Residential Rainwater Harvesting Research Articles

The Influence of Deep Uncertainties in the Design and Performance of Residential Rainwater Harvesting Systems

The Influence of Deep Uncertainties in the Design and Performance of Residential Rainwater Harvesting Systems

Impact of residential rainwater harvesting on stormwater runoff

Population increase, climate change and soil impermeability are factors causing floods in large urban centres. Such places also always have water shortage problems. This research aims to evaluate the influence of rainwater harvesting in residential buildings on stormwater in a basin located in southern Brazil (Rio Cachoeira Basin). Urbanised and non-urbanised areas, soil types, curve numbers and time of concentration of each sub-basin were taken into account. Through the HEC-HMS programme, it was possible to calculate hydrographs for the base scenario (when there is no rainwater harvesting). Then, rainwater tanks for the residential buildings were sized using the computer programme Netuno. In the second scenario, there is rainwater harvesting in all residential buildings. Thus, the hydrographs for the second scenario were also calculated. The peak flow reduction potentials for the sub-basins ranged from 2.7% to 14.3%. The highest percentage (14.3%) did not occur in the sub-basin with the most extensive roof area; such highest peak flow reduction occurred in Bom Retiro sub-basin. In Bom Retiro sub-basin, there are more houses than multi-storey residential buildings. Even when considering the full potential of rainwater harvesting for roof areas of all existing buildings in the Rio Cachoeira Basin, the average potential reduction in peak flow was 7.2%. The conclusion is that rainwater tanks in residential buildings have little influence on stormwater runoff, and the stormwater runoff will be less affected when the area of the hydrographic basin is larger. Thus, the reduction in peak flows is insignificant when considering the flooding in the region.

Financial Feasibility Analysis of Residential Rainwater Harvesting in Maringá, Brazil

Rainwater harvesting (RWH) systems are key solutions to improve water resource management in cities, and financial feasibility is essential for their diffusion. Moreover, studies about rainwater often adopt diverse design approaches, leading to incompatible results for direct comparison. This study introduces a categorised item-by-item outlay procedure and evaluates indirect (gravity) and direct (pressuriser) rainwater distribution schemes. Computer simulations were used to design 54 generic RWH system scenarios in Maringá based on a range of design variables. For each scenario, a monthly cost–benefit balance was built, and discounted payback, net present value, and internal rate of return were obtained. Similar outlays were obtained for direct and indirect rainwater distribution schemes (∆ = BRL 21.81) with an average of BRL 13,484.87 among all scenarios. Average operational costs were estimated at BRL 1.31/month.m3 of rainwater demand. On average, paybacks of 14.7 years and internal rates of return of 0.99% per month were obtained among feasible scenarios. Like in other studies, financial feasibility indicators presented significant correlations (0.88 ≤ R2 ≤ 0.94) with rainwater demand. The initial outlay distribution proposed herein provides an objective reference for result comparison among similar studies. Similar results for both rainwater distribution schemes point towards investigating alternative technical solutions for RWH systems.

Influence of rainfall time series indicators on the performance of residential rainwater harvesting systems

Despite having abundant water sources, some Brazilian regions are likely to face water scarcity within the following decades. In this sense, rainwater harvesting (RWH) systems are considered viable solutions. This study evaluates the influence of rainfall time series indicators on the tank sizes, volumetric reliability and potential for potable water savings in residential buildings in Brazil. The study aimed to determine the most suitable rainfall conditions for RWH systems design. RWH systems were simulated for 27 Brazilian cities considering a daily water balance model. Total water demands and rainfall time series were considered for each city, and RWH-relevant indicators characterised each time series. Generally, cities with higher rainfall availability required smaller tank sizes and yielded greater volumetric reliabilities and potential for potable water savings. Cluster analysis was also used to investigate if similar rainfall patterns generate similar simulation results. Euclidean distance criteria grouped similar time series into ten clustering schemes. Coefficients of variation for tank sizes decreased within each scenario as more clusters were used, i.e. this method is feasible to design rainwater storage tanks. The remaining performance indicators did not show significant variation among the tested clustering scenarios. Similarity analysis resulted in increasingly similar results within each group as the clustering became more refined. As the main conclusion, correlation analysis presented the Seasonality index and indicators related to dry periods as the most influential towards the performance of RWH systems.

The impact of climate change on rainwater harvesting in households in Poland

In water management, climate changes require adaptation, protection of existing resources and the search for alternative water sources. Rainwater harvesting (RWH) is increasingly becoming an alternative water source, applicable for many directions of its use. The aim of the research was to analyse the influence of long-term climate change on the potential for rainwater harvesting in households in Central Europe in Poland. The analysis of long-term climate changes impact on the household rainwater harvesting potential was conducted for the 50-year period for 19 cities in Poland. The water balance model was operated in a day-step mode, and the research was carried out in four “time scales approach”. For the purpose of all analyses, a standard weekly water demand profile was developed. It includes the daily sub-profiles for every working day and weekend, covering the washing and toilet flushing needs for a 4-person household. In order to evaluate the long-term changes in residential harvesting in Poland, a hypothetical residential RWH was investigated in 19 locations and rainfall conditions. To illustrate the time-spatial variation of annual rainfall amounts in the analyzed period, the heat map was prepared as the pre-simulation stage. Results show that the design of RWH systems should be based on archival data and take into account the many years of rainfall changes. This will improve performance and secure benefits for the users of this system.

Impact of Residential Rainwater Harvesting on Stormwater Runoff

Impact of Residential Rainwater Harvesting on Stormwater Runoff

Challenges of open design in low-income communities: a case study of residential rainwater harvesting systems

ABSTRACT Open design (OD) is a promising approach to address global sustainability challenges. At the same time, however, the increased use of OD brings new challenges. To understand the potential of OD in a specific context, we adopted the concept of a residential rainwater harvesting system (RWHS) as a case study. We first identified the critical design features of the RWHS. After that, we analysed the potential for local reproduction of these features at the grassroots level of low-income communities in developing countries. This analysis revealed that varying limitations related to materials, skills, and manufacturing tools may hamper the adoption of OD by local communities when trying to improve their water management. In the light of our findings, we argue that OD processes are likely to face challenges if replicability, substitutability and adaptability are not successfully integrated into the design. We suggest a design-for-frugality mindset and adoption of parametric design processes and design parameters as key strategies to boost OD processes in low-income communities. We also stress the importance of safety and liability aspects in the studied context.

Determinants for the adoption of residential rainwater harvesting systems on the slopes of Mt. Elgon, East-Africa. How do they perform?

In recent years, the mountainous regions are becoming more susceptible to devastating climatic shocks causing food insecurity and environmental degradation. In response, farmers with small landholding are gaining interest in deploying Residential Rainwater Harvesting Systems (RRWHS) to improve water supplies in homes, though diminutive consideration has been given to the performance evaluation of these systems in a mountainous landscape in the tropics. Our study intended to explicitly understand the determinants for the household adoption of RRWHS and evaluate their performance to improve domestic water supplies in the study area. The study took a cross-sectional design were 444 respondents were selected using a cluster sampling method, and administered with semi-structured questionnaires. The indicators used to assess system performances were: reliability, cost-effectiveness and efficiency. The results of this study showed that system/component price-subsidies, household income-status, landholding-size, availability of technical support and farmer education-level were the most significant determinants for the uptake of RRWHS (P < = 0.05). Performance-wise, the most reliable systems were corrugated metallic-tanks and concrete-ferro-cement tanks. The most cost-effective system was plastic jerrycans; while the most-efficient were concrete ferro-cement and plastic tanks. This study reveals that tax exemptions on the manufacture and importation of RRWHS components can increase their acquisition. The high-capacity storage RRWHS systems are preferred by the farmers due to improved water supplies to sustain domestic usage and farming requirements but also safeguard the environment from surface run-off and overexploitation. Plastic-storage facilities are preferred, because they did not react with water compared to metallic systems.

An investigation on the adaptability of residential rainwater harvesting system in Tamil Nadu – techno-economic considerations and the way forward

Abstract Rainwater harvesting (RWH) is one of the most important means of water conservation today. Although there is tremendous emphasis on the implementation of this versatile technology at various levels, many of us are unaware of its significance and its consequences. This study examines the perception and awareness of people in the state of Tamil Nadu, India, of the RWH system through a questionnaire survey. The survey was conducted to infer basic information on rainwater harvesting features, water quality and conservation, economics of implementation and financial support. The results show that there is an increasing need to promote the usage of harvested rainwater for domestic purposes rather than direct groundwater recharge. The potential risks in the reliable supply of available water sources demand large-scale implementation of RWH especially in apartments. Fewer people are aware of the technical details of operation and maintenance of the RWH system (22.2%) while more people are aware of the general layout of the system (50.5%). Longer experience in using RWH systems (for more than two years) builds confidence in using them for consumptive uses compared with the response from recent adopters. This also demonstrates the scope for a radical change in the perception of water quality by continuous awareness and financial incentives.

Long-Term Trends in 20-Day Cumulative Precipitation for Residential Rainwater Harvesting in Poland

Rainwater harvesting (RWH) for domestic uses is widely regarded as an economic and ecological solution in water conservation and storm management programs. This paper aims at evaluating long-term trends in 20-day cumulative rainfall periods per year in Poland, for assessing its impact on the design and operation conditions for RWH systems and resource availability. The time-series employed corresponds to a set of 50-year long time-series of rainfall (from 1970 to 2019) recorded at 19 synoptic meteorological stations scattered across Poland, one of the European countries with the lowest water availability index. The methods employed for assessing trends were the Mann–Kendall test (M–K) and the Sen’s slope estimator. Most of the datasets exhibit stationary behaviour during the 50-year long period, however, statistically significant downward trends were detected for precipitations in Wrocław and Opole. The findings of this study are valuable assets for integrated water management and sustainable planning in Poland.

Assessing storage requirements, water and energy savings, and costs associated with a residential rainwater harvesting system deployed across two counties in Southeast Florida

This article analyzes the feasibility of a widely-deployed residential rainwater harvesting (RWH) system for reducing demands and supplementing existing, centralized water supply systems in a heavily populated region in Southeast Florida. The analysis employs a unique integration of models and approaches, which are portable and applicable in diverse contexts and include: a nonparametric bootstrapping model for synthetically generating multiple realizations of regional rainfall, water supply and demand, and storage size and reliability outcomes; and an approach for determining expected water and energy savings and costs associated with the RWH system. Findings suggest that a RWH system designed to meet the outdoor irrigation demands of detached homes in Florida's Broward and Palm Beach Counties could meet 54% of the total additional water demand created by the growing population in this region. This is significantly greater than the percentages of demand that could be met by several proposed centralized approaches to water supply using groundwater recharge by reclaimed water, comparable to the percentage of demand that could be met by desalinating brackish water from the Floridian Aquifer, but less than the percentage of demand that could be met by a proposed new reservoir and canal system for groundwater recharge. The findings also suggest that the expected cost of water provided by the decentralized RWH system, which includes substantial savings in energy requirements and costs, would be significantly less than the expected costs of water provided by all centralized water supply system alternatives considered, with the exception of the reservoir and canal system.

Cumulative impacts of residential rainwater harvesting on stormwater discharge through a peri-urban drainage network

Green infrastructure and techniques such as rainwater harvesting have been proposed as a means to reduce stormwater discharge in developed areas prone to floods. We examined the effects of rainwater harvesting on discharge cumulatively through the Perdido River drainage network in the US state of Florida, an area prone to routine rainfall-driven nuisance flooding. We considered scenarios where rainwater is stored in parcels with structures that use septic tanks (where tanks are retired and used as cisterns, volume approximately 5.7 cubic meters); and where a similar volume of water is stored at all developed parcels. To evaluate flow reduction through the drainage network, we modeled effects relative to a flow event with a 1.5-year recurrence interval using a spatial GIS-based cumulative-effects model. Our model predicted that retired septic tanks would reduce discharge by more than 10 percent in only a few areas in the study region, almost exclusively in headwater regions and where density of houses using septic tanks is high. Analysis of all developed parcels storing rainwater indicated that discharge in several areas would be reduced by more than 20 percent. Results indicate a spatially variable potential for rainwater harvesting to reduce routine storm discharge. Spatially continuous hydrologic tools such as the one we use here may be especially useful for managers seeking to prioritize limited resources at locations for maximum benefit.

Cost Comparison and Hydraulic Design of Four Types of Residential Rainwater Harvesting Systems for Small Rural Communities, Considering Natural or Anthropogenic Climate Change Factors

This document presents the technical description and cost comparison of four rainwater harvesting systems for homes, the method for its hydraulic design and an equation to estimate the minimum catchment area, with the goal to supply drinking water to segregated small communities in Mexico considering climate change effects, both natural and anthropogenic. The four Rainwater Harvesting Systems (RHS) introduced in this work are the following: two rigid, one system built with ferrocement and the other built with clay bricks, and two flexible: one is a commercial collector while the other is a system built with a 3/8-inch reinforcing bar mesh and covered with a linear low-density polyethylene geomembrane. The RHS consist in cylindrical containers built with diverse materials, and in the case of rigid RHSs, they can store up to 50,000 liters of water. Also, rigid RHSs have a longer useful life and are more resistant than flexible RHSs, but their cost is notably higher. Rigid RHSs compete in price with commercial rainwater harvesting system brands like Rotoplas, but commercial RHSs disadvantages are their lower durability, storage capacity, and resistance. On the other hand, flexible RHSs are less durable than rigid ones, although, in the case of the rainwater harvesting system made with a 3/8-inch reinforcing bar mesh, the system can be rebuilt and reused and the cost is much lower. The design of the collectors takes into consideration the climate variability of the study area, natural or anthropogenic.

Hydrodynamic modeling of the impact of residential rainwater harvesting systems on stormwater runoff and drainage networks

This paper presents the results of hydrodynamic modeling of urbanized catchment, where rainwater harvesting systems (RWH) was applied. The catchment model was developed in the Storm Water Managment Model program and RWH was simulated as one of the LID practices available in this program - rain barrels (RB). The research was carried out for various rain barrels implementation scenarios (50% -100%) in a single-family housing estate. However, the results of the research showed that the use of rain barrels (RB) to capture rainwater discharged from the roof of buildings was not effective in significantly reducing the outflow of water from the catchment, and thus reducing the occurrence of pressure flows in the analyzed sewage system.

Residential rainwater harvesting: Effects of incentive policies and water consumption over economic feasibility

Rainwater harvesting is currently a recurring theme as part of the sustainable practices for urban constructions. The economic feasibility of implementing a system capable of capturing, treating and distributing rainwater for residential uses concerns the user who intends to benefit from such practice. To this end, twelve single-family houses of different construction standards were selected for this research in the city of Belém, Pará, Brazil. The design and budget for the installation of a rainwater harvesting system were prepared for each house. The hydrological performance and economic feasibility were evaluated under different consumption and economic policies scenarios using the rainwater harvesting simulation software. The main conclusion is that rainwater systems are more economically feasible in households with higher water demand, regardless of the size of the catchment area. The cost of implementing rainwater systems has little variation with the construction standard of the residence where it is installed. The tariff structure makes it economically unfeasible to harvest rainwater in any scenario for houses where water consumption is below the social tariff or receives fixed price water bill. A combination of rising water prices to the same level of water production costs and reduced implementation costs improves the economic feasibility of rainwater harvesting.

Lifecycle Analysis of a Single-Family Residential Rainwater Harvesting System in a Subtropical, Metropolitan Environment

AbstractPressures on water resource availability are a global concern and escalations in water prices and mandatory water rationing make alternate water sources, such as rainwater, more attractive ...

Evaluation of climate change impacts on rainwater harvesting

Water management is an important issue in urban design due to the growing concern of water scarcity. As a result, rainwater harvesting system has received notable attention as an alternative water source. Rainwater is one of purest form of waters and can easily be accessed via a rainwater harvesting system. In general, performance of a rainwater harvesting system is estimated based on historical rainfall data without the possible impacts of climate change on rainfall. However, rainfall pattern is likely to change in the future as a consequence of climate change that may affect the performance of a rainwater harvesting system. But research on climate change impacts on rainwater harvesting is limited. The objective of this study is to understand the plausible impacts of climate change on the performances (i.e. water savings, reliability and water security) of a residential rainwater harvesting system, based on the projected future rainfall conditions. A continuous daily simulation water balance model is developed based on behavioural analysis and yield-after-spillage criteria to simulate the performances of a rainwater harvesting system. The analysis is conducted at five locations in the Greater Sydney region, Australia.The results indicate that performances of a rainwater harvesting system will be impacted negatively due to climate change conditions in the future. It is found that a given tank size at the selected locations would not be able to supply expected volume of water under changing climate conditions in future. Water savings is going to be reduced from a rainwater harvesting system in future (e.g. 2%–14% reduction for 3 kL tank for indoor water demand). Moreover, number of days in a year to meet the water demand by a rainwater harvesting system (i.e. reliability) is likely to be reduced (e.g. 3%–16% reduction for 3 kL tank for indoor water demand). Also, the percentage of days a rainwater tank would remain completely empty is likely to increase in future (e.g. 12% in future climate conditions in comparison to 8% in historical conditions for indoor water demand). Furthermore, it is found that the performance of a rainwater harvesting system will be more affected in dry season than the wet season. The findings of the study will help water authorities and policy makers, as well the home owners to improve their understanding of climate change impact on residential rainwater harvesting system, and will assist them in selecting appropriate rainwater tank size in the context of climate change.

Investigation of pump and pump switch failures in rainwater harvesting systems

Summary Rainwater harvesting is an important technology in cities that can contribute to a number of functions, such as sustainable water management in the face of demand growth and drought as well as the detention of rainwater to increase flood protection and reduce damage to waterways. The objective of this article is to investigate the integrity of residential rainwater harvesting systems, drawing on the results of the field inspection of 417 rainwater systems across Melbourne that was combined with a survey of householders’ situation, maintenance behaviour and attitudes. Specifically, the study moves beyond the assumption that rainwater systems are always operational and functional and draws on the collected data to explore the various reasons and rates of failure associated with pumps and pump switches, leaving for later further exploration of the failure in other components such as the collection area, gutters, tank, and overflows. To the best of the authors’ knowledge, there is no data like this in academic literature or in the water sector. Straightforward Bayesian Network models were constructed in order to analyse the factors contributing to various types of failures, including system age, type of use, the reason for installation, installer, and maintenance behaviour. Results show that a number of issues commonly exist, such as failure of pumps (5% of systems), automatic pump switches that mediate between the tank and reticulated water (9% of systems), and systems with inadequate setups (i.e. no pump) limiting their use. In conclusion, there appears to be a lack of enforcement or quality controls in both installation practices by sometimes unskilled contractors and lack of ongoing maintenance checks. Mechanisms for quality control and asset management are required, but difficult to promote or enforce. Further work is needed into how privately owned assets that have public benefits could be better managed.

Cost-benefit analysis and equitable cost allocation for a residential rainwater harvesting system in the city of Austin, Texas

This study addresses the applicability and financial feasibility of residential rainwater harvesting systems in the city of Austin, Texas. A cost-benefit analysis is used to estimate the financial return for individual households with rainwater harvesting systems. In addition, a subsidy value that could be provided by the delay of a wastewater treatment plant expansion project is investigated. The findings suggest that a residential rainwater harvesting system would not be feasible without a sufficient subsidy. The estimated subsidy is also not enough to make the cost of the harvesting system effective; however, its multi-purpose benefits are not quantified.

Energy Intensity of Water End-Uses

Water end-use, in buildings, industrial facilities, and farms, often has the highest energy intensity. This review highlights key findings on energy intensity of water end-use in urban and agricultural sectors. In the domestic sector, energy used for water heating constitutes 14–25 % of total energy use in US households. Heat pumps for energy recovery from hot grey water in residential buildings, and micro-turbines operating from grey water in tall buildings, are being increasingly explored. In agriculture, groundwater pumping consumes most of the on-farm energy, and water-efficient pressurized delivery systems have higher energy consumption. Rainwater harvesting systems are being deployed in many regions. The energy intensity range for residential rainwater harvesting has been reported to be 0.6–5.3 kWh/m3 in Australia. However, with improved pump efficiency, the intensity can be lowered to 1.5 kWh/m3, which would be less than other non-conventional sources such as seawater desalination or indirect potable reuse.