Conflicting demands for food and water, exacerbated by increasing population, increase the risks of food insecurity, poverty and environmental damage in major river systems. Agriculture remains the predominant water user, but the linkage between water, agriculture and livelihoods is more complex than “water scarcity increases poverty”. The response of both agricultural and non-agricultural systems to increased pressure will affect livelihoods. Development will be constrained in closed basins if increased demand for irrigation deprives other users or if existing agricultural use constrains non-agricultural activities and in open basins if agriculture cannot feed an expanding or changing population or if the river system loses capacity due to degradation or over-exploitation.

Conflicting demands for food and water, exacerbated by increasing population, increase the risks of food insecurity, poverty and environmental damage in major river systems. Agriculture remains the predominant water user, but the linkage between water, agriculture and livelihoods is more complex than “water scarcity increases poverty”. The response of both agricultural and non-agricultural systems to increased pressure will affect livelihoods. Development will be constrained in closed basins if increased demand for irrigation deprives other users or if existing agricultural use constrains non-agricultural activities and in open basins if agriculture cannot feed an expanding or changing population or if the river system loses capacity due to degradation or over-exploitation.

Conflicting demands for food and water, exacerbated by increasing population, increase the risks of food insecurity, poverty and environmental damage in major river systems. Agriculture remains the predominant water user, but the linkage between water, agriculture and livelihoods is more complex than “water scarcity increases poverty”. The response of both agricultural and non-agricultural systems to increased pressure will affect livelihoods. Development will be constrained in closed basins if increased demand for irrigation deprives other users or if existing agricultural use constrains non-agricultural activities and in open basins if agriculture cannot feed an expanding or changing population or if the river system loses capacity due to degradation or over-exploitation.

O presente trabalho foi desenvolvido com a finalidade de avaliar um sistema de bombeamento de água acionado por painéis fotovoltaicos instalados nas dependências da Universidade Tecnológica Federal do Paraná, Câmpus Medianeira - PR. O município está localizado no oeste paranaense (25º17'43" S; 54º03'38" e 500,7 m). O sistema trabalhou em situação real de funcionamento, bombeando água à altura de 20 m. Foram coletados dados de fevereiro a novembro de 2005; utilizou-se coletor de dados computadorizado da Campbell Scientific INC. , que possibilitou adquirir e armazenar os dados de irradiância solar no plano do painel, tensão e corrente gerada, temperatura no painel e vazão. Por meio de cálculos, obtiveram-se os valores de potência e eficiência do sistema. O solstício de inverno apresentou eficiência de 9,58% com bombeamento diário de 2.056 litros, enquanto o solstício de verão apresentou eficiência de 9,07% com bombeamento diário de 2.377 litros. A maior eficiência nos dias de inverno está ligada às menores temperaturas se comparada aos dias de verão, e o fator que provocou a maior vazão de água bombeada nos dias de verão está atrelado ao tempo de insolação, que é maior se comparado aos dias de inverno.<br>The main objective of this paper is to evaluate a water pumping system powered by photovoltaic panels installed at Federal Technological University of Paraná - UTFPR, in Medianeira, State of Paraná, Brazil. The city is located at the West of Paraná (25º17'43"; 54º03'38" and 500.7 meters - 1,642.72 feet). The system operated in a real working situation, pumping water to 20 meters (65.62 feet) of elevation. The data were collected, from February 2005 to November 2005, by means of a computerized data collector made by Campbell Scientific Inc that made possible to acquire and store irradiance values in the panel plane, generated current and voltage, panel temperature and outflow. Through calculations, the power and the system efficiency were obtained. Winter solstice showed 9.58% efficiency with daily pumping of 2,056 liters (543.14 gallons) whereas summer solstice confirmed 9.07% efficiency with daily pumping of 2,377 liters (627.86 gallons). The higher efficiency in winter days is associated to the lowest temperature in those days compared to summer days, and the factor that led to a larger pumped water outflow in the summer days was related to solar insolation time that is longer if compared to winter days.

We cannot expect mankind to change its eating habits overnight or "deny" them a balanced diet, sot it is evident that the agriculture and water sector have to join forces and drastically reduce the use of water to produce our future food requirements by at least 50 % dieticians, food industry, higher education and restaurants have to join forces and change the way we prepare food and eat.

Irrigated agriculture is the main source of water withdrawals, accounting for around 70% of all the world's freshwater withdrawals. The development of irrigated agriculture has boosted agricultural yields and contributed to price stability, making it possible to feed the world's growing population. Rapidly increasing nonagricultural demands for water, changing food preferences, global climate change, and new demands for biofuel production place increasing pressure on scarce water resources. Challenges of growing water scarcity for agriculture are heightened by the increasing costs of developing new water, soil degradation, groundwater depletion, increasing water pollution, the degradation of water-related ecosystems, and wasteful use of already developed water supplies. This article discusses the role of water for agriculture and food security, the challenges facing irrigated agriculture, and the range of policies, institutions, and investments needed to secure adequate access to water for food today and in the future.