The Nexus of Rainwater Harvesting: Bridging Engineering Solutions with Socioeconomic Strategies for Safe Adoption

Abstract

Rainwater harvesting (RWH) is increasingly being recognized as a sustainable alternative water source, yet questions about its safety and wider acceptance remain unresolved. A qualitative narrative synthesis was employed, drawing on evidence from peer-reviewed literature, identified from major databases and chosen for their methodological rigor, relevance, and geographical spread, focusing on the interplay between engineering, environmental, and socio-economic factors influencing RWH system performance. Data extraction included roofing material type, contaminant profiles, seasonal influences, storage design, first-flush performance, and adoption drivers.

Evidence reveals the decisive role of system configuration, and roofing materials as ceramic and stone-coated tiles, along with well-maintained galvanized steel, tend to produce water with comparatively lower microbial and heavy metal contamination, while asphalt, green roofs, and some metallic surfaces often pose potential human health risks. Local environmental conditions such as seasonal variation, atmospheric deposition, and neighborhood pollution add further complexity to quality outcomes. Although first-flush systems reduce initial loads of contaminants, treatment remains necessary for potable use, and the type of storage tank continues to influence both microbial persistence and chemical leaching.

Socio-economic factors strongly influence adoption and maintenance, underscoring that technical optimization alone is insufficient. These interactions are conceptualized within the proposed Integrated Socio-Technical-Environmental (ISTE) Framework. Together, these findings point to the importance of material-specific guidelines, robust first-flush systems, affordable treatment technologies, and supportive policy frameworks to ensure harvested rainwater safety. Further research should integrate real-time monitoring, address emerging pollutants, and link engineering solutions with socio-economic strategies for broader adoption.

Keywords

Rainwater harvesting - Water quality - Storage systems - Roofing materials - Socio-economic factors - Environmental influences - Heavy metals - ISTE

Significance

Water scarcity is a growing global challenge, yet its safety and widespread adoption remain constrained. This review integrates engineering, environmental, and socio-economic insights through the Integrated Socio-Technical-Environmental (ISTE) Framework, showing that roofing materials, first-flush systems, and users' capacity jointly govern harvested water quality and system uptake. This work bridges technical and social dimensions to guide safer, more sustainable RWH Practices.

1

Introduction

Water scarcity is a growing global challenge, driven by population growth, urbanization, and climate change, which together place unprecedented stress on freshwater resources.[1] [2] [3] Even water-rich regions are increasingly experiencing prolonged dry periods, lowering reservoir levels, and compelling communities to explore alternative supply options.[1] [4] The United Nations recognizes access to safe and clean water as a fundamental human right,[5] yet over 750 million people still lack improved water sources and more than 2.6 billion remain without basic sanitation.[6] Urbanization expected to encompass nearly 70% of the world's population by 2050, while beneficial for economic and social development, also disrupts natural hydrological cycles, intensifying the need for sustainable water management.[2] [3] [7]

Rainwater harvesting (RWH) has emerged as a practical, decentralized solution to these challenges, aligning with the targets of Sustainable Development Goal 6 on clean water and sanitation.[3] [7] [8] It is increasingly implemented across diverse climatic and socio-economic contexts as a low-cost method to supplement domestic, agricultural, and industrial water needs.[9] [10] [11] In many rural and peri-urban regions, especially in the Global South, lacking centralized water supply, rooftop RWH systems using gutters, downpipes, and storage tanks offer a viable means to secure water for household consumption and other uses.[11] Furthermore, even in urban areas with centralized water supply systems, RWH systems can act as a supplementary as well as an alternative approach. Anecdotal evidence from countries such as Australia suggests that many households prefer rainwater over treated municipal supplies, highlighting its cultural and perceived quality value.[12] However, the safety of harvested rainwater is not guaranteed. Many researchers have also identified that during collection, conveyance, and storage, rainwater can become contaminated through atmospheric deposition, leaching from roofing and storage materials, and deposition of organic matter or fecal material from birds and small animals.[8] [13] [14] Roofing material type plays a particularly critical role, influencing physicochemical parameters, heavy metal leaching, and microbial quality.[15] [16] [17] Acidic precipitation can accelerate the release of toxic metals such as lead, cadmium, and zinc from roof surfaces into stored water.[18] [19]

Environmental conditions, including seasonal variation and surrounding pollution sources, further affect water quality outcomes.[20] [21] Likewise, storage tank material, presence of first-flush diversion systems, and postharvest treatment significantly influence safety.[22] [23] While many studies emphasize the engineering and environmental aspects, socio-economic and policy dimensions are equally important. Education level, household income, community networks, and government incentives all shape RWH adoption and safe use.[24] [25] In some cases, high upfront cost and limited technical knowledge impede implementation despite high willingness.[26] [27] Extension services and material subsidies have proven effective in promotion adoption and proper system management.[25] [28]

The primary aim of this mini review is to critically examine the quality and safety of roof-harvested rainwater by integrating findings from recent global studies. Specific attention is given to the influence of roofing and storage materials, environmental conditions, and socio-economic factors on contamination risks.

In addition to the conventional literature summary for providing a clear theoretical contribution, the proposed Integrated Socio-Technical-Environmental (ISTE) Framework for Rainwater Harvesting (RWH) is shown in [Fig. 1]. This novel conceptual model explicitly defines the interdependent pathways between technical/engineering solutions, socio-economic/policy strategies, and environmental dynamics in achieving safe and sustainable RWH adoption. The core insight of this review lies in recognizing mutual and often catalytic interaction between each factor. For instance, it highlights how users' income (socio-economic) dictates the quality of roofing material (technical), directly Impacting water quality, and how community initiatives enhance the management of maintenance against environmental risks. By framing the analysis around this integrated model, this mini review offers a practical tool for researchers and policy makers to diagnose barriers and design holistic RWH interventions.

Fig. 1 Proposed integrated socio-technical-environmental nexus

2

Methodology

This review follows a systematic and transparent approach by adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 framework.[29] A narrative synthesis framework was employed to consolidate evidence regarding water quality and safety of roof-harvested rainwater, along with socioeconomic dimensions impacting its implementation. The review systematically searched major academic databases, specifically Scopus, Web of Science (WoS), and PubMed for peer-reviewed publications published between January 1, 2010, and July 31, 2025. These databases were chosen for their complementary coverage of both the technical (environmental engineering, sustainability) and socio-economic/behavioral (public health, policy) dimensions of RWH and for the search period—the initial year marks a global rise in RWH studies, and the pre-SDG period (2010–2014) was deliberately included to establish a crucial baseline report against which subsequent progress under the SDGs could be evaluated.

A detailed search strategy was applied using Boolean operators and grouped keywords organized into four conceptual domains: RWH systems, water quality and safety, engineering and system design, and socio-economic policy factors. The representative Scopus search string is given in [Table 1].

Table 1 Scopus database search algorithm

TITLE-ABS-KEY("rainwater harvesting" OR "roof water harvesting" OR "roof runoff" OR "rooftop water collection") AND TITLE-ABS-KEY("water quality" OR contamination OR "heavy metals" OR microbiological OR "microbial indicators" OR pathogens OR "drinking water safety") AND TITLE-ABS-KEY(roof* OR "roof material*" OR "storage tank*" OR cistern OR "first flush" OR "treatment system") AND TITLE-ABS-KEY(adoption OR socioeconomic OR awareness OR affordability OR policy OR governance OR implementation)

Equivalent, database-specific search strings were adapted for WoS and PubMed using the same Boolean logic and concept structure. Filters were applied to restrict results to English language journal articles and reviews published during the study period from 2010 to July 31, 2025. An additional search was made on the bibliographies of included studies.

Data were extracted systematically for study location, roofing materials, evaluated parameters (e.g., pH, turbidity, heavy metals, microbial contamination), treatment techniques, and socio-economic drivers of adoption. The quality of included studies was appraised using an adapted Critical Appraisal Skills Program (CASP) basic 10-question checklist and rating[30] to ensure consistency, where ratings (“Yes”, “Can't Tell”, and “No”) were assigned numerical values (1,0.5,0) to generate scores. While all studies were retained, low-quality studies were given less weight in the discussion to ensure reliability. The study-selection process is illustrated in the PRISMA 2020 flow diagram ([Fig. 2]).

Fig. 2 Flowchart illustrating the article-selection process.

The synthesized evidence was organized into three interlinked domains: engineering/technical, environmental, and socio-economic/policy. This integrative synthesis provides a holistic understanding of how technical design, environmental dynamics, and socio-institutional conditions collectively shape the safety and sustainable adoption of RWH systems. The review also compiled qualitative data into comparative tables and figures to highlight patterns.

3

Results and Discussion

The systematic search initially identified 131 articles (66 from Scopus, 56 from WoS, and 9 from PubMed). An additional 35 articles were included after hand-searching the bibliographies of these initial papers. Following the removal of duplicates, a total of 120 unique articles proceeded to title and abstract screening. Studies were included if they focused on domestic or roof top RWH systems and assessed water quality, contamination, treatment, adoption behavior, or socio-economic and policy determinants. Consequently, 52 articles were excluded at this stage, because they were identified as review articles, conference reviews, book chapters, errata, or were focused on non-RWH specific topics like flood control, groundwater recharge, aquifer-related studies, or constructed wetlands and so on. The remaining articles underwent full-text assessment, with exclusion made for non-English, non-peer reviewed, or large-scale storm water management studies. Ultimately, 49 articles met all predefined inclusion criteria and were retained for the comprehensive narrative synthesis of this review. After quality assessment of retrieved articles using CASP, they are categorized into high quality (≥7), medium quality (4.0-6.5), and low quality (<4).

3.1

Engineering and Technical Factors

Similar findings were reported by several studies. For example, runoff quality strongly depends on roofing material and design configuration: clay tile and metal roofs at moderate pitches (15°–45°) provided the best quality water, while reinforced concrete roofs showed the highest contamination levels in Kuala Lumpur.[31] Likewise, first-flush diversion studies in Iran demonstrated that discarding the first 1–1.5 mm of rainfall substantially reduces turbidity and improves suitability for nonpotable uses, although further treatment is required for its drinking purposes.[32] Comparative analyses from Nigeria revealed that aluminum roofing produced the best overall quality among common materials, with a water quality index (WQI) of 7.83, while asbestos and zinc sheets exceeded permissible Fe and Pb concentrations.[33] Further factor-specific findings are given in the following subsections. Based on all such evidence roof type, surface coating, and early runoff management remain decisive engineering parameters for safe RWH design.

3.1.1

Impact of Roofing Materials on Rainwater Quality

The chemical interaction between precipitation and the roofing surface is a principal source of contaminants, impacting both general physicochemical characteristics and the heavy metal profile of the runoff.

3.1.1.1

Physicochemical Quality

The choice of roofing material is a critical factor for RWH, as it impacts the physicochemical parameters of water, such as its pH and turbidity. The average water quality, from lowest to highest, is ranked as: metal insulation< mixed concrete insulation< mixed asphalt = concrete insulation< water = seal coat insulation< roll asphalt < thermal insulation.[34] For instance, a study found that the highest turbidity (max. 14 NTU) came from surfaces coated with epoxy resin, while the lowest turbidity (medians of 2.0 and 1.5 NTU) was found on zinc-coated metal sheets.[16] In general, roofing materials tend to raise rainwater pH ([Table 2]), likely due to surface weathering that increases dissolved solids and replaces H⁺ ions with metal ions.[17] A study by Lee et al. found the highest pH (avg. 7.2) from concrete tile roofs, which is consistent with other findings.[14] [20] [35]

Table 2 Comparative table of roof runoff and control sample water quality parameters

Roofing material	Color (TCU)	Turbidity (NTU)	TS (mg/L)	TDS (mg/L)	EC (μS/cm)	pH	Reference
GLV	5.0 ± 0 –	0.95 ± 0.1750 2.13 ± 0.60	78.05 ± 0.7500 –	18 ± 0.4000 3.15 ± 1.58	– 2.82 ± 1.03	6.13 ± 0.000 5.3 ± 0.08	[15] [17]
ALM	5.0 ± 0 –	0.15 ± 0.1550 1.45 ± 0.27	52.55 ± 0.8500 –	14.5 ± 0.6000 4.4 ± 1.77	– 4.42 ± 1.84	6.25 ± 0.000 5.26 ± 0.13	[15] [17]
ASB	5.0 ± 0 –	0.85 ± 0.1500 3.28 ± 0.98	40.69 ± 0.7750 –	22.4 ± 0.8000 9.10 ± 5.94	– 9.15 ± 5.88	6.15 ± 0.0250 5.43 ± 0.22	[15] [17]
ALZ	– –	– 1.44 ± 0.72	–	– 3.25 ± 0.73	– 3.39 ± 0.83	– 5.20 ± 0.11	[17]
COS	–	1.56 ± 0.79	–	3.45 ± 0.82	2.78 ± 1.20	4.92 ± 0.29	[17]
WHO	15	5	–	500	700	6.5–8.5

(Heavy metals and remaining are in mg/L) (Note: GLV = Galvalume, ALM = Aluminum, ASB = Asbestos, ALZ = Alu-zinc and COS = Control Sample). Sample size for the first article (Ref. [15]) was not specifically mentioned and that for the second article (Ref. [17]) was 96.

Roofing material	Fe (mg/L)	Al (mg/L)	Cu (mg/L)	Zn (mg/L)	Pb (mg/L)	Cr (mg/L)	Cd (mg/L)	Reference
GLV	0.38 ± 0.040 1.35 ± 0.0003	0.025 ± 0.025 –	0.74 ± 0.0500 –	0.063 ± 0.004 0.45 ± 0.00037	0.605 ± 0.025 0.05 ± 0	– 0.0025 ± 0000	– 1.48 ± 0.00035	[15] [17]
ALM	0.001 ± 0.040 1.54 ± 0.00011	0.015 ± 0.010 –	0.086 ± 0.050 –	0.146 ± 0.005 0.25 ± 0.00004	0.005 ± 0.025 0.5 ± 0	– 0.019 ± 0.00002	– 2.38 ± 0.00006	[15] [17]
ASB	0.52 ± 0.050 1.55 ± 0.00123	0.045 ± 0.0150 –	0.063 ± 0.0015 –	0.125 ± 0.010 0.11 ± 0.00002	0.715 ± 0.025 0.6 ± 0.0000	– 0.1 ± 0.00002	– 1.49 ± 0.00035	[15] [17]
ALZ	– 1.56 ± 0.00034	– –	– –	– 0.57 ± 0.00033	– 0.5 ± 0	– 0.017 ± 0.00002	– 1.74 ± 0.00034	[17]
COS	1.01 ± 0.00118	–	–	0.011 ± 0.0000	0.48 ± 0.0000	0.0004 ± 0.00000	0.33 ± 0.00019	[17]
WHO	0.3	0.2	2	3	0.01	0.05	0.003

(Heavy metals and remaining are in mg/L) (Note: GLV = Galvalume, ALM = Aluminum, ASB = Asbestos, ALZ = Alu-zinc and COS = Control Sample). Sample size for the first article (Ref. [15]) was not specifically mentioned and that for the second article (Ref. [17]) was 96.

3.1.1.2

Heavy Metal Contamination

The quality of harvested rainwater can be compromised by heavy metals that are leached from specific roofing materials. Research in Lulea, Sweden, reported that copper and zinc roofs released the highest levels of metal (3.09 mg/L of copper and 7.77 mg/L of zinc),[36] while metal and thatched roofs were linked to elevated levels of Fe, Zn, Pb, Cr, and Al.[22] In Ejisu, Ghana, rainwater runoff from all four roofing materials exceeded WHO drinking water safety limits for cadmium, iron, and chromium. It has been reported that the health risk was highest for aluminum roofs, followed by Aluzinc, asbestos, and galvanized roofs.[17] However, some studies show contradictory results; for example, Zn and Fe were recorded consistently in rainwater harvested from asbestos than that from aluminum roofs.[15] On the other hand, galvanized steel was deemed more suitable than isogum for meeting Iran's drinking water standards.[37] Moreover, it was reported that rainwater from galvanized steel roofs had the lowest pH and best microbiological quality.[16] [Table 1] provides the comparisons as to how physicochemical parameters including heavy metals altered with roofing materials and different roof runoffs with direct rain as the control sample.

3.1.1.3

Microbiological Quality

The microbiological quality of harvested rainwater is another key concern. An Indian study reported that roof-harvested rainwater was generally unfit for drinking due to poor microbiological quality and improper pH.[38] In contrast, a study in Southern Nigeria found no E. coli detected in any rainwater samples.[8] Similarly, it was reported that coliforms were absent in aluminum roof samples but present in asbestos, concrete, and corrugated plastic roofs.[39] In New Zealand, E. coli was detected in 17.7% of rain-fed tanks, although this was possibly reduced by the biocidal effects of zinc from unpainted galvanized roofs.[40] E. coli counts were found to be highest in rainwater from concrete tile roofs and lowest in galvanized steel roofs, which had less than 5 cfu/100 mL.[16] The microbial quality of roof runoff was shown to vary by roofing material in the study by Tengan and Akoto (2022), where a total of 96 rainwater samples were collected, comprising 16 samples directly from the sky and 20 samples per roofing (as visually represented in [Fig. 3]).

Fig. 3 Comparison of microbial count contributed from different roofing materials.[17] Total coliforms were highest in aluminum (4222 ± 1512.28 CFU/100 mL) and aluzinc (4120 ± 544.98 CFU/100 mL), with comparatively lower levels in COS (364 ± 81.12 CFU/100 mL). Fecal coliforms followed a similar pattern, while E. coli was detected only in galvanized (24 ± 3.00 CFU/100 mL) and aluzinc roofs (19 ± 5.65 CFU/100 mL).

3.1.2

First-flush and Storage Tank Effects

Water quality varied with sampling time, with first-flush from aluminum and zinc roofs showing higher concentrations than post-flush, reflecting improved quality after initial wash-off.[41] Diverting the first flush based on turbidity, TSS, or conductivity improves water quality and lowers polycyclic aromatic hydrocarbon (PAHs) levels in harvested rainwater.[42] The quality of harvested rainwater is significantly influenced by the first-flush and the materials used for storage tanks. The initial runoff from a roof often contains a high concentration of pollutants, which necessitates the use of a first-flush diversion system to improve water quality. The first flush of rainwater consistently contains pollutant concentrations two to five times higher than those in the storage tank, including heavy metals and microbial contaminants washed off the roof, exemplified by zinc levels reaching 428 μg/L in the initial runoff from a galvanized steel roof compared to 74 μg/L in the tank.[35] Similarly, metal concentrations were significantly higher in the first-flush samples than in subsequent collections across all roofing materials.[41] Microbiological quality is a major concern during the first flush, with total coliform counts highest in samples from concrete tile (197 CFU/100 mL) and wooden shingle roofs (131 CFU/100 mL), where E. coli contamination was also notably high on concrete roofs, with average counts of 19 CFU/100 mL.[35] However, diverting this initial runoff leads to a significant reduction in microbial contaminants. Post-flush samples from galvanized steel roofs, for example, met the WHO guideline of less than 10 CFU/100 mL in 95% of samples for total coliforms, with 82.5% of samples having no detectable coliforms.[35] Remarkably, all post-flush samples from galvanized steel roofs were E. coli free, indicating that initial runoff effectively removed microbial contaminants. These results align with the Australian Drinking Water Guidelines, which recommend 0 E. coli/100 mL in safe drinking water.[35] In shingle, tile, and cool roofs, total coliform levels were reported higher in the first flush compared to after first flush samples. However, no significant change was observed for metal and green roofs.[14] Total coliform and fecal coliform concentrations in the first flush from the metal roof were significantly lower than those from the cool, shingle, and tile roofs.[14] While the quality of rainwater collected in the main rainwater tank was better than in the initial runoff in the first-flush tank, a study concluded that the water was still not safe for direct use without some form of treatment.[20] This highlights that while first flush diverters improve water quality, the harvested water still requires further processing to be considered potable.

The material of the storage tank also plays a crucial role in maintaining water quality. Stored rainwater generally shows a higher pH, particularly in concrete or cement-lined tanks, due to the leaching of alkaline substances from tank materials.[22] The presence or absence of storage systems directly influences microbial growth and metal solubility. For example, the Nigerian and Malaysian studies emphasized that storage tanks without treatment facilitated microbial persistence.[23] Meanwhile, treatment technologies like UV filters[43] and activated carbon[23] showed promise in improving water safety after harvest. Regarding specific materials, one study found that rainwater stored in PVC tanks generally had better quality than water in galvanized iron tanks, although both showed some contamination.[22] A study in Vietnam reported that rainwater collected in stainless steel tanks was contaminated with bacteria, while most heavy metal levels remained below standard limits.[43] In contrast, a study from Palestine found that samples from rain-fed cisterns met WHO standards for trace metals except for K and Al.[44] The Nigerian and Malaysian studies emphasized that storage tanks without treatment facilitated microbial persistence.[10] [23] This highlights the need for effective treatment technologies, such as like UV filters[43] and activated carbon,[23] to ensure the safety of stored rainwater.

3.2

Environmental, Seasonal, and Geographic Influence

Rainwater quality can differ depending on the season and geographical location as well as environmental setting. A study confirmed that good quality of water harvested from ceramic roofs occurred during the summer season.[20] Pollutant levels were lower in summer and autumn than in winter and spring, making rainy seasons better for rainwater harvesting.[45] Consistent with previous studies, no clear link was found between air pollution and rainwater quality in air-polluted regions of Bulgaria.[21] However, it has been reported that atmospheric deposition is the primary source of pollutants in roof runoff.[42] Harvested rainwater in areas with industrial and agricultural activities is often contaminated with heavy and trace metals.[44] Nevertheless, industrial and traffic emissions are unlikely to significantly affect rainwater quality in domestic tanks in Australia, with a similar situation expected in New Zealand.[40] Elevated total coliform levels in roof runoff can result from fecal matter of birds and animals, airborne microbes, tree litter, debris, aerosols, and organic matter accumulating on roof tops.[17]

Research in Southern Nigeria found that while stone-coated tiles provide excellent quality rainwater, materials like Cameroon zinc and asbestos roofs showed significant variations between rural and urban settings, with asbestos being particularly unfit for drinking water in urban areas.[8] A Bulgarian study found that green roofs in polluted areas caused greater changes to rainfall quality than bitumen roofs, including a 7.5-fold increase in COD.[21] Studies show that pH variations across climates from acidic (pH of 5.26–6.83) in Beirut to alkaline conditions (pH > 8.4) in Nepal were largely attributed to local deposition and tank construction materials.[46] [47] In South Korea, microbial analysis demonstrated that dark, enclosed storage conditions significantly improved quality, reducing microbial concentrations by up to 90% within one week of storage.[48] Likewise, green-roof runoff quality was strongly governed by substrate type and rainfall volume, with notable increase in nitrate and phosphate levels under specific media.[49] The findings show that the quality of harvested rainwater is strongly affected by local environmental conditions and pollution levels and there is a need to tailor design and maintenance to local environmental conditions.

3.3

Socioeconomic and Policy Factors Affecting Safe RWH Adoption

Beyond environmental variability, socioeconomic and institutional contexts critically determine how RWH technologies are adopted and sustained. These dimensions shape both the feasibility and long-term functionality of RWH systems, as education, income, and policy support strongly influence implementation success across regions. In Lebanon, household participation increased with education level and outdoor space availability, while higher-income groups (>$6000/month) were more likely to invest in rooftop systems.[46] Similarly, studies from Bangladesh and Tanzania identified a lack of technical knowledge, initial cost, and weak institutional frameworks as primary barriers.[50] [51] Conversely, awareness programs in Jordan were shown to enhance RWH management and water-quality outcomes.[52] In Tamil Nadu, India, less than one-quarter of respondents understood system operation and maintenance, underscoring the need for targeted training and incentives.[53]

3.3.1

Education and Knowledge

Education consistently emerges as a key determinant of RWH adoption across multiple regions. In Somaliland, clear differences in schooling levels were seen between adopters and non-adopters of technologies.[24] Kenyan research likewise reported that formal education had a statistically significant effect on awareness and adoption, whereas gender and broader socioeconomic status did not.[54] Similarly, the total number of years spent in school directly influenced the variety of RWH techniques practiced.[55] However, a lack of knowledge, especially among women and younger generations unfamiliar with traditional systems, can be a significant barrier to adoption.[26] [56] Promoting ongoing education and awareness at the community level is therefore crucial to ensure the sustained efficiency and safety of RWH practices.

3.3.2

Economic Status and Cost

A household's economic standing is a key predictor of RWH adoption. In West Bengal, India, a study of 923 rural households found that ownership of assets and regular savings were significant factors for RWH feasibility.[57] However, in many regions, the high upfront capital costs for installation especially for storage facilities, guttering, and filtration systems remain a major constraint.[26] [27] [58] [59] This suggests that affordability often poses a greater obstacle than willingness to adopt the technology[26]. To overcome this barrier, structured financial mechanisms such as microcredit schemes, hardware subsidies, and cost-sharing programs should be integrated into national and local RWH promotion strategies.[27] [58]

3.3.3

Social Connections and Gender

Social connections also play a crucial role. In Somaliland, 88.8% of RWH technology adopters belonged to water associations, benefiting from shared information, collective access to resources, and coordinated decision-making.[24] While gender-related effects on RWH adoption vary by context, in Pakistan, RWH initiatives have been shown to enhance women's health and economic well-being by reducing the time spent on water collection.[60] However, a Kenyan study reported no significant association between gender and adoption once education levels were accounted for.[26] These differences likely reflect variations in gender roles and education access across regions, suggesting that gender influences RWH adoption indirectly through its interaction with education, income, and social empowerment rather than as an independent determinant.

3.3.4

Government Policy and Support

Government incentives and extension services act as powerful catalysts for increasing RWH adoption rates. In Uganda, hardware subsidies were statistically more effective than cash subsidies in encouraging adoption (p < 0.05).[28] In Kenya’s Matungulu Sub-Country, local incentives from country authorities were reported to strongly encourage technology uptake, with a composite mean score of 4.04.[26] The presence of extension services often marks the difference between adoption and non-adoption. Ethiopian research identified regular access to extension officers was a critical determinant,[25] while in Somaliland, such services provided essential guidance on climate adaption, water treatment, and RWH system management.[24] Collectively, these findings highlight that institutional engagement through technical support and incentive mechanisms plays an equally crucial role as household-level economic capacity in driving sustainable RWH adoption.

3.4

Interplay of Technical, Environmental, and Socioeconomic Factors in RWH System (ISTE Framework)

The synthesized evidence from reviewed articles demonstrates that dynamic interaction of technical, environmental, and socioeconomic factors is key for safety and adoption of RWH systems, rather than from any domain in isolation. The ISTE Framework ([Fig. 1]) proposed in this review provides a conceptual structure for understanding these linkages.

In multiple case studies, the relevance of interdependencies between engineering and socio-economic factors is evident. Technically superior roofing materials such as ceramic tiles, painted metal sheets, or polycarbonate roofs as catchment material are strongly associated with higher household income and education levels.[35] [46] Conversely, low-income households often rely on zinc or asbestos sheets with poorer runoff quality,[33] indicating that engineering design decisions are largely constrained by affordability and awareness In Tamil Nadu, and fewer than one-quarter of respondents understood RWH operation and maintenance procedures despite general awareness of system layout,[53] showing how social capacity limits technical efficiency.

Environmental dynamics further mediate these socio-technical outcomes. The pH and microbial quality vary widely with rainfall pattern, storage condition, and pollution exposure, as shown in Lebanon, Nepal, and South Korea.[46] [47] [48] Properly designed first-flush systems and enclosed storage tanks significantly improve microbial safety,[48] yet their installation and maintenance depend on social awareness and economic ability to invest.

These findings highlight a feedback nexus where socioeconomic capacity determines the adoption of technical measures, engineering design influences exposure to environmental contaminants, and environmental risks reshape community willingness and affordability. Similar feedbacks have been reported across South Asia and the Middle East, where lack of institutional support and financial incentives limit the effectiveness of technically sound systems.[19] [35] [52]

4

Conclusions and Outlook

The growing global water scarcity necessitates innovative approaches to water security, with rainwater harvesting emerging as a promising decentralized alternative. Safe and sustainable RWH is achievable only when engineering performance, socio-economic acceptance, and environmental adaptability are pursued simultaneously. Technological improvements such as optimized roof materials, first-flush diversion, and enclosed or shaded storage are necessary but not sufficient without social enablement and institutional mechanisms.

A critical evaluation of existing studies reveals persistent challenges. Many technically sound RWH systems fail due to poor operation and maintenance, limited community awareness, and the absence of local support networks. Moreover, variability in rainfall, atmospheric deposition, and roof material corrosion introduce environmental uncertainty, often leading to inconsistent water quality. The widespread use of asbestos and uncoated zinc roofs in low-income areas remains a serious concern for public health and underscores the socioeconomic disparity in system quality.

To transform RWH from a supplementary measure into mainstream water supply strategy, a multilevel implementation framework is necessary. Policymakers should provide targeted subsidies or low-interest financing schemes for corrosion-resistant roofing and affordable treatment units in low-income communities. Municipal authorities and NGOs can play a critical role in establishing community-based maintenance training programs to strengthen user capacity and ensure long-term functionality. Integration of low-cost, scalable treatment methods such as chlorination, activated carbon filtration, or UV disinfection can further enhance microbial safety while maintaining cost efficiency.

Future research must address several critical gaps to advance the field. Emerging pollutants, such as microplastics, PAHs, and phthalates, remain largely unmonitored and require systematic investigation. Development of continuous and sensor-based water quality-monitoring systems is essential for improving data reliability and real-time management. Additionally, the impacts of climate change on harvesting efficiency and water quality remain underexplored. Interdisciplinary research that couples technical experiments with socio-behavioral and policy analyses is needed to quantify how environmental stressors and human factors jointly influence system performance. Comparative studies across climatic regions could help refine technical standards, first-flush volumes, and risk-management protocols.

Findings in this article reaffirm that the success of RWH initiatives lies not only in the efficiency of engineering design but also in the empowerment of users, policy integration, and environmental adaptability. The proposed ISTE Framework provides a comprehensive lens to align these domains and can serve as a diagnostic and planning tool for both researchers and practitioners. By integrating technical innovation with social inclusivity and environmental sensitivity, RWH can evolve into a resilient, community-anchored solution that contributes directly to Sustainable Development Goal 6 on clean water and sanitation thereby impacting related other goals, such as SDG 3 (good health and well-being) by providing access to safer water, SDG 4 (quality education) by reducing the time spent collecting water, and SDG 13 (climate action) by offering a method of water security in the face of variable rainfall.

Contributors’ Statement

P.A.: Conceptualization, Methodology, Data Curation, Writing – Original Draft Preparation. P.K.: Data Curation, Writing – Original Draft Preparation. B.T.: Writing – Review & Editing. B.K.K.: Conceptualization, Methodology, Supervision, Writing – Review & Editing.

Conflict of Interest

The authors declare that they have no conflict of interest.

• References

• 1 Richards S, Rao L, Connelly S. et al. J Environ Manag 2021; 286
• 2 Nations U, of Economic D. Affairs S, Division P. World Urbanization Prospects the 2018 Revision 2018
• 3 Campisano A, Butler D, Ward S. et al. Water Res 2017; 115: 195-209
• 4 Khanal G, Maraseni T, Thapa A, Devkota N, Paudel UR. Managing Water Scarcity Via Rainwater Harvesting System in Kathmandu Valley, Nepal: People’s Awareness, Implementation Challenges and Way Forward
• 5 Brief UWP. Climate Change and Water
• 6 Lester S, Rhiney K. Habitat Int 2018; 73: 129-140
• 7 Tikhatri D, Bhattarai SS. Am J Environ Clim 2023; 2 (03) 24-32
• 8 Nicholas E, obong S, Ukoha PO. Water 2023; 3 (01)
• 9 Mdee O, Tembo M, Mwegoha W. Tanzania J Eng Technol 2022; 41 (02) 109-120
• 10 Okudo CC, Ekere NR, Okoye COB. Appl Water Sci 2023; 13 (05)
• 11 Moses E, Uwah I, Ebong G. Am Chem Sci J 2016; 16 (03) 1-9
• 12 Chubaka CE, Whiley H, Edwards JW, Ross KE. J Environ Public Health 2018; 2018
• 13 Owusu S, Asante R. J Water Sanit Hygiene Dev 2020; 10 (03) 502-511
• 14 Mendez CB, Klenzendorf JB, Afshar BR. et al. Water Res 2011; 45 (05) 2049-2059
• 15 Ojo OM. J Appl Sci Environ Manag 2019; 23 (04) 735
• 16 Zdeb M, Zamorska J, Papciak D, Słyś D. Resources 2020; 9 (02)
• 17 Tengan BM, Akoto O. Sci Total Environ 2022; 819
• 18 Achadu, Ako OJ, Dalla FE. Quality Assessment of Stored Harvested Rainwater in Wukari, North-Eastern Nigeria: Impact of Storage Media. Vol. 7
• 19 Emmanuel C. Quality Assessment of Direct Harvested Rainwater in Parts of Anambra State, Nigeria
• 20 Mao J, Xia B, Zhou Y. et al. J Clean Prod 2021; 279
• 21 Tsanov E, Valchev D, Ribarova I, Dimova G. Civil Eng J 2024; 10 (05) 1589-1605
• 22 Nicholas E, obong S, Ukoha PO, Ihedioha JN. Discov Water 2024; 4 (01)
• 23 Nizam NUM, Hanafiah MM, Mokhtar MB, Jalal NA. In: IOP Conference Series: Earth and Environmental Science. Vol. 880 IOP Publishing Ltd; 2021.
• 24 Jirde M, Koech OK, Karuma AA. An Analysis of Perceptions, Knowledge, and Management of Rainwater Harvesting (RWH) Technologies among Agropastoralists in Odwayne District, Somaliland † [Análisis de Las Percepciones, el Conocimiento y la Gestión de Las Tecnologías de Recolección de Agua de Lluvia (RWH) Entre Agropastoralistas del Distrito de Odwayne, Somalilandia]. Vol. 24 2021
• 25 Mekonnen E. J Biol Agric Healthcare. 2017 7(23) www.iiste.org
• 26 Kariuki J. Assessing Factors Affecting Adoption of Roof Water Harvesting for Domestic Use: A Case Study of Kalawani & Kathiani Division. Machakos District, Kenya: 2011
• 27 Singwane SS, Matondo JI, Tevera DS. Affordability and Willingness to Install a Rooftop Rainwater Harvesting System: The Case of Rural Households in the Lowveld Region of Swaziland. Vol. 3 2013
• 28 Baguma D, Loiskandl W. Mitig Adapt Strateg Glob Chang 2010; 15 (04) 355-369
• 29 Page MJ, McKenzie JE, Bossuyt PM. et al. PLoS Med 2021; 18 (03)
• 30 Systematic Reviews Checklist – CASP. (accessed October 12, 2025) https://casp-uk.net/casp-tools-checklists/systematic-review-checklist/
• 31 Lai YH, Ahmad Y, Yusoff I, Bong CW, Kong SY. In: IOP Conference Series: Materials Science and Engineering. Vol. 401 Institute of Physics Publishing; 2018.
• 32 Allameh Z, Kouchakzadeh M, Imteaz MA. Int J Environ Sci Technol 2025; 22 (09) 8149-8166
• 33 Agbonaye AI, Eboi OE. J Sci Technol Res 2024; 6 (01) 86-97
• 34 Jordan, Al-Amoush HR, Alayyash S. Jordan J Civil Eng 2018; 12 (02) 228-244
• 35 Lee JY, Bak G, Han M. Environ Pollut 2012; 162: 422-429
• 36 Müller A, Österlund H, Nordqvist K, Marsalek J, Viklander M. Sci Total Environ 2019; 680: 190-197
• 37 Rashidi Mehrabadi MH, Saghafian B, Ghalkhani H. Desalin Water Treat 2017; 65: 125-135
• 38 Meera V, Mansoor AM. In: Urban Ecology, Water Quality and Climate Change. 2018: 195-202
• 39 Olaoye RA, Sunday OO, Olaoye RA. Int J Eng Technol. 2020 2(8)
• 40 Stewart C, Kim ND, Johnston DM, Nayyerloo M. Int J Environ Res Public Health 2016; 13 (10)
• 41 Muofunanya Francis U, Angela E. Qualitative Evaluation and Determination of Water Quality Indicators for Urban Roof Runoff: A Multivariate Statistical Approach
• 42 Lay JJ, Vogel JR, Belden JB, Brown GO, Storm DE. Water 2024; 16 (10)
• 43 Tran SH, Dang HTT, Dao DA. et al. Environ Sci Pollut Res 2021; 28 (10) 11928-11941
• 44 Al-Khatib IA, Arafeh GA, Al-Qutob M. et al. Water 2019; 11 (02)
• 45 Zhang Q, Wang X, Hou P. et al. J Environ Manag 2014; 132: 178-187
• 46 Alameddine I, Majzoub A, Najm MA, El-Fadel M. WIT Trans Ecol Environ 2019; 229: 21-32
• 47 Domènech L, Heijnen H, Saurí D. Water Environ J 2012; 26 (04) 465-472
• 48 Amin MT, Kim T, Amin MN, Han MY. Water Environ Res 2013; 85 (12) 2317-2329
• 49 Vijayaraghavan K, Joshi UM, Balasubramanian R. Water Res 2012; 46 (04) 1337-1345
• 50 Ghosh S, Ahmed T. Water 2022; 14 (21)
• 51 Dismas J, Mulungu DMM, Mtalo FW. Water Sci Technol Water Supply 2018; 18 (03) 745-753
• 52 Al-Zboon KK, Mansi OA, Ammary BY. Assessment of Rainwater Harvesting Management in Jordan 2024
• 53 Vasudevan M, Natarajan N. Water Supply 2021; 21 (05) 1927-1938
• 54 Shelburne I, Lawver DE, Fraze S, Ulmer J, Stephenson C, Magogo J. J Int Agric Extension Educ 2017; 24 (01) 74-89
• 55 Barthwal S, Chandola-Barthwal S, Goyal H, Nirmani B, Awasthi B. Urban Water J 2014; 11 (03) 231-239
• 56 Memarian H, Komeh Z, Tavasoli A, Tajbakhsh S, Abbasi AA, Parsayi L. Water Harvest Res 2017; (01) 1-12
• 57 Biswas S, Sahoo S, Debsarkar A, Pal M. Arab J Geosci 2021; 14 (16)
• 58 M WP, M NJ, M MJM Maathai W. Barriers and Enablers of Adoption of Rain Water Harvesting Technologies at County Levels: A Case of Matungulu Sub-County, Machakos County Kenya. Vol. 3 2022
• 59 Leidl C, Farahbakhsh K, Fitzgibbon J. Can Water Resour J 2010; 35 (01) 93-104
• 60 Abbas S, Mahmood MJ, Yaseen M. Pakistan Environ Dev Sustain 2021; 23 (12) 17942-17963

Publication History

Received: 23 August 2025

Accepted after revision: 27 October 2025

Accepted Manuscript online:
10 November 2025

Article published online:
22 December 2025