In this review paper we focus on the dilemma of whether or not current fresh water supply will meet the demand/needs of agricultural crops despite the continuing impact of water scarcity. In addition, we evaluate whether an increase in future population, change in water demand and supply patterns, due to climate change, will allow sustainable food production. With increased scarcity of freshwater, new water conservation technologies and biotechnology were developed, as well as newly developed water sources such as recycled wastewater, and various water institutions, which may help ease water scarcity. With new advancements in farming practices and crop innovations global food supply is still challenged by climate change effects on both water and land resources used for food production.

Ground water tables in Punjab are declining at alarming rates in most districts of Punjab. One of the major causes of declining water tables is the increased cropping intensity. Whereas cropping intensity in Punjab was only 120% until about 50 years ago, it is now 190%. With one crop per year, a balance was maintained between water extraction and aquifer recharge. With two crops per year, this balance has been altered. Homogenization of crops in the state has also exacerbated the problem. Even more serious threat to nation’s agriculture is climate change. Himalayan glaciers, which are water towers for our rivers, are retreating. This will reduce the water flow in our rivers. While the climate-change impact on our water availability is several years away, we must address immediate problem of declining water tables in the state. Suggested interventions include crop diversification, precision agriculture, including water saving technologies, and developing crop varieties with improved water-use efficiency.

Forecasts on population growth and economic development indicate that there will be substantial increases in food demand for the forthcoming decades. We focus here on the water requirements of food production, on the issue of whether there would be enough water to produce sufficient food in the future, and we offer options to face this challenge based on recent trends observed in some agricultural systems. Given the competition for water faced by the agricultural sector, and the uncertainties associated with climate change, improving the efficiency of water use in both rain-fed and irrigated systems is the main avenue to face the challenge. In rain-fed agriculture, managing the risk associated with rainfall variability is a promising option to increase productivity. In irrigated systems, a case study on the improvements in water productivity in Andalusia, Spain, is used to illustrate some of the opportunities to make progress. Progress in reducing irrigation water use in recent decades has been substantial, but decreasing the consumptive use of crops is a much more difficult challenge. The need for more research and technology transfer on improving water-limited crop production is highlighted, and emphasis is placed on interdisciplinary approaches to gain the insight needed to achieve new breakthroughs that would help in tackling this complex problem.

While agriculture places the greatest demand on water resources, increasing agricultural production is worsening a global water shortage. Reducing the cultivation of water-consuming crops may be the most effective way to reduce agricultural water use. However, when also taking food demand into consideration, sustaining the balance between regional water and food securities is a growing challenge. This paper addresses this task for regions where water is unsustainable for food production (Beijing-Tianjin-Hebei Region for example) by: (i) assessing the different effects of wheat and maize on water use; (ii) analyzing virtual water and virtual land flows associated with food imports and exports between Beijing-Tianjin-Hebei and elsewhere in China; (iii) identifying sub-regions where grain is produced using scarce water resources but exported to other regions; and (iv) analyzing the potentiality for mitigating water shortage via Land-Water-Food Nexus. In the Beijing-Tianjin-Hebei Region, the study reveals that 29.76 bn m3 of virtual water (10.81 bn m3 of blue virtual water) are used by wheat and maize production and 8.77 bn m3 of virtual water used in nearly 2 million ha of cropland to overproduce 12 million ton of maize for external food consumption. As an importing-based sub-region with high population density, Beijing & Tianjin imported mostly grain (wheat and maize) from Shandong Province. Then, Hebei Province, as an exporting-based sub-region with severe water shortage, overproduced too much grain for other regions, which aggravated the water crisis. To achieve an integrated and sustainable development of the Beijing-Tianjin-Hebei Region, Hebei Province should stop undertaking the breadbasket role for Beijing & Tianjin and pay more attention to groundwater depletion. The analysis of the Land-Water-Food Nexus indicates how shifts in cultivated crops can potentially solve the overuse of water resources without adverse effects on food supply. It also provides meaningful information to support policy decisions about regional cropping strategies.

Iran’s focus on food self-sufficiency has led to an emphasis on increasing water volumes available for irrigation with little attention to water use efficiency, and no attention at all to the role of consumption and trade. To better understand the development of water consumption in relation to food production, consumption, and trade, we carried out the first comprehensive water footprint assessment (WFA) for Iran, for the period 1980–2010, and estimated the water saving per province associated with interprovincial and international crop trade. Based on the AquaCrop model, we estimated the green and blue water footprint (WF) related to both the production and consumption of 26 crops, per year and on a daily basis, for 30 provinces of Iran. We find that, in the period 1980–2010, crop production increased by 175%, the total WF of crop production by 122%, and the blue WF by 20%. The national population grew by 92%, and the crop consumption per capita by 20%, resulting in a 130% increase in total food consumption and a 110% increase in the total WF of national crop consumption. In 2010, 26% of the total water consumption in the semi-arid region served the production of crops for export to other regions within Iran (mainly cereals) or abroad (mainly fruits and nuts). Iran’s interprovincial virtual water trade grew by a factor of 1.6, which was mainly due to increased interprovincial trade in cereals, nuts, and fruits. Current Iranian food and water policy could be enriched by reducing the WFs of crop production to certain benchmark levels per crop and climatic region and aligning cropping patterns to spatial differences in water availability and productivities, and by paying due attention to the increasing food consumption per capita in Iran.

The proliferation of food, feed and biofuels demands promises to increase pressure on water competition and stress, particularly for Thailand, which has a large agricultural base. This study assesses the water footprint of ten staple crops grown in different regions across the country and evaluates the impact of crop water use in different regions/watersheds by the water stress index and the indication of water deprivation potential. The ten crops include major rice, second rice, maize, soybean, mungbean, peanut, cassava, sugarcane, pineapple and oil palm. The water stress index of the 25 major watersheds in Thailand has been evaluated. The results show that there are high variations of crop water requirements grown in different regions due to many factors. However, based on the current cropping systems, the Northeastern region has the highest water requirement for both green water (or rain water) and blue water (or irrigation water). Rice (paddy) farming requires the highest amount of irrigation water, i.e., around 10,489 million m3/year followed by the maize, sugarcane, oil palm and cassava. Major rice cultivation induces the highest water deprivation, i.e., 1862 million m3H2Oeq/year; followed by sugarcane, second rice and cassava. The watersheds that have high risk on water competition due to increase in production of the ten crops considered are the Mun, Chi and Chao Phraya watersheds. The main contribution is from the second rice cultivation. Recommendations have been proposed for sustainable crops production in the future.

This study evaluates the strategic importance of gray water, which is a component of virtual water, defined as “the water embedded in key water-intensive commodities such as wheat” or “the water required for the production of commodities.” Estimation of gray water plays a role in ensuring water and water-dependent food security for both importing and exporting countries. Methodologies towards reducing virtual water for strategic crops in the Tunisian semi-arid region include irrigation techniques and the control of runoff. Resources management practices that improve family income especially for women and children, all contribute to food security.