Domestic Rainwater Harvesting Systems Research Articles

Optimization of Domestic Rainwater Harvesting Systems in Guangxi and Guangdong Provinces, Southern China

The optimization of domestic rainwater harvesting systems (RWHS) in the rural areas of Guangxi and Guangdong provinces, Southern China, offers a viable solution to address water scarcity and enhance water security. This research focuses on designing, implementing, and evaluating RWHS tailored to local climatic, topographical, and social conditions. By capturing and storing rainwater, these systems reduce reliance on groundwater, improve local water management, and provide a sustainable water source for domestic and agricultural use. Key components of an effective RWHS include rooftop catchments, gutters, downpipes, storage tanks, and filtration units. The study also involves community engagement, training, and capacity-building to ensure the long-term sustainability and effectiveness of the systems. Performance monitoring and data collection on water usage patterns and system reliability are essential to optimize the RWHS. The economic and social impacts, as well as the environmental benefits, are assessed to provide comprehensive insights into the benefits and challenges of RWHS implementation. Policy recommendations and support mechanisms are proposed to promote the widespread adoption of RWHS in rural communities, enhancing water security and sustainability.

Public perceptions of rainwater harvesting (RWH): comparing users and non-users of RWH systems

ABSTRACT The UK’s abundant municipal water supply has resulted in slow progress with the uptake of rainwater harvesting (RWH) systems within the home. Research has indicated that exploring public preferences for domestic RWH are necessary for increasing demand. Here, we use explicit and implicit tests to investigate public perceptions of RWH for non-potable uses, and compare perceptions of respondents with and without domestic RWH systems. RWH is perceived positively by most respondents indicating an openness and acceptance of this technology (and/or lack of strong negative attitudes). Implicit attitudes are generally more positive than explicit, especially in respondents with RWH systems, implying that the positivity is deep-seated in their subconsciousness. We also reveal differences between subconscious (implicit) beliefs and practical difficulties (explicit opinions). Outdoor uses of rainwater are preferred, hence, more work in promoting indoor uses is needed to maximise the resource potential of UK rainfall and uptake of RWH systems.

Characterization and multicriteria prioritization of water scarcity in sensitive urban areas for the implementation of a rain harvesting program: A case study for water-scarcity mitigation

An estimated 933 million people worldwide face water scarcity in urban environments with marginalized low-income populations. Rainwater harvesting has been proposed as an adaptable mitigation strategy to reduce water scarcity in those environments. As a case study, the present work proposes the implementation of a rainwater harvesting program aimed at the mitigation of water scarcity in highly vulnerable areas within the Metropolitan Area of Guadalajara, Mexico. The program was developed and structured based on an innovative strategy with replicable multicriteria characterization and prioritization, to allocate the rainwater harvesting systems in areas with a high sensitivity to water scarcity. The areas were selected based on territorial, hydrologic, and social parameters. The prioritization methodology was successfully applied for the selection of clusters for the allocation of domestic rainwater harvesting systems. A total of 4550 rainwater harvesting units were implemented leading to an estimated total yearly capture of 163,444.88 m3. Based on surveys a 14.2% reduction in water scarcity related diseases was observed in the participant households after 3 months of the systems’ implementation. The developed prioritization methodology offers an alternative for science-based resource allocations aimed at the resolution of specific complex challenges. This methodological approach could be adapted and replicated for other spatial-based decision-making and public policy applications. The implemented program offered an alternative for water scarcity mitigation in an urban environment and its application showed potential to improve the quality of life of the population, who benefited by increasing water access and availability.

Potential of traditional domestic rainwater harvesting systems: current trends and future directions

ABSTRACT Although the potential of traditional domestic rainwater harvesting systems (RWHSs) is easily determined, objective knowledge is required to determine their sustainability or scientific validity. We aimed to broadly review recent trends and emerging opportunities for research on the potential of RWHSs in the global context. We reviewed three types of representative RWHSs: water cellars, stepwells, and qanats. In total, 16 potential categories were defined. First, to date, 50% of the categories of potential have been demonstrated but are not considered beneficial, have been proven only in limited locations, only in limited sampling sets, or are theoretical. Second, whether the involvement of other disciplines has resulted in an expansion of the research scope or whether a particular potential has not been comprehensively explained remains to be determined by researchers. Third, potential that has emerged in the 21st century is not beyond our imagination such as tourism potential and ecological potential. Therefore, researchers should actively explore and incorporate new innovative technologies with RWHSs to explore new potential. The findings of this study offer a viable research framework for investigating the evolution of the discipline and contribute to the development of critical thinking in the analysis of the potential of RWHSs.

On the Effectiveness of Domestic Rainwater Harvesting Systems to Support Urban Flood Resilience

The effectiveness of domestic rainwater harvesting (DRWH) systems to support urban flood resilience is analysed at the sub-catchment scale, according to a specific DRWH conversion scenario, under 4 degrees of urbanization, 3 drainage network configurations, 4 precipitation regimes and 3 return periods of the rainfall event. At this aim, a suitable modelling framework is implemented: the semi-distributed hydrologic-hydraulic model is undertaken using EPASWMM 5.1.007 where specific tools are developed to simulate DRWH systems at high spatial resolution. The effectiveness of the DRWH systems simulated for the 144 different cases, is analysed at the event scale by using the Volume and Peak Reduction indexes to measure the hydrologic performance. The dimensionless variable, namely the event storage fraction, is defined in order to easily describe the DRWH effectiveness. The event storage fraction is defined as the ratio between the event runoff volume resulting from the impervious surface of the urban catchment in the reference scenario and the storage capacity of the DRWH systems. Modelling results confirm that DRWH catchment-scale applications allow to support specific stormwater control requirements based on peak-flow or volume regulations strategies. Findings of the elaboration reveal for a typical residential catchment in the Italy-France cross-border coastal area, that DRWH effectiveness in supporting the urban flood management becomes significant (i.e. Volume and Peak Reduction indexes greater than 0.2) starting from a storage event fraction of 0.4 that means realizing storage tanks able to contain at least the 40% of runoff volume generated by the targeted event at the sub-catchment scale.

Rainwater harvesting for domestic applications: The case of Asunción, Paraguay

Cities in tropical and subtropical regions of developing countries often have precarious rain drainage networks and rainfalls may cause floods and torrents that pose risks to people and properties, as is the case of Asunción, in Paraguay. Minute-by-minute rainfall data measured in the city of Asunción are used as input to simulate domestic rainwater harvesting (RWH) systems. It is found that the payback period to install an RWH system in Asunción is large and unattractive for most domestic consumers because of the low cost of water from the public supplier. If water prices were similar to those of some large cities of neighboring countries, individual investments in domestic RWH systems would be more attractive in Asunción. However, as such systems can reduce the impact of heavy rainfalls in urban areas, municipalities with inadequate rainwater drainage should consider providing incentives for their installation.

Traditional domestic rainwater harvesting systems: classification, sustainability challenges, and future perspectives

ABSTRACT Traditional domestic rainwater harvesting systems (RWHSs) are often at risk of being destroyed. The wide variety of traditional domestic RWHSs across the globe makes defining the sustainability challenges difficult. We conducted a literature review and created a classification system for traditional domestic RWHSs, and selected three representative RWHS types: water cellars, stepwells, and qanats. We then determined the sustainability challenges faced by each of the three RWHS types. In total, 20 challenges were identified and subsequently analyzed to establish: 1) the similarities and differences among the challenges faced by each RWHS type, 2) the most pressing challenges that need to be addressed, and 3) the research disciplines required to address each challenge. Most of the challenges require interdisciplinary cooperation and sociological investigation. Finally, two priorities for future research were identified. First, sustainability in terms of traditional domestic RWHSs must be defined and conceptual frameworks must be developed to help to integrate research from multiple disciplines. Second, preservation of the architecture or structural body of traditional domestic RWHSs should be prioritized.

Optimal Tank Sizing, Reliability, and Financial Feasibility Analysis of Domestic Rainwater Harvesting Systems for Semi-Arid Climate: A Daily Linear Programming Model

Optimal Tank Sizing, Reliability, and Financial Feasibility Analysis of Domestic Rainwater Harvesting Systems for Semi-Arid Climate: A Daily Linear Programming Model

Stochastic Rainwater Harvesting System Modeling Under Random Rainfall Features and Variable Water Demands

AbstractA stochastic rainwater harvesting system modeling (StRaHaS) method is developed to enhance both accurateness and applicability of hydrologic modeling in guiding extensive applications of individual rainwater harvesting (RWH) systems (especially over large data‐scarce regions). The reliability of a RWH system is characterized as the fraction of time water demands being satisfied by a rainwater storage unit (RWSU). The variations of water balances, the post‐rainfall RWSU full‐storage probability, and the system reliability with random rainfall features, variable water demands, and the other RWH system characteristics are derived as analytical, accurate, and easily applied models through stochastic integration. StRaHaS is applied to three domestic RWH systems in Toronto, Canada. Due to high accurateness and low complexity in modeling, designing, assessing, and analyzing the RWH systems, StRaHaS outperforms existing methods (e.g., inaccurate water‐balance estimation, complicated continuous simulation, and simplified stochastic simulation). Based on StRaHaS, we quantitatively expound the increases in the reliability of the systems with higher rainwater supplies (corresponding to higher rainfall depths, and lower rainfall losses and first‐flush depths), lower water demands (in shorter wet and dry periods), and higher RWSU capacities. Long dry periods are lengthened by climate change and play dominant roles in low, spatially heterogeneous reliability of the systems. Synchronic changes and extremely high values of rainfall features do not significantly affect the reliability. Overall, StRaHaS is a promising method in modeling RWH systems, revealing RWH mechanisms, scientizing RWH applications, and facilitating the Sustainable Development Goals for addressing global water issues.

The Web-GIS TRIG Eau Platform to Assess Urban Flood Mitigation by Domestic Rainwater Harvesting Systems in Two Residential Settlements in Italy

Urban flooding has become one of the most frequent natural disasters in recent years, and the low-impact development (LID) approach is currently recognised as an alternative to traditional grey infrastructure to mitigate the negative impact of urbanisation on hydrological processes. The main objective of the present research was to develop a web-GIS platform in order to assess the impact of LID systems on mitigating urban flooding and to support their implementation at the urban catchment scale. The TRIG Eau platform, developed in the framework of the homonymous INTERREG MARITTIMO IT-FR project, is configured as a web-GIS application of the stormwater management model (SWMM). Urban flood conditions were examined for two case studies in Liguria and Tuscany (IT), where DRWH systems are proposed as a mitigation strategy. The presented results and their visualisation showcase the potential of the TRIG Eau platform to better support the implementation of LIDs. Findings from the flood analysis confirm that even for the 10-year return period event, DRWHs are effective in reducing network stress by more than 70% in cases of empty tanks, thus underlining the need for RTC technology to pre-empty the system.

Contribution of Rainfall on Rooftop Rainwater Harvesting and Saving on the Slopes of Mt. Elgon, East Africa.

Despite the achievements reported from using rainwater harvesting systems, the contribution and drawbacks that affect their usage in mountainous landscapes have received little attention. The uptake and usage of domestic rooftop rainwater harvesting systems (RRWHS) in developing countries is on the increase due to increasing water scarcities. We explored the effect of rainfall variability on water supply and the downsides of using the systems by rural households in Uganda. The objectives were to assess the variability of rainfall (1985–2018), categorise RRWHS used, and examine the influence of slope ranges on the placement of systems and also to quantify the harvested and saved rainwater and establish the factors that affected system usage. Rainfall variability was assessed using a Mann–Kendall test, while system contributions and drawbacks were examined using socioeconomic data. A representative of 444 households were selected using a multicluster sampling procedure and interviewed using semistructured questionnaires. Findings revealed that the months of March, April, September, August, and October experienced an upward trend of rainfall with a monthly coefficient of variation between 41 and 126%. With this, households responded by employing fixed (reinforced concrete tanks, corrugated iron tanks, and plastic tanks) and mobile RRWHS (saucepans, metallic drums/plastic drums, jerrycans, and clay pots). At the high altitude, households deployed mostly plastic jerrycans and industrial plastic/metallic drums to harvest and save water. Overall, the mean annual volume of rainwater harvested on the slopes of Mt. Elgon was 163,063 m3/yr, while the potential to save water ranged from 4% to 7% of the annual household water demand. The factors that hindered the deployment of RRWHS to harvest and save water were high operational costs, price fluctuations, unreliable rainfall pattern, inadequate funds, and limited accessibility. The rainfall received if well-harvested and saved can redeem households of water insecurity, though there is an urgent need of subsidies from the government to increase accessibility of the systems.

A Critical Evaluation of the Water Supply and Stormwater Management Performance of Retrofittable Domestic Rainwater Harvesting Systems

Rainwater harvesting systems are often used as both an alternative water source and a stormwater management tool. Many studies have focused on the water-saving potential of these systems, but research into aspects that impact stormwater retention—such as demand patterns and climate change—is lacking. This paper investigates the short-term impact of demand on both water supply and stormwater management and examines future and potential performance over a longer time scale using climate change projections. To achieve this, data was collected from domestic rainwater harvesting systems in Broadhempston, UK, and used to create a yield-after-spillage model. The validation process showed that using constant demand as opposed to monitored data had little impact on accuracy. With regards to stormwater management, it was found that monitored households did not use all the non-potable available water, and that increasing their demand for this was the most effective way of increasing retention capacity based on the modelling study completed. Installing passive or active runoff control did not markedly improve performance. Passive systems reduced the outflow to greenfield runoff for the longest time, whereas active systems increased the outflow to a level substantially above roof runoff in the 30 largest events.

Optimal sizing of rainwater harvesting systems for domestic water usages: A systematic literature review

Abstract Rainwater harvesting systems (RWHS) are increasing in popularity because of their ability to alleviate water pressure on centralized systems, minimize or delay rainfall runoff, and fit relatively easily in both the centralized/decentralized infrastructure organization. Adequately sizing RWHS is critical to optimizing their operation because under-sizing results in systems that are unable to provide a sufficient, reliable source of water while oversizing increases the capital costs incurred with limited marginal benefits and poses potential water quality risks. In this paper, we conduct a systematic literature review to assess the state-of-art in the field of optimization of domestic rainwater harvesting systems. Sizing of storage is identified as the most important objective of optimization, yet sizing for cost is the most frequently implemented outcome of optimization. Optimizing for a local maximum is often favored over simulation-based optimization methods that produce global maxima. To derive more realistic sizing estimates, future optimization studies will have to take into account greater variation in water demands as well as various climate change scenarios, especially given that rainfall frequency and quantity are critical design variables of a rainwater harvesting system.

Water efficiency and economic assessment of domestic rainwater harvesting systems in buildings with one- to three-floor elevations

Abstract The focus of the paper is the evaluation of the performance of domestic rainwater harvesting (DRWH) systems in multi-family buildings with one- to three-floor elevations by means of a cost–benefit analysis. The rainwater is here used for both indoor and outdoor non-potable water consumption. The study was carried out with reference to different residential building typologies (flat and condominium) in a specific local climate condition (Ancona). The buildings are characterized by different rooftop areas (100–400 m2), building floor elevations (one to three floors) and inhabitant numbers (3–54 persons). Moreover, in order to highlight the role of the tank capacity on the performance of DRWH, its capacity was changed in the range 50–200%. The combinations of all these parameters led to 276 test cases. The technical performance is evaluated by means of the water saving and retention efficiencies. The economical assessment is provided by comparing the costs and the savings due to the replacement of the water supplied with the rainwater. It is found that the payback periods changed in the range 10–35 years for the site-specific variables such as local rainfall and water service tariff. Cost–benefit analysis can help the design of DRWH systems, with particular attention to the sizing of the tank.

Sustainable Water Resources Management in Small Greek Islands under Changing Climate

Five different water resource management scenarios are examined on eight dry islands of the Aegean Sea in Greece, pitting the current practice of water hauling via ship against alternative water supply schemes in delivering a sustainable solution for meeting water demand. The first scenario employs current water supply practices along with the operation of domestic rainwater harvesting systems. Desalinated water, provided through the operation of wind-powered desalination plants, is considered the main source of potable water in the rest of scenarios. Wind-powered desalination may be combined with rainwater harvesting as a supplementary source of water and/or seawater pumping and an additional source of energy that is supplied to the system. All different alternatives are evaluated for a 30-year lifespan, and an optimal solution is proposed for each island, based on a life cycle cost (LCC) analysis. The performance of this solution is then assessed under six climate change (CC) scenarios in terms of the rate of on-grid versus off-grid renewable energy that is required in order to achieve a certain reliability level. Overall, the examined scenarios show a decreasing performance in terms of reliability under CC for the eight islands.

Optimum tank size for a rainwater harvesting system: Case study for Northern Cyprus

The available freshwater is limited on earth. On the other hand, available water resources on earth have been depleting and being polluted due to climate change and population growth. In order to reduce the risk of water scarcity and water resources contamination, Integrated water resources management (IWRM) is required. IWRM is a concept to manage water resources that aims to balance economic efficiency, social equity, and environmental sustainability. When rainwater harvesting systems (RWHS), one of the techniques of IWRM, are implemented, the stress on water resources is reduced. Since the installation cost of rainwater harvesting systems significantly depends on the size of the rainwater storage tanks, in the implementation of rainwater harvesting, the selection of tank size is one of the main concerns for the feasibility of the system. This study aims to investigate the feasibility of domestic rainwater harvesting systems for a single house. In order to find the optimum storage tank size of the rainwater harvesting system, a linear programming (LP) optimization model is employed. As a case study, the LP model is applied to six regions from semi-arid Eastern Mediterranean island Northern Cyprus, where water resources are limited. The model considers thirty-seven years monthly rainfall data, the roof area of the building, the water consumption per capita, the discount rate, the cost of the rainwater storage tank, and the number of residents. The results of the selected study areas show that the implementation of the RWHS for a single house is infeasible due to the substantial installation costs and maintenance expenses. The financial losses caused by the implementation of the RWHS are found higher than the installation costs and maintenance expenses for all regions. In addition to economic analyses, environmental benefits of the RWHS should be included into the feasibility analysis.

Sizing of Domestic Rainwater Harvesting Systems Using Economic Performance Indicators to Support Water Supply Systems

This paper presents a monitoring-based investigation of rainwater collection systems using economic performance indicators in a group of households with nonconventional end-uses for rainwater that are not traditionally associated with rainwater supply. The monitored data for five household rainwater tank systems were analysed in two stages. For the first stage, the data was empirically analysed to develop a method to predict effective roof catchment areas. For the second stage, the effective roof catchment areas, together with roof area connection percentages, were analysed against different types of water demands in individual households. The individual systems were investigated for yield capacities, costs and water security using a modified Roof Runoff Harvesting Systems average annual yield model based on daily water balance procedures. The Life Cycle Costing analysis of the systems using the model was based on the Capital Recovery Method by taking into consideration the capital costs as well as ongoing costs for maintenance, replacement and operation of the systems. The analysis established the optimal sizing requirements for the studied rainwater tanks and their corresponding roof area connectivity.

Economic analysis and risk-based assessment of the financial losses of domestic rainwater harvesting systems

The considerable potential for rainwater harvesting (RWH) opens the door for the study of economic viability and risk indicators in this kind of system. The aim of this paper was to present economic and risk analyses of three RWH systems intended for water supply to single-family residences. The systems were analyzed based on water demand, degree of treatment and distribution arrangement. Economic, sensitivity and risk analyses were performed. The system with the basic treatment of rainwater and distribution by pressure (BX Pressure) was the most economically viable. The Net Present Value and the Intern Return Rate of the BX Pressure system was 480.36 USD and 6.85%, respectively. In the sensitivity analysis, both basic treatment systems were viable at any considered discount rate (0.00%–10.00%) and at a water price ranging from 1.58 USD to 2.72 USD for BX Pressure. In the risk analysis, BX Pressure was also the most viable system, presenting a risk probability of viability of 95.9% at current water prices. Water price, demand, lower discount rates and initial investment costs determined the greater economic viability and lower economic risk associated with domestic RWH systems.

Microbial source tracking markers associated with domestic rainwater harvesting systems: Correlation to indicator organisms

Domestic rainwater harvesting (tank water) systems were screened for the presence of a panel of microbial source tracking (MST) markers and traditional indicator organisms. The indicator organisms were enumerated utilizing traditional culture-based methods, while the MST markers were quantified by quantitative PCR (qPCR). The indicators Escherichia coli (E. coli) and enterococci were also quantified using qPCR. Correlations and concurrence between these parameters were then investigated to determine which markers could be utilized to supplement traditional indicator analysis. Quantitative PCR analysis indicated that Bacteroides HF183, adenovirus, Lachnospiraceae and E. coli were detected and quantifiable in 100% of the tank water samples collected throughout the sampling period, while human mitochondrial DNA (mtDNA) was quantifiable in 90% of the tank water samples and Bifidobacterium adolescentis (B. adolescentis) and enterococci were quantifiable in 67% of the tank water samples, respectively. Significant positive correlations were recorded for Lachnospiraceae versus heterotrophic bacteria (p = 0.000), adenovirus versus E. coli (culturing) (p = 0.000) and heterotrophic bacteria (p = 0.024), the HF183 marker versus E. coli (qPCR) (p = 0.024) and B. adolescentis versus fecal coliforms (p = 0.037). In addition, 100% concurrence was observed for the HF183 marker, adenovirus and Lachnospiraceae versus E. coli (qPCR), enterococci (qPCR) and heterotrophic bacteria, amongst others. Based on the correlations and the concurrence analysis, the HF183 marker, Lachnospiraceae and adenovirus may be utilized to supplement indicator organism analysis for the monitoring of harvested rainwater quality.

County‐Scale Rainwater Harvesting Feasibility in the United States: Climate, Collection Area, Density, and Reuse Considerations

AbstractRoof rainwater harvesting (RWH) has the potential to augment water supplies for urban and suburban uses throughout the United States (U.S.). Studies of the performance of RWH at the building and city scales in the U.S. are available, but a countrywide overview of the potential performance of RWH at the county scale has not been done before. Three approaches were taken: (1) assess the viability of RWH in terms of the rainfall that could be captured in relation to the water demand in each county (excluding agriculture), (2) evaluate the performance of a “typical” domestic RWH system across all counties with metrics related to its ability to supply the potable and nonpotable demand, and (3) evaluate the effect of adding a 50% rainwater reuse component to the analysis. We find RWH could be a viable supplemental water source in the U.S., particularly in counties of the Pacific Northwest, Central, and Eastern regions (percent demand covered >50%). Low population density counties have the potential to meet their annual water needs with RWH, while high‐density counties could only source a small portion (~20%) of their annual demand with RWH. Typical RWH systems in counties in the Central and Eastern U.S. performed better than in Western counties. Adding a reuse component can be a key factor in making RWH attractive in many areas of the country. This work can inform future water infrastructure investment and planning in the U.S.