Nutritional Water Productivity Research Articles

A Review of Nutritional Water Productivity (NWP) in Agriculture: Why It Is Promoted and How It Is Assessed?

Assessment of nutritional water productivity (NWP) combines a metric of crop or livestock production per unit water consumed and human nutritional value of the food produced. As such, it can rationalize the use of scarce water for a portfolio of crop and livestock production systems that jointly match human nutritional needs and reduce water scarcity impacts. However, a comprehensive search and review of 40 NWP studies highlighted that current NWP studies vary widely in terms of their methodological approaches, the data and tools used and the water flows and nutrient content accounted for. Most of the studies accounted for evapotranspiration stemming from precipitation and technical water, and/or inclusion of the withdrawn technical water. Water scarcity was only addressed in four studies. The reported NWP values also varied for accounting of macro- (energy, protein, fat and carbohydrates) and micro-nutrient (minerals and vitamins) content. The methodological differences, however, severely limit the informative value of reported NWP values. A multidisciplinary research effort is required to further develop standardized metrics for NWP, including its local environmental water scarcity impacts. A robust NWP analysis framework in agriculture should focus on the integration of assessments of NWP and water scarcity impact (WSI), and development of more field measurements and locally calibrated and validated agrohydrological and farm production models to quantify reliable NWP values and their associated WSI of agriculture production systems worldwide.

Nutrition quality response of orange‐fleshed sweet potato (Ipomoea Batatas L. Lam) varieties to deficit irrigation in Tanzania

AbstractMalnutrition in all its forms is a global problem, with the worst effects felt in developing countries. The importance of producing food to improve nutrition security is self‐evidently a promising approach to combating malnutrition. The present study assessed the nutritional quality response of orange‐fleshed sweet potato (OFSP) varieties to deficit irrigation (DI). The study's specific objectives were to (i) evaluate yield and root quality and (ii) assess the nutritional root yield and nutritional water productivity of selected OFSP varieties under full and DI. Beta‐carotene, iron, and zinc were the root quality parameters studied. A factorial arrangement of treatments was laid out in a randomized complete block design (RCBD). The irrigation rates used for scheduling were 100% (full irrigation), 60% (60 [DI]), and 30% (30 [DI]) of total available water (TAW). The test varieties were Naspot‐13 and Jewel of the OFSP crop. The beta‐carotene content of the Jewel cultivar was 27% higher than that of the Naspot‐13 cultivar. However, neither cultivar's root quality changed under DI. The results show that serving 125 g of boiled OFSP varieties provides more than 100% of vitamin A, sufficient iron, and minimal zinc dietary requirements for 4‐ to 8‐year‐old children and 10‐ to 50‐year‐old pregnant women. In general, the nutritional water productivity of root quality parameters increased with a decrease in water application. In conclusion, a positive water‐food‐nutrition nexus was established under the Naspot‐13 variety, suggesting a capacity for alleviating vitamin A, iron, and zinc deficiency health‐related problems, particularly in children and pregnant women in regions with limited water resources. Therefore, adoption of DI strategies for underutilized crops using smart pressurized irrigation systems could be significant in undertaking water management reforms.

Reconciling crop production and ecological conservation under uncertainty: A fuzzy credibility-based multi-objective simulation-optimization model

To cope with the problems of agricultural water conflicts and secondary soil salinization in arid regions, a fuzzy credibility-based multi-objective simulation-optimization model is proposed for optimizing irrigation water allocation and crop area planning under uncertainty. This model combines simulation module of enabling to quantify daily physical process of water-salt movement among soil water, crop root zone and groundwater aquifers, optimization module of managing water resources and fuzzy credibility-constrained programming into a general framework. It's applied to a case study in the Jiefangzha Irrigation Subarea in Hetao Irrigation District, Northwest China. Three objectives encompassing maximizing net economic benefits, maximizing nutritional water productivity and minimizing carbon emissions from agricultural system are interconnected through decision variables. Four credibility scenarios of fuzzy constrains including β = 0.6 to 0.9 are presented for obtaining decision-making solutions. Through NSGA-III, such a high-dimensional multi-objective problem is solved. This study uses the multi-objective constraint-handling strategy to handle constraints, which exploits the effective information within infeasible solutions. Moreover, it emphasizes the importance of soil water-salt movement processes in determining optimal solutions and helps decision makers weigh the system outputs and risk level of violating constraints. Results illustrate that when β increases from 0.6 to 0.9, net economic benefit decreases from 1.742 × 109 Yuan to 1.706 × 109 Yuan, nutritional water productivity decreases from 9136.0 kcal/m3 to 8819.6 kcal/m3, and carbon emissions increase from 439.6 × 106 kg. C to 441.6 × 106 kg.C, which shows that an increasing credibility level leads to lower system benefits and conservative system outputs. The results can provide valuable information for managing irrigation water resources and controlling salinity accumulation. Furthermore, dynamic decisions related to water-salt movement processes can be readily generated. These findings show that the developed approach is globally applicable for managing irrigation water in arid and semiarid regions that face similar problems.

Assessing impacts of climate variability and changing cropping patterns on regional evapotranspiration, yield and water productivity in California’s San Joaquin watershed

Climate variability and changing cropping patterns are two main factors directly influencing catchment hydrological processes and agricultural productivity. Assessing the response of hydrological processes and agricultural production to the combined impacts is of great importance for enhancing water resources management, water productivity and agriculture sustainability. SWAT (Soil and Water Assessment Tools) models embedded with 2007 and 2018 land use were built for the San Joaquin watershed (SJWS) in California’s Central Valley. Global sensitivity analysis were conducted to select parameters that have the largest influence on evapotranspiration (ET) processes. The model was calibrated and validated produced good agreement for monthly ET from remote sensing and yield of 8 major crops using county level reported yields during the periods of 2001–2009 and 2010–2018. Based on the outputs of the calibrated SJWS SWAT model, regional ET showed a significant increase, which was caused by rises in temperature and changing cropping patterns associated with increase in area under nut crop production. Seven major crop yields increased excluding alfalfa, implying that the impacts of increasing temperature and small decreases in precipitation were not dominant factors in explaining observed changes in yield. From periods 2001–2009–2010–2018, total water productivity (WP) increased slightly from 2.11 to 2.15 kg/m3, associated with more water-intensive permanent crop production systems. Total economic water productivity (EWP) increased significantly by 111% from 0.55 to 1.16 US$/m3, which also indicated the substantial economic benefit brought to the SJWS by expanding the land area under high-EWP crops such as nut crops and vegetables. Nutritional water productivity (NWP) for energy, protein and fat were reduced from 1211 kcal/m3, 183 g/m3 and 105 g/m3 to 1141 kcal/m3, 111 g/m3 and 88 g/m3 during the period 2010–2018 mostly due to high water use. Total NWP for calcium was increased from 114 to 145 mg/m3, respectively. This study provides initial insights into the response of WP, EWP and NWP to the changing cropping patterns and climate variability for major crops in the SJWS, which could be used by a wide range of stakeholders including farmers, commodity boards, irrigation districts, groundwater sustainability basins, environmental justice groups and policy makers to optimize water resources planning and management. We recommend creating a comprehensive index that incorporates WP, EWP and NWP for making sustainable water resources planning and management decisions.

Drip irrigation provides a trade-off between yield and nutritional quality of tomato in the solar greenhouse

To address the twin issues of food and nutrition security, the focus of agricultural production should be shifted from biomass productivity to nutritional gains. The objectives of this study were to evaluate the impact of conversion from furrow to drip irrigation on the yield components, water productivity (WP), nutritional yield (NY) and nutritional water productivity (NWP) of tomato during two consecutive growth cycles (2017–2018) in a greenhouse in the arid area of Northwest China. Results showed that the environment under drip irrigation was more beneficial to the accumulation of phytochemicals and the formation of total antioxidant activity in tomato fruits, which also significantly increased the NWP. However, the notable decline in single fruit fresh weight reducing the tomato yield significantly under drip irrigation in summer, while the WP and NY were similar to furrow irrigation. This indicated that the NY of tomato was mainly determined by the fruit yield, while the NWP was strongly affected by the mass concentration of nutrients. In contrast, no difference was found in the single fruit fresh weight and tomato yield between drip and furrow irrigation in winter, which related to the similar environmental conditions, while the WP and NY were significantly higher under drip irrigation. In summary, the potential and water use efficiency in nutrient production of tomato were enhanced under drip irrigation, and the improvement of fruit quality can offset the negative effect of yield reduction. Therefore, drip irrigation can achieve a good balance between the high yield and superior quality of tomato fruits, meanwhile reducing the pressure on the environment caused by horticultural production. We propose that the drip irrigation should be employed in the greenhouse in arid areas for tomato production, and the concepts of NY and NWP can be further applied to other horticultural crops with high nutritional value.

Assessing Suitability of Sorghum to Alleviate Sub-Saharan Nutritional Deficiencies through the Nutritional Water Productivity Index in Semi-Arid Regions.

Lack of cereal nutritional water productivity (NWP) information disadvantages linkages of nutrition to water–food nexus as staple food crops in Sub-Saharan Africa (SSA). This study determined the suitability of sorghum (Sorghum bicolor L. Moench) genotypes to alleviate protein, Zn and Fe deficiency under water-scarce dryland conditions through evaluation of NWP. Sorghum genotypes (Macia, Ujiba, PAN8816, IsiZulu) NWP was quantified from three planting seasons for various sorghum seed nutrients under dryland semi-arid conditions. Seasons by genotypes interaction highly and significantly affected NWPStarch, Ca, Cu, Fe, and significantly affected NWPMg, K, Na, P, Zn. Genotypic variations highly and significantly affected sorghum NWPProtein, Mn. Macia exhibited statistically superior NWPprotein (13.2–14.6 kg·m−3) and NWPZn (2.0–2.6 g·m−3) compared to other tested genotypes, while Macia NWPFe (2.6–2.7 g·m−3) was considerably inferior to that of Ujiba and IsiZulu landraces under increased water scarcity. Excellent overall NWPprotein, Fe and Zn under water scarcity make Macia a well-rounded genotype suitable to alleviating food and nutritional insecurity challenges in semi-arid SSA; however, landraces are viable alternatives with limited NWPprotein and Zn penalty under water-limited conditions. These results underline genotype selection as a vital tool in improving “nutrition per drop” in semi-arid regions.

Nutritional yield and nutritional water productivity of cowpea (Vigna unguiculata L. Walp) under varying irrigation water regimes

There is a need to mainstream traditional crops in sub-Saharan Africa, in order to tackle food and nutritional insecurity through incorporating nutritional quality into crop water productivity, in the wider context of the water–food–nutrition–health nexus. The objective of the study was to determine the effect of irrigation water regimes on the nutritional yield (NY) and nutritional water productivity (NWP) of cowpea under Moistube irrigation (MTI) and subsurface drip irrigation (SDI). We hypothesized that NY and NWP of cowpea were not different under MTI and SDI and that deficit irrigation improved NWP. The experiment was laid as a split-plot design arranged in randomized complete blocks, replicated 3 times, with 3 irrigation water regimes: 100% of crop evapotranspiration (ETc), 70% of ETc, and 40% of ETc. Irrigation type and water regime did not significantly (p > 0.05) affect the nutritional quality of cowpea. Similarly, NWP of crude fat (28.20–39.20 g∙m-3), ash (47.20–50.70 g∙m-3) and crude fibre (30.70–48.10 g∙m-3) did not vary significantly. However, protein and carbohydrate NWP showed significant (p < 0.05) differences across irrigation water regimes and irrigation type. The highest protein NWP (276.20 g∙m-3) was attained under MTI at 100% ETc, which was significantly (p < 0.05) higher than SDI (237.1 g∙m-3) and MTI (189.8 g∙m-3) at 40% ETc. Cowpea is suited for production in water-scarce environments; however, there are trade-offs with carbohydrate NWP. This should not be of concern as often diets are already energy-dense but lacking in other micronutrients.

Reducing water footprints through healthy and reasonable changes in diet and imported products

This study investigated the effects of diet change on reducing water consumption in Iran, while meeting its nutrition requirements. It also addresses how such a national policy could be effective at global scale in order to reduce water consumption. To address the issues, the concept of water footprint (WF) was employed for Iranian food basket which was divided into 12 groups. The evaluated diets included current (reference) diet, healthy recommended diet under the national food-based dietary guidelines and two optimized diets (minimized total consumption WF diet and minimized internal blue WF diet) with minimum deviation from the reference diet. It avoids, when possible, elimination of one or more food groups as this would be unacceptable for consumers and has not generally been considered in previous studies. The results of the minimized total consumption WF scenario showed a reduction of intake in food groups having low nutritional water productivity, such as red meat and vegetable oil, and an increase in, high nutritional water productivity food groups, such as wheat and vegetables. A similar pattern was followed for the minimized internal blue WF diet; however, greater reductions were applied to fruits and rice, which have high internal blue WF values. The minimized internal blue WF scenario reduced the internal blue WF by 7.5 BMC/yr. The minimized total consumption WF diet had no effect in this regard, but was effective at global scale and reduced the blue WF consumption by 4.5 BCM/yr. The modeling setup of this research work with high flexibility can be recommended as being applicable to similar research projects.

The dual-purpose use of orange-fleshed sweet potato (Ipomoea batatas var. Bophelo) for improved nutritional food security

Orange-fleshed sweet potato (OFSP) leaves can be utilised as a fresh green leafy vegetable, in addition to the traditional use of storage root; therefore, OFSP can be seen as a “dual-purpose’’ crop. We hypothesized that no vine harvesting combined with fertiliser application and irrigation will improve the storage root yield and selected plant parameters (water productivity, leaf and storage root nutrient concentrations, nutritional yield, and nutritional water productivity). The objectives of the study were to (i) evaluate the effect of vine harvesting on the selected plant parameters, and, (ii) assess the effect of irrigation regimes and soil fertilisation on these selected parameters. Field experiments were conducted at ARC-VOP, Pretoria, South Africa, during the 2013/14 and 2014/15 seasons. Treatments included irrigation regimes [well-watered (W1) and supplemental irrigation (W2)], soil fertilisation [well-fertilised (F1) and no fertiliser application (F2)], and vine harvesting [no vine harvesting (H1) and vine harvesting (H2)]. For the 2014/15 season, the well-watered regime improved total storage root yield (W1 = 13.0 t DM ha−1; W2 = 7.5 t DM ha−1). Under the practice of vine harvesting, soil fertility treatments did not affect (total dry storage root yield and dry marketable storage root yield) storage root production. Our results further revealed that vine harvesting reduced storage root nutrient concentrations (23% for iron; 14% for zinc; 12% for β-carotene). Nevertheless, total nutritional yields increased; the highest total nutritional yields for iron, zinc, and β-carotene were found under the water and nutrient input regime (W1F1). Assessments showed that boiled orange-fleshed sweet potato aboveground edible biomass could potentially contribute to the daily-recommended nutritional requirement of iron and vitamin A for a family of six people. More water was needed to meet the daily-recommended nutrient intake (iron, zinc, and vitamin A) with OFSP grown as a storage root crop only than when grown as a dual-purpose crop. Our results indicated that there is an opportunity to utilise OFSP as a dual-purpose crop for rural resource-poor households because total nutritional yields (iron, zinc, and β-carotene) and total nutritional water productivities (iron, zinc, and β-carotene) were improved. More research is needed to assess the effect of vine harvesting on a range of OFSP varieties and should be conducted on the farm. Rural resource-poor households are encouraged to produce OFSP for their own consumption and the surplus could be sold at the local market.

A comparison of the Mediterranean diet and current food consumption patterns in Spain from a nutritional and water perspective

The promotion of responsible consumption is a key strategy to achieve environmental benefits, sustainable food security, and enhance public health. Countries like Spain are making efforts to reverse growing obesity and promote healthy diets, such as the recommended and traditional Mediterranean, recognized as a key strategy to improve the population's health with locally grown, traditional, and seasonal products like fruits, vegetables, olive oil, and fish. With a view to connecting water, agriculture, food security, nutrition and health, this research aims to investigate and compare the nutritional and water implications of the current food consumption of Spanish households with the recommended Mediterranean diet. Besides, we calculate their nutritional composition, compare their water footprints, and develop a new methodological approach to assess nutritional water productivity (i.e. the nutritional value per unit of embedded water). Results show that the current Spanish diet is shifting away from the recommended Mediterranean towards an alternative one containing three times more meat, dairy and sugar products, and a third fewer fruits, vegetables, and cereals. The Mediterranean diet is also less caloric, as it contains smaller amounts of proteins and fats and is richer in fiber and micronutrients. Due to the high-embedded water content in animal products, a shift towards a Mediterranean diet would reduce the consumptive WF about 750 l/capita day. Additionally, the Mediterranean diet has better water-nutritional efficiency than the current one: it provides more energy, fiber, and nutrients per liter of consumptive water. The study confirms the Mediterranean diet is a healthier and more sustainable diet with strong cultural heritage.

Nutritional water productivity of selected leafy vegetables

The major challenge affecting rural resource-poor households (RRPHs) in South Africa is deficiencies in micronutrients (iron and zinc) and vitamin A. Traditional leafy vegetables (TLVs) are dense in iron, zinc, and β-carotene concentrations. Therefore, they are deemed suitable to improve the dietary diversity of RRPHs. The main objective of this study was to assess the effect of irrigation regimes on nutritional water productivity (NWP) of selected leafy vegetables [Amaranthus cruentus (Amaranth) and Cleome gynandra (Spider flower), both TLVs, and Beta vulgaris (Swiss chard)]. Experiments were conducted under a rain shelter at the ARC-VOP, Pretoria, South Africa, during two consecutive seasons (2013/14 and 2014/15). Leafy vegetables were subjected to three irrigation regimes [well-watered (I30), moderate water stress (I50), and severe water stress (I80)]. Data collected [(aboveground biomass (AGB), aboveground edible biomass (AGEB), actual evapotranspiration, and nutrient concentrations (iron, zinc and β-carotene)] were used to calculate NWP of leafy vegetables. Swiss chard exhibited a higher portion of AGEB compared to TLVs due to its larger harvest index (0.57-0.92). Selected TLVs displayed superiority in terms of nutrient richness compared to Swiss chard, under I50. Results indicated that TLVs could provide more than the daily-recommended nutrient intake (DRNI) for vitamin A to all age groups. For iron, Spider flower could supply more than the DRNI to infants between 1 and 3 years of age, whereas for zinc, it could supply approximately 11% to this age group. However, higher micronutrient and β-carotene concentrations did not translate to superior nutritional yield (NY). Swiss chard showed higher Fe-NY and Zn-NY, whereas TLVs were rich in β-carotene-NY. Similarly, Swiss chard demonstrated the highest Fe-NWP (1090 mg m−3) and Zn-NWP (125 mg m−3), whereas Amaranth was larger in β-carotene-NWP (1799 mg m−3), under moderate water stress. These results show that there may be an opportunity to improve NWP under drought conditions. There is a need for future studies that will assess NWP for a wider range of leafy vegetables. These studies should be conducted in different locations and explore the effect of management factors (fertiliser, water stress, planting density and planting date), and soil type on NWP of micronutrients and β-carotene.

Nutrient Content and Nutritional Water Productivity of Selected Grain Legumes in Response to Production Environment.

There is a need to incorporate nutrition into aspects of crop and water productivity to tackle food and nutrition insecurity (FNS). The study determined the nutritional water productivity (NWP) of selected major (groundnut, dry bean) and indigenous (bambara groundnut and cowpea) grain legumes in response to water regimes and environments. Field trials were conducted during 2015/16 and 2016/17 at three sites in KwaZulu-Natal, South Africa (Ukulinga, Fountainhill and Umbumbulu). Yield and evapotranspiration (ET) data were collected. Grain was analysed for protein, fat, Ca, Fe and Zn nutrient content (NC). Yield, ET and NC were then used to compute NWP. Overall, the major legumes performed better than the indigenous grain legumes. Groundnut had the highest NWPfat. Groundnut and dry bean had the highest NWPprotein. For NWPFe, Zn and Ca, dry bean and cowpea were more productive. Yield instability caused fluctuations in NWP. Water treatments were not significant (p > 0.05). While there is scope to improve NWP under rainfed conditions, a lack of crop improvement currently limits the potential of indigenous grain legumes. This provides an initial insight on the nutrient content and NWP of a limited number of selected grain legumes in response to the production environment. There is a need for follow-up research to include cowpea data. Future studies should provide more experimental data and explore effects of additional factors such as management practices (fertiliser levels and plant density), climate and edaphic factors on nutrient content and NWP of crops.

Food and Nutrition Insecurity in Selected Rural Communities of KwaZulu-Natal, South Africa-Linking Human Nutrition and Agriculture.

Lack of access to nutritious and balanced diets remains a major impediment to the health and well-being of people living in rural areas. The study utilizes a qualitative systematic approach to conduct an environmental scan and review of scientific literature of studies conducted in South Africa, specifically KwaZulu-Natal (KZN). Availability and access to nutritious, diverse and balanced diets were identified as key constraints for achieving food and nutrition security as well as for human health and well-being. This has led to both under- and over-nutrition, with the former, in particular stunting, affecting children under 5 years. A high incidence of over-nutrition, both overweight and obesity, was observed among black African females. In South Africa, poor people rely mostly on social grants and cannot afford a balanced diet. Under these circumstances, agriculture could be used to increase availability and access to diverse and nutritious foods for the attainment of a balanced diet. The wider use of traditional vegetable crops and pulses could improve availability and access to healthy and locally available alternatives. The promotion of household and community food gardens, and the use of nutrient dense crops with low levels of water use, i.e., high nutritional water productivity, offers prospects for addressing malnutrition in poor rural areas.

Water-Food-Nutrition-Health Nexus: Linking Water to Improving Food, Nutrition and Health in Sub-Saharan Africa.

Whereas sub-Saharan Africa’s (SSA) water scarcity, food, nutrition and health challenges are well-documented, efforts to address them have often been disconnected. Given that the region continues to be affected by poverty and food and nutrition insecurity at national and household levels, there is a need for a paradigm shift in order to effectively deliver on the twin challenges of food and nutrition security under conditions of water scarcity. There is a need to link water use in agriculture to achieve food and nutrition security outcomes for improved human health and well-being. Currently, there are no explicit linkages between water, agriculture, nutrition and health owing to uncoordinated efforts between agricultural and nutrition scientists. There is also a need to develop and promote the use of metrics that capture aspects of water, agriculture, food and nutrition. This review identified nutritional water productivity as a suitable index for measuring the impact of a water-food-nutrition-health nexus. Socio-economic factors are also considered as they influence food choices in rural communities. An argument for the need to utilise the region’s agrobiodiversity for addressing dietary quality and diversity was established. It is concluded that a model for improving nutrition and health of poor rural communities based on the water-food-nutrition-health nexus is possible.

Nutritional Water Productivity and Global Food Security

Water is life and is one of the major inputs for agriculture. Earth has a finite supply of fresh water and therefore, demands that every drop of annual rainfall should be conserved and judiciously utilized for production and post- production agriculture to get maximum nutrients per unit of water. The concept of water productivity in agriculture is now shifting from harvest index per unit of land and water to nutrients (protein, carbohydrate, fat, etc.) produced per unit of water. This varies with food commodities and locations. For example, the total dietary energy produced by potato, maize, peanut, wheat, milk, egg and beef using one m3of water are about 5600 kcal, 3800 kcal, 2300 kcal, 2280 kcal, 660 kcal, 520 kcal and 100 kcal, respectively. Similarly, the production of protein using one m3 of water by potato, peanut, maize, wheat, egg, milk, chicken, and beef are 150 g, 111 g, 77 g, 74 g, 41 g, 40 g, 33 g and 10 g, respectively. This paper describes the water nutrient productivity of some of the crops and livestock products and suggests as to how to provide food and nutritional security through an appropriate and balanced diet design, to the maximum number of people of the world from the limited and dwindling land, water and bio resources.

Linking smallholder agriculture and water to household food security and nutrition

Promoting household food security and reducing malnutrition rates of a growing population with the same amount of water is a challenge facing South African nutritionists and agriculturalists alike. Apart from non-food related effects of agriculture in general, the crop and livestock production practices of the South African smallholder farmer may have nutritional implications, primarily when practised on residential land and resulting in home consumption. Yet, few studies have systematically investigated the impact thereof. It appears that crop diversification, gender issues and nutrition education are among the important factors that strengthen the link between agriculture and nutrition. Since food production is the most water-intensive activity in society, nutritional water productivity (i.e. nutrition per volume water) of foods and the nutritional water footprint of diets should be investigated in order to achieve a sustainable solution. This implies that both the demand for a diet consisting predominantly of water-productive plant products, as well as the supply thereof, be addressed.

Nutritional water productivity and diets

The increase in water productivity is likely to play a vital role in coping with the additional requirement for food production and the growth of the uses of water other than in agriculture in the coming century consistent with the shift from productivity per unit land to productivity per unit water, the nutritional productivity of water is calculated as energy, protein, calcium, fat, Vitamin A, iron output per unit water input. Nutritional productivity is estimated in the agricultural context of California for the main crops and food products. In general vegetal products are much more productive than animal products. Four crops emerge as highly productive for one or several key nutrients: potato, groundnut, onion and carrot. A balanced diet based on these four crops requires a consumption of water (evapotranspired) of 1000 l per capita per day, while the current needs for the diet in the USA is 5400 l, and 4000 l for developed countries. On the basis of nutritional productivity analysis it is further demonstrated that a significant part of the additional water resource to produce food for the next century population can be generated by changes in food habits. A reduction of 25% of all animal products in the developed countries’ diet generates approximately 22% of the additional water requirements expected by the year 2025.