In Singapore, active, beautiful, clean waters design features (ABCWDFs), such as rain gardens and vegetated swales, are used as a sustainable approach for stormwater management. Field monitoring studies characterising the performance of these design features in the tropical region are currently limited, hampering the widespread implementation of these systems. This study characterised the performance of individual ABCWDFs in the tropical climate context by monitoring a rain garden (FB7) and a vegetated swale (VS1) that were implemented in a 4-ha urban residential precinct for a period of 15 months. Results showed that total suspended solids (TSS), total phosphorus (TP) and total nitrogen (TN) concentrations were low in the new residential precinct runoff, leading to poor removal efficiency despite the effluent concentrations of individual ABCWDFs that were within the local stormwater treatment objectives. Average TSS, TP and TN EMCs of four sub-catchment outlets were lower (23.2 mg/L, 0.11 mg/L and 1.00 mg/L, respectively) when compared to the runoff quality of the major catchments in Singapore, potentially demonstrating that the ABCWDFs are effective in improving the catchment runoff quality. Findings from this study can help to better understand the performance of ABCWDFs receiving low influent concentrations and implications for further investigations to improve stormwater runoff management in the tropics.
Many parts of the world, including Australia, are facing acute groundwater shortages. Recycled wastewater is emerging as an important alternative, sustainable, substitute for groundwater. However, before water utilities can invest in water recycling projects, they need information on the demand for recycled water. A comprehensive literature search revealed no study reporting a price elasticity estimate for recycled water for outdoor use by large non-residential users. This paper contributes to this knowledge gap by conducting a case study in Perth, Western Australia. Using a contingent behaviour method, we find that the price elasticity varies between -0.76 and -0.97, depending on the extent of restriction placed on access to groundwater. Using a contingent valuation method, we estimate the willingness-to-pay for recycled water for outdoor use, by a representative organisation to be $AUD112/ML. We also find that the willingness-to-pay for recycled water varies with land use type, with agriculture and horticulture the sector with the highest willingness-to-pay.
Microbial pathogens present in stormwater, which originate from human sewage and animal faecal matters, are one of the major impediments in stormwater reuse. The transport of microbes in stormwater is more than just a physical process. The mobility of microbes in stormwater is governed by many factors, such as dissolved organic matter, cations, pH, temperature and water flow. This paper examined the roles of three environmental variables, namely: dissolved organic matter, positive cations and stormwater flow on the transport of two faecal indicator bacteria (FIB), Enterococcus spp. and Escherichia coli. Stormwater runoff samples were collected during twelve wet weather events and one dry weather event from a medium density residential urban catchment in Brisbane. Enterococcus spp. numbers as high as 3 × 104 cfu/100 mL were detected in the stormwater runoff, while Escherichia coli numbers up to 3.6 × 103 cfu/100 mL were observed. The dissolved organic carbon (DOC) in the stormwater samples was in the range of 2.2–5.9 mg/L with an average concentration of 4.5 mg/L in which the hydrophilic carbon constituted the highest mass fraction of 60–80%. The results also showed that the transport of FIB in stormwater was reduced with an increasing concentration of the hydrophilic organic fraction, especially the humic fraction. On the contrary, the concentration of trivalent cations and stormwater flow rate showed a positive correlation with the FIB numbers. These findings indicated the potentiality to make a good use and measurement of simple environmental variables to reflect the degree of microbe transport in stormwater from residential/suburban catchments.
Infill development is an unprecedented opportunity to reshape cities incorporating innovative design to address urban water challenges such as pluvial flooding, water insecurity, and degraded receiving water bodies.This study aims to address the influence of architectural design (before and after infill) on the urban water flows by studying the water performance of 28 design typologies in three cities of Adelaide, Brisbane, and Melbourne.Design typologies were categorised based on the scale of infill (e.g.Small Infill vs apartments) and infill typologies: representing before infill or existing case (EX) and two categories for after infill namely businessas-usual (BAU) demonstrating developments under current planning policies and building design codes and Alternative (ALT) designs following Water Sensitive Urban Design principles.We used Site-scale Urban Water Mass Balance Assessment (SUWMBA) tool to estimate urban flows into and out of development sites to quantify the local influence on the urban water cycle.The results showed design typologies exhibit a varying performance in different cities, calling for city-specific rather than generic designs.BAU infill, in particular, demonstrates the most disruption to the natural hydrology by increasing stormwater discharge up to 442% and decreasing evapotranspiration and infiltration down to 31% and 36% of the flows in the natural landscape.The implication of this disruption on stormwater management (i.e.urban drainage), risk of pluvial flooding, and urban heat was discussed.ALT designs show a lower degree of disruption of natural hydrology while providing more densification compared to BAU.Despite this relative success, all designs failed to restore natural hydrology fully.We argue that improvements in architectural designs combined with Water Sensitive Urban Design technologies (e.g.local harvest of rain and stormwater) to a varying degree are needed to achieve net-zero water impact.
Many global cities and towns are facing complex and interrelated challenges associated with population growth, resource constraints, aging infrastructure, and degraded environments, exacerbated by increasing climate uncertainty. The United Nation's Agenda 2030 is a global call to action with 17 Sustainable Development Goals (SDGs). Water is the common currency linking nearly every SDG. SDG 11 aspires to "Make cities and human settlements inclusive, safe, resilient, and sustainable'' and the water-sensitive city represents an aspirational future state for water management where servicing strategies deliver long-term sustainability, liveability, resilience, and prosperity. This social-technical endeavor is based on three principles of practice proposed in 2009. They have since been operationalized and adapted in many projects globally, and across a range of social, institutional, and biophysical contexts. In this Perspective, we reflect on lessons learned, required actions for mainstreaming water-sensitive practices, the next-wave research agenda, and opportunities to catalyze actions in sectors beyond water.
