Urban Water Cycle Research Articles

Mapping 10 m global impervious surface area (GISA-10m) using multi-source geospatial data

Abstract. Artificial impervious surface area (ISA) documents the human footprint. Accurate, timely, and detailed ISA datasets are therefore essential for global climate change studies and urban planning. However, due to the lack of sufficient training samples and operational mapping methods, global ISA datasets at a 10 m resolution are still lacking. To this end, we proposed a global ISA mapping method leveraging multi-source geospatial data. Based on the existing satellite-derived ISA maps and crowdsourced OpenStreetMap (OSM) data, 58 million training samples were extracted via a series of temporal, spatial, spectral, and geometric rules. We then produced a 10 m resolution global ISA dataset (GISA-10m) from over 2.7 million Sentinel optical and radar images on the Google Earth Engine platform. Based on test samples that are independent of the training set, GISA-10m achieves an overall accuracy of greater than 86 %. In addition, the GISA-10m dataset was comprehensively compared with the existing global ISA datasets, and the superiority of GISA-10m was confirmed. The global road area was further investigated, courtesy of this 10 m dataset. It was found that China and the US have the largest areas of ISA and road. The global rural ISA was found to be 2.2 times that of urban while the rural road area was found to be 1.5 times larger than that of the urban regions. The global road area accounts for 14.2 % of the global ISA, 57.9 % of which is located in the top 10 countries. Generally speaking, the produced GISA-10m dataset and the proposed sampling and mapping method are able to achieve rapid and efficient global mapping, and have the potential for detecting other land covers. It is also shown that global ISA mapping can be improved by incorporating OSM data. The GISA-10m dataset could be used as a fundamental parameter for Earth system science, and will provide valuable support for urban planning and water cycle study. The GISA-10m can be freely downloaded from https://doi.org/10.5281/zenodo.5791855 (Huang et al., 2021a).

Multi-Isotope Characterization of Water in the Water Supply System of the City of Ljubljana, Slovenia

Urban water supply systems (WSS) are complex and challenging to manage since the properties of water in the WSS change from source to the end user over time. However, understanding these changes requires a more profound knowledge of the WSS. This study describes the urban water cycle within the WSS of Ljubljana, Slovenia, where different water parameters such as temperature, electrical conductivity, total alkalinity, δ2H, δ18O, and δ13CDIC were monitored from September to November 2018. Altogether 108 samples were collected, including from the source (3) and at different levels of the WSS: wells (41), joint exits from water pumping stations (7), reservoirs (22), water treatment locations (2), drinking fountains (13), taps (19) and wastewater system (1). The data show that although the ranges of δ2H and δ18O values were small, each well is represented by a unique fingerprint when considering additional parameters. A statistically significant difference was observed between sampling months, and temperature and most parameters showed higher variability within the wells than across the WSS, suggesting a more unified WSS. Finally, based on δ13CDIC values, a distinction could be made between river/groundwater interactions within the WSS and between shallower and deeper wells and their distance from the river bank.

Understanding the effects of site-scale water-sensitive urban design (WSUD) in the urban water cycle: a review

AbstractWith city growth, the development of vacant or under-used land parcels is becoming more common compared to the past. The current ‘water-sensitive urban design (WSUD)’ approach to such development will improve resource efficiency, liveability, and the amenity of cities, especially natural water systems. However, there is a need to quantify the water performance of site-scale WSUD options, especially about how these options impact the ‘natural’ and ‘anthropogenic’ flows in the urban water cycle. This study reviewed research about site-scale applications, summarizing the urban water cycle studies from before development to after development. Key findings (i) include very big margin was quantified by (a) water retention (30–100%) and (b) portable water demand reduction (18–100%) for selected site-scale WSUD options through six research studies; (ii) still unclear about the selected site-scale WSUD options’ interaction performance in the urban water cycle between each water accounts, and (iii) need to clarify the site-scale WSUD option's contribution under specific rainfall scenarios. In summary, this study aims to review the literature on the urban water cycle; review the effects of site-scale WSUD options in the urban water cycle; review the water mass balance and relevant evaluation application, and highlight the opportunities for the future urban water cycle studies.

ARCHITECTURAL & URBAN PLANNING STRATEGY "SPONGE CITY" AS A MEANS OF FIGHTING THE CONSEQUENCES OF GLOBAL CLIMATE CHANGE

The article sheds light on a number of architectural and urban planning principles of the WSUD (Water Sensitive Urban Design) strategy and the Sponge City concept as the effective means of fighting the effects of global climate change. The global practice of flood control in recent years has led to the emergence of a range of urban strategies that anticipate future flood risks and allow them to be managed more effectively in the context of urban transformation and climate change. Water Sensitive Urban Design (WSUD) is a new paradigm of urban development based on interdisciplinary collaboration between experts in water management, architecture, engineering, urban planning and landscape design, aimed at minimizing the hydrological impact of urban development on the environment. This approach considers all components of the urban water cycle and combines the functionality of water resources management with the principles of urban design. The analysis of successful world practice of implementation of city strategies of struggle against consequences of global climate change is carried out and the potential for its realization in Ukraine is revealed.

Measuring urban water circularity: Development and implementation of a Water Circularity Indicator

Urban Water Management (UWM) involves balancing the inflows and outflows of water such that water entering and leaving the system boundary reduces with time. Several frameworks and indicators have been formulated for UWM with a limited focus to achieve circularity of water flows at all the phases of the engineered urban water cycle. A novel indicator called ‘Water Circularity Indicator’ (WCI) is developed in this study to assess, monitor and improve the circularity of urban water flows. The WCI is derived from Material Circularity Indicator developed by Ellen McArthur Foundation and Granta design. In the current study, WCI is initially validated using 100 scenarios considering the variation of 5Rs, i.e., reduce, reuse, recycle, reclaim and restore. Further, WCI is compared with other indicators focusing on urban water management from the literature. The evaluation of results indicate that WCI correlates with most of the indicators selected for comparison. The WCI uses the water mass balance principle in its derivation and distinctively captures reuse, recycling, reclamation and restoration strategies in a single indicator value compared to other indicators. The WCI provides maximum information in a single indicator value ranging from 0 to 1.0. A higher value of WCI indicates lesser extraction of virgin water resources and wastewater disposal with maximum water circulation within the city under consideration. The novelty of WCI lies in its unique approach of considering all 5Rs and easy interpretation for decision-makers across multiple domains. WCI is recommended to be used by city authorities and policy makers for achieving water goals and for Circular Economy (CE) implementation. Policies can be formulated based on WCI to enhance CE in the water sector and reduce virgin water consumption, ultimately leading to water conservation.

Environmental impact assessment of discharge of treated wastewater effluent in Upper Iskar sub-catchment

The upper Iskar sub-catchment is one of Bulgaria’s most important economic and socially significant water sources because of its role in supplying Sofia with drinking water. Among the critical factors that carry potential high-risk levels for water quality in this hydrosystem are the discharge from the Samokov Wastewater Treatment Plant (WWTP), diffuse pollution from agriculture, and the percolation of untreated sewage from the small villages. In this study, we assessed the effect of treated wastewater effluent on water quality, and on the ecological state and microbial communities in the river sector of Samokov’s WWTP discharge area. The assessment was based on the complex use of chemical and microbiological indicators and biological quality elements. The concentrations of organics, nutrients and microcomponents were determined with results confirming the expected increase for parameters associated with the discharge of urban wastewater. The ecological state, according to macrozoobenthos indicators, was “good” throughout the river sector but local deterioration was registered in a proximal location downstream of the WWTP outfall. The analysis of stream water and bed sediment microbial communities by a fluorescent technique showed the high metabolic activity and intensive transformation processes in addition to high abundance registered with standard cultivation methods. The importance of the studied sub-catchment for the functioning of the urban water cycle, and for the quality of Sofia’s drinking water, underlines the need to extend an existing monitoring program with a more detailed assessment of the environmental impact of wastewater discharge.

Digitalization in Urban Water Governance: Case Study of Bengaluru and Singapore

Urban water governance aims to ensure equitable access to adequate quality water and related services to rapidly growing urban population while protecting the environment. Rapid urbanization and changing climate are posing challenges to the formal and informal institutions responsible for governing and managing water resources. Complexities existing due to the interaction between societal and environmental subsystems of urban water cycle adds pressure on institutional capabilities to cope up with various uncertainties. Emergence of digital technologies has provided the necessary tools in urban water governance to strengthen capabilities through effective monitoring, decision making, and forecasting. The paper examines how sequencing and leveraging the synergies of different digital technologies can help mitigate various problems and challenges faced in urban water governance. The paper analyses three digital technologies, Smart Water Metering Supervisory Control and Data Acquisition and Flood Alert System (FAS) using the case studies of Bengaluru and Singapore to understand the transformative capabilities of digitalization in urban water governance. It is assumed that the learnings from this study can be generalized to a large extent. The paper indicates that to unlock the full potential and derive best returns of investment, digitalization needs to have broader objectives. Multi-purpose use of digital tools can contribute effectively to the implementation of Integrated Urban Water Management. The results highlighted that societal acceptability of digitalization depends majorly on the mode of implementation and not so much on the technology.

Review: Suspended Sediments and their interaction in Water Supply Chain Network

There have been several problems caused by sediments which have never been addressed before now in the water supply chain and have therefore been overlooked as not having sizable consequences; however, they actually do and these problems over a period have demanded the attention of sediment in urban water cycle to be given due scrutiny to understand the connection between sediments and the derivative problems in the water supply chain. This review article examines the problems associated with sediments along the water supply chain from the drainage basin, water bodies, treatment plants, water distribution system and end consumers. More so, this review article proposes policies that can be adopted to reduce the influx of sediment in the various stages of the water supply chain.

Incorporating an urban canopy model with artificial water dissipation into weather research and forecasting: A case study for Beijing

AbstractUrban artificial water dissipation is a concomitant process of human water use in built‐up areas that can absorb heat through evapotranspiration, reduce air temperature, transfer surface water to the atmosphere, and participate in the urban water cycle. In the context of increased urbanization, the impact of artificial water dissipation on urban climates cannot be ignored. In this study, calculation models for artificial water dissipation from different underlying surface types (buildings, hardened ground, soil, and vegetation) were introduced into an urban canopy model and coupled with the weather research and forecasting (WRF) model for mesoscale weather simulations of the Beijing area. Observational datasets of temperature and humidity from automatic weather stations in Beijing were used for validation. Results showed that the coupled model could reproduce the temperature and humidity of urban weather stations in Beijing more accurately compared to simulations that did not employ an urban canopy model or that adopted a traditional urban canopy model. In the Beijing urban area, the latent heat flux of NON, urban canopy model, and artificial water dissipation into the UCM are approximately 0, 35, and 65 W/m2, respectively, and the anthropogenic latent heat is about 30 W/m2. Incorporating urban artificial water dissipation into the urban canopy model reduced the urban air temperature by 0.2°C and increased the specific humidity by 0.6 g/kg, alleviating urban heat island effects and increasing humidity. These findings indicate that artificial urban water dissipation plays an important role in urban weather and climate that should be considered by urban canopy models. In the future, this model can be coupled into WRF for more accurate mesoscale weather simulations.

The Digital Revolution in the Urban Water Cycle and Its Ethical–Political Implications: A Critical Perspective

The development and application of new forms of automation and monitoring, data mining, and the use of AI data sources and knowledge management tools in the water sector has been compared to a ‘digital revolution’. The state-of-the-art literature has analysed this transformation from predominantly technical and positive perspectives, emphasising the benefits of digitalisation in the water sector. Meanwhile, there is a conspicuous lack of critical literature on this topic. To bridge this gap, the paper advances a critical overview of the state-of-the art scholarship on water digitalisation, looking at the sociopolitical and ethical concerns these technologies generate. We did this by analysing relevant AI applications at each of the three levels of the UWC: technical, operational, and sociopolitical. By drawing on the precepts of urban political ecology, we propose a hydrosocial approach to the so-called ‘digital water ‘, which aims to overcome the one-sidedness of the technocratic and/or positive approaches to this issue. Thus, the contribution of this article is a new theoretical framework which can be operationalised in order to analyse the ethical–political implications of the deployment of AI in urban water management. From the overview of opportunities and concerns presented in this paper, it emerges that a hydrosocial approach to digital water management is timely and necessary. The proposed framework envisions AI as a force in the service of the human right to water, the implementation of which needs to be (1) critical, in that it takes into consideration gender, race, class, and other sources of discrimination and orients algorithms according to key principles and values; (2) democratic and participatory, i.e., it combines a concern for efficiency with sensitivity to issues of fairness or justice; and (3) interdisciplinary, meaning that it integrates social sciences and natural sciences from the outset in all applications.

Study of Damage Quantification of Concrete Drainage Pipes Based on Point Cloud Segmentation and Reconstruction

The urban drainage system is an important part of the urban water cycle. However, with the aging of drainage pipelines and other external reasons, damages such as cracks, corrosion, and deformation of underground pipelines can cause serious consequences such as urban waterlogging and road collapse. At present, the detection of underground drainage pipelines mostly focuses on the qualitative identification of pipeline damage, and it is impossible to quantitatively analyze pipeline damage. Therefore, a method to quantify the damage volume of concrete pipes that combines surface segmentation and reconstruction is proposed. An RGB-D sensor is used to collect the damage information of the drainage pipeline, and the collected depth frame is registered to generate the pipeline’s surface point cloud. Voxel sampling and Gaussian filtering are used to improve data processing efficiency and reduce noise, respectively, and the RANSAC algorithm is used to remove the pipeline’s surface information. The ball-pivoting algorithm is used to reconstruct the surface of the segmented damage data and pipe’s surface information, and finally to obtain the damage volume. In order to evaluate, we conducted our research on real-world materials. The measurement results show that the method proposed in this paper measures an average relative error of 7.17% for the external damage volume of concrete pipes and an average relative error of 5.22% for the internal damage measurements of concrete pipes.

Overall Rate Kinetics Model for Chlorine Demand of Urban Rainfall Runoff

The built environment significantly alters the rainfall-runoff response and associated transport of particulate matter (PM), chemicals, and pathogens in the urban water cycle. Urban water sustainability requires mitigation of runoff impacts while providing a potential resource to traditional water supply sources. Chlorination for wastewater, combined sewer overflows (CSOs), and reuse waters is the most common disinfection practice to ensure public health. Chlorinated wastewater effluent is a common reclaimed water for reuse applications such irrigation and mixing with source-area runoff during wet-weather events. Chlorine demand models have been developed for source waters and wastewaters. The current study adds to this knowledge base through modeling of sodium hypochlorite demand kinetics for source-area runoff PM and also dissolved phases utilizing dissolved chemical oxygen demand (CODd). Second-order rate models of hypochlorite demand are developed for both phases, with the PM phase subdivided into three fractions on a granulometric basis. PM (suspended, settleable, and sediment) fractions exert a significant hypochlorite demand compared with the dissolved fraction. Ultimate chlorine demand translates to 36% of the CODd, of which 39% of the demand is exerted in less than 5 min, which is in the range of residence times for small manufactured unit operations that are common for best management practices (BMPs). Chlorine demand is 350 mg/g for suspended, 320 mg/g for settleable, and 650 mg/g for sediment PM.

Rainfall Interception Characteristics of Dracaena Sanderiana and Breynia Distincha

Interception of plants commonly used in urban landscape has not been widely studied compared to forested and cultivated area. Understanding the interception characteristics of these plants can facilitate the selection of the right plant type or combination in order to promote interception as a mean to improve the urban water cycle and urban built environment. Two (2) tropical plants are considered in this study, namely, Dracaena Sanderiana and Breynia Distincha, both with distinct plant structure, plant height, canopy size, number of leaves per plant, leaf size and leaf shape. Rainfall interception characteristics are investigated in laboratory environment using standard hydrology apparatus for different plant density. Artificial rainfall intensity of fixed duration is varied to measure the volume and duration of outflow, and volume intercepted. Results show that runoff begins earlier for higher rainfall intensity and lower plant density. The volume and duration of outflow increases with rainfall intensity and interception increases with canopy cover ratio and leaf area ratio for both plants. At lower plant density, Breynia Distincha has lower interception compared to Dracaena Sanderiana. However, at high plant density, Breynia Distincha demonstrates much better interception capacity even though the canopy cover and leaf area ratios are smaller than Dracaena Sanderiana. The phenomenon may be attributed to coalescence of water droplets that either flow down as stemflow or drip off the leaves under gravitational action. The firm small leaves of Breynia Distincha oriented at near horizontal are more likely to retain the intercepted rainwater compared to the slender soft leaves of Dracaena Sanderiana. This shows that closely spaced Breynia Distincha can be effective in increasing urban interception.

What roles do architectural design and on-site water servicing technologies play in the water performance of residential infill?

More than half of new urban residential developments are planned as infill in Australia's major cities. This provides an unprecedented opportunity to use innovative design and technology to address urban water challenges such as flooding, reduced water security and related infrastructure and urban heat island issues. However, infill can have positive or negative water impacts, depending on architectural design and on-site water servicing technologies implemented. In this study we asked, “What influence does residential infill development have on the local urban water cycle?” and “What roles do architectural design and technologies play?” To answer these questions, a set of 196 design-technology configurations were developed by combining 28 architectural designs and 7 on-site water-servicing technology options. The configurations represent three cases: (i) existing (EX) or before infill, (ii) business-as-usual development (BAU), and (iii) alternative development (ALT). Using the Site-scale Urban Water Mass Balance Assessment (SUWMBA) model and a set of water performance indicators, the impact of configurations on the urban water cycle was quantified. The results showed BAU, on average, increases population density, stormwater discharge, and imported water by 98%, 44% and 85%, and decreases evapotranspiration and infiltration by 53% and 34%, compared to the EX conditions. More population density (141%) with lower impacts on the urban water cycle (21% and 64% increase for stormwater discharge and imported water, and 29% and 17% reduction in evapotranspiration and infiltration) can be achieved by appropriate integration of ALT designs and technologies. Architectural design has a greater influence on urban water flows than the implementation of on-site water servicing technologies. The results have a great implication for sustainable urban water management for managing the risks associated with pluvial flooding, water insecurity, and urban heat. It also highlights the underutilised role of architects and urban planners to address urban water issues.

Occurrence and fate of poly- and perfluoroalkyl substances (PFAS) in urban waters of New Zealand

Information on the occurrence of PFAS in aquatic matrices of countries with no PFAS manufacturing, e.g., New Zealand, is limited. Also, the fingerprint of PFAS along an urban water cycle, following water path from wastewater treatment plant (WWTP) effluent to treated drinking water has not been widely assessed. Hence, 38 long-, short-, ultrashort-chain PFAS and fluorinated alternatives (including precursors) were monitored in this study by collecting composite samples from two urban WWTPs of New Zealand and grab samples from the water bodies receiving the WWTPs’ effluents and a drinking water treatment plant, whose source water received the effluent of one of the studied WWTPs. ∑PFAS at concentrations 0.1 – 13 ng/L were detected in all wastewater samples, including influents and different treatment stages of the two WWTPs (WW1 and WW2). The fate of most PFAS was similar in the two WWTPs, despite large differences in WWTPs’ PFAS loads in the influents, serving populations (1.6 vs 0.16 million), total capacities (300 vs 54 million liters per day), and designs (aerobic and anoxic secondary treatment vs aerobic only). The fate of PFAS in WWTPs appeared to be driven by a range of processes. For instance, a simultaneous increase (41.6%) in short-chain perfluorohexanoic acid (PFHxA) concentrations and decrease (49.7%) in precursor 6:2 fluorotelomer sulfonate (6:2 FTS) concentrations after secondary biological treatment suggested possible transformation of 6:2 FTS into PFHxA during the treatment. In contrast, the reason behind an average decrease of 35% in ultrashort-chain perfluoropropionic acid (PFPrA) concentrations after treatment was unclear, and further studies are recommended. The concentrations of a linear isomer of long-chain perfluorosulfonic acid (PFOS-L) decreased (48%) in the effluent, possibly due to its partitioning to sludge. Although the concentrations of PFAS in coastal waters suggested that the WW1 effluent is a potential source of PFAS, earlier dispersion model and no detection of PFAS in the receiving waters of WW2 implied that other sources, such as septic systems, peripheral industries, and the airport, could also be contributing to PFAS in coastal waters. The source of ultrashort-chain PFPrA (5.5 ng/L) detected in the treated drinking water produced from that river was unclear. The monitoring results confirm incomplete removal of PFAS in WWTPs, indicate a possible transformation of unknown precursors present in wastewater into short-chain perfluoroalkylcarboxylic acids (PFCAs) during biological treatment, and reveal a possible accumulation of perfluoroalkylsulfonic acids (PFSAs) in the sludge, overall suggesting the circulation of PFAS in urban water systems.

Measuring operational and quality-adjusted efficiency of Chilean water companies

The path to a sustainable management of the urban water cycle requires the assessment of both operational and quality-adjusted efficiency in a unified manner. This can be done by the use of non-radial Data Envelopment Analysis models. This study used Range Adjusted Measure models to evaluate the operational, quality-adjusted, and operational & quality-adjusted efficiency (O&QAE) scores of the Chilean water industry including water leakage and unplanned interruptions as undesirable outputs. It was found that on average water utilities presented large O&QAE scores over time. The mean O&QAE score was 0.964 which means that water utilities could further reduce costs and undesirable outputs by 3.6% on average, while trying to expand the scale of operation. This finding suggests that excellent quality-adjusted efficiency at an efficient expenditure could be feasible. It was also evidenced that customer density, mixed water resources, and ownership influenced the O&QAE of Chilean water companies.

Managing Water and Energy on Small Islands Study Case Caye Chapel

Small islands that support urban communities provide a unique opportunity to study the urban water cycle, its energy needs, and possible links to renewable energy. In this paper, models for an energy generation system and the processes in the urban water cycle are formulated. These are combined and then used to determine optimal parameters for 12 different possible alternatives in two scenarios.

Determination and Risk Assessment of Pharmaceutical Residues in the Urban Water Cycle

Determination and Risk Assessment of Pharmaceutical Residues in the Urban Water Cycle

Rapid Detection of Eskape Bacteria Using Tapered Dielectrophoresis and Their Presence in Urban Water Cycle

Rapid Detection of Eskape Bacteria Using Tapered Dielectrophoresis and Their Presence in Urban Water Cycle

Circular economy and payment for ecosystem services: A framework proposal based on water reuse

Water scarcity forces the use of non-conventional water sources, to satisfy water demand, such as the effluent of wastewater treatment plants (WWTPs). Water reuse helps to close the urban water cycle and reduce pressure on available water resources, providing a bases for circular economy in the water sector. Under an ecosystem services (ES) point of view, if water reuse is considered the best management option in water scarcity areas, WWTPs are responsible for the ES of provisioning. One of the main requirements for the ES of provisioning is to guarantee the reclaimed water quality due to this water being discharged back into the ecosystem. Hence why removing pollutants, such as pharmaceutical and personal care products (PPCPs), is necessary to reduce the environmental impact of reused water. Considering the lack of legislation about PPCPs in effluents, this study proposes the use of the Payment for Ecosystem Services (PES) approach as an innovative solution to provide reclaimed water without PPCPs considering both the environmental and institutional context and the importance of WWTPs as non-conventional water sources. This study contributes to consider the PES as a water cycle management tool and its suitability to be used to remove PPCPs is highlighted, with the purpose of promoting water reuse in water scarcity areas under circular economy approach.