This paper highlights the difficult choices that must be made as mounting pressure from the world’s growing population for more food could lead to greater water consumption and increasing environmental degradation. Globally, agriculture uses between 70 to 90% of developed water supplies and the livelihoods of 70% of the world’s poor depend largely on farming. Despite the benefits, large-scale irrigation systems have led to pollution in rivers and the drying up of wetlands: at least 30% of the world’s river flows need to be used to maintain the condition of freshwater ecosystems worldwide.The paper argues that there is less water available for the competing demands for water (water to feed people, water to reduce poverty and water to sustain natural ecosystems) because of increasing water demands by cities and industries. It identifies a number of ways of resolving this dilemma: <B>Improved water productivity:</B> this might be achieved through improved crop varieties, combined with better tillage methods and more precise drip or micro irrigation. Drought resistant seeds, water harvesting schemes and small plot technologies such as manually operated treadle pumps have the potential to boost yields by 100% in many areas of sub- Saharan Africa where most farmers depend on rain fed agriculture. An improvement of water productivity by 40% over the next twenty five years would be reduce the global need for extra water for irrigation to zero. <B>Influencing peoples’ diets:</B> Western diets based on meat from grain fed cattle account for as much as 5,000 liters per capita per day while vegetarian diets deplete less than half as much water. With prevailing land and water management practices, a balanced diet requires 3287 liters of water per day compared to the 50 used for an average household’s domestic needs. <B>Increasing the trade of ‘virtual water’: </B>this trade in food from water abundant countries to water scarce ones is another option to be considered, but it is questionable whether low income countries will be able to afford ‘virtual water’ and there may be negative consequences for poor farmers. <B>Increasing the use of urban wastewater for irrigation: </B> up to one-tenth of the world’s population eats food produced using wastewater from towns and cities. Using wastewater and saline water for irrigation may improve the quality of water available for ecosystems in basins where there is still some outflow<B>Reforming agricultural policy: </B> agricultural subsidies in the west are a major factor in keeping prices low for agricultural producers in developing countries. However, decisions on diet and trade tend not to factor in water issues directly. While diet transitions in developing countries increase water demands, and some farm practices can be changed, influencing people's diets may not be a practical means of addressing water scarcity across the world. Global trade flows similarly resist influence, as economic and political motivations tend to override environmental ones.Of these options, increasing water productivity and the upgrading of rain-fed systems have the most potential to improve food security and reduce poverty at the lowest environmental cost. The paper finds that gains from increased irrigation efficiency are a lot less than imagined.This draft version of the report was prepared for a World Water Week 2004 event held in Stockholm

Oil and gas extraction in the western United States generates significant volumes of produced water (PW) that is typically injected into deep disposal wells. Recently, crop irrigation has emerged as an attractive PW reuse option, but the impact on plant immune response is not known. In this study, we conducted a 3-month greenhouse pot study. Spring wheat (Triticum aestivum) was irrigated 3 times a week with 150 mL (∼80–100% of soil water holding capacity) with one of four irrigation treatments: tap water control, 10% PW dilution, 50% PW dilution, and salt water (NaCl50) control containing the same amount of total dissolved solids as PW50 to determine the effect on disease resistance. The wheat leaves were inoculated with either bacterial or fungal pathogens and changes in pathogenesis-related PR-1 and PR-5 gene expression were measured from the leaf tissue. PW50 experienced the largest relative suppression of PR-1 and PR-5 gene expression compared to noninfected wheat, followed by PW10, NaCl50, and the tap water control. A combination of PW contaminants (boron, total petroleum hydrocarbons, and NaCl) are likely reducing PR-gene expression by reallocating metabolic resources to fight abiotic stresses, which then makes it more challenging for the plants to produce PR genes to fight pathogens. This study provides the first evidence that plant disease resistance is reduced due to irrigation with reused PW, which could have negative implications for food security.

Aims of this experiment, to examined the effects of food density and water salinity on filtration rate of oyster (Crassostrea belcheri) for fundamental data on assessing the suitable use of oyster as an alternative of biofilter in wastewater from an intensive shrimp pond. From the experimentation showed that an average of filtration rate within 24 hours of both size of oysters at different food density were significantly different (p0.01). The Filtration rate of oysters were decreased with increasing the food density. The average of filtration rate of oysters when exposed to different water salinity were significantly different (p0.01). The decrease in filtration rate of oyster was correlated with water salinity. The average filtration rate of oyster was high at water salinity range 15-25 ppt for small size and 10-25 ppt for large size.