Peer Reviewed | Postprint (published version)

Pregrado | Ingeniero(a) Civil

Under the European system of agri-environmental indicators, the Council of the European Union recognized the need for comparable data on agricultural activities, especially with regard to farm management practices and use of agricultural inputs, including the use of irrigation water, having been enshrined this principle in the Regulation (EC) 1166/2008. To meet this legal requirement, established a partnership between the INE and ISA / CENTROP to develop the MECAR - Methodology for Estimating Irrigation Water in Portugal. After the comparative approach of different methodologies, it was considered that the use of estimation models based on water balance would be the best approach to achieve these objectives. The methodology was based on soil water balance, which is done by the mathematical model ISAREG (Teixeira and Pereira, 1992 and Teixeira, 1994), which is based on the procedure of the FAO (Doorenbos and Pruit, 1977 and Doorenbos and Kassam, 1979) determining the water requirements of crops, which apply correction factors for loss of efficiency that stem from the characteristics of irrigation systems used and the conditions of irrigation, particularly in their management of their respective owners. The validation of results produced by MECAR, to prove that the volumes obtained by simulation were located close to the actual values, it was considered satisfactory. However, it is recommended that a second validation be performed, comparing the annual simulated data recorded by the irrigation farmers associations and individual farmers for the same period. The application of MECAR to actual data from IE 2007 is an operational test of this solution is adequate as it allowed to obtain reliable information and consistent with the requirements of the regulation.

Under the European system of agri-environmental indicators, the Council of the European Union recognized the need for comparable data on agricultural activities, especially with regard to farm management practices and use of agricultural inputs, including the use of irrigation water, having been enshrined this principle in the Regulation (EC) 1166/2008. To meet this legal requirement, established a partnership between the INE and ISA / CENTROP to develop the MECAR - Methodology for Estimating Irrigation Water in Portugal. After the comparative approach of different methodologies, it was considered that the use of estimation models based on water balance would be the best approach to achieve these objectives. The methodology was based on soil water balance, which is done by the mathematical model ISAREG (Teixeira and Pereira, 1992 and Teixeira, 1994), which is based on the procedure of the FAO (Doorenbos and Pruit, 1977 and Doorenbos and Kassam, 1979) determining the water requirements of crops, which apply correction factors for loss of efficiency that stem from the characteristics of irrigation systems used and the conditions of irrigation, particularly in their management of their respective owners. The validation of results produced by MECAR, to prove that the volumes obtained by simulation were located close to the actual values, it was considered satisfactory. However, it is recommended that a second validation be performed, comparing the annual simulated data recorded by the irrigation farmers associations and individual farmers for the same period. The application of MECAR to actual data from IE 2007 is an operational test of this solution is adequate as it allowed to obtain reliable information and consistent with the requirements of the regulation.

This study determined a function demand for residential water. The data were stratified by geographic areas according to the level of regularity of water supply to the households. Income, price, number of rooms and persons in the households were found to be the main variables influencing the level of water consumption. Differences between: i) households connected to the water and sewage systems and those connected only to the water system; ii) households with up to 20 m3 of water consumption and those with consumption between 20 and 50 m3 and finally those with consumption above 50 m3 were surveyed. The results of the residential water demand were, in general, statistically significant and the coefficients presented the expected sign. These results are important tools to help decide on the tariffs to be charged to the consumers and on the investments to be made in the sector. | Nos últimos anos, muitas companhias estaduais de saneamento vêm cobrando tarifas sem conhecer a mudança do estilo de vida no meio urbano. Para conhecer melhor o mercado, a fim de poder adotar uma política tarifária compatível com a demanda por água, determinou-se uma função da demanda residencial por água no estado do Ceará, segmentando-a por áreas geográficas. No total, 1.437 domicílios foram pesquisados. Como procedimento de análise, utilizou-se o método dos mínimos quadrados ordinários (MQO), em que foram estimadas diversas regressões lineares, semilog e log-linear. No caso, a variável dependente considerada foi o consumo de água por pessoa nos domicílios pesquisados, enquanto as principais variáveis explicativas da demanda por água que apresentaram significação estatística foram: a tarifa que o entrevistado está disposto a pagar para manter um abastecimento de água regular, a renda familiar, uma variável dummy que indica se o domicílio está conectado à rede de esgoto ou não, o número de cômodos do domicílio pesquisado, o número de moradores do domicílio pesquisado, uma variável dummy que assume o valor 1 para os domicílios que consomem até 20 m3 de água e zero em caso contrário, e outra variável dummy que assume o valor 1 para os domicílios que consomem mais de 50 m3 de água e zero em caso contrário. Em termos gerais, os resultados apresentaram bom nível de significação estatística para as funções demanda. Os parâmetros apresentaram sinal esperado e, na grande maioria dos casos, foram significativamente diferentes de zero. Conclui-se que os resultados obtidos representam um instrumento de grande importância para a tomada de decisões sobre tarifas.

The knowledge of the water volume used in rice farming is of fundamental importance for the solution related to water distribution problems between the multiple uses and the grant concession. In this way, the objective of this work was to quantify the water volume used in rice farming, through simplified methods of flow measurement in different soils classes, as subsidy to the administration of water resources and to relate it to soil attributes. The study was implanted in four municipal districts, producers of irrigated rice, of the State of Rio Grande do Sul: Cacequi, Cachoeira do Sul, Manoel Viana and Santa Maria, totaling seven areas with extensions between 0.66 to 30.1 ha. Were measured the flow and classified the soils of each area. The methodology of flow measurement consisted of the installation of simple hydraulic structures. The structures were installed in the irrigation channels and in some drainage ones. This methodology transforms the flow in volume through empiric equations. Later, the monitored volume was compared to real hydric balance volume to validation of flow measurement method (automonitoring). The characterization of the soil was accomplished through the profile description for obtaining the pedogenetic horizons. Later, physical analyses were accomplished, in laboratory, as the density (soil and particle), the porosity (macro, micro and total), the texture (clay, silte and sand), the hydraulic conductivity and the chemical analyses as soil pH, calcium, magnesium, aluminum, saturation (bases and aluminum). The rate of water infiltration into soil in the field was obtained through the double concentric rings infiltrometer. The soils classification was determined to the fourth categorical level adopted by the Brazilian System of Soil Classification (EMBRAPA, 2006). The results showed similarity comparing the automonitoring technique and the real hydric balance. Only two soil classes occurred: Planossolos end Gleissolos. The relation between the soil sandy layer thickness and water volume used in irrigation was directly proportional. Already the clay fraction and volume relationship was inversely proportional. Most of the areas showed high soil density and low total porosity. The saturated hydraulic conductivity was classified between very slow to slow. The areas that presented larger infiltration rates, in the beginning of the test, were: Cacequi (No Till) and Cachoeira do Sul (Conventional). In the first, due to the high concentration sand, and in the second, due to soil surface was turned over before the infiltration test. In this way, was concluded that the automonitoring technique was validated. The Manoel Viana area showed discrepant conflicting volume from the others. The quantification of water volume used depends almost exclusively of the soil class and only a few of the soil management system. An increase in clay content in the layer under the sand layer decreases the water volume in irrigation. The area that not showed B horizon had the greater volume. Soil density data, total porosity, the saturated hydraulic conductivity and infiltration rate did not have similar behavior in all evaluated areas. | Coordenação de Aperfeiçoamento de Pessoal de Nível Superior | O conhecimento do volume de água utilizado em lavouras orizícolas é de fundamental importância para a solução de problemas relativos à distribuição da água entre os usos múltiplos e à concessão da outorga. Deste modo, o objetivo deste trabalho foi quantificar o volume de água usado em lavouras orizícolas, por meio de métodos simplificados de medição de vazão em áreas de diferentes regiões produtoras no sul do Rio Grande do Sul, como subsídio à gestão de recursos hídricos e relacioná-lo com atributos do solo. O estudo foi implantado em quatro municípios, produtores de arroz irrigado, no Estado do Rio Grande do Sul: Cacequi, Cachoeira do Sul, Manoel Viana e Santa Maria, totalizando sete áreas com extensões entre 0,66 a 30,1 hectares. Foi calculada a vazão e classificado o solo de cada área de várzea. A metodologia de medição de vazão consistiu na instalação de estruturas hidráulicas simples. As estruturas foram instaladas nos canais de irrigação e em alguns de drenagem. Esta metodologia transforma a vazão em volume por meio de equações empíricas. Posteriormente o volume monitorado foi comparado ao volume do balanço hídrico real para a validação do método de medição de vazão (automonitoramento). Foi realizada a caracterização do solo através da descrição de perfil para a obtenção dos horizontes pedogenéticos. Em seguida, foram realizadas análises físicas, em laboratório, para determinar parâmetros como a densidade (do solo e de partícula), a porosidade (macro, micro e total), a textura (argila, silte e areia), a condutividade hidráulica saturada, e as análises químicas como pH do solo, cálcio, magnésio, alumínio, saturação (bases e alumínio).A taxa de infiltração de água no solo foi realizada à campo e obtida por meio do infiltrômetro de duplo anéis concêntricos. A classificação dos solos foi determinada até o quarto nível categórico adotada pelo SBCS (EMBRAPA, 2006). Os resultados mostraram similaridade na comparação entre a técnica de automonitoramento e o balanço hídrico real. Ocorreram apenas duas classes de solo: Planossolos e Gleissolos. A relação entre a espessura da camada arenosa e o volume de água utilizado na irrigação foi diretamente proporcional. Já a fração argila e o volume foi inversamente proporcional. A maioria das áreas apresentaram alta densidade do solo e baixa porosidade total. A classificação da condutividade hidráulica saturada foi de muito lenta à lenta. As áreas que apresentaram maiores taxas de infiltração, no início do teste foram: Cacequi (Plantio Direto) e Cachoeira do sul (Convencional). Na primeira, devido à elevada concentração de areia, e, na segunda pelo revolvimento da superfície do solo antes do teste de infiltração. Desta forma, conclui-se que a técnica de automonitoramento foi validada. A área de Manoel Viana apresentou volume discrepante das demais. A quantificação do volume de água usado depende quase exclusivamente da classe de solo e muito pouco do sistema de cultivo. Um aumento no teor de argila na camada subjacente à camada arenosa diminui o volume de água na irrigação. A área que não apresentou o horizonte B registrou o maior volume utilizado. Os dados de densidade do solo, porosidade total, condutividade hidráulica saturada e infiltração não tiveram comportamento semelhante em todas as áreas avaliadas.

The present work aimed to obtain a mathematical expression to calculate the amount of EDTA required to produce calcium-free and low-calcium water ([Ca2+] < 5 mg L-1). Initially, a pilot test was carried out to confirm the effectiveness of EDTA as a chelating agentof waterborne calcium and to evaluate its effect on water pH. Five application rates of Na- EDTA (25, 50, 75, 100 and 125 mg L-1) were tested. The concentration of calcium in water was determined initially (before the application of EDTA) and after one hour. Linearregression analysis was performed to find out the relationship between the desired calcium concentration in water and the required EDTA: initial calcium hardness ratio. The expression . = -0.0911x + 3.3628 (R2 = 0.933) was derived from the linear regression analysis carried out, in which x represents the desired calcium concentration in water and y the required EDTA: initial calcium hardness ratio.<br><br>O presente trabalho teve como objetivo determinar a quantidade de EDTAnecessaria para se produzir agua sem calcio e agua mole ([Ca2+] < 5 mg L-1) para experimentacao em aquicultura. Inicialmente, realizou-se teste-piloto para confirmar a efetividade do EDTA como agente complexante do calcio presente na agua e avaliar seu efeito no pH da agua. No teste principal, cinco taxas de aplicacao de Na-EDTA (25, 50, 75, 100 e 125 mg L-1) foram avaliadas. A concentracao de calcio da agua foi determinada inicialmente (antes da aplicacao de EDTA) e apos 1h. Analise de regressao linear foi feita para se descobrir a relacao entre a concentracao desejada de calcio na agua e a relacaoEDTA/dureza calcica inicial da agua necessaria. A expressao . = -0,0911x + 3,3628 (R2 = 0,933) foi obtida a partir da regressao realizada na qual x representa a concentracao desejada de calcio na agua e y a relacao EDTA/dureza calcica inicial da agua.