Sustainable use of water resources should include the recognition that water has a social value, an environmental value and an economic value. The economic value of irrigation water should be expressed based on its price, which in turn is determined by the interplay of three factors: the cost of irrigation water (supply side), the willingness to pay for irrigation water (demand side) and public policies. This paper presents an analysis of the key methodological issues involved ineach of the above mentioned factors and how they influence the economic value of water

Sustainable use of water resources should include the recognition that water has a social value, an environmental value and an economic value. The economic value of irrigation water should be expressed based on its price, which in turn is determined by the interplay of three factors: the cost of irrigation water (supply side), the willingness to pay for irrigation water (demand side) and public policies. This paper presents an analysis of the key methodological issues involved ineach of the above mentioned factors and how they influence the economic value of water

Human consumption of water outside of the microbiological standards for drinking constitutes a health and disease risk factor. Through the process of infiltration in the soil, groundwater may be contaminated by the waste generated by human activity and deposited in the soil, waterways or air. The consumption of water in natura, captured in a spring, may lead to the risk of disease. One of the alternative technologies for disinfecting water that has shown promise is the generation of an oxidant solution in loco. The electrochemical reaction of sodium chloride produces oxidizing gases, which reacts with the water to produce the hypochlorite ion in balance with hypochlorous acid, along with traces of other oxidants. In the present study the development of a device based on an imported model that uses this type of technology wassought in order to reduce the cost of acquisition and makeit more available to disadvantaged communities with water quality issues. The evaluation of the efficiency of this technology in disinfecting water with different qualities (color and turbidity) was also sought, using total coliforms and Escherichia coli as indicator organisms of contamination. In each experimentthe quality of untreated water, and water after adding the oxidant was examined on turbidity, true color, residual chlorine, pH, temperature, and quantification of microorganism indicators. In the experiments performed we found that the adapted equipment showed to be as efficient in the production of disinfectant agents as the original equipment. In the microbiological assays performed on water contaminated with E. coli (synthesized water in a laboratory and natural) and total coliforms (natural water), the inactivation of these organisms was observed to be effective with the use of gases that came from the adapted equipment, taking into account the content of chlorine in water treated with the equipment. | Human consumption of water outside of the microbiological standards for drinking constitutes a health and disease risk factor. Through the process of infiltration in the soil, groundwater may be contaminated by the waste generated by human activity and deposited in the soil, waterways or air. The consumption of water in natura, captured in a spring, may lead to the risk of disease. One of the alternative technologies for disinfecting water that has shown promise is the generation of an oxidant solution in loco. The electrochemical reaction of sodium chloride produces oxidizing gases, which reacts with the water to produce the hypochlorite ion in balance with hypochlorous acid, along with traces of other oxidants. In the present study the development of a device based on an imported model that uses this type of technology wassought in order to reduce the cost of acquisition and makeit more available to disadvantaged communities with water quality issues. The evaluation of the efficiency of this technology in disinfecting water with different qualities (color and turbidity) was also sought, using total coliforms and Escherichia coli as indicator organisms of contamination. In each experimentthe quality of untreated water, and water after adding the oxidant was examined on turbidity, true color, residual chlorine, pH, temperature, and quantification of microorganism indicators. In the experiments performed we found that the adapted equipment showed to be as efficient in the production of disinfectant agents as the original equipment. In the microbiological assays performed on water contaminated with E. coli (synthesized water in a laboratory and natural) and total coliforms (natural water), the inactivation of these organisms was observed to be effective with the use of gases that came from the adapted equipment, taking into account the content of chlorine in water treated with the equipment. | Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

O estudo do fluxo de água em zonas não saturadas do solo é de grande importância para pesquisas relacionadas à disponibilidade hídrica para o desenvolvimento das plantas. Devido ao alto custo, ao tempo demandado e ao esforço humano nas investigações de campo, os modelos matemáticos, aliados às técnicas numéricas e avanços computacionais, constituem-se em uma ferramenta importante na previsão desses estudos. No presente trabalho, objetivou-se solucionar a equação diferencial parcial não linear de Richards mediante a aplicação do Método de Elementos Finitos. Na aproximação espacial, foi empregada a adaptatividade com refinamento "h" na malha de elementos finitos e, na derivada temporal, foi aplicado o esquema de Euler Explícito. A função interpolação polinomial utilizada foi de grau 2, e a que garantiu a conservação de massa da estratégia de adaptação. Para a validação do modelo, foram utilizados dados disponíveis em literatura. A utilização da função interpolação polinomial de grau 2 e o refinamento "h", com considerável redução do tempo de execução da rotina computacional, permitiram uma boa concordância do modelo em comparação a soluções disponíveis na literatura.<br>Study of water flow in the unsaturated soil zone is of great importance for research related to the water availability for crop development. Due to the high cost, the time required and the human effort in the field investigations, mathematical models combined with numerical techniques and computational advances are important tools in the prediction of these studies. This work aimed to solve the Richards's non-linear partial differential equation by applying the Finite Element Method. Adaptability with "h" refinement of the finite element mesh was used in the spatial approximation, while Explicit Euler scheme was applied for the time derivative. The polynomial interpolation function used was of degree two, and ensured the mass conservation of the adaptation strategy. To validate the model, data available in the literature were used. Use of the polynomial interpolation function with degree two and the "h" refinement, with considerable reduction of the computational runtime allowed good agreement in comparison to solutions available in the literature.

Tomato (Lycopersicon esculentum Mill.) is one of the most consumed vegetables in the world. In Paraiba State, the yield is bellow the national average, and the salinity has contributed for this. This work aimed to evaluate the salinity effects in growth, plant nutrition and yield on two tomato cultivars. Santa Adelia and Meia Estaca cultivars were irrigated with saline water (0.4; 1.5; 3.0; 3.5; and 6.0 dS m-1), in a 2x5 factorial design, with 3 replications. Shoots and roots dry matter, the relative growth rate, N, K, Ca, Mg, S, and Na contents in the leaves, and fruits yield were analyzed. The salinity reduced shoot dry matter in Santa Adelia cultivar. Both cultivars had different behaviors related to leaf ion contents. The salinity reduced the fruit yield. Meia Estaca cultivar was more salt tolerant than Santa Adelia cultivar.<p><p>O tomateiro (Lycopersicon esculentum Mill.) é uma das hortaliças mais consumidas no mundo. No Estado da Paraíba, sua produtividade encontra-se abaixo da média nacional e a salinidade é um dos fatores que têm contribuído para isso. Esse trabalho teve como objetivo avaliar os efeitos da salinidade no crescimento, na nutrição mineral e na produção de duas cultivares de tomateiro rasteiro. Foram estudadas as cultivares Santa Adélia e Meia Estaca, irrigadas com água apresentando condutividades elétricas de 0,4; 1,5; 3,0; 4,5 e 6,0 dS m-1, constituindo um fatorial 2x5, com 3 repetições. Analisaram-se a massa seca da parte aérea e das raízes, a taxa de crescimento relativo, os teores foliares de N, K, Ca, Mg, S e Na, e a produção de frutos. Observou-se que a salinidade reduziu a massa seca da parte aérea nas plantas da cultivar Santa Adélia. As cultivares apresentaram comportamento diferenciado quanto aos teores dos nutrientes nas folhas. A salinidade reduziu a produção de frutos. A cultivar Meia Estaca foi mais tolerante à salinidade do que a Santa Adélia.

Os efeitos de diferentes tensões de água no solo aplicadas em dois estádios fenológicos da cultura da berinjela (Solanum melongena L.) foram avaliados por meio de dois experimentos, ambos conduzidos em um delineamento experimental inteiramente casualizado com 5 tratamentos e 6 repetições. Os tratamentos se constituíram de 5 diferentes tensões de água no solo: 15, 30, 45, 60 e 80 kPa. Os resultados permitiram concluir que efeitos significativos foram encontrados para todas as variáveis analisadas apenas quando os tratamentos foram aplicados na fase de formação de frutos/colheita, demonstrando que esta fase é mais sensível à escassez de água no solo, prejudicando o desenvolvimento da cultura; obtiveram-se maiores produções com irrigação realizada sob a tensão de 15 kPa.<br>Effects of different water tensions in soil applied in two phenological stages in eggplant (Solanum melongena L.) crop were evaluated in two experiments, both carried out in a totally randomized experimental design with 5 treatments and 6 repetitions. The treatments consisted of 5 different soil water tensions: 15, 30, 45, 60 and 80 kPa. The results showed significant efects on all the analysed variables only when treatments were applied in the fruit formation/harvest phase, showing that this phase is more sensitive to soil water tensions and which damages crop development. The best yields were obtained with irrigation carried out under 15 kPa tension.

The objective of this work was to determine the best condi ons for the water immersion test and to evaluate its e ciency for applica on on rice seeds. Five seed lots of cv. rice IRGA 417 were used, which were submited to immersion treatments tests for periods of 24, 48, 72, 96 and 120 hours at 25 C. After treatments, germina on test, par al and total length of seedlings and seedlings dry mater were accomplished. Water immersion test in the condi on of 24 hours of immersion of the seeds at 25 C, with evalua on of normal seedlings developed, is viable to evaluate vigor on rice seeds. | O presente trabalho teve por objeivo determinar as condiç es para a conduç o do teste de imers o em água como teste de vigor em sementes de arroz. Uilizaramrse cinco lotes de sementes de arroz cv. IRGA 417, caracterizados quanto à qualidade fisiológica inicial e submeidos aos tratamentos de imers o em água por períodos de 24, 48, 72, 96 e 120 horas a 25 C. Após os tratamentos, foram realizadas as avaliaç es de germinaç o, comprimento da raiz, parte aérea e total e massa seca das plântulas. O teste de imers o em água na condiç o de 24 horas a 25 C, seguido da avaliaç o da formaç o de plântulas normais, é viável para avaliar o potencial fisiológico de sementes de arroz.

Los metales pesados (MP) pueden afectar las relaciones hídricas de la planta de muchas formas. El Hg inhibe la actividad de las acuaporinas, proteínas que forman los canales transportadores de agua, y de esta manera afecta la conductividad a nivel celular y de tejidos en zonas específicas de la raíz, así como el volumen de las células guarda modificando los movimientos estomáticos. Además, junto con otros metales pesados, el Hg produce cambios morfológicos como el acortamiento o modificación en la elasticidad de las raíces, disminuyendo el área efectiva para la toma de agua. En hojas, el cambio en el número de estomas y de tricomas causado por el Hg, altera la tasa de transpiración. En este artículo se revisa el efecto del Hg sobre el transporte de agua en la planta a nivel celular y su relación con el estatus hídrico de ésta. Además, se presentan avances recientes en el conocimiento de las acuaporinas basados en la utilización del Hg como inhibidor de su actividad.Palabras clave adicionales: acuaporinas, conductividad hidráulica, raíces, estomas. | Heavy metals could affect hydric relationships in plants in many ways. Mercury inhibits activity of aquaporins, the proteins that form the chanels-transporters of water and, thus, affects water conductivity of cells and tissues of special root zones as well as volume of guard cells modifying stomatal movements. Mercury produces morphological changes in plants, the effects typical for other heavy metals, such as shortening of root or decrease in root elasticity, thus reducing effective area for water absorption. In leaves, the changes in number of stomata and trichomes caused by the effects of Hg alter the transpiration rates. In the present article, the effects of Hg over the water transport in plants at cellular level and whole hydric status of plants are revised. Additionally, the recent studies on aquaporin functioning are discussed, with Hg used as an agent to inhibit aquaporin activity.

Dentro del análisis económico que la Directiva Marco del Agua (DMA) prescribe para alcanzar una gestión sostenible de los recursos hídricos, destaca la necesidad de evaluar los beneficios y costes ambientales. Dada la falta de una definición explícita de estos conceptos en el texto de la Directiva y, al mismo tiempo, la necesidad acuciante de evaluar la desproporcionalidad de los costes de la implementación de la DMA, este artículo pretende contribuir a la reflexión sobre los conceptos de beneficio y coste ambiental en este contexto. Se discuten la diferentes interpretaciones y valoraciones que se han hecho hasta el momento en Europa y se profundiza en aspectos claves para su estimación. | Environmental costs and benefits play a major role in the economic analysis prescribed by the Water Framework Directive for the achievement of a sustainable management of water resources. The definition of these concepts is not explicit in the text of the Directive, while there is an urgent need to apply then for analysing whether the implementation of the WFD is disproportionately costly. This paper tries to contribute to the reflexion on the concepts of environmental costs and benefits in the context of the WFD. We discuss the different interpretations and valuations that have been made up to date in Europe and some of the key issues for their estimation.