production) identified those WMAs where maize production is highly water inefficient (e.g. Lower Orange and Limpopo WMAs). Results suggest that, while a national estimate of the virtual water content of a crop may indicate a relatively efficient use of water, an analysis of the virtual water content at smaller scales can reveal inefficient use of water for the same crop. Therefore, analysis of the virtual water content of crops and trading of agricultural products at different spatial scales (i.e. regional, national and WMA) could be an important consideration within the context of water allocation, water use efficiency and alleviation of water scarcity.

scholarly journals Implications of water policy reforms for virtual water trade between South Africa and its trade partners: economy-wide approach

Water Policy ◽  
2014 ◽  
Vol 17 (4) ◽  
pp. 649-663 ◽  
Author(s):  
Rashid Hassan ◽  
Djiby Racine Thiam
Keyword(s):  
South Africa ◽  
Water Use Efficiency ◽  
Water Use ◽  
Water Policy ◽  
Virtual Water ◽  
Policy Reforms ◽  
Virtual Water Trade ◽  
Agricultural Exports ◽  
Recent Trends ◽  
Use Efficiency

This paper employs an economy-wide framework to evaluate impacts of water and trade policy reforms in South Africa (SA) on virtual water flows. To pursue this analysis, the study derives net virtual water trade flows between SA and its partners to assess implications of recent trade agreements within the South African Development Community compared to economic cooperation with other major trading blocks (e.g. European Union, Asia, and Brazil, Russia, India and China (BRIC)). Recent trends in actual trade confirm model predictions that liberalization of water allocation would switch water from field crops to horticulture and promote growth in non-agricultural exports. The results suggest that it is necessary to introduce policies that enhance likely outcomes of liberalization promoting higher water use efficiency within irrigation agriculture such as increased adoption of more efficient irrigation methods (sprinkler, drip, etc.) as water becomes more expensive under wider open competition. Moreover, investment in higher water use efficiency and improved competitiveness of dryland agriculture therefore represent the sound economic options for strengthening the capacity to achieve food security objectives as the country strives to lower net water exports. Finally, careful coordination of trade and water policy reforms is another necessary challenge for SA's strive to manage a water stressed economy.

scholarly journals A preliminary investigation of the water use efficiency of sweet sorghum for biofuel in South Africa

Water SA ◽  
2016 ◽  
Vol 42 (1) ◽  
pp. 152 ◽  
Author(s):  
MG Mengistu ◽  
JM Steyn ◽  
RP Kunz ◽  
I Doidge ◽  
HB Hlophe ◽  
...  
Keyword(s):  
South Africa ◽  
Water Use Efficiency ◽  
Water Use ◽  
Sweet Sorghum ◽  
Preliminary Investigation ◽  
Use Efficiency

scholarly journals Determination of virtual water content of rice and spatial characteristics analysis in China

2014 ◽  
Vol 18 (6) ◽  
pp. 2103-2111 ◽  
Author(s):  
L. J. Zhang ◽  
X. A. Yin ◽  
Y. Zhi ◽  
Z. F. Yang
Keyword(s):  
Water Content ◽  
Water Use ◽  
Southwest China ◽  
Virtual Water ◽  
Northwest China ◽  
Green Water ◽  
Blue Water ◽  
Grey Water ◽  
Spatial Characteristics ◽  
Water Values

Abstract. China is a water-stressed country, and agriculture consumes the bulk of its water resources. Assessing the virtual water content (VWC) of crops is one important way to develop efficient water management measures to alleviate water resource conflicts among different sectors. In this research, the VWC of rice, a major crop in China, is taken as the research object. China covers a vast land area, and the VWC of rice varies widely between different regions. The VWC of rice in China is assessed and the spatial characteristics are also analysed. The total VWC is the total volume of freshwater both consumed and affected by pollution during the crop production process, including both direct and indirect water use. Prior calculation frameworks of the VWC of crops did not contain all of the virtual water content of crops. In addition to the calculation of green, blue and grey water – the direct water in VWC – the indirect water use of rice was also calculated, using an input–output model. The percentages of direct green, blue, grey and indirect water in the total VWC of rice in China were found to be 43.8, 28.2, 27.6, and 0.4%. The total VWC of rice generally showed a roughly three-tiered distribution, and decreased from southeast to northwest. The higher values of direct green water usage were mainly concentrated in Southeast and Southwest China, while the values were relatively low in Northwest China and Inner Mongolia. The higher direct blue water values were mainly concentrated in the eastern and southern coastal regions and Northwest China, and low values were mainly concentrated in Southwest China. Grey water values were relatively high in Shanxi and Guangxi provinces and low in Northeast and Northwest China. The regions with high values for indirect water were randomly distributed but the regions with low values were mainly concentrated in Northwest and Southwest China. For the regions with relatively high total VWC the high values of blue water made the largest contribution, although for the country as a whole the direct green water is the most important contributor.

scholarly journals Water saving through international trade of agricultural products

2006 ◽  
Vol 10 (3) ◽  
pp. 455-468 ◽  
Author(s):  
A. K. Chapagain ◽  
A. Y. Hoekstra ◽  
H. H. G. Savenije
Keyword(s):  
Water Resources ◽  
Water Use ◽  
Virtual Water ◽  
Water Saving ◽  
Agricultural Products ◽  
Green Water ◽  
Blue Water ◽  
Water Flows ◽  
Global Water ◽  
National Water

Abstract. Many nations save domestic water resources by importing water-intensive products and exporting commodities that are less water intensive. National water saving through the import of a product can imply saving water at a global level if the flow is from sites with high to sites with low water productivity. The paper analyses the consequences of international virtual water flows on the global and national water budgets. The assessment shows that the total amount of water that would have been required in the importing countries if all imported agricultural products would have been produced domestically is 1605 Gm3/yr. These products are however being produced with only 1253 Gm3/yr in the exporting countries, saving global water resources by 352 Gm3/yr. This saving is 28 per cent of the international virtual water flows related to the trade of agricultural products and 6 per cent of the global water use in agriculture. National policy makers are however not interested in global water savings but in the status of national water resources. Egypt imports wheat and in doing so saves 3.6 Gm3/yr of its national water resources. Water use for producing export commodities can be beneficial, as for instance in Cote d'Ivoire, Ghana and Brazil, where the use of green water resources (mainly through rain-fed agriculture) for the production of stimulant crops for export has a positive economic impact on the national economy. However, export of 28 Gm3/yr of national water from Thailand related to rice export is at the cost of additional pressure on its blue water resources. Importing a product which has a relatively high ratio of green to blue virtual water content saves global blue water resources that generally have a higher opportunity cost than green water.

Film mulch with irrigation and rainfed cultivations improves maize production and water use efficiency in Ethiopia

2019 ◽  
Vol 175 (2) ◽  
pp. 215-227 ◽  
Author(s):  
Zi‐Qiang Yuan ◽  
Rong Zhang ◽  
Bin‐Xian Wang ◽  
Ben‐Qiang Gao ◽  
Getachew Ayana ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Maize Production ◽  
Use Efficiency

scholarly journals Water relations of chives in function of salinity and circulation frequency of nutrient solutions

2019 ◽  
Vol 23 (5) ◽  
pp. 359-365 ◽  
Author(s):  
Fernando J. da Silva Júnior ◽  
José A. Santos Júnior ◽  
Manassés M. da Silva ◽  
Ênio F. de F. e Silva ◽  
Edivan R. de Souza
Keyword(s):  
Water Use Efficiency ◽  
Water Content ◽  
Water Use ◽  
Nutrient Solution ◽  
Water Consumption ◽  
Dry Matter ◽  
Saline Water ◽  
Dry Matter Partitioning ◽  
Use Efficiency ◽  
Supply Water

ABSTRACT Hydroponic cultivation using saline waters is an alternative for agricultural production, especially in the cultivation of vegetables. Therefore, the present work was conducted with the objective of evaluating the water consumption, water use efficiency and water content, as well as dry matter partitioning of chives (Allium schoenoprasum), cv. Todo Ano Evergreen – Nebuka exposed to six levels of nutrient solution salinity (1.5, 3.0, 4.5, 6.0, 7.5 and 9.0 dS m-1), applied at two circulation frequencies (twice a day at 8 and 16 h; and three times a day - at 8, 12 and 16 h). The level in the nutrient solution reservoir, which decreased according to the water consumption by plants, was replaced with the respective saline water (Experiment I) and supply water (Experiment II). Both experiments used a completely randomized design, in a 6 x 2 factorial scheme, with five replicates. It was observed that increased circulation frequency and the use of supply water in the replacement mitigated the effects of salinity on water consumption, water use efficiency and water content in the plant. However, with the increase in nutrient solution electrical conductivity, dry matter allocation in the roots increased, to the detriment of the shoots.

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