Hydrological Modelling and Evaluation of Detention Ponds to Improve Urban Drainage System and Water Quality

Fernanda Pereira Souza,Sergio Koide,Maria Elisa Leite Costa

doi:10.3390/w11081547

Abstract

Paranoá Lake is an urban lake and it is being used as a source for urban water supply since last year. Until 1990, algal blooms occurred and improvements on wastewater treatment plants carried out improved the water quality very rapidly due to phosphorus load reduction. Recently, water quality is deteriorating, which is probably due to diffuse pollution. In Brazil, we adopt separated pipe networks for sewage and stormwaters, although cross flows occur. The evaluation of urban drainage stormwaters entering the lake and proposition of technical alternatives is crucial in minimizing the impacts on lake water quality. Quantitative and qualitative behavior of urban stormwaters were analyzed by means of monitoring the runoff flows and pollutant concentrations. Mathematical modelling while using the Storm Water Management Model—SWMM was carried out, and good correlations were found for flow modelling. However, poor response was achieved for water quality simulations, affecting the simulated pollutant loads entering the lake. The simulation of 13 alternatives for detention ponds location was also evaluated, as well as their influences on flow damping capability. The detention ponds that were tested were placed in line in the drainage mains to study the effects of their location on the removal of pollutants. As expected, the results showed that ponds located near the outfall are more efficient in reducing flow peaks. However, this layout requires construction woks in areas that are more sensitive to environmental and urbanistic problems and with higher land commercial values. Alternatives with smaller volumes in public areas near the center of the catchment area can lead to the peak flow damping required by the existing drainage network to avoid overflows. In conclusion, detention ponds can be a good alternative for improving the stormwater quantity and quality, but also alternatives that promote increased infiltration, should also be considered for compensating the infiltration lost due to urbanization.

Highlights

The redesign of the stormwater management systems is fundamental in addressing the issues that lead to the decaying situation of flooding and water pollution in most Brazilian large cities, in which the upstream flows increase by urbanization and stormwater removal only by means of structures to take out the water rapidly, leading to significant impacts on receiving water bodies
Sewage is treated by wastewater treatment plants (WWTP) in part of the cities, but stormwaters are usually discharged into the receiving watercourses without any treatment and, in many cases, neither peak discharge attenuation
After simulated 13 detention pond alternatives, with different sizes and location along the drainage system, it was observed that the detention ponds that were located at the center of the watershed had little effect on damping final flow, they contributed to better drainage promoted by the pipe network by reducing the drainage system point overflows

Summary

Introduction

The redesign of the stormwater management systems is fundamental in addressing the issues that lead to the decaying situation of flooding and water pollution in most Brazilian large cities, in which the upstream flows increase by urbanization and stormwater removal only by means of structures to take out the water rapidly, leading to significant impacts on receiving water bodies.New technologies emerged, which consider other aspects of urban stormwater management, such as sustainable management solutions. The redesign of the stormwater management systems is fundamental in addressing the issues that lead to the decaying situation of flooding and water pollution in most Brazilian large cities, in which the upstream flows increase by urbanization and stormwater removal only by means of structures to take out the water rapidly, leading to significant impacts on receiving water bodies. According to Kourtis et al [1] some examples of improvements on stormwater management systems have been achieved: (i) runoff quality; (ii) visual amenity; (iii) recreational value; and, (iv) ecological protection. Nowadays, these techniques are widely recommended and applied in different cities around the world, and a common application is focused. Sewage is treated by wastewater treatment plants (WWTP) in part of the cities, but stormwaters are usually discharged into the receiving watercourses without any treatment and, in many cases, neither peak discharge attenuation

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