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Mexico City, Mexico

Marengo H.,Comision Federal de Electricidad | Arreguin F.I.,Comision Nacional del Agua | Romero I.,Comision Federal de Electricidad
Tecnologia y Ciencias del Agua | Year: 2010

This article presents the procedure and application of several methods of risk and reliability analysis to a simple problem, such as the discharge capacity of a sewer. The analysis considers that the three variables of roughness, diameter, and slope have normal probability distributions and are applied for comparing direct integration methods; the Monte Carlo Method; Mellin Transform, with first-order variance estimation; Rosenblueth's and Harr's Point Estimation Method; the First Order Second Moment Method (MFOSM); and two versions of the Advanced First Order Second Moment Method (AFOSM): Hasofer-Lind's and Tang's. The result of the probability of failure obtained with the direct integration method is taken as true (which is not possible in complex analyses, especially when uncertainties are significant) and results are compared. Most methods can be applied, and it is possible to obtain reliable estimations when the methods come close to linear behaviors, but when the variables are not linear or when uncertainties increase significantly, the accuracy of some methods deteriorates rapidly. Such is the case of the MFOSM method. For methods with samples with sizeable variables, the Monte Carlo method is the most commonly applied, but the reliability of the method converges when there is a large number of simulations, and the final result of the probability of failure is strictly unknown; another important limitation is that the number of variables may cause the problem not to have a practical solution. Methods where point estimation is used (Rosenblueth and Harr) may be very attractive from a computational perspective in as much as the number of variables increases and may seem to be good to use, since they offer similar results to those obtained with the Monte Carlo method and the direct integration method. However, if uncertainties are significant, there may be meaningful differences. The MFOSM method is applicable only in very simple cases where the behavior function is clearly defined and there is variable linearity; however, it rapidly looses accuracy in complex problems. The MFOSM method is quite applicable and can take into account uncertainties in case the analyst decides to make correlations of the variables that intervene in the problem and that most of the times are associated with uncertainties. This seems to be a great advantage over the other methods, since it is possible to involve variables that are many times ignored or undervalued because they cannot be analyzed. The Hasofer Method seems to be quite appropriate for simple problems; however, the Tang Method is quite attractive for analyzing the failure limit state of the problem studied.

Alcocer-Yamanaka V.H.,Mexican Institute of Water Technology | Tzatchkov V.G.,Mexican Institute of Water Technology | Arreguin-Cortes F.I.,Comision Nacional del Agua
Water Resources Management | Year: 2012

Residential water demand is one of the most difficult parameters to determine when modeling drinking water distribution networks. It has been proven to be a stochastic process that can be characterized as a series of rectangular pulses with a set intensity, duration and frequency. These parameters can be determined using stochastic models such as the Neyman-Scott Rectangular Pulse (NSRP) model. The NSRP model is based on the solution of a non-linear optimization problem. This solution involves theoretical moments that represent the synthetic demand series (equiprobable) and the observed moments (field measurements) that statistically establish the measured demand series. The NSRP model has been applied for residential demand, and the results have been published. However, this model has not been validated for a real distribution network or compared with traditional methods. The present study compared the results of synthetic stochastic demand series, which were calculated using the NSRP model, applied to the determination of pressures, flow rates and leaks; to the results obtained using traditional simulation methods, which use the curve of hourly variation in demand, and to actual pressure and flow rate measurements. The Humaya sector of Culiacan, Sinaloa, Mexico, was used as the study area. © Springer Science+Business Media B.V. 2012.

Ahumada-Santos Y.P.,Autonomous University of Sinaloa | Baez-Flores M.E.,Autonomous University of Sinaloa | Diaz-Camacho S.P.,Autonomous University of Sinaloa | Uribe-Beltran M.J.,Autonomous University of Sinaloa | And 8 more authors.
Ciencias Marinas | Year: 2014

The agricultural drainage water from the Sinaloa valley (Mexico) is often reused in agriculture and aquaculture before reaching coastal water bodies. Discharged water must be of good quality to maintain the health of ecosystems and prevent damage to the organisms that compose them. This research determined the occurrence of coliforms in a drainage ditch known as La Michoacana (Sinaloa) that receives contaminated water from agricultural and urban sources. A section of 3.6 km was studied during 2013 and samples were obtained monthly from five equidistant sampling sites. Each water sample was analyzed for total coliform (TC) and fecal coliform (FC) content, pH, salinity, temperature, and dissolved oxygen percentage (%DO). The sampling sites with the highest bacterial contamination were associated with direct discharges of domestic wastewater and those with the lowest to the output drain. The performance of this agricultural ditch decreased the concentration of coliforms, with median and average values of 96% and 87% for TC, and 98% and 85% for FC, respectively. The most common bacteria were Escherichia coli (67.7%), Kluyvera cryocrescens (10.2%), and Enterobacter agglomerans (6.3%). Coliform concentration was positively correlated with temperature and negatively with %DO. The ditch improved the microbiological quality of the water, demonstrating remediation activities in the system. Proper management and maintenance of agricultural drainage ditches would favorably impact the health and biodiversity, as well as the intensive aquaculture and agricultural activities of the Sinaloa valley. © 2014, Universidad Autonoma de Baja California. All rights reserved.

De Jesus Lopez-Cantens G.,National Autonomous University of Mexico | Prado-Hernandez V.,National Autonomous University of Mexico | De Leon-Mojarro B.,Comision Nacional del Agua | Ruiz-Carmona V.M.,Instituto Mexicano Of Tecnologia Del Agua | And 3 more authors.
Tecnologia y Ciencias del Agua | Year: 2014

Applying Saint Venant equations in reaches of irrigation canals requires defining internal boundary conditions at the sites where they are located control structures like gates, considering the dynamic equation to transmit hydraulic information from one side of the structure to continue on the other. In this study three numerical procedures for maneuvering gates are tested to verify whether they represent the movement of these control structures, minimizing flow phase shifts after a maneuver. To this end, the Rehbock canal of the Autonomous University of Chapingo was used. Automated measurements of water depth and flow were taken. Results show that in progressive maneuvering with restart of water depth, flow through the gate and near it tends to be similar, while oscillations diminish over time, a phenomenon which is characteristic of water dynamics in canals. Moreover, when depth is the variable to be regulated it is advisable to use instantaneous or progressive maneuvering with restart of flow. On the other hand, if the variable is flow, progressive maneuvering with restart of depth is preferred. Simulation of progressive maneuvering with restart of depth is the procedure that best represents water dynamics in the structure.

Mejia-Gonzalez M.A.,Instituto Mexicano Of Tecnologia Del Agua | Gonzalez-Hita L.,Instituto Mexicano Of Tecnologia Del Agua | Briones-Gallardo R.,Autonomous University of San Luis Potosi | Cardona-Benavides A.,Autonomous University of San Luis Potosi | Soto-Navarro P.,Comision Nacional del Agua
Tecnologia y Ciencias del Agua | Year: 2014

In order to elucidate the processes that causes high concentrations of arsenic in the aquifer of the Comarca Lagunera were conducted geochemical studies of groundwater and sediment. The results of the sediment geochemistry indicate that arsenic is mainly adsorbed on amorphous and crystalline Fe oxides. The results of the groundwater geochemistry indicate: 1) Cation Exchange between calcium and sodium, 2) Dissolution of calcite due to cation exchange, 3) Increase in pH due to the dissolution of calcite, and 4) high concentrations of arsenic due to elevated pH values.

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