Rainwater Harvesting Research Articles

Financing diversified water strategies for megacities: the case of Mexico City and rainwater harvesting

Abstract Megacities are increasingly confronted with water supply challenges, requiring innovative and diversified management strategies to ensure sustainability. This study examines Mexico City’s Cosecha de Lluvia program, a government initiative promoting residential rainwater harvesting (RWH). This case study offers valuable lessons for other megacities facing similar water security issues. The study particularly explores result-based financing (RBF) as a promising strategy to strengthen Mexico City’s RWH sector. Despite its potential, research on RBF for water supply diversification remains limited, especially from the perspective of practitioners. To address this gap, the study employs a systems thinking approach supported by qualitative methods, including a literature review and interviews. Thematic networks analysis revealed that RBF could enhance Cosecha de Lluvia by improving monitoring and results measurement, facilitating information exchange, and increasing transparency—key factors for successful water supply diversification. While these identified benefits do not address all of Cosecha de Lluvia’s challenges and RBF could have implementation challenges, there is a clear opportunity for this financial mechanism to enhance programs like the one studied and have a positive impact on several of its elements. As part of the RBF suitability assessment, three different funding sources were evaluated—public, private, and philanthropic—to determine their effectiveness in overcoming Cosecha de Lluvia’s challenges. The findings suggest that no single source of finance markedly influences the program’s effectiveness alone. Instead, a blended financing approach that integrates all three sources is recommended as a strategy to explore further for implementing RBF in water supply diversification efforts. Overall, the study highlights the necessity of diversifying water supply to build climate resilience in megacities. While programs like Cosecha de Lluvia are crucial, significant room for improvement exists. RBF offers a promising mechanism to enhance such initiatives, and its potential merits further exploration.

Water drop transportation on wettability switchable surface via anisotropic molecules

Active control of the transportation of liquid drops on a horizontal surface is achieved using surfaces with switchable wettability via remote stimuli. However, the mechanism how the dynamic wettability influences drop dynamics is rarely reported. In this paper, we demonstrate that a surface with switchable wettability induces depinning of the contact line through re-orientation of anisotropic molecules. We investigated the dynamics of contact lines and contact angles during the initiation of drop movement by the advancing and receding angles of the surface. We found that imbalance between advancing and receding angles with respect to the dynamic contact angle provides the force needed to overcome the energy barrier due to contact angle hysteresis on the surface. We discovered that the driving energy is accumulated with oscillations in contact angle until it breaks the pinning energy barrier. Understanding the role of dynamic contact angles in drop movement on switchable surfaces paves the way for designing effective fluid manipulation devices, such as water harvesters, biosensors, and oil–water separators.

Salinity challenges and adaptive strategies in salinization-affected coastal Bangladesh: Implications for agricultural sustainability and water resource management

Abstract Salinization has become a rising global concern due to its notable effects on agriculture and freshwater resources. Coastal region of Bangladesh has been struggling with elevated levels of soil and water salinity, exacerbated by storm surges and rising sea levels. We assessed nutrient and salinity contents in agricultural and homestead lands, and the level of salinity in pond and canal water in six sub-districts in coastal Bangladesh. Finally, using household (HH) survey, focus group discussion (FGD) and key informant interview (KII), we explored the adaptive practices and challenges of salinity issues in agriculture and drinking water management. Soil nitrogen, phosphorus, and potassium contents exhibited significant variations across the sub-districts, which reflect the diversity of agricultural practices and soil management strategies. However, there was no notable difference in soil salinity across the sub-districts, which underscores the commonality of soil salinity as a pressing concern. Shyamnagar (13.99 dS m−1) recorded the highest level of pond water salinity, followed by Assasuni (13.96 dS m−1), Dacope (13.91 dS m−1), Koyra (13.58 dS m−1), Morrelganj (13.33 dS m−1), and Mongla (13.19 dS m−1) sub-districts, which highlights that water salinity decreased from exposed coast to the landward areas. Respondents in HH surveys, FGDs and KIIs identified salinity as a major challenge in agriculture and drinking water. Furthermore, climate-related stresses were recognized as significant challenges impacting crop productivity. The research highlights the feasibility of rainwater harvesting, with 89%–100% of HHs harvest rainwater in HH tanks, as an effective adaptive practice for managing drinking water. The study emphasizes the positive impact of vermicompost in reducing soil salinity levels, which is demonstrated by the 43%–88% of HHs using this practice, indicating its potential as a nature-based solution to address soil salinization. The findings underscore the need for resilient agricultural systems and sustainable water management approaches to tackle these challenges.

Enhanced Hydrophilicity of DAAQ-TFP COFs via Sulfonate Modification for Air Water Harvesting in Arid Environment.

The poor ability of covalent organic frameworks (COFs) based adsorbents at low relative humidity (RH) conditions limits their applications for air-water harvesting in arid environments. In the present work, the sulfonated COFs (DAAQ-TFP-SO3H@LiCl) composites are prepared through the functionalization of sulfonic acid and LiCl composite to improve its hydrophilicity. TheDAAQ-TFP-SO3H@LiCl composites exhibit a good adsorption performance, outperforming many other COF adsorbents developed so far. It can absorb 0.22±0.005g g-1 and 1.01±0.027g g-1 of water at room temperature under 20% RH and 90% RH, respectively while demonstrating good cyclic stability. Compared with the isotherm of the DAAQ-TFP, the introduction of the sulfonic acid group shifts the inflection point of the water isotherm toward low humidity, indicating that the sulfonic acid group effectively expends the working humidity range of the adsorbent and enables the effective water adsorption in an arid environment. Furthermore, the DAAQ-TFP-SO3H@LiCl composites display rapid kinetics during both the adsorption and desorption processes, reaching saturation within 60min in the equilibrium adsorption test and completing desorption within 12min at 50°C. This innovative approach provides a new method for designing adsorbent materials with low energy input requirements and high daily water consumption capabilities.

Sustainable Water Conservation Techniques for an Office Building

The research paper titled "Sustainable Water Conservation Techniques for an Office Building" explores methods to reduce water consumption and promote sustainable practices in office buildings. The study focuses on the rising global water crisis due to population growth and increasing urbanization, advocating for the reuse of rainwater and wastewater as alternatives to conventional water sources. Key objectives include assessing current water distribution systems, comparing existing water management techniques, and proposing sustainable water-saving measures. By integrating solutions such as water-efficient fixtures, greywater recycling, and rainwater harvesting, the study aims to significantly reduce water demand and operational costs, contributing to long-term sustainability​.

Extremely Fast Wicking Self‐Layered Interpenetrating Network Hydrogel for Rapid All Day Collection of Atmospheric Water

AbstractHygroscopic salt hydrogel photothermal composites and related technology are a promising pathway for water harvesting. However, due to the overly cumbersome preparation process, the distribution of the surface photothermal layer is difficult to control and the photothermal efficiency is low. In this paper, a method is proposed to greatly simplify the preparation process of photothermal layer hydrogels and improve their atmospheric water harvesting performance by constructing temperature‐sensitive interpenetrating networks. Due to the decomposition of some reversible hydrated structures in the network during heating and warming, carbon nanotubes move autonomously to form a layered structure with a photothermal effect on the upper surface, which can return to its original state after cooling and remain stable at room temperature or under solar illumination. Compared with hydrogels with general layered structure or overall distribution of photothermal materials, agar/GG/PAM/CNT hydrogel has faster moisture adsorption efficiency and higher desorption efficiency, and during the 24 h continuous sorption–desorption cycle is capable of achieving high water yield of 2.57 Lwater kgsorbents−1 day−1, superior to most recent hydrogel adsorbents. Simplifying the preparation process while maintaining high efficiency, while greatly improving photothermal performance, paves the way for cost‐effective mass production applications for a wide range of hygroscopic salt‐hydrogel photothermal composites.

Analysis of Rainwater Quality and Temperature Reduction Effects Using Rainwater Harvesting Facilities

As eco-friendly complexes develop, interest in eco-friendly facilities is also growing. Particularly, rainwater harvesting facilities have demonstrated positive effects by reducing runoff to mitigate urban flooding and recycling water for landscaping and cleaning purposes. In this study, we analyzed the quality of stored rainwater, which has improved by excluding initial runoff, and examined the temperature reduction effects of road sprinkling and mist spraying. Road sprinkling decreased the temperature of asphalt and permeable pavements by approximately 15 °C, with permeable pavements maintaining the reduced temperature for a longer time. The indoor experiments with mist spraying showed a temperature reduction effect of 3.4 °C. The quality analysis of the rainwater harvesting facilities revealed that the water quality was suitable for irrigation and landscaping by excluding the initial runoff. This study confirms the effectiveness of rainwater utilization in mitigating urban heat islands and improving water circulation within cities.

Rainfall water collection and irrigation via stone bud and karren on karst rocky desertification slopes: Application and benefit analysis

Lack of surface water is a key factor leading to agricultural drought in karst regions and exacerbates the karst rocky desertification, which is characterized by high rate of exposed bedrock. With the characteristics of impermeability, runoff collection, and wide distribution, stone bud and karren (SBK), a unique karst landscape type composed of exposed bedrock and gullies, has a great potential to solve water shortage in agricultural irrigation, especially in the rain-rich karst regions of Guizhou Province, China. Using unmanned aerial vehicle images to identify SBK and measured rainfall–runoff data for validation, we applied SBK as a basic unit to harvest rainfall water on rocky desertification slopes and analyzed the benefits of rainfall water collection and irrigation via SBK. The results showed the following: (1) Karrens on rocky desertification slopes could be identified using a method coupling terrain opening difference and depression filling, and the simulated runoff on SBK could achieved the average NSE and R2 of 0.82 and 0.86, with RMSE and RSR less than 0.03 m3 and 0.51, respectively. (2) The exposed bedrock utilization rate and rainfall water collection coefficient of SBK were 0.62 and 0.55, respectively, such that the area ratio of exposed bedrock to the cultivated land meeting irrigation water demand reached 1:3.1, 1:3.7 and 1:7.0 under 90 %, 80 % and 50 % possibilities of irrigation. (3) Implementing SBK for rainfall water harvesting and irrigation could efficiently avoid crop failure in the karst regions where crops faced drought within only one week after rainfall, and was at an affordable cost to local farmers with limited environmental damage. The use of SBK to harvest rainfall water could also alleviate surface water shortages in karst regions caused by problems such as uneven temporal distribution of rainfall and engineering water shortages. Consequently, SBK demonstrate a strong application potential to alleviate agricultural drought in karst rocky desertification regions.

Nanoporous MOF-303 Performance for Atmospheric Water Harvesting in the Presence of Airborne Contaminants: GCMC and DFT Simulations

Nanoporous MOF-303 Performance for Atmospheric Water Harvesting in the Presence of Airborne Contaminants: GCMC and DFT Simulations

Site selection and storage system design for rainwater harvesting with artificial recharge based on hydrogeological and socio-economic consideration in qualitative and quantitative water-stressed areas of North 24 Parganas, India

Site selection and storage system design for rainwater harvesting with artificial recharge based on hydrogeological and socio-economic consideration in qualitative and quantitative water-stressed areas of North 24 Parganas, India

Continuous and multicyclic sorption-based atmospheric water harvesting with heat recovery in arid climate

Nowadays, two-thirds of the global population are grappling with water scarcity. Sorption-based water harvesting (SAWH), which does not depend on conventional water sources and provides decentralized clean water, is steadily gaining popularity. However, the contradiction between the low daily water production in arid climates and the high energy consumption of large-scale devices has become a pivotal limitation for efficient water harvesting. Here, we report a multicyclic SAWH device with heat recovery equipped with 3 sorbent beds that alternatively desorb in automatic switching mode to achieve all-day continuous water harvesting. Furthermore, based on the rapid sorption and desorption kinetics of the adsorbent in the initial stages, employing a rapid-cycling operation strategy contributes to realize an outstanding water productivity of 8.07 kg day−1 and 0.21 kg kgsorbent−1 day−1 under practical arid conditions (15 °C/25 % RH). Besides, the apparatus equipped with heat regenerator showed a significant decrease in energy consumption from 12.17 kWh to 10.65 kWh during a desorption cycle (4 h). Moreover, a hybrid desorption mode driven by a combination of solar collector and electric heater is demonstrated in an island. This SAWH system is anticipated to provide a promising approach for large-scale efficient water harvesting in all-day arid regions (RH<35 %).

A top-down spatial scenario approach for identifying the locations of rainwater harvesting sites in an urban region.

Alternative water sources are necessary in developing nations because surface water is not always accessible, and groundwater is depleted. In such situations, rainwater harvesting is considered a promising sustainable water resource management solution. Numerous studies have been conducted to determine suitable locations for rainwater harvesting (RWH) using bottom-up approaches applied to large watersheds. The bottom-up methods begin with various geographic criteria and end with regions suitable for RWH intervention, even considering the distance from settlements to be one of the criteria, excluding urban areas from RWH site identification. This study developed a top-down methodology that began with the distributed pinpoint locations of potential RWH sites, as determined by distributed flow accumulation values produced from a digital elevation model (DEM), and then filtered out the sites based on various criteria in the context of urban areas. The flow accumulation values were apportioned according to the flow-contributing area of each RWH site. Five flow-contributing areal scenarios corresponding to 1 km2, 2.5 km2, 5 km2, 7.5 km2, and 10 km2 were considered in this study, as it is challenging to choose a suitable location for RWH sites in urban zones for efficient water storage owing to a variety of land uses. Based on this technique, a case study was conducted in Jaipur, Rajasthan, India, where it was found that the volumetric potential of rainwater storage is maximum (403,679,424.9 cu. m) for 1 km2 and minimum (169,951,322 cu. m) for 10 km2 flow contributing areal distribution per RWH site.

The Adoption and Impact of Climate-Smart Water Management Technologies in Smallholder Farming Systems of Sub-Saharan Africa: A Systematic Literature Review

Agriculture plays a significant role in global water consumption, accounting for approximately 70% of the world’s freshwater usage. This makes this sector a critical factor in the depletion of water resources. Accordingly, this paper explores potential mitigatory impacts of climate-smart water management (CSWM) technologies in sub-Saharan Africa. About 70% of the population in sub-Saharan Africa is dependent on agriculture for sustaining their livelihoods. This is despite the low agricultural output in smallholder farming systems (SFS) due to water scarcity. This has spurred several attempts to promote the adoption of climate-smart agriculture (CSA) to raise agricultural outputs and improve smallholder farmers’ livelihoods. However, there has not been a comprehensive analysis of data categorised by various aspects of climate-smart water management technologies. In this systematic literature review, climate-smart water management technologies in sub-Saharan Africa’s agricultural sector were identified and analysed to determine strategies that could enhance their adoption and impact. To this end, academic articles reporting on the adoption of climate-smart water management technologies in databases were reviewed. Four significant literature databases were used. These were limited to Springer Link, ScienceDirect, MDPI, Wiley Online, and Google Scholar. The findings demonstrate that rainwater harvesting and micro-irrigation are the primary climate-smart water management technologies used by smallholder farmers. The literature review shows that adoption of CSWM practices is constrained by inadequate technological infrastructure, financial implications, unsuitable policies, and low user skills, particularly. It is therefore recommended that government agricultural departments and relevant advocates of CSA should incentivise and subsidise smallholder farmers to encourage CSWM technology adoption. This can be achieved through the implementation of suitable policies directed at technological infrastructure development, financial support for adoption, and technical skills training.

Sustainable Development of Agro-Based Industries and Agricultural Practices: An Analytical Study of Rajasthan

Background: Agriculture plays a pivotal role in Rajasthan's economy, supporting a significant portion of the population. However, the sector faces numerous challenges, including water scarcity, soil degradation, and climate change impacts. This study investigates the sustainable development of agro-based industries and agricultural practices in Rajasthan, analyzing current practices, challenges, and potential solutions. Materials and Methods: The research employed a mixed-methods approach, combining qualitative interviews and focus group discussions with a quantitative survey of 500 participants across various districts of Rajasthan. Data were collected on agricultural practices, challenges faced by farmers, and perspectives on sustainable development. Statistical analysis was performed using SPSS, while qualitative data were analyzed through thematic analysis. Results: The study revealed a blend of traditional (68% using rainwater harvesting) and modern (42% adopting precision farming) agricultural practices. Water scarcity emerged as the most critical challenge, reported by 85% of farmers. Sustainable strategies showed promising results, with organic farming increasing income by 20% and water-efficient irrigation reducing water usage by 40%. Agro-based industries, particularly food processing and textiles, contributed significantly to the state's economy. Conclusion: The findings underscore the need for integrated approaches to address water scarcity, promote sustainable farming practices, strengthen agro-based industries, and enhance farmers' access to markets and credit facilities. Policy recommendations include prioritizing water management, climate change adaptation, and farmer education to ensure a sustainable and resilient agricultural future for Rajasthan

Assessment of the impact of greenhouse rainwater harvesting managed aquifer recharge on the groundwater system in the southern Jeju Island, South Korea: Implication from a numerical modeling approach

Managed aquifer recharge (MAR) is increasingly being adopted worldwide to mitigate groundwater depletion and ensure the sustainability of water resources. Rainwater harvesting (RWH)-MAR can augment aquifer storage and reduce flood damage in rural areas with dense greenhouse facilities. This study has assessed the feasibility of greenhouse RWH-MAR in Namwon agricultural areas in the southern part of Jeju Island, South Korea, by considering the injection rate and location of MAR using a numerical model. The model results showed that groundwater level increases were directly related to the infiltration rate, although spatial differences in head rise were observed owing to the spatial variability of hydraulic conductivity. In addition, installing the RWH-MAR in highland areas (>100 masl) enhanced the water level rise when compared to the expected values, indicating that a higher hydraulic gradient and thick unsaturated zone facilitated more effective MAR outcomes than in lowland areas. To optimize the contribution of source water to the agricultural water demand, placing the RWH-MAR near the pumping well improved the availability of injected rainwater to agricultural wells. This study highlights the importance of designing RWH-MAR schemes considering MAR objectives and the topographic and hydrogeological characteristics of the site.

The Potentiality of Eco-Library Design in Medan City Towards Sustainability Development

Abstract Sustainable development has become an important concern over the last three decades. The Eco-library design concept has gained popularity due to its environmentally friendly approach. However, the government and citizens of Medan must continue discussing this matter. The library serves as an information hub, significantly promoting sustainable development. This study investigates the benefits of the green building concept and the design strategy for the Eco-Library in Medan City through literature reviews, interviews, and questionnaires distributed to local visitors and experts. In the past, the conventional library used only an air conditioner to maintain its collection, contributing to high electricity expenses. By analysing the context of climate of Medan city, this paper demonstrates how the concept of Eco-Library can reduce negative environmental impacts through the use of sustainable materials, renewable energy sources, solar panels, rainwater harvesting, floating boxes concept, motion-sensor lighting systems, and eco-friendly air conditioners. Contemporary tropical architecture was utilized in the design of this Eco-Library, which includes an overhanging roof and a double facade-oriented east and west, with the longest side facing north and south. In addition, encouraging the use of rooftop gardens in Medan can help reduce indoor heat and air pollution.

Integrating atmospheric water harvester with hydrovoltaics: Simultaneous freshwater production and power generation

Integration of an atmospheric water harvester (AWH) with hydrovoltaic (HV) technology poking a new technology and notification to the arid region people to harvest freshwater and electricity simultaneously from the humid atmosphere even in the non-water region. In this work, we have fabricated a composite material by attaching the sulfonic groups to the graphitic oxide substrate (SGhO) through a one-step reflux method. The material delivers an excellent water absorbing ability of 0.3 g g−1h−1and 2 g g−1in 19 h under a 40–60 % humid environment. The electrical experiments show during moisture absorption, a specific voltage and current are generated indicating the dissociation of sulfonic groups in the graphitic structure creates a drift movement of H+ions through the composite. Our device delivers a voltage of 0.25 V and a high current of 160 µA from a single device during moisture movements through the structure under the relative humidity of 60–65 %. The rapid enhancement of the interfacial temperature from 31 °C to 44 °C within a minute due to the presence of graphitic oxide shows excellent photothermal capacity for the light-induced evaporation mechanism and collecting the condensed water as freshwater. The composite can evaporate all absorbed water within 0.5 h in one sun illumination (1 kW/m2) under the ambient relative humidity (RH) of 40–60 %. Several trials of washing treatments were done to ensure the chemical bonding of sulfonic groups into the graphitic structure. Therefore, it was confirmed the excellent stability, and repeatability for repeatable practical applications. Furthermore, the purity of the collected water is conducted with various analyses such as pH, TDS, and UV–Vis absorption studies and confirmed the excellent purified water which highly meets the global drinking water standards. Therefore, this work demonstrates a single way to achieve dual goals such as water harvesting as well as power generation for a better tomorrow.

Capillary rise on rounded polygon corners of pillar and array structures

Capillary rise, where liquid climbs narrow spaces against gravity, plays an important role in both natural and technological processes. This study investigates capillary wetting in rounded polygon corners, a less-studied area in microfluid mechanics with significant implications for industries such as nanotextured surface cleaning, micro-soldering, food technology, and water harvesting. Through experimental analysis, we examine the relationship between capillary rise height and the geometric parameters of curvature radius and angle in rounded polygonal pillar and array structures. Our findings reveal a direct correlation where the capillary rise height increases as the radius of the corner increases, emphasizing the critical role of corner geometry in enhancing capillary action. This research not only deepens understanding of capillary behavior in complex geometries but also provides valuable insights for optimizing capillary-based applications across. By considering the influence of geometric complexity on capillarity, our study paves the way for innovative approaches in the design and development of efficient systems for fluid manipulation and control.

Fresh water production via atmospheric water harvesting using solar energy for green hydrogen production

Abstract Solar energy is used to drive an atmospheric water harvesting unit to produce fresh water needed for the electrolysis process to produce hydrogen, as well as to drive the electrolyzer. So, the system can be considered as a solar powered hybrid system for fresh water harvesting and green hydrogen production implementing the electrolysis concept. Implementation of the system specially in arid regions with high levels of water scarcity and high relative humidity levels helps in achieving SDGs 3, 7, 9, and 13 progressively, improving health and wellbeing, reducing water scarcity, using clean renewable energy, and limiting climate change. The system is proposed and investigated for the production of both fresh and clean water and green hydrogen gas. To improve the productivity of the overall system, performance enhancement of the atmospheric water harvesting subsystem is experimentally investigated to assure the reliability and continuous operation of the overall green hydrogen hybrid system. It was investigated in summer and winter using different number of porous sheet metals with the silica gel bed. The results show that the productivity of the atmospheric water harvesting system can be increased by a minimum of 6% with one mesh metal sheet and 30% with two meshes, and increases by a maxinmum of 60% with one mech and 260% with two meches.

Enhancing wetting and adhesion of stainless steel (SS304) surfaces with dielectric barrier discharge (DBD) plasma jet treatment

Enhancing the adhesion of coatings to metallic surfaces can be achieved through decontamination and increased surface energy. Among the various techniques used for functionalizing metallic surfaces, such as chemical etching, laser etching, flame treatment, and ultraviolet radiation; dielectric barrier discharge (DBD) plasma stands out as a promising option. It offers low-power, cost-effective, room-temperature operation and provides treatment with minimal alteration of subsurface properties. This study investigates using a DBD plasma jet to increase the treatment area, surface wettability, organic decontamination, and paint adhesion on stainless steel (SS304). The impact of different plasma treatments and aging times on the liquid contact angles and corresponding surface energies are experimentally examined. The results indicate that the surface energy of SS304 increases with treatment time. X-ray photoelectron spectroscopy (XPS) measurements are carried out to correlate this increase in surface energy to an increase in oxide bonds and decontamination of organic species, resulting in surface activation. However, it is observed that the plasma-treated surfaces exhibit no significant alterations in surface morphology, as confirmed through analyses of surface roughness and micro-hardness. Cross-hatch adhesion tests are carried out to demonstrate that the plasma surface treatment results in a significant improvement in surface adhesion to external coatings. Furthermore, the study evaluates the impact of DBD plasma jet treatment speed and dose on coating adhesion, providing valuable insights for making a trade-off between treatment quality and energy efficiency. The findings could extend the applicability of the DBD plasma jet to various areas, including anti-fogging surfaces, water harvesting, paints and coatings, and organic decontamination of surfaces.