Browsing by Author "Jerves Cobo, Ruben Fernando"

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Analysis of the behavior of abstractions in two urban micro-basins of the city of Cuenca (Ecuador), through an aggregate model
(2021) Jerves Cobo, Ruben Fernando
Several cities in developing countries are challenging the permanent process of urbanization. This generates a great disturbance on the hydrological response of the urbanized area during rainfall events, which can cause floods. Among the disturbances that urbanized basins may suffer, it is found that variations in rain losses (hydrological abstractions) can be estimated by the named volumetric runoff coefficient (CVOL) methodology. In the present study, this methodology is used in an attempt to estimate the hydrological abstraction of two nearby urbanized basins, with different degrees of impermeability, located in the city of Cuenca in Ecuador. The data for that analysis were collected between April and May of 2017. The results obtained indicate that the micro-basin with the largest impervious area presents the higher initial hydrological losses, the higher rate of decrease in abstractions, and the higher stormwater runoff flows per unit area. In addition, the abstractions found in the two urban micro-basins show great sensitivity to the maximum rainfall intensity and do not relate to the antecedent soil moisture. These results demonstrate the importance of having higher pervious surfaces in urbanized areas because they lead to reduce negative impacts associated with increased stormwater runoff on impervious surfaces.
Determination of pollution loads in spillways of the combined sewage network of the city of Cuenca, Ecuador
(2020) Montalvo Cedillo, Cesar Augusto; Jerves Cobo, Ruben Fernando; Dominguez Granda, Luis Rigoberto
Combined sewer overflow (CSO) is one of the main causes of contamination in receiving bodies during the rainy period. The objective of this research was to evaluate the behavior of three combined sewage discharges into the Tomebamba River in the city of Cuenca, Ecuador. For this, the registration of 18 CSO events was carried out. The following water quality parameters were analyzed from the field survey (March 2017 to May 2018): conductivity, turbidity, BOD5, COD, fecal and total coliforms, nitrates, nitrites, ammoniacal nitrogen, dissolved orthophosphate and total phosphorus. The results show that CSOs contribute to the deterioration of the water quality of the Tomebamba River during the rainy season. The analysis of the dynamics of the pollutants determined that the maximum conductivity values occur at the beginning of the discharge, and the maximum turbidity is located near the peak discharge flow. The relationship between rain and the characteristics of the CSO was also analyzed through a canonical correlation analysis and partial least squares regression, obtaining a prediction model of pollutants based on the precipitation parameters. These results can be used for the implementation of integrated ecological models that enable a complete analysis of the city’s sanitation systems, their impact on the receiving bodies and their restoration.
Estimación de las pérdidas de la precipitación en una cuenca hidrográfica urbana de la Ciudad de Cuenca
(Universidad de Cuenca, 2017) Rubio Ramirez, Mario Ricardo
La ciudad de Cuenca en Ecuador, enfrenta un permanente proceso de urbanización de su territorio, provocando considerable alteración en la respuesta hidrológica de la cuenca hidrográfica ante las lluvias. Entre las alteraciones que sufre una cuenca urbanizada se tiene la variación de la pérdida de la lluvia en la cuenca (abstracciones), existiendo diversas metodologías para su estimación. Entre ellas se cuenta con el método de Coeficiente de escorrentía volumétrico Cv. Con el presente trabajo, a través de la metodología señalada se plantea estimar las pérdidas o abstracciones que experimenta una cuenca urbana en la ciudad de Cuenca mediante el análisis de información recopilada entre Marzo y Mayo del 2017. Los resultados que se obtuvieron indican que para precipitaciones con intensidades que varían entre 4.8 y 38.4 mm/h las pérdidas en la cuenca se encuentran entre el 18% y 60%.
Greenhouse gas dynamics in an urbanized river system: influence of water quality and land use
(2022) Ho, Long; Jerves Cobo, Ruben Fernando; Barthel, Matti; Seis, Johan; Bodé, Samuel; Boeckx, Pascal; Goethals, Pedro
Rivers act as a natural source of greenhouse gases (GHGs). However, anthropogenic activities can largely alter the chemical composition and microbial communities of rivers, consequently affecting their GHG production. To investigate these impacts, we assessed the accumulation of CO2, CH4, and N2O in an urban river system (Cuenca, Ecuador). High variation of dissolved GHG concentrations was found among river tributaries that mainly depended on water quality and land use. By using Prati and Oregon water quality indices, we observed a clear pattern between water quality and the dissolved GHG concentration: the more polluted the sites were, the higher were their dissolved GHG concentrations. When river water quality deteriorated from acceptable to very heavily polluted, the mean value of pCO2 and dissolved CH4 increased by up to ten times while N2O concentrations boosted by 15 times. Furthermore, surrounding land-use types, i.e., urban, roads, and agriculture, could considerably affect the GHG production in the rivers. Particularly, the average pCO2 and dissolved N2O of the sites close to urban areas were almost four times higher than those of the natural sites while this ratio was 25 times in case of CH4, reflecting the finding that urban areas had the worst water quality with almost 70% of their sites being polluted while this proportion of nature areas was only 12.5%. Lastly, we identified dissolved oxygen, ammonium, and flow characteristics as the main important factors to the GHG production by applying statistical analysis and random forests. These results highlighted the impacts of land-use types on the production of GHGs in rivers contaminated by sewage discharges and surface runoff.
Integrated mechanistic and data-driven modeling for risk assessment of greenhouse gas production in an urbanized river system
(2021) Ho, Long; Jerves Cobo, Ruben Fernando; Forio, Marie Anne Eurie; Mouton, Ans; Nopens, Ingmar; Goethals, Peter
Surrounded by intense anthropogenic activities, urban polluted rivers have increasingly been reported as a significant source of greenhouse gases (GHGs). However, unlike pollution and climate change, no integrated urban water models have investigated the GHG production in urban rivers due to system complexity. In this study, we proposed a novel integrated framework of mechanistic and data-driven models to qualitatively assess the risks of GHG accumulation in an urban river system in different water management interventions. Particularly, the mechanistic model delivered elaborated insights into river states in four intervention scenarios in which the installation of a new wastewater treatment plant using two different technologies, together with new sewage systems and additional retention tanks, were assessed during dry and rainy seasons. From the insights, we applied fuzzy rule-based models as a decision support tool to predict the GHG accumulation risks and identify their driving factors in the scenarios. The obtained results indicated the important role of new discharge connection and additional storage capacity in decreasing pollutant concentrations, consequently, reducing the risks. Moreover, among the major variables explaining the GHG accumulation in the rivers, DO level was considerably affected by the reaeration capacity of the rivers that was strongly dependent on river slope and flow. Furthermore, river water quality emerged as the most critical variable explaining the pCO2 and N2O accumulation that implied that the more polluted and anaerobic the sites were, the higher were their GHG accumulation. Given its simplicity and transparency, the proposed modeling framework can be applied to other river basins as a decision support tool in setting up integrated urban water management plans.
Spatial and temporal variations of greenhouse gas emissions from a waste stabilization pond: effects of sludge distribution and accumulation
(2021) Ho, Long; Jerves Cobo, Ruben Fernando; Morales Matute, Oscar Patricio; Larriva Vasquez, Josue Bernardo; Arevalo Durazno, Maria Belen; Barthel, Matti; Six, Johan; Bode, Samuel; Boeckx, Pascal; Goethals, Peter
Due to regular influx of organic matter and nutrients, waste stabilization ponds (WSPs) can release considerable quantities of greenhouse gases (GHGs). To investigate the spatiotemporal variations of GHG emissions from WSPs with a focus on the effects of sludge accumulation and distribution, we conducted a bathymetry survey and two sampling campaigns in Ucubamba WSP (Cuenca, Ecuador). The results indicated that spatial variation of GHG emissions was strongly dependent on sludge distribution. Thick sludge layers in aerated ponds and facultative ponds caused substantial CO 2 and CH 4 emissions which accounted for 21.3% and 78.7% of the total emissions from the plant. Conversely, the prevalence of anoxic conditions stimulated the N 2 O consumption via complete denitrification leading to a net uptake from the atmosphere, i.e. up to 1.4 ±0.2 mg-N m −2 d −1 . Double emission rates of CO 2 were found in the facultative and maturation ponds during the day compared to night-time emissions, indicating the important role of algal respiration, while no diel variation of the CH 4 and N 2 O emissions was found. Despite the uptake of N 2 O, the total GHG emissions of the WSP was higher than constructed wetlands and conventional cen- tralized wastewater treatment facilities. Hence, it is recommended that sludge management with proper desludging regulation should be included as an important mitigation measure to reduce the carbon foot- print of pond treatment facilities.