Rooftop Rainwater Harvesting Research Articles

Water quality assessment of rooftop harvested rainwater across different roof types in a semi-arid region of South Africa.

Uneven distribution of precipitation and climate change have led to water shortages, adversely impacting numerous countries worldwide. Rooftop rainwater harvesting (RWH) has emerged as a crucial method for providing water for domestic uses. However, there are concerns about the quality of rainwater collected from roofs, as it may be contaminated with pollutants such as metals and microbiological pathogens. This study investigates the common roof types used as catchments for rainwater harvesting with the aim of establishing the quality and usefulness of the harvested water resource. Compliant levels of major and trace metals were recorded across various roof types in the three study areas. Metals of concern, such as lead (below detection limit to 0.69 μg/l), arsenic (0.06-0.13 μg/l), and cadmium (0.02-0.13 μg/l), were also within acceptable limits at all study sites. However, the average levels of E. coli detected ranged from 4.32 to 27.97 cfu/100 ml, exceeding the recommended limits set by both the World Health Organization and the South African National Standards. The trace metal levels in water collected from slate roofs were slightly higher than those from other roof types for most of the metals studied. The quality of the water obtained from various roof types indicates it is suitable for all domestic purposes, including drinking after disinfection. No significant differences were observed in the water quality across the different rooftops in the study areas. PRACTITIONER POINTS: Different roofing materials did not significantly affect the quality of the harvested rainwater. Water quality of the harvested rainwater complied with regulatory standards except for microbial water quality parameters. Rainwater can be used for several domestic purposes without treatment except for drinking purposes where it should be treated with a simple point-of-use water treatment system. First flush should be discarded as it impacts greatly on the water quality parameters determined. Rainwater harvesting offers an alternative and supplementary form of water supply in the semi-arid region of South Africa.

Technical assessment combined with an extended cost–benefit analysis for the restoration of groundwater and forest ecosystem services – an application for Grand Bahama

Abstract. A large storm surge caused by Hurricane Dorian in 2019 resulted in extensive flooding and saltwater intrusion into the aquifers of the island of Grand Bahama. This caused about 40 % of the island's water supply to become brackish with no or slow recovery to date and damage to more than 70 % of mangroves and forests on Grand Bahama. Managed aquifer recharge (MAR) and reforestation were considered nature-based solutions (NBS) to mitigate the impacts of Hurricane Dorian. First, a technical assessment of MAR investigated (hydro)geological aspects. As a result, potential locations for a MAR scheme are proposed. Further, a financial and an extended cost–benefit analysis (CBA) integrating ecosystem service (ES) assessments are conducted for proposed MAR and reforestation measures. Based on the current data availability, results indicate that the MAR scheme of rooftop rainwater harvesting is technically feasible. However, based on our first estimate with limited data, this MAR scheme will be able to provide only about 10 % of the water demand in the study area and thus would not be favorable from a financial perspective. Since MAR has a range of positive aspects (including potential reduction of desalinization efforts and improvement freshwater-dependent ecosystems), we recommend reassessment with more detailed hydrogeological data. On the other hand, reforestation measures are assessed to be financially profitable. The results of this study not only prove the technical feasibility and the added value of restoring groundwater and the forest ecosystem on Grand Bahama, but also highlight the associated high costs. The developed methods for investigating ecosystem services from an economic perspective was proven to allow for a systematic comparison of NBSs and reverse osmosis costs and benefits helping, e.g., policy- and decision-makers and to justify their implementation.

Disaster Resilience Through Rainwater Flood Management: The Case of Zaatari Refugees Camp, Jordan

Rainwater floods significantly affect urban areas with vulnerable infrastructure and social systems, worsened by climate change. This study examines flood risk management and its potential for agricultural development in the Zaatari Refugee Camp and surrounding areas. Using GIS-based mapping, hydrology analysis, rainfall data review, and analytical hierarchy process weighting, the research identifies flood risk zones and proposes rainwater harvesting solutions at macro and micro levels. At the macro level, the area is predominantly moderately risky (61.1 percent), with high-risk (22.42 percent) and very high-risk (0.84 percent) zones. Rainwater harvesting structures can reduce runoff to the camp by 83.3 percent (1.211 million m3 [MCM]) overall and 45.6 percent (0.824 MCM) at intervention sites, easing pressure on drainage systems and improving adaptability. Micro-level solutions target high-risk zones, including rooftop rainwater harvesting, which could collect 98,616 m3 annually. The findings highlight the potential of integrating flood risk reduction with water resource development, offering a replicable framework for disaster resilience and sustainable rainwater management. The study bridges gaps between urban and environmental science, moving beyond partial solutions to deliver comprehensive, adaptable strategies.

Climate change adaptation through rainwater harvesting to enhance food security in Diamaré, Cameroon

ABSTRACT Climate change and variability pose significant challenges in Cameroon's Far North Region. Relying predominantly on rainfed agriculture, this region faces heightened rainfall fluctuations and droughts, severely impacting agricultural output and pushing farmers into precarious socioeconomic conditions. Despite other adaptive strategies, access to water remains a challenge, prompting this study to assess the impact of rainwater harvesting (RWH) on crop yields in the Diamaré area. In a farm experiment, the growth of okra, cucumber, lettuce, and cowpea grown purely under rainfed conditions was compared to those that were rainfed as well as supplemented with harvested rainwater during the dry spell of the rainy season. A rooftop RWH system was adopted for irrigation, and data on crop growth and final yields were collected. Statistical analysis revealed a statistically insignificant yet positive influence of rainwater on the growth, development, and ultimate yield of okra, lettuce, and cucumber. The insignificant impact was due to minor differences in means of crop growth parameters. Despite minimal differences in means, the study underscores the positive impact of RWH on crop yields in Diamaré. The findings advocate for the adoption of rooftop and other cost-effective RWH techniques to enhance farmers’ resilience and long-term economic benefits.

Analysis and Validation of Sponge City Construction in Mountainous Cities based on SWMM - Taking Nanan District of Chongqing as an Example

Sponge city construction is one of the key topics in today’s research. China’s sponge city construction has gradually entered the stage of optimization and effect evaluation. However, there are still some gaps in issues such as the verification of the effect of sponge cities. Therefore, in this paper, Storm Water Management Model (SWMM) is carried out by collecting data on surface runoff, waterlogging, peak flow, control rate, etc. in Nanan District of Chongqing City. At the same time, reasonable Low Impact Developments (LID) facilities such as rain gardens, permeable paving, bioretention tanks, rain barrels, rooftop rainwater harvesting and rooftop gardens are incorporated into the sponge city design and verified by using a typical rainfall process with a return period of 5a and a duration of 3 hours. The results of the study showed that the surface runoff drainage time in one catchment was 11.1% faster before and after the LID facilities were installed in contrast, the peak flow reduction rate of the main pipe was 71.55%, and the average runoff control rate in each catchment was around 40.57%. In conclusion, the LID facilities are not effective enough to reduce the rainfall runoff above the medium rainfall, while they are more effective below the medium rainfall.

Modelling scenarios for water supply and sanitation technologies in Jordan

The influx of refugees, population growth and current agricultural practices have led to an increase in water demand in Jordan, placing pressure on existing water provision. Climate change further exacerbates declining water availability. Against this backdrop, the techno-economic feasibility of four water supply and sanitation alternatives for small and medium scale cities in Jordan were explored, using local unit costs and Al-Mafraq as a case study. City level piped network combined with household rooftop rainwater harvesting and surface runoff collection into local ponds and piped networks with treatment using the nature-based solution of root-zone for sanitation were demonstrated to provide the highest benefits in terms of cost, convenience and water conservation. Our work highlights the need to invest in long-term urban infrastructure networks to promote sustainable future growth of cities. This is vital to address severe water scarcity challenges that ultimately impact those at the urban fringes most.

Feasibility of Rooftop Rain Water Harvesting at Grey Iron Foundry, Jabalpur, Madhya Pradesh, India

Feasibility of Rooftop Rain Water Harvesting at Grey Iron Foundry, Jabalpur, Madhya Pradesh, India

Assessment of rainwater harvesting potential from rooftops in Jordan's Twelve Governorates.

Rooftop rainwater harvesting (RRWH) offers a potential solution to Jordan's pressing water scarcity problems. Yet, its feasibility and benefits necessitate a thorough assessment, particularly as existing studies on the subject are outdated and often constrained by limited scope or small data sets. To this end, our study assessed the potential of RRWH in Jordan's 12 governorates, utilizing historical rainfall data from 1987 to 2018 and official statistics on population and rooftop areas. The analyses used the Ripple Method and Water Balance Model to determine potential harvestable water volumes, potential water-saving percentages, and optimal tank sizes under different scenarios (i.e., using rainwater to meet the total consumption or only for toilet flushing). The findings reveal that Jordan has a total potential for rooftop rainwater harvesting amounting to 23.74 Mm3/year, corresponding to 4.54% of the total water demand. Should RRWH be implemented across all rooftops, the projected financial savings for Jordan could range from $170 million to $678 million. Among the governorates, Irbid and Amman have the highest potential, with estimated yields of 7.754 Mm3 and 8.453 Mm3 per year, respectively. Based on the best results for the scenario where harvested rainwater is only used to flush toilets, the optimal tank sizes for storing rainwater were estimated to be 2.7 m3 and 2 m3 per household in Ajlun and Irbid, respectively. For a regularized case (October-May), a payback period of 12.5-24 years based on desalination cost was found for an RRWH system capable of meeting thrice the flushing needs of a household. RRWH was showcased as a sustainable solution to Jordan's water scarcity, emphasizing the necessity for broader implementation.

Evaluating rooftop rainwater harvesting potential to satisfy urban water demand in Hosaena City, South Central Ethiopia

ABSTRACT The assessment of the rainwater harvesting (RWH) potential in Hosaena City from medium to large public buildings is the main objective of the study. ArcGIS with Google Earth Pro was used to calculate the rooftop area of the selected building, and RWH from each category of public buildings was evaluated by considering rooftop areas, monthly rainfall, and runoff coefficient. The result shows that the highest amount of rainwater was harvested from the City Administration building in August (197.1 m3), whereas the lowest was collected from the Health Center building in December (1.8 m3). Additionally, the contribution of RWH from individual public buildings for each month was evaluated, and its values ranged from 0.073 to 1.8%. The comparison shows that Wachemo University, Nigist Eleni Comprehensive Hospital, a technical and vocational institute, and teacher training center buildings, could have a significant potential for rainwater storage, ranging from 1.56 to 28.41%. This implies that, besides saving a noteworthy volume of potable water, the excess rainwater can be stored and utilized for the later dry months. As a result, it is recommended that rooftop RWH in Hosaena be the best source of the city's water supply system to reduce the current water supply shortage.

The potential of rainwater harvesting and greywater recycling as an alternative domestic water resource in Bahnstadt-Heidelberg, Germany

ABSTRACT The use of high-quality potable water for non-essential activities results in substantial water waste. Therefore, treating and utilizing rainwater and greywater which contain low concentrations of organic substances and microbes as alternative domestic water resources can enhance the resilience and sustainability of water in urban areas. However, it encounters several challenges. This study was conducted in Banhstadt-Heidelberg, Germany, to estimate domestic water consumption patterns, evaluate the potential of rainwater harvesting from green roofs, and assess the public acceptability of greywater recycling. The primary data were collected from 361 Bahnstadt residents through the questionnaire to estimate water consumption. The non-potable water demand in Bahnstadt was estimated at 228 m3/day for 5,700 Bahnstadt residents. The harvestable rainfall volume was 16,017.58 m3/year. When rainwater supply was compared to water demand, the potential for rooftop rainwater harvesting was 19.25%. This value indicates that the amount of rainwater collected is less than that of non-potable water required per year. To meet the demand, rainwater harvesting will need to be supplemented with treated greywater. However, only 20.78% of respondents are willing to install a greywater recycling system, mostly because of public health concerns. Overall, this study shows the tendencies toward having green roofs with integrated rainwater harvesting and greywater recycling for the possible account of water saving.

Application of GIS & RS in Rainwater Harvesting for an Arid Region

In dry areas with variable rainfall, water shortages severely affect the livelihoods of local populations. Rainwater harvesting from land sites and roof-tops is a readily available solution to this problem. This study presents a GIS & RS-based methodology to identify potential land sites and roof-top rainwater harvesting potential using easily obtainable and freely available data. Slope, land cover, soil, and drainage maps were used to identify suitable rainwater harvesting land sites, which were further analyzed for surface runoff using the curve number method. This research also incorporated obtainable socio-economic factors in identifying the suitable locations of dams considering the implementation stage. Based on the proposed criteria, 44 suitable locations for dams were identified and validated using a validation map and Google Earth images. CROPWAT model analysis revealed that paddy water demand in Batticaloa would increase threefold if all available land for paddy cultivation was utilized. Therefore, abandoned lands can be utilized by erecting dams at those identified locations. Analysis of Google Earth images also revealed that roof rainwater harvesting would be sufficient to meet the basic water demand in the area. This study demonstrates that rainwater harvesting can be an effective strategy for addressing water scarcity in dry areas.

Necessity and Design of Roof Top Rain Water Harvesting System

Necessity and Design of Roof Top Rain Water Harvesting System

Assessment of Rooftop Rainwater Harvesting Potential: A Case Study for Nagaland

Abstract: Water scarcity has become a serious global threat due to hazardous population growth frequent droughts and changing climate pattern (Carolina B. Mendez et. al). Water is scarce natural resource, even though 71% of land is covered by water out of total water on the earth near about 25% are fresh which is being utilized for various purposes viz. domestic, irrigation and industrial are common. Nowadays the need of commercial water is magnifying tremendously in a developing country like India which has long tradition of rural culture. Here in this study, an attempt was made to estimate the potential of rooftop rainwater harvesting in the state of Nagaland, India. The results showed that the total domestic water demand of Nagaland was estimated at 62,012,868,550 liters and domestic supply potential only from rooftop rainwater harvesting was estimated to fulfill about 64.70% of total water demand and the shortage which is about 35.3% can be through state governments water supply scheme, from the private sector and also other sources like pond, river, spring water, etc

Health Burden of the Consumption of Rooftop Rainwater Harvesting Systems in Buea Sub–Division, Cameroon

Health Burden of the Consumption of Rooftop Rainwater Harvesting Systems in Buea Sub–Division, Cameroon

Assessment of Low-Cost Filter Material for Rooftop Rainwater Harvesting Structure

Assessment of Low-Cost Filter Material for Rooftop Rainwater Harvesting Structure

Rainwater Harvesting System Analysis for Semi-Arid Climate: A Daily Linear Programming Model

Rainwater harvesting has proven to be an alternative water supply scheme for sustainable water management of regions with limited water resources. In this paper, a linear programming (LP) model with daily time steps, which minimizes a rooftop rainwater harvesting system (RWHS) cost, is developed and used to calculate the optimum RWH tank size. The developed LP model is applied to the semi-arid Northern Cyprus in the Eastern Mediterranean. The analysis is carried out for 33 sites which receive average annual rainfall ranging from 292 mm to 548 mm to evaluate the spatial effect of rainfall characteristic and the water cost on the financial feasibility and performance of the RWHS. At 29 out of 33 sites, RWHS investments are found to be financially feasible with discounted payback periods ranging from 12 to 28 years. The optimum RWH tank sizes are determined to be between 2 m3 and 6 m3 resulting in up to 20 % reliability with more than 50 m3 of average annual water savings per house. It is observed that the cost of water is a critical factor that affects the financial feasibility and water savings of a RWHS, especially in regions with limited rainfall. The comparison of the developed daily LP model with an LP model with monthly time steps demonstrates that the financial feasibility and the optimum tank size can only be assessed realistically when daily time steps are used. Finally, the sensitivity analysis shows that the discounted payback period is highly sensitive to the collector area.

Estimation of Roof Top Rain Water Harvesting Potential: A Proposed Solution to Water Scarcity in Shrigonda Town, Maharashtra, India

The burning issue in cities will be water scarcity in the coming years. The world population in cities has increased from 29.6 percent to 56.2 percent and is predicted to reach 68.4 percent by 2050. Therefore, this study has attempted to find a solution to tackle the urban water scarcity issue. Recently, rainwater harvesting has emerged as a sustainable and effective system for water conservation in urban areas. Hence, the ward-wise rooftop area was calculated and the rooftop rainwater harvesting potential was estimated by applying the Gould & Nissen, formula for Shrigonda Town. The result reveals that the total water demand in the water stress period was 41,34,41,010 litres while the total rainwater harvesting potential was 39,07,42,128 litres, which means about 94.51 % of the total demand will be met after the rooftop rainwater harvesting system is installed. The study concludes that rooftop rainwater harvesting is considered a sustainable and best alternative tool to tackle urban water scarcity.

Rooftop rainwater harvesting potential for kitchen gardening in the Rawal watershed, Pakistan

Rooftop rainwater harvesting potential for kitchen gardening in the Rawal watershed, Pakistan

Dilution of Salinity Using Rainwater Harvesting System - An Innovative Approach

In view of the increasing water demand, this paper recognizes rainwater harvesting as an innovative approach to the dilution of salinity. It proposes dilution of salinity to reduce both the direct and indirect effects of salinity on human health and well-being. This paper focuses on the saline regions of the Union Territory of Delhi. It identifies possibilities for salinity dilution by proposing an innovative approach to implement rainwater harvesting. For this purpose, this paper evaluates the rooftop rainwater harvesting potential for roof area including 100, 200, 300, 400 and 500 square meter area, in the identified saline regions of National Capital Territory (NCT) Delhi. To assess the impact of the rainwater harvesting system on salinity dilution, different maps and data were analysed. These maps include a salinity map of Delhi, a depth-to-water level map of Delhi, water level fluctuation map of Delhi, isohytal map of Delhi, etc.

Contribution of rooftop rainwater harvesting to climate adaptation in the city of Hannover: Water quality and health issues of rainwater storage in cisterns and ponds

Rooftop rainwater harvesting systems and blue-green infrastructure are becoming important resilience alternatives for urban climate adaptation. This study sheds light on the largely unreported physicochemical and microbiological quality of private roof-harvested rainwater (RHRW). We aimed to identify the physicochemical and microbiological characteristics of RHRW, explore potential correlations between them and assess probable health risks associated with recreational interactions of children with the water. RHRW was collected from cisterns and ponds located in an inner courtyard in Hanover, Germany. Physicochemical parameters were measured on site and samples were collected once a month in two campaigns in 2020 and 2021. Escherichia coli concentrations ranged from 1 × 10° to 24.1 × 102 MPN/100 mL, Enterococci from 1 × 10° to 19.7 × 102 MPN/100 mL, Salmonella from 1 × 102 to 39 × 103 CFU/100 mL and Pseudomonas aeruginosa from 1 × 10° to 3 × 103 MPN/100 mL. Correlation analysis indicated potential relationships between bacteria, oxygen, and water temperature. The results of the health risk assessment indicated a potential risk of gastrointestinal illnesses due to exposure to Enterococci and Salmonella spp. present in the cisterns and ponds, highlighting the need for appropriate regulations and guidelines for RHRW aimed for non-potable uses. Blue-green infrastructure, when effectively managed and maintained, can offer benefits both by enhancing urban climate resilience and promoting citizens well-being.