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Rapid and even disruptive innovations are needed to make cities fit for the future. The particular challenge will be to transform existing urban spaces in order to increase climate resilience. Along these lines, rainwater harvesting has taken place insufficiently to date, even when Sponge City concepts are implemented. Thus, the concept presented here addresses existing urban neighborhoods and proposes to collect rainwater from nearby rooftops and treat it in decentral treatment units called “City Water Hubs” (CWH) equipped with modular coupled low-energy technologies to produce various customized “City Water” qualities, and store it until it can be used or distributed. A feasibility study with a focus on the campus area at the main building of the Leibniz University of Hannover, the determined rainwater qualities, and the results from investigations with two laboratory test plants provided the basis for the technical design of the pursued concept. The feasibility study showed how sufficient rainwater for irrigation purposes can be made available for the listed large university park even under extreme dry and heat wave conditions. If large portions of the roof area (11,737 m2) of the university’s main building were activated, even in a dry year with only 49.8% of the average precipitation, only 19.8% of the harvested stormwater would be needed for irrigation. The rainwater samples showed TSS concentrations of up to 7.54 mg/L, COD of up to 58.5 mg/L, and NH4 of up to 2.21 mg/L, which was in line with data reported in the literature. The treatment technologies used for the two pilot plants are proven approaches for stormwater treatment and were composed as follows: (1) gravity-driven membrane filtration (GDM) and (2) slow sand filter with integrated activated carbon (AC) layer. The treatment with both (1) and (2) clearly improved the rainwater quality. The GDM reduced turbidity by 90.4% and the Sand/AC filter by 20.4%. With regard to COD, the studies for GDM did not show a clear elimination trend; the Sand/AC filter reduced the COD by 77%. Taken together, decentralized low-energy rainwater treatment can reliably provide quality-assured City Water for any specific use. Regarding the treatment design, GDM is preferable and can be better operated with downstream UV disinfection, which might be needed to reduce the pathogenic load, e.g., for local heat control measures. The research steps presented here will pioneer the development of a city-wide rainwater harvesting infrastructure on the way of establishing stormwater as a resource for a new wing of urban water supply. The presented findings will now result in the implementation of a full-scale CHW on the campus to ensure long-term irrigation of the listed park, relieving the public drinking water supply.

Flooding is one of the climatic change consequences that has become a dangerous threat to many coastal cities. Pervious concrete is considered a solution to decrease rainwater runoff and mitigate flood effects, as it allows water to percolate through the ground and prevent possible damage. Using waste products as aggregates in pervious concrete not only exploits waste materials and makes it valuable but also reduces the amount of this waste ending in the landfill or harming the environment, and it decreases the demand for natural resources. Infiltration rate test and compressive strength tests were conducted to investigate the effect of using waste plastic and/or recycled rubber as concrete coarse aggregates with different ratios (5%, 10%, 15%, 20%, and 25%) on the pervious concrete. The results showed that increasing the waste materials in concrete decreased the compressive strength for all ratios while increased the infiltration rate values.

Preventive Drought Management Measures (PDMMs) aim to reduce the chance of droughts and minimize drought-associated damages. Selecting PDMMs is not a trivial task, and it can be asserted that actual contributions to drought alleviation still need to be adequately researched. This study evaluates the effects of three potential PDMMs, namely, rainwater harvesting ponds, forest conservation, and check dams, on agricultural and hydrological drought severity. The Soil Water Assessment Tool is used for hydrological modeling and representing PDMMs. The threshold level method is applied to analyze droughts and evaluate the impact of PDMMs on drought severity. Findings show that rainwater harvesting ponds applied on agricultural land reduce the severity of agricultural droughts and hydrological droughts, particularly during the first months of the drought events observed in the rainy season. Results also reveal that forest conservation contributes to reducing the severity of hydrological droughts by up to 90%. Finally, check dams and ponds in upstream subbasins considerably reduce agricultural and hydrological drought severity in the areas where the structures are applied; however, they exacerbate drought severity downstream. The analysis was developed in the Torola River Basin (El Salvador) for the period spanning 2004 to 2018.

Rainwater harvesting attracts rising interest in solving the new challenges associated with climate change and socio-economic development. Rainwater harvesting is addressed in various policies, but standards related to the harvested rainwater quality (HRWQ) are currently set mostly for reuse for agricultural purposes. This paper discusses the necessity for the introduction of specific legislative requirements for the HRWQ tailored to the reuse purpose, which would reduce the health and environmental risks. Based on a literature review of research outcomes regarding HRWQ parameters and existing legislation, the paper discusses the complexity of the factors influencing HRWQ and provides some thoughts for possible actions forward that could be undertaken toward the development of specific legislation. The actions include the application of a risk-based approach, the development of a database and guidance with technological solutions.

The aim of this study was to determine the suitability of a rainwater harvesting system to cover the water demand for indoor hydroponic lettuce cultivation located in Wrocław (Poland). The analysis was performed on the basis of the recorded rainfall in Wrocław in 2000&ndash, 2019. The analyzed cultivation is located in a hall with an area of 300 m2, where the lettuce is grown vertically by the hydroponic method. The calculations of the rainwater harvesting (RWH) system were carried out considering the selection of the tank capacity for the collected water. The operation of the water storage is simulated using a yield after spillage (YAS) algorithm. It was evident that the proposed system might be an auxiliary system that relieves the water supply network or supports other water recovery systems (e.g., the water vapor condensation in a cross-flow heat exchanger operating as an element of the air conditioning system, proposed in Part 1 of this study). The harvesting system for the selected vertical farming indoor hall covers an average of 35.9% of water needs and allows a saving of 146,510 L of water annually for the cultivation. An average water demand coverage increases up to 90.4%, which allows a saving of 340,300 L per year when the RWH system is combined with water recovery from exhaust air from the hall.

The increasing population and urban sprawl will continue to add significant pressure to natural resources in arid and semi-arid zones. This study evaluates the theoretical effectiveness of adapting resilient strategies such as water conservation and green infrastructure to mitigate the water scarcity faced by the inhabitants of a residential area with a semi-arid climate. Three scenarios were analyzed at a micro-basin level to determine the mitigation of surface runoff and the volume that can be theoretically intercepted for further use: (a) unaltered natural watershed (scenario 1), (b) currently urbanized watershed (scenario 2), and (c) watershed adapted with resilient strategies (scenario 3). For this last scenario, the annual usable volume of rainwater intercepted on the dwelling rooftops was obtained. The runoff and peak flow in the natural watershed were lower than in the other two scenarios. In contrast, a decrease in the runoff was observed in scenario 3 concerning scenario 2, which indicates that the interception of rainwater on house roofs and the adoption of green infrastructure solutions would significantly reduce the diameter of urban drainage pipes required in new developments, as well as the dependency of inhabitants on potable water services. In sites with semi-arid climates, it is possible to take advantage of the rainwater harvested on rooftops and the runoff intercepted through green infrastructure to mitigate local water scarcity problems, which should be considered and adopted in new residential developments.

Zero-emission technology for palm oil mill effluent (POME) has led to a breakthrough in the palm oil industry in relation to the goal of sustainable development. However, there are limited resources on how this technology has affected the bacterial community in the receiving river that has previously been polluted with POME final discharge. Thus, the current study assessed the recoverability of the unexplored bacterial community in the receiving water of a constructed river water system post-zero emission of POME final discharge. An artificial river water system was constructed in this study, where the viability status and the composition of the bacterial community were assessed for 15 days using a flow cytometry-based assay and high-throughput sequencing by Illumina MiSeq, respectively. The zero-emission of POME final discharge reduced not only the physicochemical properties and nutrient contents of the receiving water, but also the bacterial cells’ viability from 40.3% to 24.5% and shifted the high nucleic acid (HNA) to low nucleic acid (LNA) content (38.7% to 34.5%). The proposed POME bacterial indicators, Alcaligenaceae and Chromatiaceae were not detectable in the rainwater (control) but were detected in the artificial river water system after the introduction of POME final discharge at the compositions of 1.0–1.3% and 2.2–5.1%, respectively. The implementation of a zero-emission system decreased the composition of Chromatiaceae from 2.2% on day 8 until it was undetectable on day 15, while Alcaligenaceae was continuously reduced from 1.2% to 0.9% within that similar time frame. As indicated by principal coordinate (PCO) analysis, the reductions in biological oxygen demand (BOD5) would further diminish the compositions of these bioindicators. The zero-emission of POME final discharge has demonstrated its efficacy, not only in reducing the polluting properties, but also in the bacterial biodiversity rebound in the affected water system.

Mine wastes from the La Aurora mine in the state of Guanajuato were generated by the flotation process and placed in four tailing dumps on the local stream while the plant operated. Given that these wastes contain toxic elements, it is important to establish their impact on the quality of several surrounding natural sources of water that are considered potential drinking water supplies. This study identified four water source types, in which the contents of arsenic (As), mercury (Hg), and thallium (Tl) were exceeded, according to international guideline values for drinking water quality. The first type of aqueous sample corresponded to leachates produced by rainwater infiltration in tailings and water–mineral waste interactions. The second type corresponded to surface water along the Xichú and La Laja Streams, and the third and fourth types involved two groundwater well samples and spring samples, respectively. The Chiquito Stream was used as a reference area that had not been impacted by the mine wastes. The isotopic signatures associated with δ34Ssulfate and δ18Osulfate compositions from the El Ojo de Agua spring are similar to those of the Santa María River and are different from those of the mine waste leachates. This study shows evidence of the presence of As in the El Ojo de Agua spring, which results from dissolution of secondary mineral phases that were produced by alteration of the mine wastes, which then migrated along the Xichú Stream system until reaching the spring. These As-bearing fine particles are prone to dissolution when in contact with this water source. Principal component analysis revealed that the observed As, Tl, and Hg can be attributed to weathering of the mine wastes. However, the results suggest that a natural contribution of these elements could be associated with rainwater–igneous rock interactions.

Rural areas in southern China receive ample rainfall annually as well as over 1600 h of annual sunshine. Despite a generally severe urban–rural development imbalance, these rural areas feature well-developed basic infrastructure and diverse economic activities. Rural revitalization policies in these areas have emphasized the development of cultural and ecological tourism, which has spurred economic development and given rise to a trend of villa construction. Residential buildings sit on large areas where natural resources are abundant. These advantages are conducive to the development and use of sustainable resources. This study proposes an incentive policy encouraging rural residents to renovate their buildings to include rainwater conservation and solar power generation. The Delphi method, an analytic hierarchy process, and fuzzy logic theory were combined to establish an AI-MCDM model, with applications of artificial intelligence and multiple-criteria decision making. Using Conghua District, Guangdong Province as an example, the study suggested that the model is beneficial to increasing the willingness of rural residents to reconstruct and renovate their residences, promoting the development of a low-carbon ecological region, Wenquan Township. We conducted the Delphi process twice to assess and validate incentives for installing natural resource conservation structures in agricultural areas. Nine criteria were identified, which can be divided into three main dimensions of participation situation, generating capacity, and storage facilities. The proposed AI-MCDM model developed using the Delphi–Fuzzy Analytic Hierarchy Process Model has high objectivity and can support rural areas in developing low-carbon, sustainable characteristics. The findings can serve as a reference for governments formulating incentives to encourage the installation of rainwater conservation and solar energy generation structures by rural households.

Municipalities, their utilities and resource managers are designing and implementing policies and programs toward climate adaptation, which means governing urban water resources differently. Urban water managers are thus expanding their roles and responsibilities through the installation and maintenance of green stormwater infrastructure (GSI) systems. This system expansion is perhaps more striking for water utilities administering GSI-related programs because they acquire a role that has an impact on how residents and neighborhoods will differentially experience the effects of climate change. Through an in-depth qualitative study of a GSI program in Tucson, Arizona, USA, we contribute to the socio-environmental justice framework with specific attention to distributive, procedural, recognition, interactional, and mobility justice. We highlight that a socio-environmental justice approach requires resource managers and decision-makers to recognize and respect the ways in which people’s everyday relationship to water and water infrastructure is impacted by culturally mediated social norms and values, as well as legacies of exclusion and inclusion in urban development and resource governance. Thus, we argue that discussions around water equity in urban water governance need to be placed within a socio-environmental justice framework to address historical inequalities and ensure these are not reproduced through GSI.

Factors affecting rainwater resource management for the present and future include population growth, urbanization, and climate change. Rainwater harvesting (RWH) allows multiple urban water-related issues to be mitigated. In this study, a spreadsheet-based daily water balance model was developed to analyze the existing laws and regulations regarding the storage tank size of RWH facilities. Six buildings at different locations were selected for this study. Two are office buildings, two are school buildings, and two are sports buildings. The term “RWH facility evaluation criteria” is collectively used for rainwater supply satisfaction rate, rainwater guarantee rate, and rainwater utilization rate. A green roof can hold the rainwater for some time, reducing the peak flow and runoff volume. The results provide evidence that, among the selected studied buildings, buildings having a combination of a green roof and RWH facility score the highest in terms of RWH facility evaluation criteria, even though the actual tank size is much smaller than the standard tank size. This is the case with the Yesan County Office, in which a green roof connected to a small (66 m3) rainwater storage tank is installed. As a green roof can decrease the runoff volume, the rainwater can be managed efficiently with less pumping energy and only a small storage tank.

Green Infrastructure measures such as seepage troughs are an integral part of sustainable urban rainwater management. In Austria, seepage troughs are currently almost exclusively produced with a 30 cm thick active soil filter passage made of topsoil. A standard seed mix is used as vegetation, which usually consists of only three different turfgrass species. During a three-year trial, engineered soils with improved properties (increased water storage capacity, infiltration rate and pore volume) were tested for their suitability as seepage troughs compared to topsoil. In addition to the standard turf seed mix, a flowering turf seed mix (34 species) and flowering meadow seed mix (53 species) were applied. The engineered and reference soils were analyzed for infiltration rate, vitality, cover ratio and inflorescence. The results were further assessed with the evaluation chart showing quantitatively the suitability of the tested soils for rainwater management. The investigations showed that engineered soils in combination with flowering meadow seed mix lead to the best results. Therefore, this type of vegetation for seepage troughs is recommended for future applications. The reference alternatives cannot be recommended.

Concerns over freshwater scarcity for agriculture, ecosystems, and human consumption are driving the construction of infiltration trenches in many mountain protected areas. This study examines the effectiveness of infiltration trenches in a subalpine forested catchment in central Mexico, where public and private organizations have been constructing trenches for ~60 years. We rely on empirical data to develop rainfall-runoff models for two scenarios: a baseline (no trenches) and a trenched scenario. Field measurements of infiltration capacities in forested and trenched soils (n = 56) and two years of meteorological data are integrated into a semi-distributed runoff model of 28 trenched sub-catchments. Sensitivity analysis and hydrographs are used to evaluate differences in total runoff and infiltration between the two scenarios. Multiple logistic regression is used to evaluate the effects of environmental and management variables on the likelihood of runoff response and trench overtopping. The findings show that soil infiltration capacity and rainfall intensity are primary drivers of runoff and trench overtopping. However, trenches provided only a 1.2% increase in total infiltration over the two-year period. This marginal benefit is discussed in relation to the potential adverse environmental impacts of trench construction. Overall, our study finds that as a means of runoff harvesting in these forested catchments, trenches provide negligible infiltration benefits. As a result, this study cautions against further construction of infiltration trenches in forested catchments without careful ex ante assessment of rainfall-runoff relationships. The results of this study have important implications for forest water management in Mexico and elsewhere, where similar earthworks are employed to enhance runoff harvesting and surface water infiltration.

Rainwater harvesting is an ancient water management practice that has been used to cover potable and non-potable water needs. In recent years, this practice is adopted as a promising alternative and sustainable source of water to meet irrigation needs in agriculture in arid and semi-arid regions. In the present study, a daily water balance model was applied to investigate the size of rainwater tanks for irrigation use in greenhouse begonia and tomato cultivation in two regions of Greece with significant greenhouse areas. For the application of the water balance model, daily rainfall depth values of a 12-year time series (2008–2020) from representative rainfall stations of the study areas were used, as well as the daily water needs of the crops. The greenhouse roof was assumed to be the water collection area of the rainwater harvesting system with values ranging from 1000 to 10,000 m2. The analysis of the results showed that in the case of the begonia crop, the covered tanks ranged from 100 to 200 m3 per 1000 m2 greenhouse area with a reliability coefficient that ranged from 65 to 72%, respectively, to meet the water needs of plants. Further increase of the reliability coefficient was carried out with disproportionately large volumes of tanks. In the case of the tomato crop, covered tank volumes ranged from 100 to 290 m3 per 1000 m2 of greenhouse area, and had a reliability coefficient of 90% to 100%, respectively, while uncovered tanks had a maximum reliability coefficient of 91% for a critical tank volume of 177 m3 per 1000 m2 of greenhouse area and decreased for any further increase of tank volume.

Wildfires can change ecosystems by altering solutes in streams. We examined major cations in streams draining a chaparral-dominated watershed in the Santa Ynez Mountains (California, USA) following a wildfire that burned 75 km2 from July 8 to October 5, 2017. We identified changes in solute concentrations, and postulated a relation between these changes and ash leached by rainwater following the wildfire. Collectively, K+ leached from ash samples exceeded that of all other major cations combined. After the wildfire, the concentrations of all major cations increased in stream water sampled near the fire perimeter following the first storm of the season: K+ increased 12-fold, Na+ and Ca2+ increased 1.4-fold, and Mg2+ increased 1.6-fold. Our results suggested that the 12-fold increase in K+ in stream water resulted from K+ leached from ash in the fire scar. Both C and N were measured in the ash samples. The low N content of the ash indicated either high volatilization of N relative to C occurred, or burned material contained less N.

This study characterises high-fluoride groundwater in the aquifer system on the flanks of Mount Meru, focusing on parts of the flanks that were only partially or not at all covered by previous research. Additionally, we analyse the impact of rainwater recharge on groundwater chemistry by monitoring spring discharges during water sampling. The results show that the main groundwater type in the study area is NaHCO3 alkaline groundwater (average pH = 7.8). High F− values were recorded: in 175 groundwater samples, the concentrations range from 0.15 to 301 mg/L (mean: 21.89 mg/L, median: 9.67 mg/L), with 91% of the samples containing F− values above the WHO health-based guideline for drinking water (1.5 mg/L), whereas 39% of the samples have Na+ concentrations above the WHO taste-based guideline of 200 mg/L. The temporal variability in F− concentrations between different seasons is due to the impact of the local groundwater recharge. We recommend that a detailed ecohydrological study should be carried out for the low-fluoride springs from the high-altitude recharge areas on the eastern and northwestern flanks of Mount Meru inside Arusha National Park. These springs are extracted for drinking purposes. An ecohydrological study is required for the management of these springs and their potential enhanced exploitation to ensure the sustainability of this water extraction practice. Another strategy for obtaining safe drinking water could be to use a large-scale filtering system to remove F− from the groundwater., info:eu-repo/semantics/published

Water is life, and without water, there would be no civilizations and a vacant Earth. Water is considered an abundant natural resource on the earth. Water covers 3/4 of the surface. However, 97% of the available water on the earth is salty oceanic water, and only a tiny fraction (3%) is freshwater. This small portion of the available water supplies the needs of humans and animals. However, freshwater exists in underground, rivers, and lakes and is insufficient to cover all the world’s water demands. Thus, water saving, water reuse, rainwater harvesting, stormwater utilization, and desalination are critical for maintaining water supplies for the future of humanity. Desalination has a long history spanning centuries from ancient times to the present. In the last two decades, desalination has been rapidly expanding to meet water needs in stressed water regions of the world. Yet, there are still some problems with its implementation in several areas of the world. This review provides a comprehensive assessment of the history of desalination for wiser and smarter water extraction and uses to sustain and support the water needs of the earth’s inhabitants.

In arid areas, the forecast of runoff is problematic for ungauged basins. The peak discharge of flashfloods and rainwater harvesting (RWH) was assessed by the integration of GIS, the RS tool and hydrologic modeling. This approach is still under further improvement to fully understand flashflood and rainwater harvesting potentialities. Different morphometric parameters are extracted and evaluated; they show the most hazardous sub-basins. Vulnerability potential to flooding is high relative to steep slopes, high drainage density, and low stream sinuosity. Using hydrologic modeling, lag time, concentration time, peak discharge rates, runoff volume, rainfall, and total losses are calculated for different return periods. The hydrologic model shows high rainfall rates, and steep slopes are present in the southeastern part of the study area. Low rainfall rates, moderate–high runoff, and gentle slopes are found in the central and downstream parts, which are suitable sites for rainwater harvesting. An analytic hierarchy process is utilized for mapping the best sites to RWH. These criteria use land-cover, average annual max 24 h rainfall, slope, stream order, and lineaments density. About 4% of the basin area has very high potentialities for RWH, while 59% of the basin area has high suitability for RWH. Ten low dam sites are proposed to impact flooding vulnerability and increase rainwater-harvesting potentialities.

The supply of various non-potable water usages based on the harvesting and management of rainwater in urban areas allows to save high-quality water resources for strictly potable use and to limit the squandering of precious freshwater resources. A rainwater harvesting system included in a reconversion project of a former military area located in the town of Genova (Italy) is examined. Rainwater is collected and used for the landscape irrigation of public areas. Three rainwater collection scenarios are considered while varying the size of the storage tank, using daily rainfall data from a local long-term record as the reference rainfall climatology. A behavioural model is adopted to simulate the operation of the rainwater harvesting system and improved with a dedicated algorithm to account for the actual soil water availability for the vegetation and its temporal decay, based on the specific soil type and vegetation. For each scenario/tank size combination, reliability indices are calculated and compared, while the detention time and the annual usage volume per unit tank capacity are used as indicators of water quality deterioration in the tank and the economic benefit associated with the exploitation of the resource. The best solution in terms of rainwater collection scenario and tank size is identified.

Residential areas are important for the underlying surface of a city, and the sponge construction of a residential area is a key topic in sponge city construction. Taking the Zi-Jing community as the research case, the SWMM model was established for simulation, and the rainwater runoff control, collection, and utilization were compared and analyzed before and after the implementation of sponge transformation for the designed rainfall conditions of once in 3, 5, 10, 20, and 50 years. The results showed that the water depth of the four outlet pipes was not a full tube at the first peak time. The full duration time was reduced to 1–5 h at the second peak, and the flow reduction rate at the pipe outlet was between 30% and 100%. The water storage of sub-catchments A1, A3, and A4 increased significantly and continued to increase after the peak rainfall occurred, while that of A2 decreased significantly after the transformation after the transformation. For the whole residential area, the surface runoff decreased by 37–47%, while the surface water storage and infiltration increased by 8–14% and 23–39% respectively after reconstruction. The direct storage volume of rainwater in the four sub-catchment areas was filled at least once above a once in 5 years scenario. The main conclusions were as follows: Sponge transformation in residential areas with 17.46% sunken greenbelt and 40.85% permeable pavement, and the time of the pipe outlet in full status can be shortened by 30–200 min in different rainfall return periods. With the increase in the rainfall return period, the improvement range of the infiltration increased from 23.36% to 39.54%, the improvement range of the storage capacity for rainwater decreased from 14.36% to 8.06%, and the reduction degree of surface runoff increased from 37.73% to 47.43%. The water consumption for flushing is about 30 m3 per day for 1000 people, and the rainwater storage volume of 765 m3 in this study can meet the flushing water demand of 5000 residents in the community for 3–5 days.

The Sustainable Development Goals of the United Nations strive to maximize development needs, while minimizing environmental deterioration, without jeopardizing the needs of future generations. Nevertheless, due to urbanization, the escalating trend in natural-resource use, particularly electricity and water, is currently a crucial challenge for sustainable development. One of the promising options is the smart home, which is an extension of building automation with smart characteristics in monitoring, analyzing, controlling, and cloud computing with networked smart devices. Due to the lack of appropriate infrastructure and conscious consumption, its global adoption in the construction industry remains low. We present a technical feasibility of a multi-functional experimental smart home to support the Sustainable Development Goals of the United Nations in terms of water and energy conservation. The layered architecture of the cloud platform with an application program interface enables seamless integration of heterogeneous smart-home technologies and data sources. Use cases demonstrated its capacity to conserve electrical energy and water resources in support of the United Nations’ Sustainable Development Goals. Aside from that, the smart home’s electricity self-consumption of at least three autonomy days was confirmed with zero emissions and electricity bills, and a reduced supply-water consumption.

Despite the growing interest in implementing sponge cities (SPC), their potential is not yet being tapped in many fast-growing Sub-Saharan African cities. This is remarkable because SPC interventions can contribute considerably to increasing water safety and availability in a city. By means of a three-stage potential assessment, this study provides the first analysis of what concrete options can be identified for implementing the SPC concept in Sub-Saharan cities. The methodology was filled with information obtained especially from expert interviews, literature reviews, and satellite imagery. Thus, the analysis also considers what obstacles impede SPC implementation, and, in particular, what technical and socioeconomic constraints need to be taken into account. The cities of Hawassa (Ethiopia), Beira (Mozambique), Kigali (Rwanda), Ouagadougou (Burkina Faso), and Cotonou (Benin) are examined in detail. Additionally, a local SPC implementation was conceptualized and evaluated for two districts in Ouagadougou and Cotonou. The first finding is that, when geographical and socioeconomic aspects such as climatic patterns, migration flows, health risks, and existing infrastructure are sufficiently taken into account, SPC interventions would massively help African cities to mitigate current and urgent challenges such as water scarcity and urban flooding. In terms of water safety, the second key finding is that rainwater harvesting solutions at the household level could be implemented quickly; however, there would be substantial difficulties such as lack of financing and maintenance as well as claims of ownership, especially in informal settlements and slums. Thus, it seems quite promising to directly strive for a rapid “centralization” of SPC implementation in individual neighborhoods. This neighborhood approach paves the way for SPC measures to receive public acceptance and constant maintenance. When this mosaic of implementations comes together, many individual instances of SPC implementation can help to improve urban resilience and living conditions for the city dwellers as is here demonstrated for the districts in Cotonou and Ouagadougou.

Norfolk Island, like many islands in the subtropical Pacific, is at increasing risk of drought. To test the hypothesis that desalination is the most cost-effective technology for providing potable water during ‘water emergencies’, this study calculated and compared the levelised cost on Norfolk Island of seven ‘centralised’ intervention options and two ‘diffuse’ options for increasing groundwater accessions. Gully dams were the ‘centralised’ intervention option found to have the lowest levelised cost but had the largest percentage reductions in yield (i.e., 39% for 1 ML storage) under a projected drier future climate, greater than twice the percentage reduction in rainfall (16%) but less than the percentage reduction in runoff (44%). Cluster-scale roof-harvested rainwater systems with ‘turkey nest’ earth embankment had the second lowest levelised cost but are probably socially unacceptable due to siting on the community’s premier sporting oval. Desalination had the third lowest levelised cost, followed by the use of existing deep groundwater bores to pump and store water exclusively for use during a water emergency. Although desalination was not the most cost-effective technology, it is likely to be more socially acceptable than the two more cost-effective options. After gully dams, rainwater harvesting intervention options had the second highest proportional reductions in yield under a projected drier future climate (~10%); however, the reductions were less than the percentage reductions in rainfall. The yield from desalination and groundwater were unaffected under a drier future climate projected for ~2060.

This research investigates the effect of heavy rain on highway traffic volume and average speed, and proposes a recharging well harvesting system as an alternative freshwater source in the context of climate change. The Cairo Autostorad highway was taken as a case study. The highway climate data were collected, and traffic was measured using Metrocount equipment during the period from 2008 to 2020. The results show that the studied road is about 12 km long, and about 40 water ponds exist along the route. Each pond has an estimated water volume of 300 m3, and a 30 cm recharging well, with a maximum recharging capacity of 25 m3/h with satisfactory performance, is recommended to be constructed for rainwater harvesting. The recharging wells will clear the ponding volume within 2.5 to 3.5 h after the rainfall has stopped. The design incorporates a 1.2 safety factor against blockage inside the well. In addition, a model was established between the average rainfall depth and the average measured highway speed for the period (2008–2020) during rainy months, indicating an exponential function with a determination factor R2 = 0.7076. The present rainfall (2020) and the representative concentration path (RCP) for 4.5 and 8.5 emissions scenarios were used to simulate the rainfall for future years: the 2040s, 2060s, 2080s, and 2100s. The results show that in the winter season for the current scenario (2020), the average rainfall depth was 45 mm, and the highway speed was 78 km/h. For the RCP 4.5 emission scenarios for the 2040s, 2060s, 2080s, and 2100s, the rainfall depths were 67.8, 126.4, 131.2, and 143.9 mm, and the corresponding reductions in the highway speeds were 23, 34, 35.3, and 36.9%, respectively, compared to the baseline scenario (2020). On the other hand, the RCP 8.5 emission scenarios show a reduction in the highway speed of 23, 34.5, 36.9, and 36.9% for the years 2040, 2060, 2080, and 2100, respectively, due to rainfall depths of 68.7, 128.4, 143.9, and 143.9 mm, respectively. This study helps policymakers to make wise decisions regarding sustainable water resource management and highway traffic problems related to rainwater depths in the context of climate change.

Due to the rapid urbanization in the context of the conventional linear economy, the vulnerability of the urban ecosystem to climate change has increased. As a result, connecting urban ecosystem services of different urban land uses is imperative for urban sustainability and resilience. In conventional land use planning, urban agriculture (UA) and urban stormwater management are treated as separate economic sectors with different-disconnected-ecosystem services. Furthermore, few studies have synthesized knowledge regarding the potential impacts of integration of UA and stormwater green infrastructures (GIs) on the quantity and quality of urban ecosystem services of both economic sectors. This study provides a detailed analysis of the imperative question—how should a city integrate the developments of both urban agriculture and stormwater green infrastructure to overcome barriers while enhancing the ecosystem services? To answer this question, we conducted an extensive literature review. The results show that integrating UA with GIs can enhance urban food production while protecting urban water quality. This paper provides an initial context and mechanisms for future researchers and city planners regarding the manner in which the synergies between UA and stormwater GIs can create greater value for the wellbeing of urban ecosystems and resilience in the circular economy.

Rainwater harvesting (RWH) has been recognized as one of the most reliable and efficient methods for water supply, especially in arid and semi-arid regions (ASARs) facing freshwater scarcity. Nevertheless, due to the inherent uncertainty of input data and subjectivity involved in the selection of influential parameters, the identification of RWH potential areas is a challenging procedure. In this study, two approaches for locating potential RWH sites were implemented. In the first approach, a frequently-used method of the multi-criteria decision analysis and geographic information system (MCDA-GIS) was utilized, while, in the second approach, a novel strategy of integrating the soil and water assessment tool (SWAT) model as a hydrology model into an MCDA-GIS method was proposed to evaluate its performance in locating potential RWH sites. The Mashhad Plain Basin (MPB) was selected as a case study area. The developed potential RWH maps of the two approaches indicated similar patterns for potential RWH areas, in addition, the correlation coefficient (CC) between the two obtained maps were relatively high (i.e., CC = 0.914) revealing that integration of SWAT as a comprehensive hydrologic model does not necessarily result in very different outputs from the conventional method of MCDA-GIS for RWH evaluation. The overlap of developed maps of the two approaches indicated that 3394 km2 of the study area, mainly located in the northern parts, was identified as high-potential RWH areas. The performed sensitivity analysis indicated that rainfall and slope criteria, with weights of 0.329 and 0.243, respectively, had the greatest sensitivity on the model in the first approach while in the second approach, the criterion of runoff coefficient (with weights of 0.358) had the highest impact. Based on results from the identification of the potential locations for conventional RWH techniques, pond and pan techniques are the most proper options, covering high-potential areas of RWH more effectively than other techniques over MPB.

Rainwater harvesting (RWH) is generally perceived as a promising cost-effective alternative water resource for potable and non-potable uses (water augmentation) and for reducing flood risks. The performance of RWH systems has been evaluated for various purposes over the past few decades. These systems certainly provide economic, environmental, and technological benefits of water uses. However, regarding RWH just as an effective alternative water supply to deal with the water scarcity is a mistake. The present communication advocates for a systematic RWH and partial infiltration wherever and whenever rain falls. By doing so, the detrimental effects of flooding are reduced, groundwater is recharged, water for agriculture and livestock is stored, and conventional water sources are saved. In other words, RWH should be at the heart of water management worldwide. The realization of this goal is easy even under low-resource situations, as infiltration pits and small dams can be constructed with local skills and materials.

In the urban drainage system, the formation of sewer sediments is inevitable, and the removal of sewer sediments is necessary for system maintenance. Disposal of arisings from sewer sediment removal is becoming a serious environmental issue. The current knowledge of sewer sediments is limited, which is restrained to sewer sediments management. To better understand this municipal waste, the sewer sediments of a combined sewer system in Longgang District, Shenzhen were collected and characterized, and the spatial distribution characteristics of contaminants were analyzed. Based on the bivariate correlation analysis, it is found that many contaminants in sewer sediments have a strong relationship with spatial variables. Compared to the sewer sediments in industrial areas, those in residential areas contain higher concentrations of Hg and phosphorus. The sediments in the sewage conduit also contain more organic matter (OM), phosphorus, Cu, and Ni, and the sediments in the rainwater conduit contain a higher concentration of Cd. Moreover, the sediments produced in different catchments also show huge differences in the content of contaminants. These spatial distribution characteristics may provide help for the further classification of sewer sediments, thereby making the disposal of sediments more targeted. According to the local standards of sludge disposal, land application and incineration are not suitable for managing sewer sediments due to the low OM content and poor lower heating value (LHV). Although sanitary landfill is feasible for sewer sediments disposal, the complicated composition of sewer sediments still poses the risk of polluting the surrounding environment. The management of sewer sediments via the production of building materials is a promising technical route that can avoid the migration of hazardous contaminants and produce valuable products. This study may improve our understanding of sewer sediments and provide a reliable recommendation for sewer sediment management.

Vertical greenery systems (VGS) are promoted as a nature-based solution to mitigate the urban heat island effect. In order to ensure the long-term provision of this function, sufficiently available irrigation water is the key element. Currently, potable water is one of the main resources for irrigation of VGS. While rainwater is often mentioned as an alternative, only a few studies investigate the actual application of rainwater for irrigation. In this study a conceptual model is developed to present the processes and influencing factors for a holistic investigation of rainwater use for irrigation. In this model, five sub-modules are identified: the atmospheric, hydraulic, quality, rainwater harvesting and VGS sub-module. The conceptual model depicts which processes and influencing factors are involved in the water demand of VGS. Thus, the conceptual model supports a holistic understanding of the interrelations between the identified sub-modules and their relevance for VGS irrigation with harvested rainwater. The results of this study support the implementation of rainwater harvesting as a sustainable resource for VGS irrigation.

Nowadays, the rapidly growing population, climate change, and environment pollution put heavy pressure on fresh water resources. The atmosphere is the immense worldwide and available water source. The Adsorptive Water Harvesting from the Atmosphere (AWHA) method is considered a promising alternative to desalination technologies for remote arid regions. The development of novel adsorbents with advanced water-adsorption properties is a prerequisite for practical realization of this method. Metal–organic frameworks (MOFs) are a novel class of porous crystalline solids that bring a great potential for AWHA due to their extremely high specific surface area, porosity, and tailored adsorption properties. This work addresses MIL-160 as a water adsorbent for AWHA. The water-adsorption equilibrium of MIL-160 was studied by volumetric method, the isosteric heat of adsorption was calculated, and finally, the potential of MIL-160 for AWHA was evaluated for climatic conditions of the deserts of Saudi Arabia, Mongolia, the Sahara, Atacama, and Mojave as reference arid regions. MIL-160 was shown to ensure a maximum specific water productivity of 0.31–0.33 gH2O/gads per cycle. High fractions of water extracted (0.90–0.98) and collected (0.48–0.97) could be achieved at a regeneration temperature of 80 °C with natural cooling of the condenser by ambient air. The specific energy consumption for water production varied from 3.5 to 6.8 kJ/g, which is acceptable if solar heat is used to drive the desorption. The AWHA method employing MIL-160 is a promising way to achieve a fresh water supply in remote arid areas.

Urban flooding has become a serious but not well-resolved problem during the last decades. Traditional mainstream facilities, such as vegetated roofs, permeable pavements, and others, are effective to eliminate urban flooding only in case of small rains because the water-retaining and detaining capacities of these traditional facilities are limited. Here, we propose a new buffer tank buried in soil to deal with rainwater onsite as peak-flow control for urban flooding mitigation. Experiments showed that the buffer tank intercepts the surface runoff and discharges the intercepted water through a designed outlet orifice. By properly setting the cross-sectional area of the orifice, the tank extends the drainage duration several times longer than that of the rainfall duration. It is found that the buffer tank attenuates the peak flow greater at heavier rain. At small rain (&lt, 2.5 mm), the tank is always unfilled, preserving storage spaces for detaining rainwater in case of heavy rain. The buffer tank is thus greatly helpful to mitigate the flooding problem, avoiding being saturated by small long-lasting rain.

Urban flooding has become one of the most frequent natural disasters in recent years, and the low-impact development (LID) approach is currently recognised as an alternative to traditional grey infrastructure to mitigate the negative impact of urbanisation on hydrological processes. The main objective of the present research was to develop a web-GIS platform in order to assess the impact of LID systems on mitigating urban flooding and to support their implementation at the urban catchment scale. The TRIG Eau platform, developed in the framework of the homonymous INTERREG MARITTIMO IT-FR project, is configured as a web-GIS application of the stormwater management model (SWMM). Urban flood conditions were examined for two case studies in Liguria and Tuscany (IT), where DRWH systems are proposed as a mitigation strategy. The presented results and their visualisation showcase the potential of the TRIG Eau platform to better support the implementation of LIDs. Findings from the flood analysis confirm that even for the 10-year return period event, DRWHs are effective in reducing network stress by more than 70% in cases of empty tanks, thus underlining the need for RTC technology to pre-empty the system.