Residential Rainwater Harvesting System 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

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.

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.

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.

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.

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 ...

Harvested Rainwater Quality Before and After Treatment and Distribution in Residential Systems

Rainwater harvesting (RWH) is an alternative method of providing water for indoor domestic use, but the water quality after treatment and distribution at individual residences is not well documented. In this study, water quality parameters were measured at the cistern and indoor cold‐water taps of six residential RWH systems that use various treatment processes. Potential human pathogens (Mycobacterium avium, Mycobacterium intracellulare, Aspergillus flavus, Aspergillus fumigatus, and Aspergillus niger) were found frequently in cisterns and in treated rainwater delivered at the tap; Legionella pneumophila was not detected as frequently, but it persisted in a system after its first detection. The observed decreases in bacterial concentrations from the cistern to the tap after filtration/ultraviolet (UV) treatment and distribution were less than expected; this suggests deficiencies in the effectiveness of the filtration/UV processes employed and/or degradation in water quality in the distribution system due to the absence of a disinfectant residual.

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.

A preliminary sustainability assessment of innovative rainwater harvesting for residential properties in the UK

Rainwater harvesting (RWH) has yet to see significant uptake in UK households, primarily due to a lack of innovation in residential RWH system types. This paper presents the results of preliminary investigations into a range of traditional and innovative residential-scale RWH systems. These systems are examined using a patent application search, informal interviews with industry professionals, cost-benefit analysis and a simple multi criteria analysis (MCA). The latter examines the sustainability of the systems, based on a priori social, economic and environmental criteria. Two of the innovative systems are subject to a more detailed analysis and benchmarked against a traditional system. Results of the MCA indicate that the innovative RWH systems achieve better sustainability scores than the traditional RWH with a lower capital cost. Further research is focused on monitoring the identified systems to generate empirical datasets, in order to undertake the WLC/LCAs and to identify challenges associated with installation. © Copyright.

Water Supply and Stormwater Management Benefits of Residential Rainwater Harvesting in U.S. Cities

AbstractThis article presents an analysis of the projected performance of urban residential rainwater harvesting systems in the United States (U.S.). The objectives are to quantify for 23 cities in seven climatic regions (1) water supply provided from rainwater harvested at a residential parcel and (2) stormwater runoff reduction from a residential drainage catchment. Water‐saving efficiency is determined using a water‐balance approach applied at a daily time step for a range of rainwater cistern sizes. The results show that performance is a function of cistern size and climatic pattern. A single rain barrel (190 l [50 gal]) installed at a residential parcel is able to provide approximately 50% water‐saving efficiency for the nonpotable indoor water demand scenario in cities of the East Coast, Southeast, Midwest, and Pacific Northwest, but &lt;30% water‐saving efficiency in cities of the Mountain West, Southwest, and most of California. Stormwater management benefits are quantified using the U.S. Environmental Protection Agency Storm Water Management Model. The results indicate that rainwater harvesting can reduce stormwater runoff volume up to 20% in semiarid regions, and less in regions receiving greater rainfall amounts for a long‐term simulation. Overall, the results suggest that U.S. cities and individual residents can benefit from implementing rainwater harvesting as a stormwater control measure and as an alternative source of water.