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Essay on Water Productivity
Essay Contents:
- Essay on the Definition of Water Productivity
- Essay on the Importance of Water Productivity in Agriculture
- Essay on the Concepts and Issues of Water Productivity
- Essay on the Rationale for Increasing Water Productivity
- Essay on the Key Principles for Improving Water Productivity
- Essay on the Opportunities for Water Productivity Improvement in Agriculture
- Essay on the Policy Tools for Promoting Water Productivity Gains
- Essay on Virtual Water and Water Footprint
Essay # 1. Definition of Water Productivity:
In broadest sense, water productivity (WP) reflects the objectives of producing more food, income, livelihoods and ecological benefits at less social and environmental cost per unit of water, where water use means per either water delivered to a use or depleted by a use.
Crop water production is governed only by transpiration. As it is difficult to separate transpiration from evaporation from the soil surface between the plants (which does not contribute directly to crop production), defining crop water productivity using evapotranspiration rather than transpiration makes practical sense at field and system level.
In irrigated saline areas, the leaching requirement should also be included together with evapotranspiration in the amount of water that is necessarily depleted during plant growth. Other non-productive but beneficial uses could be included. Examples are evapotranspiration by windbreaks, cover crops and the water used in wetting seedbeds to enhance germination.
The question of considering water losses from seepage and field percolation as consumption does not receive a unique response. If this water is of no use at downstream or if it generates further pollution such as that resulting from geological salt leaching (eg SanJoaquin valley, California, the United States of America), then it must be accounted for as consumption.
Solutions to minimise these losses, such as canal lining or water improvement application, then have a positive effect on productivity. However, from a broader environmental point of view, it can be important to consider the impact of the outflow of an irrigation system on the overall productivity of an ecosystem.
As with the numerator, the choice of the denominator (which drops to be included) should depend on the scale, the point of view and the focus. At basin level, the choice might be between water diverted from the source and the same minus water restored, whereas at field level one might consider useful rain, irrigation water and supplemental irrigation.
Essay # 2. Importance of Water Productivity in Agriculture:
i. Producing More with Less Water:
Growing more food and gaining more benefits with less water have received a significant attention recently. Many countries in the world and regions within countries are reaching the thresholds of water scarcity. Most feasible option for increasing crop production under growing water scarcity is to increase the water productivity in exiting uses of water.
The concept of growing more crops from every unit of land is not new. It gathered momentum in the 1970’s leading to a remarkable increase in crop yield or land productivity leading to green revolution. Doubling land productivity over the next five decades could help India to meet most of its additional food demand.
As such, increasing land productivity is still relevant for many countries and regions within countries. In fact, with decreasing size of land holding per person, improving economic productivity per unit of land should be the primary concern for India now. But, unlike five decades ago, water, a critical input for agriculture and human well being and ecosystems, has also become a constraint in sustaining the benefits achieved so far and expanding the irrigated areas for enhanced crop production. As a result, increasing water productivity is also gaining new impetus.
Securing more crop per drop is extremely important in today’s context where climate change and energy crisis are affecting vast populations, especially the rural poor in developing nations. Future foodgrain requirements will have to be met with lesser amount of additional land and water, which calls for increasing land and water productivity in foodgrain production.
In fact, if land productivity (yield) of grains increases at a rate of 1.04 per cent annually, India can easily meet the projected food and feed grain requirement of about 380 m t by 2050 without any addition to the consumptive water use (CWU). In other words, such growth pattern would require no additional or perhaps less irrigation water for food production.
ii. Increasing Water Productivity of Foodgrains:
There are mainly two potential ways of increasing water productivity of foodgrains in India:
(i) Increasing foodgrain yield with a little or no additional CWU:
There are a large number of low productivity areas having high potential for increasing crop yields by combining better water management, including improving reliability of irrigation deliveries in irrigated areas or providing a little supplementary irrigation in dryland areas and agronomic practices and technology inputs
(ii) Reducing the amount of water depleted in irrigation with only a little or no negative impacts on yield:
Water thus saved can be used for expanding the cultivated area and increase crop production or for beneficial uses in other sectors. These are essentially areas receiving intensive irrigation and high dosage of crop inputs such as fertilisers and pesticides and recording high crop yields, but with high incidence of over-irrigation resulting in non beneficial evaporation.
Significant potential exists for increasing water productivity and production through:
1. Bridging the gap between the actual and the maximum land productivity (yield). This can be done at any level of CWU, where a significant gap exists between actual and maximum yield
2. Providing additional irrigation to increase CWU in dryland areas. A small increase in CWU can have large increase in land and water productivity and production
3. Practicing deficit irrigation for not meeting full water requirement in irrigated areas with large irrigation application and poor water management. Reducing CWU in this region would in fact increase land and water productivity and hence production.
iii. Water Productivity of Foodgrains – Present Status:
At present, water productivity of food grains in India is significantly lower when compared to other major foodgrain producing countries in the world. In 2000, water productivity of foodgrains in India was only 0.48 kg m-3 of CWU. This was primarily due to low growth in yields. India’s foodgrain yield was 1.7 t ha-1 in 2000, which has increased to only 1.0 t ha-1 during 1960-2000.
Meanwhile, China with a similar level of yield in 1960 (0.9 t ha-1) has increased to about 4.0 t ha-1 by 2000. The USA made vast strides by increasing foodgrain yield from 2.5 t ha-1 in 1960 to 5.8 t ha-1 over the same period. Also, India produces less grain in more cropped area (205 M t in 124 m ha), while China and US have much larger production and with less water from a significantly smaller crop area.
Indeed, India has a significant scope for raising the levels water productivity by increasing its crop yield alone. Better water management can create additional increase in water productivity in many regions.
iv. Spatial Variability of Water Productivity:
Reported data on water productivity with respect to evapotranspiration (WPET) show considerable variation (wheat 0.6 to 1.9 kg m-3, maize 1.2 to 2.3 kg m-3, rice 0.5 to 1.1 kg m-3, forage sorghum 7 to 8 kg nr3 and potato tubers 6.2 to 11.6 kg m-3) with incidental outliers obtained under experimental conditions.
Data on field level water productivity per unit of water applied (WPirrig), as reported in the literature, are lower than WPET and vary over an even wider range. For example, grain WPirrig for rice varied from 0.05 to 0.6 kg m-3, for sorghum from 0.05 to 0.3 kg m-3 and for maize from 0.2 to 0.8 kg m-3.
The variability occurs because data were collected in different environments and under different crop management conditions: These affected the yield and the amount of water supplied. Furthermore, it is often difficult to determine the real crop yield over a large area (large irrigation system). When asked for yield figures, individual farmers are likely to give a figure that depends on the situation.
For a loan application, they may overstate the yield, whereas for payment of a debt or a tariff, they will probably understate the yield obtained. Vegetable yields may change every day and unless good records are kept, no one will know exactly how much was harvested during the total harvest period. Yields expressed in monetary terms are more doubtful as prices on the local market may fluctuate considerably over time.
Essay # 3. Concepts and Issues of Water Productivity:
Increasing water productivity is a relatively new concept. Seckler (1996), Molden (1997), Koppen (1999) discussed different dimensions of enhancing water productivity, which included more crop or value or job per drop of water.
i. Water Scarcity Vs Increasing Water Productivity:
Water scarcity exists when the demand for water exceeds the supply and it can be classified based on the context as:
1. Physical water scarcity in which water availability is limited by natural availability
2. Economic water scarcity when human and financial resources constraints availability of water
3. Managerial water scarcity where availability is constrained by management limitations
4. Institutional water scarcity where water availability is constrained by institutional short comings
5. Political water scarcity where political forces bar people from accessing available water resources.
These types of scarcity can occur concomitantly, increasing both the severity and impacts of water scarcity. Molden et al (2003) estimated that by 2020 approximately 75 per cent of the world’s population will live in areas experiencing physical or economic water scarcity.
ii. Assessing Water Productivity:
Productivity is a ratio between a unit of output and a unit of input. Here, the term water productivity is used exclusively to denote the amount or value of product over volume or value of water depleted or diverted. The value of the product might be expressed in different terms (biomass, grain, money). For example, the so called crop per drop approach focuses on the amount of product per unit of water.
Another approach considers differences in the nutritional values of different crops or that the same quantity of one crop feeds more people than the same quantity of another crop. When speaking of food security, it is important to account for such criteria. Another concern is how to express the social benefit of agricultural water productivity.
All the options that have been suggested can be summarised by the phrases nutrient per drop, capita per drop, jobs per drop and sustainable livelihoods per drop. There is no unique definition of productivity and the value considered for the numerator might depend on the focus as well as the availability of data.
However, water productivity defined as kilogram per drop is a useful concept when comparing the productivity of water in different parts of the same system or river basin and also when comparing the productivity of water in agriculture with other possible uses of water.
Indeed, there are many definitions of water productivity. For crops, it relates to plant biomass per unit of transpiration and between them there exists a liner relationship. At field scale, farmers would like to know the physical production per unit of water allocated to different crops or the net return from the water delivered to the entire farm.
At the level of irrigation system, irrigation managers would be interested in knowing the value of production per unit of water delivered. Indeed, at the field or system scales, part of the water delivered is often reused within the field or system or elsewhere in the basins. Thus, for comparison between systems or between fields/farms at different locations, value of production per unit of consumptive water use (evapotranspiration) could be a better measure.
The maximum of crop water productivity estimated in relation to evapotranspiration is close to the water productivity estimated in relation to transpiration under a given set of climate and soils. Thus, the difference between maximum yield and actual yield under a given agroclimatic condition shows the extent of increase in yield and water productivity possible through increased transpiration.
Water productivity simply means growing more food or gaining more benefits with less water. Simplest definition of water productivity is foodgrain production from a unit of water depleted.
iii. Factors Influencing Water Productivity:
Water productivity will depend on many factors other than quantity of water applied or depleted. Though, water is only one of the factors of agricultural production and cannot be meaningfully separated from the others, an estimate of its productivity and knowledge about the factors which influence it will help in understanding the pathway to improve water productivity.
Agricultural water productivity takes into account multiple water use, including conventional crops, horticulture, forestry, livestock, fisheries, environment etc. It means that if all water users are taken into account and concept of recycling and reuse of water is considered in agricultural production system, then agricultural output per unit of total water input is referred as agricultural water productivity.
Since agricultural water productivity assessment considers multiple uses of water, its value represents composite or integrated picture is higher than the crop water productivity. Water productivity analysis can be applied to crops, livestock, tree plantation, fisheries and mixed systems at selected scales-crop or animal, field or farm, irrigation system and basin or landscape, with interacting ecosystems.
Since expressions for water productivity differ in each context, it is important to be clear about the agricultural output and input terms used. From an agricultural systems perspective, agricultural water productivity will be sum total of factor productivity from crops, livestock, fishery, horticulture etc. The care will have to be exercised to avoid multiple accounting of same input.
Livestock water productivity is a measure of the ratio of outputs such as meat, milk, eggs or traction to water depleted and is defined as scale dependent ratio of livestock production (services) produced per unit of water depleted. Methodology must be integrated with other crop, forestry and fisheries uses of water resources in the watershed/basin in order to harness full advantage of multiple uses in integrated farming systems approach.
Livestock produced solely with irrigated forage and grain crops will have far low water productivity when compared with livestock production relying on consumption of crop residues, grazing and tree fodder as the water used for plants would have been used with or without livestock feeding on it and feed is a by product of crops.
iv. Water Productivity and Efficiency:
Productivity is a measure of performance expressed as the ratio of output to input. Productivity may be assessed for the whole system or parts of it.
It could account for all or one of the inputs of the production system giving rise to two productivity indicators:
(i) Total productivity-the ratio of total tangible outputs divided by total tangible inputs
(ii) Partial or single factor productivity – the ratio of total tangible output to input of one factor within a system. In farming systems, the factors could be water, land, capital, labor and nutrients.
Water productivity (WP), like land productivity, is a partial factor productivity that measures how the systems convert water into goods and services.
Its generic equation is:
Water productivity was introduced to complement existing measures of the performance of irrigation systems, mainly the classic irrigation and effective efficiency. Classic irrigation efficiency focuses on establishing the nature and extent of water losses and included storage efficiency, conveyance efficiency, distribution efficiency and application efficiency.
These measures are particularly useful for managers of water system who use them to:
(i) Assess how much water they were losing in the storage, conveyance, distribution, and application subsystems
(ii) Identify interventions to improve performance.
In assessing the performance of water use in a large system, a basin or sub-basin, classic efficiency fails to capture the water reuse aspect. It ignores the beneficial use put to water recaptured and reused in one part of the basin as a consequence of deep percolation and/or runoff losses that takes place elsewhere in the basin.
To address this problem, Keller et al (1996) introduced the concept of effective efficiency, which takes into account the quantity of water delivered from and returned to a basin’s water supply. In an irrigation context, effective irrigation efficiency is the amount of beneficially used water divided by the amount of water used during the combined processes of conveying and applying that water.
Introduction of measures of water productivity makes it possible to undertake a holistic and integrated performance assessment by:
1. Including all types of water uses in a system
2. Including a wide variety of outputs
3. Integrating measures of technical and allocative efficiency
4. Incorporating multiple use and sequential reuse as the water cascades through the basin
5. Including multiple sources of water
6. Integrating non water factors that affect productivity.
Crop water productivity or water use efficiency (kg m3) is an efficiency term, expressing the amount of marketable product (kg grain) in relation to the amount of input needed to produce that output (m3 water). The water used for crop production is referred to as crop evapotranspiration.
This is a combination of water lost by evaporation from the soil surface and transpiration by the plant, occurring simultaneously. Except by modeling, distinguishing between the two processes is difficult. Representative values of water productivity for cereals at field level, expressed with evapotranspiration in the denominator, can vary between 0.10 and 4 kg m-3.
v. Water Productivity and Water Saving:
Real water saving is defined as the process of reducing non beneficial water uses and making the water saved available for a more productive use. In situations where water is scarce, reducing non beneficial uses becomes one of the main ways for reducing water scarcity. Improving water productivity seeks to get the highest benefits from water and hence can be viewed as a major contributor to water saving.
Real water saving by reducing non beneficial depletion can be accomplished through: reducing flows to sinks and reducing non beneficial evaporation. For example, improving irrigation efficiency is considered to be the most appropriate way to reduce non beneficial depletion and save water.
Before this can be done, it is important to understand the water pathways of non-beneficial water use and its reuse. For example seepage losses may be the main way in which shallow groundwater aquifers used for downstream irrigation and domestic water supply are recharged.
By failing to take a basin perspective when planning and implementing water interventions, we run the risk of not achieving real water saving and of having a negative impact on water quality, drinking water supply, groundwater balance and downstream human and ecological users.
Guerra et al (1998) noted that in most cases the arguments regarding water saving do not address other important factors that determine water saving such as the cost of water development and recovery. Increasing water productivity often requires greater use of other resources such as labor, capital and management.
Hence, at the basin level it is important to address the following key questions:
1. What happens to the water that is lost through runoff and deep percolation?
2. What effect does reducing non beneficial use have on systems that were dependent on the water that it provided?
3. What happens to the water that is saved through reduced runoff and deep percolation losses?
vi. Indicators of Water Productivity:
Water productivity is a very robust measure that can be applied at different scales to suit the needs of different stakeholders. This is achieved by defining the inputs of water and outputs in units appropriate to the users indicator needs.
The numerator (output derived from water use) can be defined in two ways:
(i) Physical output, which can be total biomass or harvestable product
(ii) Economic output (the cash value of output) either gross benefit or net benefit.
The water input can be specified as volume (m3) or as the value of water expressed as the highest opportunity cost in alternative uses of the water. Combination of different numerator and denominator parameters yield a wide range of water productivity indicators (kg m-3, Rs m-3, Rs Rs-1).
vii. Increase of Water Productivity in Agriculture:
Despite concerns about the technical inefficiency of water use in agriculture, water productivity increased by at least 100 per cent between 1961 and 2001. The major factor behind this growth has been yield increase. For many crops, the yield increase has occurred without increased water consumption and sometimes with even less water given the increase in the harvesting index.
Example of crops for which water consumption experienced little if any variation during these years are rice (mostly irrigated) and wheat (mostly rainfed), for which the recorded increases worldwide amount to 100 and 160 per cent respectively. At the global level, the increase in water consumption for agriculture in the past 40 years has been 800 km3 while world population has doubled to 6000 M.
Considering that the arable rainfed area has not increased, one can conclude that with an additional 800 km3 of water, the world has been able to feed an additional 3000 M people. This gives a rough estimate of 0.720 m3 day-1 capita-1. This figure is low compared to the estimated global average for 2000 of 2.4 m3 day-1 capita-1, which includes water for food at field level not including water losses.
This is a good indicator of the significant productivity gain recorded in agriculture, a gain that has enabled the world to accommodate the doubling of the population and also increase intake. As a whole, one can estimate that the water needs for food per capita halved between 1961 and 2001 from about 6 m3 day-1 to less than 3 m3 day-1.
Importance of water needs for food makes any small relative gain in this sector equivalent to a significant gain for other uses. For example, given the water needs for capita in 2000, a 1.0 per cent increase in water productivity in food production generates a potential of water use of 24 liters day-1 capita-1.
In order to produce the equivalent of the domestic water supply, a gain of 10.0 per cent in agricultural water productivity would be required, which is a matter of years. Therefore, it can be argued that investing in agriculture and in agricultural water is the best avenue for freeing water for other purposes.
However, future agricultural gains will need to be split into several components:
(i) Compensation for the reduction of agricultural production areas as a result of urban encroachment, soil degradation and the depletion of water resource availability or access (groundwater)
(ii) Increased water access for the rural poor and vulnerable groups
(iii) Generation of wealthier farming systems
(iv) Freezing water for other uses including the environment.
Essay # 4. Rationale for Increasing Water Productivity:
i. Global Imperatives:
The global population, which reached 6 billion in 1999 and is expected to reach 7.8 billion in 2025, is putting enormous pressure on the finite renewable water resources as the demand for food and other water dependent goods and services increases. Irrigated agriculture, which accounts for 72 per cent of global and 90 per cent of developing countries’ water withdrawal, will have to increase its productivity to mitigate the growing water crisis. Other agricultural water uses will also have a role to play. It is estimated that increases of 30 and 60 per cent in water productivity from rainfed and irrigated agriculture, respectively will be required to meet the demands for food security.
ii. Basin Level Rationale:
At the basin level, the rationale for increasing water productivity lies in the need to:
1. Increase water availability to users and uses that are disadvantaged. For example, the need to increase water productivity in the upper reaches of rivers so as to reduce water depletion and hence increase water availability in downstream reaches
2. Reduce overall water demand and develop additional water resources (dam development, groundwater exploitation and water transfers from regions with excess water to regions that experience water scarcity)
3. Increase total basin level water benefits through more productive use of the available water resources.
Several basins are exploring options for enhancing water productivity to achieve various social, economic and environmental goals.
iii. System Level Rationale:
At the level of the irrigation system, increases in water productivity may be required to:
1. Secure water for downstream farmers who experience water shortages
2. Reduce operation and maintenance costs associated with desilting and water outtake including the costs of pumping
3. Make water available for expansion of the irrigated perimeter where the cost of saving water through increasing water productivity is less than the cost of developing additional water resources
4. Comply with water permit and pollution regulations to ensure adequate provision of safe water for non-agricultural users.
iv. Farm Level Rationale:
At the farm level, increases in water productivity are required to:
1. Reduce water costs (costs of pumping, delivering water or water fees)
2. Reduce loss of land productivity associated with soil erosion, waterlogging and salinisation
3. Expand irrigated areas with the same amount of irrigation water available
4. Increase agricultural output, food security and profitability.
Essay # 5. Key Principles for Improving Water Productivity:
The three key principles for improving water productivity at field, farm and basin level, which apply regardless of whether the crop is grown under rainfed or irrigated conditions, are:
1. Increase the marketable yield of the crop for each unit of water transpired by it
2. Reduce all outflows (drainage, seepage and percolation), including evaporative outflows other than the crop stomatal transpiration
3. Increase the effective use of rainfall, stored water and water of marginal quality.
The first principle relates to the need to increase crop yields or values. The second one aims to decrease all losses except crop transpiration. Its phrasing does not imply that it will be impossible to increase water productivity by reducing stomatal transpiration. It is conceivable that plant breeding may find ways to overcome this constraint. The third principle aims at making use of alternative water resources.
The second and third principles should be considered parts of basin wide integrated water resource management (IWRM) for water productivity improvement. IWRM recognises the essential role of institutions and policies in ensuring that upstream interventions are not made at the expense of downstream water users.
These three principles apply at all scales/from plant to field and agro-ecological levels. However, options and practices associated with these principles require different approaches and technologies at different spatial scales.
i. Enhancing Water Productivity at Plant Level:
Plant level options rely mainly on germplasm improvements:
1. Improving seedling vigour
2. Increasing rooting depth
3. Increasing the harvest index (economic yield as part of total biomass)
4. Enhancing photosynthetic efficiency.
The most significant improvements in yield stability have usually resulted from breeding programmes to develop an appropriate growing cycle such that the duration of the vegetative and reproductive periods are well matched with the expected water supply or with the absence of crop hazards. Planting, flowering and maturation dates are important in matching the period of maximum crop growth with the time when the saturation vapour pressure deficit is low.
The periods of maximum crop growth can be optimised through breeding. Improved varieties with a deeper rooting system contribute to drought avoidance and the effective use of water stored in the soil profile. Drought escape and increasing drought tolerance are also important strategies for increasing water productivity. Day length insensitive varieties of short to medium duration (90-120 days) enabled crops, such as wheat, rice and maize varieties developed as part of the green revolution, to increase water productivity by escaping late season drought that adversely affects flowering and grain development.
The modern rice varieties have about a threefold increase in water productivity compared with traditional varieties. Progress in extending these achievements to other crops has been considerable and will probably accelerate following the recent identification of the underlying genes. Genetic engineering, if properly integrated in breeding programmes and applied in a safe manner, can further contribute to the development of drought tolerant varieties and to increasing the water use efficiency.
ii. Rising Water Productivity at Field Level:
Improved practices at field level relate to changes in crop, soil and water management.
They include:
1. Selecting appropriate crops and cultivars
2. Planting methods (raised beds, broad beds and furrows)
3. Minimum/conservation tillage
4. Irrigation at most sensitive growing periods
5. Nutrient management
6. Micro irrigation and improved drainage for water table control
7. Timely plant protection etc.
Water depletion occurs when water evaporates from moist soil, from puddles between rows and before crop establishment. All cultural and agronomic practices that reduce these losses (row spacing, application of mulches etc.) improve water productivity. Irrigation method also affects these evaporative losses. Drip irrigation causes much less soil wetting than sprinkler irrigation. Significance of soil improvement in enhancing water productivity is often ignored.
However, integrated crop and resource management practices, such as improved nutrient management, can increase water productivity by raising the yield proportionally more than it increases evapotranspiration. This principle applies to both irrigated and rainfed agriculture. Integrated weed and integrated pest management have also contributed effectively to yield increases.
One of the field level methods for increasing water productivity is deficit irrigation, where deliberately less water is applied than that required to meet the full crop water demand. The prescribed water deficit should result in a small yield reduction that is less than the concomitant reduction in transpiration. Therefore, it causes a gain in water productivity per unit of water transpired.
In addition, it could lower production costs if one or more irrigation could be eliminated. For deficit irrigation to be successful, farmers need to know the deficit that can be allowed at each of the growth stages and the level of water stress that already exists in the root zone. Most importantly, they need to have control over the timing and amount of irrigations.
Deficit irrigation carries considerable risk for the farmers where water supplies are uncertain, as is the case with rainfall or unreliable irrigation supplies. Where water availability falls below a certain level, the value of the crop can fall to zero, either because the crop dies or because the product is of such low quality as to be unmarketable. When water is scarce, farmers could reduce the irrigation as appropriate to maximise returns to water if they have control over the timing and amount of irrigations.
This degree of flexibility is usually the case with sprinkler and drip irrigation and also with pumped groundwater if the farmer owns the pump. A totally flexible delivery system for surface irrigation in large irrigation systems is expensive because of the required overcapacity in the conveyance system.
The trade-off between reduced yield and higher water productivity needs to be quantified in economic terms before recommending deficit irrigation (other water saving irrigations in rice production).
The often cited low water productivity per unit of water supply in rice cultivation derives from considering as losses the percolation resulting from the standing water layer on the field surface. However, this water is often recycled and rice water productivity generally compares well with that of a dry cereal. Nevertheless, water saving irrigation techniques such as saturated soil culture and alternate wetting and drying can reduce the unproductive water outflows drastically and increase water productivity.
These techniques generally lead to some yield decline in the current lowland rice high yielding varieties. However, some experiments are reporting substantial yield increases for local varieties using a technique called system rice intensification (SRI), a technique which originated in Madagascar.
Here again there is no unique response; the fit with local resources and capacity is the most important feature to account for. Without anticipating results of current investigations in many countries, it seems that the potential of the SRI technique for the poor to increase the productivity of scarce land and water is significant provided that enough family labour is available.
Other approaches are being researched as part of efforts to increase water productivity without sacrificing yield. One of these is to develop so called aerobic rice systems that allow rice cultivation in non-flooded conditions. The development of these new rice varieties is essential if rice is to be grown like other irrigated upland crops and the deep percolation associated with paddy rice is to be avoided.
Water related problems in rainfed agriculture are often related to large spatial and temporal rainfall variability rather than low cumulative volumes of rainfall. The overall result of rainfall unpredictability is a high risk for meteorological droughts and intraseasonal dry spells. Bridging crop water deficits during dry spells through supplementary irrigation stabilises production and increases both production and water productivity dramatically if water is applied at the moisture-sensitive stages of plant growth.
Water harvesting for agriculture involves a storage reservoir, while in runoff farming the collected runoff is applied directly to the cultivated area. Either way, the investments in the construction of the ditches that take the runoff to the storage reservoir and of the reservoir itself are relatively small. Maintaining these structures may be more difficult if heavy rains periodically wash them away. Many factors affect the success of rainwater harvesting.
These include:
1. Method used for runoff collection and storage
2. Topography
3. Soil characteristics (especially the infiltration rate)
4. Choice of crop to be planted
5. Fertiliser availability
6. Effectiveness of the soil crust in the catchment area.
However, probably more important than any of these physical parameters is the involvement of the beneficiaries in the design and implementation of the water harvesting structures.
Water Saving Irrigation Technologies in Rice Production:
Exploring ways of producing more rice with less water is essential for food security in Asia while also protecting the environment. The International Rice Research Institute has studied various field level water saving technologies (alternate wetting and drying, SRI, saturated soil culture, aerobic rice, ground cover systems).
Each of these techniques reduces one or more of the unproductive water outflows (seepage, percolation and evaporation) and hence increases water productivity. However, they also introduce periods in which the soil is not flooded or not even saturated, which usually leads to yield decline. Recent results from northern China and the Philippines indicate that with current germplasm and management technologies, aerobic rice yields are about 40 per cent lower and reduce water requirements by about 60 per cent compared with flooded lowland systems.
The shift from flooded systems to partly aerobic (non saturated) conditions also has profound effects on soil organic matter turnover, nutrient dynamics, carbon sequestration, weed ecology and greenhouse gas emissions. Whereas some of these changes are positive, others, such as the release of nitrous oxide and the decline in organic matter, are perceived as negative effects. The challenge is to balance the negative and positive effects through the development of effective integrated water saving technologies that can ensure the sustainability of rice-based ecosystems and environmental services.
iii. Water Productivity at System and Basin Level:
Changing the focus from the field level to system and river basin level changes the relative importance of the various water management processes. At the larger scale, the effect of agriculture on other water users, human health and the environment becomes at least as important as production issues.
Options for improving water productivity at the agro-ecological or river basin level are found in:
1. Better land use planning
2. Better use of medium term weather forecasts
3. Improved irrigation scheduling to account for rainfall variability
4. Conjunctive management of various sources of water, including water of poorer quality where appropriate.
Therefore, integrating germplasm improvement and resource management is crucial in the enhancement of water productivity at the field scale and above.
Gains in water productivity are possible by providing more reliable irrigation supplies through precision technology and the introduction of on demand delivery of irrigation supplies. However, an increase in water productivity may or may not result in greater economic or social benefits. The social benefits represent the benefits to society resulting from the water productivity enhancing interventions. Water in the rural areas of developing countries has many uses.
Thus, water is both a public and a social good, a fact that complicates value calculations. These many uses of water include: the production of timber, firewood and fiber and raising fish and livestock. Non agricultural uses of water include domestic (drinking and bathing) and environmental uses.
An IWMI study of an irrigation system in Kirindi Oya in southern Sri Lanka illustrates the importance of the multiple roles of water in agriculture. The study found that at system level, crops consumed only 23 per cent of the total water supply, including both rainfall and external irrigation water. Of the remainder, 8 per cent was used for grazing land, 6 per cent evaporated from the reservoir, 16 per cent was lost to the sea, 3 per cent drained into lagoons, while as much as 44 per cent of the water supply went to perennial vegetation that had developed since the construction of the scheme.
This perennial vegetation was there because of irrigation seepage and recharge of the shallow groundwater. Tree growth is important to the people living in the area as it provides them with shade and thus improves their environment. In this project, as well as in many places in southern India, it also provides income from coconut and materials for construction (beams and ropes).
Other trees are important for additional nutritional values (fruits) and some are crucial for their medicinal properties. A changeover to total control of irrigation outflow in order to increase water productivity would cause the collapse of the entire local agroforestry system.
Another example of the economic and social benefits of agroforestry is a project located along the Niger River in Mali. In this project, trees were planted on the bunds of rice fields and also in the middle of the rice fields without affecting rice yields adversely. In this remote arid part of Mali, the value of the wooden poles of seven year old eucalyptus trees was so high that the farmers could pay for the operation and maintenance of the irrigation system from the sale of the trees.
In another irrigation system, in southwest Burkina Faso, oil palm and fruit trees were combined successfully with irrigated crops (mainly maize, groundnuts and industrial tomatoes). Trees were planted on ridges or on the boundaries between parcels.
On the sandy, percolating soils of the irrigation system, the trees produced an important amount of complementary food and income, while the impact on the main crop was minimal. Traditional agriculture had greater benefits for society than did large scale irrigation.
Essay # 6. Opportunities for Water Productivity Improvement in Agriculture:
There are several opportunities for improving the water productivity both in rainfed and irrigated agriculture:
i. Rainfed Agriculture:
With rapid expansion in well irrigation, India does not have purely rainfed areas now in the strict sense of the definition. Some crops are always irrigated in every region, though some farmers might be growing those crops under rainfed condition there. Often, farmers who do not have irrigation facilities resort to purchase of water to provide critical supplementary irrigation. An example is cotton growing in Maharashtra and Madhya Pradesh.
Most of India’s rainfed (drylands) areas are in central India and Peninsular region. Of these, the central Indian belt deserves special mention. In spite of abundant natural resources the population in this region is not able to improve their farming considerably and they mostly practice subsistence farming and grow most crops under rainfed condition.
Development of water resources for irrigation is poor and adoption of modern farming practices is extremely low. The result is that the productivity is low for cereals and total factor productivity growth is also very poor. Hence, this region is characterised by agricultural backwardness. Large area is under coarse grains, including greengram, blackgram and horsegram with low grain yields and low water productivity.
Studies indicated that supplemental irrigation can boost both yield and water productivity significantly. This would be from framers shifting to short duration foodgrain crops to long duration irrigated crops such as wheat in winter and irrigated rice in rainy season. Large scale irrigation projects coming up in Narmada valley can bring substantial rainfed areas under irrigation leading in significant improvement in water productivity.
There are still a few basins, where small scale water resources are possible without causing negative effect on downstream. They are Tapi, Mahanadi and a few small river basins in south Gujarat. Since the geohydrological conditions are not ideal for storage of harnessed water underground, due to hard rock strata, water can be stored in small reservoirs such as anicuts, check dams, ponds and tanks. Before the harnessed water during the monsoon is lost through evaporation, it should be put to beneficial use. Supplementary irrigation to kharif crops is the ideal option for the harvested water.
In Peninsular India, rainfed crops are still grown in many parts due to low and erratic rainfall and poor surface water availability and groundwater endowment. Small water harvesting interventions in the upper catchments of basins would only help basin wide redistribution of water, with negative implications for basin water use efficiency.
The only exception to this is the Godavari river basin, which is water surplus. Augmentation in water resources would be possible and the same water could be used to bring rainfed crops under irrigation to boost crop yields.
In addition to the low water (ET) consuming short duration rainfed (food) crops, which experience water stress, there are rainfed crops, which have moderate consumptive use of water (300-425 mm) in 117 districts of India. These crops, which are essentially long duration, fine cereals, are concentrated in eastern India and central India. The yield gap of these food grain crops is very high. Use of better crop technologies and better inputs could result in significant improvement in water productivity.
ii. Irrigated Agriculture:
There are six avenues for improving water productivity in irrigation crops:
a. Water delivery control,
b. Improving reliability of irrigation water (deficit irrigation),
c. Optimising the agronomic practices,
d. Use of micro-irrigation systems,
e. Growing certain crops in regions where they secure high water productivity, and
f. Crop shifts.
a. Water Delivery Control:
Studies shows opportunities for improving water productivity (in economic terms) through control over water delivery by allocating less water in many instances with a resultant reduction in yield but rise in water productivity for allocating more water in certain instances with resultant increase in both yield and water productivity. Water productivity in irrigated crops could be enhanced significantly through deficit irrigation, a key strategy in water delivery control.
b. Deficit Irrigation:
Deficit irrigation (DI) is an optimisation strategy in which irrigation is applied during drought sensitive growth stages of a crop. Outside these periods, irrigation is limited or even unnecessary if rainfall provides a minimum supply of water. Water restriction is limited to drought tolerant phenological stages, often the vegetative stages and the late ripening period.
Total irrigation application is, therefore, not proportional to irrigation requirements throughout the crop cycle. While this inevitably results in plant drought stress and consequently in production loss, deficit irrigation maximises irrigation water productivity, which is the main limiting factor. In other words, DI aims at stabilising yields and at obtaining maximum crop water productivity rather than maximum yields.
For certain crops, experiments confirm that deficit irrigation can increase water use efficiency without severe yield reductions. For example for winter wheat in Turkey, planned deficit irrigation increased yields by 65 per cent as compared to winter wheat under rainfed cultivation and had double the water use efficiency as compared to rainfed and fully irrigated winter wheat.
Similar positive results have been described for cotton. Experiments in Turkey and India indicated that the irrigation water use for cotton could be reduced up to 60 per cent of the total crop water requirement with limited yield losses. In this way, high water productivity and a better nutrient-water balance was obtained.
Certain under-utilised and horticultural crops also respond favorably to deficit irrigation, such as tested at experimental and farmer level for the crop quinoa. Yields could be stabilised at around 1.6 tons per hectare by supplementing irrigation water if rainwater was lacking during the plant establishment and reproductive stages. Applying irrigation water throughout the whole season (full irrigation) reduced the water productivity. Also in viticulture and fruit tree cultivation, deficit irrigation is practiced.
For other crops, the application of deficit irrigation will result in a lower water use efficiency and yield. This is the case when crops are sensitive to drought stress throughout the complete season, such as maize. Apart from university research groups and farmers associations, international organisations such as FAO, ICARDA, IWMI and the CGIAR Challenge Program on Water and Food are studying deficit irrigation.
c. Optimising Agronomic Practices:
Large irrigated area in eastern India is dominated by food crops. Yield of rice and wheat is low in these areas with high yield gap. There are around 200 districts in India which fall under this category of irrigated crops. Improved agronomic practices including high yielding varieties and application recommended fertiliser schedule can significantly raise the yields.
This will have a positive impact on water productivity, though water productivity is not a concern for farmers in this water abundant region of the country. In central India, there are areas where better use of fertilisers along with optimum irrigation can increase crop yield to achieve high water productivity. Importance of other agronomic practices for increasing the crop yield and hence water productivity needs no elaboration.
d. Use of Micro-Irrigation Systems:
Different types of micro-irrigation systems that are amenable to different crops and cropping systems are available. While some are only technically feasible and economically viable for row crops and orchards, some are feasible and economically viable for field crops also.
They can improve crop water productivity through reducing the non beneficial evaporation or non recoverable deep percolation in the field, resulting in total depletion or consumed fraction. Or they can increase the proportion of the beneficial fraction of the applied water that leads to improved crop yield. Nevertheless, in both the cases water productivity improvements come without reduction in yields.
e. Growing Certain Crops in Regions where they Secure High Water Productivity:
The determinants of physical productivity of water such as yield and evapotranspiration are influenced by climatic factors—with solar radiation and temperature affecting yield, solar radiation, temperature, wind speed and humidity affecting ET and agronomic factors— with crop variety affecting the potential yield and ET requirement.
Since yield affects the gross returns, the climate would have implications for water productivity in economic terms as well. Hence, certain crops give higher water productivity in both physical and economic terms by virtue of the climate under which they are grown without any additional inputs of nutrients and improved crop technology. Studies in Narmada basin show major differences in water productivity of wheat and irrigated rice across nine agro-climatic sub-regions.
In the case of wheat, the physical productivity of applied water for grain production during the normal year was estimated to be highest for northern region of Chhattisgarh in Mandla district (1.80 kg m-3 and it was lowest for Jabalpur in Central armada valley (0.47 kg m-3). This is mainly due to the major difference in irrigation water applied, which is 127 mm against 640 mm for Jabalpur. The difference in irrigation can be attributed to the difference in climate between Jabalpur (dry semi-humid) and Mandla (moist sub-humid), which changes the crop water requirement.
As regards rice, physical productivity for grain during the normal year was higher for northern region of Chhattisgarh in Mandla district (2.13 kg m-3) where as it was only 1.62 kg m-3 in Jabalpur district of central Narmada valley. Likewise, the combined physical and economic efficiency of water use was higher for Chhattisgarh (Rs. 3.59 m-3) against Rs. 1.43 m-3 for Jabalpur in central Narmada valley.
f. Crop Shifts:
Another major opportunity for water productivity improvement comes from crop shifts. In every region, the agroclimate permits growing of several different crops in the same season. Several of the cash crops such as castor, cotton, fennel, cumin and groundnut and vegetable such as potato are found to have higher water productivity than the cereals grown in the same region.
If we consider the food security benefits of growing cereals, the opportunity available for water productivity improvement through crop shift may not be significant in major food producing areas. In such areas, the opportunities for shifting from less water efficient non food crops to water efficient cash crops and fruits should be explored. Semi arid pockets such as north Gujarat, Saurashtra, central Madhya Pradesh, Western Rajasthan, northern Karnataka, parts of Tamil Nadu and western parts of AP are ideal for such crop shifts to improve crop water productivity and reduce the stress on groundwater. These are not major food producing areas.
Water use efficiency is presently (2006) estimated to be only 38 to 40 per cent for canal irrigation and around 60 per cent for groundwater schemes. It is estimated that with 10 per cent increase in the present level of water use efficiency in irrigation projects, an additional 14 M ha area can be brought under irrigation from the existing irrigation capacities which would involve a very moderate investment as compared to the investment that would be required for creating equivalent potential through new schemes.
Essay # 7. Policy Tools for Promoting Water Productivity Gains:
i. Price Policies:
Using price policies to promote the economic productivity of water requires significant government intervention in order to ensure that equity of access to water and public good issues are covered adequately. Some studies in the Indian subcontinent and elsewhere have suggested that the price for water that would be required to affect demand substantially would be about ten times the charge required to cover the operation and maintenance of the irrigation system.
A charge sufficient to cover operation and maintenance would have a minimal effect on water demand. Moreover, introducing volumetric charges for irrigation water is difficult and involves considerable expense for the installation of measuring structures and for fraud prevention. Last, in most rice based systems in Asia, volumetric charging at individual user level or even group level is unsuitable given the permanent overflow and recycling water flows throughout the command area.
ii. Availability of Water to Farmers:
The groundwater market in India illustrates the perhaps unintended impact of government policies on the availability of water to farmers and others. Farmers in Gujarat paid about four times as much for pumped groundwater compared with farmers in Punjab and Uttar Pradesh.
This difference was attributed to:
1. Differences in the way farmers were charged for the electric power to run their pumps (flat rate versus per unit consumed)
2. The tube-well spacing policy in Gujarat that gave each tube-well owner a monopoly over some 203 ha
3. The scarcity of public tube-wells in Gujarat, which also reduced competition among groundwater suppliers.
The high prices for tube-well water in Gujarat discriminated against small and poor farmers. However, some simple changes in water policies for power pricing, tube-well spacing and public tube-wells could transform groundwater markets in Gujarat into powerful instruments for small farmer development.
iii. Political Desire for National Food Security:
Aiming for the highest economic productivity of water in agriculture may conflict with the political desire for national food security. More often than not, the economic productivity of water in growing staple crops is less than that for growing vegetables or flowers for export markets. Crop substitution involves switching high water consuming crops for less water consuming crops or for crops with higher economic productivity. The approach provides a strategy for increasing crop water productivity at the agro-ecological system level as well as at the global level.
iv. Policies and Incentives:
Policies and incentives are important in the adoption of changes from traditional agronomic and cultural practices. However, it is necessary to identify the types of policies and incentives that will work best. Experience with conservation agriculture indicates that the short term interests of the farmers often differ from the long term interests of society and that the financial benefits that accrue from changes in cultural practices often take a long time to materialise.
In addition, although there are large differences between individual farms, external factors also play a role, e.g., the transmission of information (via policy related activities and social processes). Of particular importance is the fact that the inconsistent and sometimes contradictory results from studies on the adoption of new practices suggests that the decision making process is highly variable.
This decision making process needs to be understood more fully as it will affect the lead time from study to field practice. This lead time is often unacceptably long considering the urgent character of water scarcity problems. Experience from participatory research and extension could help reduce this lead time.
Essay # 8. Virtual Water and Water Footprint:
Water is required for the production of food such as cereals, vegetables, meat and dairy products and other commodities such as steel, petrol, paper etc.
i. Virtual Water:
Virtual water was defined at the beginning of the 1990s by Allan (1993) as ‘water embedded in commodities’. The amount of water consumed in the production process of an agricultural or industrial product is called the virtual water contained in the product. This water is ‘virtual’ because it is not physically contained anymore in the product.
The real water content of products is, generally, negligible if compared to the virtual water content. For example, to produce one kg of wheat in India, we need 1654 l of water, whereas to produce one kg of maize 1937 l of water is required. Producing livestock products, generally, requires more water per kg of the product. For instance, one kg of cheese requires about 5000 -7000 l of water. A cup of coffee uses about 140 l of water, whereas tea requires only one-eighth of that quantity. About 3200 l of water is required to produce a 32- megabyte computer chip of 2 g.
Allan (2005) stated:
“Water is said to be virtual because once the crop is grown, the real water used to grow it is no longer actually contained in the crop. The concept of virtual water helps us realise how much water is needed to produce different goods arid services. In semi- arid and arid areas, knowing the virtual water value of a good or service can be useful towards determining how best to use the scarce water available.”
Daily amount of water we consume through our food is much more than we use daily for drinking, washing, sanitation and other household tasks. Some countries of the world do not have adequate water to meet their current and projected water needs, while in some other countries available water is more compared to the demands.
Further, in big countries there are regions of surplus or deficient water availability. Water deficit countries/regions in countries can overcome the water scarcity problem through import of water (virtual) by importing foodgrains etc. from water surplus countries/regions in countries instead of producing it locally. Of course, in reality things are not so simple and additional questions of food security, energy security, employment etc enter in the picture.
Virtual Water in Various Products:
Agricultural products:
It is essential to recognise that virtual water is cumulative. To produce one kg of wheat about 1000 l of water are needed, but for beef about 15 times as much is required. Majority of the water that we consume is embedded in food.
Average virtual water content of some of the agricultural products is indicated below:
1. Production of 1 kg wheat costs 1,300 l of water
2. Production of 1 kg eggs costs 3,300 l of water
3. Production of 1 kg broken rice costs 3,400 l of water
4. Production of 1 kg beef costs 15,500 1 of water.
Household products:
Not only is there virtual water in food, but it is in various products in common use:
1. Jeans (1000 g) contain 10,850 l of embedded virtual water
2. A cotton shirt (medium sized, 500 g) contains 4,100 l of water
3. A disposable diaper (75 g) contains 810 1 of water
4. A bed sheet (900 g) contains 9,750 l of water.
Industrial products:
Industrial goods also contain embodied water. One needs to understand how internal water resources are being used to produce cars, bicycles, teacups and the like – particularly because industry usually uses only blue water for production. On average, a 1.1 t passenger car has about 400,000 l of water embedded in it. Virtual water content of a product consists of three components, called green, blue and grey components.
Green virtual water:
Green virtual water content of a product is the volume of rainwater that evaporated during the production process. This is mainly relevant for agricultural products, where it refers to the total rainwater evaporation from the field during growing period of the crop (including transpiration by the plants and other forms of evaporation).
Blue virtual water:
Blue virtual water content of a product is the volume of surface water or groundwater that evaporated as a result of the production of the product. In the case of crop production, blue water content of a crop is defined as the sum of evaporation of irrigation water from the field and evaporation of water from irrigation canals and artificial storage reservoirs.
In the cases of industrial production and domestic water supply, blue water content of the product or service is equal to part of the water withdrawn from ground or surface water that evaporates and thus does not return to the system where it came from.
Grey virtual water:
Grey virtual water content of a product is the volume of water that becomes polluted during its production. This can be quantified by calculating the volume of water required to dilute pollutants emitted to the natural water system during its production process to such an extent that the quality of ambient water remains beyond agreed minimum water quality standards.
Despite the intuitive appeal of the concept of virtual water, the idea has some limitations too. Analysis of country level data on freshwater availability and net virtual water trade of 146 nations showed that a country’s virtual water trade is not determined by its water situation.
In many instances, virtual water flows out of ‘water-poor’ but ‘land-rich’ countries to ‘water-rich’ and ‘land-poor’ countries. For a water-poor but land- rich country, virtual water import offers little scope as a sound water management strategy, since what is often achieved through virtual water trade is improved ‘global land-use efficiency’.
Further, if a nation facing water shortage also faces food shortage, it will import the kind of food its population requires rather than importing food with the maximum virtual water content. Importing countries also may stay away from large scale virtual water import because of the fear of paying ‘political ransom’ to the exporter of virtual water in case of a confrontation.
Also for many countries like India and China, self-sufficiency in food is still a national priority. According to Horlemann and Neubert (2007), virtual water strategy is suitable more as a complement to other necessary steps in sustainable water management and tends to be harmful as a separate strategy. Including virtual water as a policy option requires thorough understanding of the impact and interactions of virtual water trade on the local, social, economic, environmental and cultural situation.
Virtual water content of a product depends upon the technology and conditions of production. Considerable saving of water is possible if water efficient technology is employed to produce the product. Further, water consumed in a production process also depends upon climate; more water is needed to produce each unit of a crop in arid climates compared to that in humid areas.
Virtual water content of various primary and processed crop products, livestock products and industrial products for different countries was estimated by Chapagain and Hoekstra (2004). While computing the virtual water content of products, a distinction is made between primary products (e.g., vegetables), processed products (e.g., sugar) and transformed products (e.g., cheese).
Some processes may yield multiple products and in this case, total quantity of water used is allocated amongst these. Further, not all products require water and for such items virtual water content is nil. Virtual water content of a crop in a country is calculated as the ratio of total water used for the production of the crop to the total volume of the crop produced in that country.
Crop water use is assumed to be equal to the crop water requirement, which is calculated by accumulation of data on daily crop evapotranspiration over the complete growing period. Crop water requirements for different crops have been calculated using the CROPWAT model of the Food and Agriculture Organization (FAO), United Nations.
Virtual water content of an animal, at the end of its lifespan, is defined as the total volume of water that was used to grow and process its feed, for its drinking needs and to clean its housing and the like. Virtual water content of a processed product depends on the virtual water content of the primary item or live animal from which it is derived.
Virtual water content of the primary crop or live animal is distributed over the different products from that specific crop or animal. Virtual water content of industrial products is estimated on a country average basis, by dividing the individual water withdrawn by a particular country with the value added from the industrial sector for that country.
Detailed methodology to estimate the virtual water content of various primary and processed crop products, livestock products and industrial products has been given by Chapagain and Hoekstra (2004). Table 18.1 gives the virtual water content of selected crops and livestock products calculated for India. Average virtual water content of industrial products for India is estimated as 4.75 l per rupee or 0.215 m3 per US dollar. Virtual water content of various crop and crop products is calculated considering the country’s average climate data.
As the climate in India significantly varies spatially, virtual water content of various crops and crop products will also have large spatial variations. Another shortcoming of the above assessment is that the estimates of virtual water content of crops are based on crop water requirements, which leads to overestimates in those cases where actual water availability is lower than the crop water requirement.
Virtual Water Trade:
Virtual water trade refers to the transfer of water (virtual) that takes place during trade of various goods and services. Virtual water trade is not new; it is as old as food trade. Virtual water trade is becoming an important concept of water management on a global as well as regional level, particularly in regions where water is scarce.
Many countries are involved in virtual water trade consciously relating to water policies. Some countries where these conscious choices have been made are Morocco, Jordan, Israel and Egypt, which are importers of virtual water. Many studies have estimated the magnitude of virtual water trade between various countries.
In these studies, the basic approach has been to multiply trade volumes by their associated virtual water content. In a recent estimate, global virtual water flow was found to be of the order of 1625 x 109 m3 yr-1 (Cm3 yr-1) during the period 1997-2001, of which 61 per cent was related to international trade of crops, 17 per cent to trade of livestock and livestock products and the remaining 22 per cent to trade of industrial products.
Different water productivities -volume of water required per unit of product – for different countries give rise to the concept of national and global water saving through international virtual water trade. However, according to de Fraiture (2004), this is not always true and sometimes trade in virtual water may lead to the ‘loss’ of water resources if the importer can produce the commodity.
According to Hofwegen (2007), virtual water trade could deprive farmers and their families of their livelihoods, unless alternatives are developed in terms of crops or employment which saves water. Virtual water trade should contribute to local, national and regional food security, which requires not only appropriate trade agreements that respect a nation’s right to decide on food security measures, but also local distribution mechanisms ensuring access to food.
Virtual Water Trade from India:
Virtual water trade for India has been estimated by various authors over the years. Hoekstra and Hung (2002) estimated net virtual water export from India, related to trade of crops of the order of 32.2 Gm3 yr-1 during the period 1995-99. During the same period, net virtual water export trade of livestock was estimated as 2.3 Gm3 yr-1.
During these five years, India exported 191.8 Gm3 of virtual water and imported 19.5 Gm3 of virtual water, leading to a net export of 172.3 Gm3. India ranked sixth among countries with net export.
According to Chapagain and Hoekstra (2004), India has exported 42.5 Gm3 yr-1 of virtual water with net export of 25.4 Gm3 yr-1 during the period 1997-2001. Out of the total export of 42.5 Gm3 yr-1, crop trade contributed 76 per cent, livestock 8 per cent and industrial products 16 per cent, whereas out of total import, 81 per cent trade was related to crop, 2 per cent to livestock and the remaining 17 per cent to industrial products.
Soybean and palm oil were the major crops for virtual water export and import respectively. During this period, India was among the 16.83 Gm3 of green water (effective rainfall), 5.75 Gm3 of blue water (irrigation water) and the remaining 3.08 Gm3 for dilution water. Dilution water is the volume of water required to dilute waste flow to such an extent that the quality of water remains within the agreed quality standards.
Considering the FAO data on import and export from India, virtual water trade for India has been calculated for the five year period 2001-05 (Table 18.2). Crop and livestock product import and export data also include the crop and livestock products received/given as food aid. The quantity of virtual water trade as given in Table 2 is calculated by multiplying the trade volume of a product with the virtual water content of that product for India, as calculated by Chapagain and Hoekstra (2004).
TABLE 18.2: Virtual water trade related to crop and livestock products from India
As seen from Table 18.2, India has exported 228.61 Gm3 of virtual water with an average of 45.72 Gm3 yr1 and imported 358.27 Gm3 of virtual water with an average of 71.65 Gm3 yr-1 during these five years. According to these calculations, India was a net importer of 25.93 Gm3 yr-1 of virtual water related to crop and livestock products during the period 2001-05.
Computing Virtual Water Content:
Evaluating virtual water of primary products:
The principle of calculation of water productivity is rather simple: crop water requirements ETa (m3 ha-1) are calculated from the climatic demand (ET) adjusted with crop coefficients. Software like CROPWAT can be used for this purpose. Water productivity is then obtained by dividing the crop yield Y (kg ha-1) by these crop water requirements.
Virtual water value (VWV), the inverse of water productivity is then given by the following equation:
Virtual water of transformed and processed products: Assessment of virtual water content of transformed and processed products pose specific problems linked to the yields of the processes utilised and to the fact that primary products may be used to produce various products. Animals are classified in this category and pose also difficulties due to the various allocations of their meat and byproducts.
Vegetal transformation usually is made considering both a processing yield factor (kg of primary product amount to produce 1 kg of end product) and the VWV of the primary product.
Byproducts:
For this category, different methods of estimation of virtual water are possible:
1. A first method consists in allocating virtual water of all sub-products proportionally to the quantities produced; for instance, each kg of cotton provides 0.625 kg of fiber and 0.375 kg of cotton seed and the water consumed is allocated proportionally to these values
2. A second method consists in allocating virtual water proportionally to the economic values of various products.
This second method may seem preferable but it has also some drawbacks:
i. Economic values may be quite variable in space and time
ii. In case of byproducts, the value may be very low because the product has little attracted for the market and cannot be substituted to another product
3. A third method consists in dissociating the value from the real process and to determine the value of virtual water by considering the nutritional equivalence principle. For instance in the case of cotton oil, it consists in affecting the value that is recorded for another oil product.
Multiple products and non-water consumptive products:
For these two last categories of products associating the food product to real water consumption is difficult. It is proposed to dissociate virtual water from the real process and estimate the virtual water value with the nutritional equivalence principle.
Regarding sea products and most of the fish (except inland fisheries), production does not consume any water through evapotranspiration. Thus these products can be accounted for either with a nil virtual water value or with the virtual water content of other agricultural products by which they can be substituted. This is the assumption adopted here.
With this assumption, virtual water value of sea food products and fish has been evaluated at 5 m3 kg-1 with an equivalence based on alternative animal products equivalent for energy and proteins. The share of sea food and fish products in virtual water trade is important (14%).
This method applies also for other transformed products, when accounting for primary product is difficult or pointless. Examples of that are cattle on grazing lands (not easy to account for grass) or backyard animal production such as pigs in China.
Water Management in India – Role of Virtual Water:
India is a country with a large geographical area (3.29 M km2) and the culturable area is 1.43 M km2. Annual average precipitation is about 4000 km3. There are large variations in climate and land productivity. Often, there are questions as to whether the regions with scarce rainfall should adopt water-guzzling crops. For example, Punjab is facing water scarcity.
Number of dark blocks (where the exploitation of groundwater is more than 85 per cent of the annual potential) in Punjab has increased from 64 in 1984-85 to 83 in 1997-98. Despite this, rice is grown over extensive areas in Punjab and most of the harvest goes to the central grain pool. In this way, Punjab is exporting large quantities of virtual water.
At the same time, its neighbouring states claim that Punjab does not give them adequate water on the pretext that it is facing a water shortage. This paradox can only be explained by the fact that the farmers and the economy of the state earn through virtual water export, but they do not get anything by physical transfer of water.
Northeastern region of the country is bestowed with high water resources potential. This region gets high rainfall and the Brahmaputra River flowing through this area, has surface water potential of 677.41 km3. This river basin has large hydroelectric potential (= 34900 MW), which can be tapped and transmitted to other regions of the country having shortage of electric power. Transfer of water from the northeastern region to the other parts of the country is difficult due to topographical and other reasons.
However, transfer of virtual water in the form of electricity will be somewhat easier (although there will be other issues). Besides meeting the much desired energy demands of the country, additional income to the northeastern states can be used for their economic development.
ii. Water Footprint:
People use lots of water for drinking, cooking and washing, but even more for producing things such as food, paper, cotton clothes etc. Water footprint is an indicator of water use that looks at both direct and indirect water use of a consumer or producer. Water footprint of an individual, community or business is defined as the total volume of fresh water that is used to produce the goods and services consumed by the individual or community or produced by the business.
Relation between Consumption and Water Use:
“Interest in the water footprint is rooted in the recognition that human impacts on freshwater systems can ultimately be linked to human consumption and that issues like water shortages and pollution can be better understood and addressed by considering production and supply chains as a whole,” says Prof Arjen Y Hoekstra, creator of the water footprint concept and scientific director of the Water Footprint Network.
“Water problems are often closely tied to the structure of the global economy. Many countries have significantly externalised their water footprint, importing water-intensive goods from elsewhere. This puts pressure on the water resources in the exporting regions, where too often mechanisms for wise water governance and conservation are lacking. Not only governments, but also consumers, businesses and civil society communities can play a role in achieving a better management of water resources”.
Global Water Footprint Standard:
The Global Water Footprint Standard (GWFS) – developed through a joint effort of the Water Footprint Network, its partners and scientists of the University of Twente in the Netherlands – has garnered international support from major companies, policymakers, NGOs and scientists as an important step toward solving the world’s ever increasing water problems.
Some facts and figures are presented below:
Production of 1.0 kg of beef requires 15,000 l of water (93% green, 4% blue, 3% grey water footprint). There is huge variation around this global average. The precise footprint of a piece of beef depends on factors such as the type of production system and the composition and origin of the feed of the cow.
Water footprint of a 150 g soy burger produced in the Netherlands is about 160 l. A beef burger from the same country costs about 1000 l.
Water footprint of Chinese consumption is about 1070 m3 per year per capita. About 10 per cent of the Chinese water footprint falls outside China.
Japan with a footprint of 1380 m3 per year per capita, has about 77 per cent of its total water footprint outside the borders of the country.
Water footprint of US citizens is 2840 m3 per year per capita. About 20 per cent of this water footprint is external. The largest external water footprint of US consumption lies in the Yangtze River basin, China.
The global water footprint in the period 1996-2005 was 9087 Gm3 yr-1 (74% green, 11% blue, 15% grey). Agricultural production contributes 92 per cent to this total footprint.
Four major factors determining water footprint of a country are:
1. Volume of consumption (related to gross national income)
2. Consumption pattern (high versus low meat consumption)
3. Climate (growth conditions)
4. Agriculture practices (water use efficiency).
Water footprint of a nation consists of both internal and external components. The volume of water used from domestic water resources to produce goods and services consumed by the inhabitants of the country constitutes the internal water footprint of a nation. External water footprint of a country is the volume of water used in other countries to produce goods and services imported and consumed by the inhabitants of the country.
Total water footprint of a nation is a useful indicator of a nation’s call on the global water resources. At the consumer’s level, it is useful to show people’s individual footprint as a function of food diet and consumption pattern. The impact of consumption by people on global water resources can be mapped with the concept of the water footprint.
Based on the analysis of 1997-2001 data, global water footprint is calculated as 7450 Gm3 yr-1, which is 1240 m3 capita-1 yr-1. Water footprint for India has been estimated by Chapagain and Hoekstra (2004) as 980 m3 capita-1 yr-1 (Table 18.3).
Internal water sources constitute 98.4 per cent, whereas external water sources constitute 1.6 per cent of India’s water footprint. Consumption of agriculture goods contributes 94 per cent, domestic water contributes 3.9 per cent and industrial goods contribute the remaining 2.1 per cent.
In absolute terms, India has the largest footprint in the world, i.e., 987 Gm3 yr-1. On per capita basis, USA has the largest water footprint with 2480 m3 yr-1 per capita. Water footprint of worldwide cotton consumption was estimated as 256 Gm3 of water per year.
For India, the water footprint related to consumption of cotton products is 31024 M m3 yr-1 which includes 30441 M m3 yr-1 as internal and 583 M m3 yr-1as external water footprint. This footprint is the third largest in the world, after China and USA.