Evaluation of rainwater harvesting in Portugal: Application to single-family residences

https://doi.org/10.1016/j.resconrec.2014.11.004Get rights and content

Highlights

  • Monitoring of water consumption in a single-family house in Portugal.

  • Characterization of two precipitation patterns in Portugal, Porto and Almada.

  • Evaluation of the technical feasibility of rainwater harvesting in Portugal.

  • Evaluation of the economical viability of rainwater harvesting in Portugal.

  • Sensitivity analysis of rainwater harvesting solutions in Portugal.

Abstract

Because water is a key at-risk resource, improved water management is essential. In terms of quantity, the two major alternatives in water management can be grouped into: (i) improving efficiency in water use; and (ii) exploring alternative water sources. Rainwater harvesting (RWH) is one of the most promising alternative water sources, since rainwater can easily be collected and used without significant treatment for non-potable purposes. However, the economical viability of these systems is not always assured. This paper examines the most relevant technical and economical issues in designing domestic RWH systems, evaluating the technical feasibility and economical viability of this technology in the particular weather and water use in Portugal. The evaluation is performed for a single-family residence, where the water use pattern was monitored. The precipitation pattern is characterized for two locations in Portugal, Porto and Almada, since they represent two different scenarios for RWH. The RWH and water savings efficiency were assessed and payback period estimated for both cities. It was found that, for an optimum rainwater tank, the water savings potential are similar for both locations, despite the differences in the average annual precipitation. A simple rule for estimating the optimum tank capacity for single-family households in Portugal is proposed. A sensitivity analysis shows an important influence of water fees on the economical viability of RWH systems in single-family houses in Portugal, namely when compared to changes in the consumption pattern.

Introduction

The goal of reducing by half the proportion of people without sustainable access to safe drinking water until 2015 set in 2000 by UN Millennium Development Goals is far from being fulfilled in some parts of the globe (UN, 2013). Currently, it is estimated that roughly one billion people do not have access to safe drinking water (Helmreich and Horn, 2009). This is more critical in developing countries, particularly in poor rural areas, where at least one-third of the population has little or no access to safe drinking water and results in major health problems from waterborne diseases (WHO, 2002; UN, 2013). In addition, several parts of the globe already face water scarcity, most notably in Africa, and it is estimated that by 2025 two thirds of the world's population will face water related challenges (UNEP, 2002). Therefore, water is a key at-risk resource and improved water management of it is essential since resource optimization benefits the economy, environment and society (UN-HABITAT, 2005, White et al., 2007).

In Europe, generally, the risk of water scarcity is smaller. However, providing public water supply consumes a significant amount of other resources, e.g., building, maintaining, operating and rehabilitating/replacing the supporting infrastructures (USDE, 2006, Arpke and Hutzler, 2006). Consequently, even in countries with a favorable balance between water demand and water availability, there is interest in evaluating alternatives for improving the efficient use of water. Therefore, organizations with responsibilities in the water sector have been motivated to promote a more efficient water use. In developed nations, there has been a stabilization or reduction of the water use in various sectors (e.g., residential; industry; agriculture) due to the combined implementation of structural (e.g., reduction of water losses) and non-structural (e.g., education campaigns) measures (Dworak et al., 2007).

In order to optimize water management, two main categories of solutions can be identified: (i) reduction of water consumption; and (ii) identification of new water sources. The former includes solutions that promote changing consumption habits and the adoption of lower consumption devices, such as low-flush toilets. The latter includes exploring alternative sources for public water supply. For buildings in general, and residential buildings in particular, one of the most common alternative sources is the rainwater – the scope of the present paper. This reviews the most relevant technical and economical issues in designing domestic rainwater harvesting systems, evaluating the technical and economical feasibility of implementing this technology in Portugal. The evaluation is performed for single-family residences from data gathered by Carvalho (2011).

Section snippets

General context of rainwater harvesting

Rainwater harvesting (RWH) comprises the collection, storage, treatment and use of rainwater as either a principal or supplementary source of water. This water source has been used for thousands of years throughout the world for both potable and non-potable applications (Fewkes, 2006). In developing countries such as Bangladesh, Botswana, China, India, Kenya, Mali, Malawi or Thailand (UN-HABITAT, 2005, TRCA, 2010), RWH is being used mostly to cope with water shortages for potable and

Methodology

One way to evaluate the economical viability of the installation of a RWH system is to estimate the time period required to recover the project investment. In order to be competitive, a return on investment is expected within a reasonable period of time, the so-called payback period. The lower the payback period, the more interesting the investment becomes. The limit when an investment is no longer attractive depends on several factors. For buildings, it is common to use a 50 year timescale,

Discussion of results

The methodology described in the previous section was applied to a single-family house consistent of 2 bedrooms, 1 living room, 1 bathroom and 1 kitchen. Next to the house there is a detached single car garage. The roof view is schematically presented in Fig. 9 and three collection areas were considered: A – 78.6 m2; B – 103.4 m2; and C – 131.4 m2.

The RWH efficiency, defined as the ratio between the harvested rainwater and the available rainwater is presented in Fig. 10 for the different

Conclusions and future developments

The results of the economical viability analysis performed should be considered conservative, i.e., the projected payback periods may be shorter than predicted. Directly related to water supply, RWH has the potential for reducing resources consumption in providing water supply that were not considered (e.g., IPCC, 2007, Fowler et al., 2007 refer to the reduction of greenhouse gas emissions from water storage reservoirs and water treatment processes which contribute to climate change). However,

Acknowledgements

The authors acknowledge ICIST-IST Research Institute. The authors would like to thank the anonymous reviewers for their valuable constructive comments and suggestions that improved the manuscript significantly.

References (145)

  • R. Farreny et al.

    Roof selection for rainwater harvesting: quantity and quality assessments in Spain?

    Water Res

    (2011)
  • G. Fengtai et al.

    Study on rainwater utilization engineering mode in northern cities of China

    Procedia Eng

    (2012)
  • A. Fewkes

    The use of rainwater for WC flushing: the field testing of a collection system?

    Build Environ

    (1999)
  • A. Fewkes

    Modelling the performance of rainwater collection systems: towards a generalised approach?

    Urban Water

    (2000)
  • E. Ghisi

    Potential for potable water savings by using rainwater in the residential sector of Brazil?

    Build Environ

    (2006)
  • E. Ghisi et al.

    Rainwater tank capacity and potential for potable water savings by using rainwater in the residential sector of southeastern Brazil?

    Build Environ

    (2007)
  • E. Ghisi et al.

    Short-term versus long-term rainfall time series in the assessment of potable water savings by using rainwater in houses

    J Environ Manag

    (2012)
  • E. Ghisi et al.

    Potential for potable water savings by using rainwater: an analysis over 62 cities in southern Brazil?

    Build Environ

    (2006)
  • E. Ghisi et al.

    Potential for potable water savings by combining the use of rainwater and greywater in houses in southern Brazil?

    Build Environ

    (2007)
  • E. Ghisi et al.

    Rainwater harvesting in petrol stations in Brasília: potential for potable water savings and investment feasibility analysis

    Resour Conserv Recycl

    (2009)
  • E. Ghisi et al.

    Potential for potable water savings by using rainwater and greywater in a multi-storey residential building in southern Brazil?

    Build Environ

    (2007)
  • G.D. Gikas et al.

    Assessment of water quality of first-flush roof runoff and harvested rainwater

    J Hydrol

    (2012)
  • L. Handia et al.

    Potential of rainwater harvesting in urban Zambia

    Phys Chem Earth

    (2003)
  • B. Helmreich et al.

    Opportunities in rainwater harvesting

    Desalination

    (2009)
  • M.A. Imteaz et al.

    Reliability analysis of rainwater tanks using daily water balance model: variations within a large city

    Resour Conserv Recycl

    (2013)
  • C. Matos et al.

    Domestic water uses: characterization of daily cycles in the north region of Portugal

    Sci Total Environ

    (2013)
  • C.B. Mendez et al.

    The effect of roofing material on the quality of harvested rainwater

    Water Res

    (2011)
  • J.S. Mun et al.

    Design and operational parameters of a rooftop rainwater harvesting system: definition, sensitivity and verification

    J Environ Manag

    (2012)
  • S. Muthukumaran et al.

    Quantification of potable water savings by residential water conservation and reuse – a case study

    Resour Conserv Recycl

    (2011)
  • Rainwater – catchment of roofs in urban areas for non-potable purposes – requirements

    (2007)
  • O.O. Aladenola et al.

    Assessing the potential for rainwater harvesting

    Water Resour Manag

    (2010)
  • M.C. Almeida et al.

    Efficient use of water in the urban sector

    (2006)
  • M.P. Amado et al.

    Sustainable construction: water use in residential buildings in Portugal?

    Int J Sustain Construct Eng Technol

    (2013)
  • S. Antunes et al.

    Detecting spatio-temporal precipitation variability in Portugal using multichannel singular spectral analysis?

    Int J Climatol

    (2006)
  • APA Ecoprogresso

    Fifth national communication to the United Nations framework convention on climate change. Second National Communication in the context of the Kyoto Protocol, Portuguese Environment Agency (APA) with the cooperation of Ecoprogresso – Environment and Development Consultants, SA

    (2010)
  • A. Arpke et al.

    Domestic water use in the United States: a life-cycle approach?

    J Ind Ecol

    (2006)
  • ARSCA

    Rainwater catchment design and installation standards

    (2009)
  • G. Barret

    Water conservation: the role of price and regulation in residential water consumption?

    Econ Pap.

    (2004)
  • L.P.M.B. Barroso

    Sustainable construction – comparative solutions for efficient use of water in residential buildings

    (2010)
  • A. Belmeziti et al.

    A new methodology for evaluating potential for potable water savings (PPWS) by using rainwater harvesting at the urban level: the case of the municipality of Colombes (Paris region)?

    Water

    (2013)
  • E. Bertolo

    Rainwater harvesting in buildings

    (2006)
  • O.M. Brandes et al.

    Thinking beyond pipes and pumps: top 10 ways communities can save water and money

    (2006)
  • Rainwater harvesting systems – code of practice. Technical committee CB/506

    (2009)
  • M.J. Burns et al.

    Can allotment-scale rainwater harvesting manage urban flood risk and protect stream health?

  • N.V. Carvalho

    Sustainable solutions for water supply

    (2011)
  • J.C. Chilton et al.

    Case study of a rainwater recovery system in commercial building with a large roof?

    Urban Water

    (1999)
  • P.J. Coombes et al.

    Figtree Place: a case study in water sensitive urban development (WSUD)

    Urban Water

    (1999)
  • P.J. Coombes et al.

    The effect of selection of time steps and average assumptions on the continuous simulation of rainwater harvesting strategies?

    Water Sci Technol

    (2007)
  • J. Corte-Real et al.

    Regional climate change in Portugal: precipitation variability associated with large-scale atmospheric circulation?

    Int J Climatol

    (1998)
  • A.C. Costa et al.

    Trends in extreme precipitation indices derived from a daily rainfall database for the South of Portugal?

    Int J Climatol

    (2009)
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