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Green roofs are an effective green infrastructure tool to reduce stormwater runoff in cities, but their considerable weight is a constraint on widespread uptake. Consequently, lightweight green roof substrates with high water retention are desirable. Biochar addition to green roof substrates may reduce green roof weight and improve stormwater retention by increasing water holding capacity. However, the effects of biochar on substrate properties can vary due to differences in biochar particle size and amendment rate that influence substrate porosity and therefore substrate water and air-content. Additionally, differences in the feedstock used to produce biochar also mean that biochars are highly variable in their internal porosity, affecting their water retention and weight. To determine how biochar particle size, amendment rate and feedstock density influence substrate water retention, bulk density, air-filled porosity and infiltration we tested substrate properties of a scoria-based green roof substrate mixed with two different biochars contrasting in feedstock type, at three different biochar particle size fractions (coarse 2 mm – 10 mm, fine

Constructed wetlands (CWs) are a promising sustainable water-management measure where hydrology plays a fundamental role as the basic driver of mass and energy. Various designs of CWs exist, and these have unique hydrological characteristics that are distinct from those of natural wetlands. However, there have been few reviews of the hydrology and responses of CWs, such that not enough is known of the possible responses of hydraulic, water quality and biology to changing hydrological conditions, especially for different CWs systems. Thus, this paper commences with a review of the basic features of common CWs and their different hydrological conditions. This is followed by the responses of CWs to the hydraulic parameters hydraulic retention time (HRT), hydraulic loading rate (HLR) and water depth that control the changing hydrological conditions of CWs. It is shown that water quality responses are highly related to HRT and HLR and thus a simple method is proposed to predict the responses to the changes of HRT and HLR through a statistical analysis of previous studies. While water depth and inflow patterns appear to have a greater influence on biological responses and some suitable water depths for different species are summarized from papers. Future researchers should pay more attention to the regional ecohydrological patterns of CWs. Long-term hydrological and biological management of CW systems will require the development of frameworks based on an index system for monitoring the responses of interventions.

The review paper sis based on the analysis or nearly 700 research papers published during 2019 and the first half of 2020 and indexed by Web of Science under the password “constructed wetlands for wastewater treatment”. Out of this number 132 papers dealing with “new” topics such as new wastewaters treated in constructed wetlands (CW), new filtration materials, role of vegetation, floating treatment wetlands, microbiology of CW, greenhouse gas emissions from CWs, sustainability and secondary benefits of CWs. For the deeper analysis the supporting literature from previous periods has been cited. The analysis indicates increasing popularity and diversification of types and tasks of CWs. This supports the need for further research of processes and design-related properties of CWs. The research in full scale CWs and long-term studies are only rare and in order to upgrade the CWs technology, research must be also carried out in the field under full-scale conditions.

The large-scale and high intensity mining of coal resources has further worsened the already fragile plant ecosystem in Western China. On the basis of strictly following the developmental law of regional natural ecosystems, guiding the restoration of damaged vegetation is one of the important measures for ecological restoration in mining areas. However, there are still some problems to achieve the guided restoration of damaged vegetation in semiarid mining areas: how to configure different plant species, and what is the control threshold of vegetation coverage under different site conditions among others. In this paper, based on DEM, slope, aspect and soil type data, 12 different site conditions were obtained by using overlay analysis function of ArcGIS software. The trend of interannual variation of vegetation coverage was analyzed using Landsat Normalized Difference Vegetation Index (NDVI) time series data, and the spatial distribution of areas of degraded vegetation under 12 site conditions was identified. Based on the Fully Constrained Least Square (FCLS) unmixing algorithm, typical native plants were classified using Aerial Hyperspectral data. Finally, through the comparative analysis of plant composition and abundance under 12 site conditions, the control thresholds of vegetation coverage ranged from 36.60% to 45.30% in the early stage of vegetation restoration. The thresholds of steep slope are lower than that in gentle and flat slope, which is mainly related to the fact that steep slope is more prone to soil erosion and is not conducive to the conservation of soil water and nutrients. According to the calculation results of different plant allocation proportion under 12 site conditions, the proportion of herbs and shrubs is higher than that of trees. When selecting species for vegetation configuration, native herbs and shrubs with strong adaptability, fast growth and strong drought resistance should be preferred. It is suggested that trees should be planted properly after the site conditions of vegetation growth are effectively restored or the vegetation community structure tends to be stable. In the process of vegetation restoration in semiarid mining area, not only the appropriate threshold of vegetation coverage should be considered, but also the proportion of trees, shrubs, and herbs has an important impact on the effect of vegetation restoration. The results of this paper will provide guidance for the orderly restoration of damaged vegetation in semiarid mining areas.

Nature-Based Solutions (NBS) provide a systemic approach to promote the maintenance, enhancement, and restoration of biodiversity and ecosystem services (ES) in urban areas, helping to enhance urban resilience in the water sector. Within the sustainable development goals proposed by UNHABITAT, resilience in cities was established as a critical issue. The assessment of the NBS contribution to urban resilience and the development of tools to determine the long-term value of these solutions comprise a most needed step forward. A comprehensive Resilience Assessment Framework to assess the NBS contribution to urban resilience (RAF), focused on NBS for stormwater management and control, was proposed and developed ( Beceiro et al., 2020 ). This assessment framework aims to support the diagnosis, decision-making, implementation, planning, and management of the NBS and to identify the solutions with greater potential to contribute to city resilience drawbacks. This paper aims to demonstrate the purpose and relevance of the RAF, by presenting its application to a case study, highlighting both data demands (given different complexity requirements for metric's determination) and specific considerations regarding the level of assessment (either to the overall city area or to specific NBS). The application to the case study allows assessing the contribution to urban resilience of the main NBS in the urban area of Porto and, specifically, the contribution of an infiltration basin, which will be implemented in the Asprela catchment. Main resilience shortcomings in the city that may be upgraded by NBS are also identified, as recommendations for future urban planning in Porto. This application also intends to deliver a thorough example for other cities aiming to assess NBS contribution to urban resilience using the proposed RAF. At the city level, the main opportunities to improve the NBS contribution identified corresponded to the Governance and stakeholders' involvement, Environmental resilience and Resilience engaged service. On the other hand, the Social involvement and co-benefits and the Service management (obj.6) are identified as consolidated aspects across the urban area. At the NBS level, it was possible to conclude that the infiltration basin, considering the design characteristics, will enhance significantly the contribution to urban resilience in the Asprela catchment, based on the results for the model based metrics and the defined scenarios. Furthermore, it was possible to conclude that the NBS will operate in overall good hydraulic condition, even for the most severe rainfall conditions.

Coal extraction by opencast mining involves the dumping of overburden or mine spoil as large heaps. These large heaps of overburdened materials can act as a serious threat to ecological integrity and, therefore, overall societal well-being. Plantations are often employed to establish revegetation and management of mine spoil, thus mitigating the effects of mining on the environment. However, the performance of plant species can be highly variable due to environmental and species-specific effects. Therefore, the present paper's primary objective is to compare exotic (Acacia auriculiformis, Cassia siamea, Casuarina equisetifolia and Grevillea pteridifolia) and native (Albizia lebbeck, Albizia procera, Dendrocalamus strictus and Tectona grandis) species' performance on the coal mine spoils. Previous studies on the Singrauli coalfields allowed us to compare the growth performance, standing biomass, and net primary production (NPP) of four exotic and four native species plantations. Our results showed that native species have significantly higher survival, stem diameter, biomass, and NPP than exotic woody plantations. Thus, exotic species might not be useful in mine spoil rehabilitation than the native species. Overall, this study suggests that native species are useful for mine spoil rehabilitation despite the faster growth of exotic species.

Agricultural ditches can be an efficient method for removing nutrients in wetlands and rivers. In this paper, we document that additionally, ditches offer other ecosystem services (ES) such as providing bird habitat and sediment retention. A typical ditch reach of 6 km with variable width between 3 and 80 m and water depth from 0.06 and 0.5 m, was selected as a monitoring site among 1492 km of a drain network in the agricultural Mexicali Valley located in the Colorado River Delta. Nitrogen and phosphorus concentration and discharge flow rate determinations were obtained monthly during a year, at three stations along the ditch, dividing the reach into two segments. Total nutrient removal efficiency of 39%, along the monitoring year was observed. Additionally, nutrient mass flow had a significant winter-spring seasonal increment associated with crop irrigation, up four times for total nitrogen, nearly 2.5 times for nitrogen-based nutrients, and five times for PO4. Monthly estimations of normalized difference vegetation index (NDVI) from Sentinel images were obtained to evaluate the response of riparian vegetation to high flow discharge seasonal fluctuations, from 0.072 to 1.219 m3 s−1, and nutrient mass flow changes. No correlation among them was found, as riparian species are tolerant to high water levels and nutrient concentration fluctuation. Downstream changes in water electrical conductivity from 6.06 to 8.45 mS cm−1 along the resulted in the shift from Typha domingensis to Phragmatis australis which has a higher salinity tolerance. An intensive bird census showed ditch vegetation provided suitable habitat and refuge to 29 different bird species, including five common birds of the flooded remnant areas of the Colorado River Delta, as well as migratory birds. By using slope criteria of drainage network, 47% of it has a high and moderated potential of sediment retention. These ES are fundamental in semiarid regions because of the intense land-use changes from riparian and desert ecosystems to irrigation lands, as well as water being diverted from natural streams to irrigation channels. This study highlights the importance of considering agricultural ditches as helpful, not only as a natural water treatment of agricultural pollutants, but also as providers of resident and migratory bird habitat and vegetation diversity and erosion regulation by sediment retention on desert agricultural valleys.

The problem of water scarcity in the world has gained great relevance in recent decades. One of the fields of study that has been developed as an ecological alternative to combat the water demand is the reuse of greywater. Greywater corresponds to domestic wastewater that excludes water from the toilet. These waters have the potential to be reused after simple treatments for non-potable uses. In the last decade, Chile has gone through the most intense mega-drought in its history. One of the most affected regions is the Coquimbo Region, located in the north-central zone, with a semi-arid climate and extensive agricultural activity. This paper presents the first results of pilot greywater treatment systems installed in rural public schools in the Coquimbo Region. In the first instance, different sorbent materials such as sand, zeolite, acid-activated carbon (AAC), base-activated carbon (BAC) and heat-activated carbon (HAC) were studied for the removal of organic matter and turbidity. It was found that the adsorbent materials based on carbon were more efficient for the removal of organic matter, registering maximum mean sorption capacities of 107.7 mg/g, 77.5 mg/g and 78.5 mg/g, for AAC, BAC and HAC, respectively. On the one hand, the treatment columns composed HAC, zeolite and sand, were very effective for removing turbidity, reaching removal percentages over 90%. On the other hand, pilot treatment systems were efficient in reaching the water quality levels required by Chilean legislation for the use of irrigation of recreational areas and services, and in some cases for the use of ornamental irrigation. The advantage of these systems is their simplicity and low installation cost. These systems have allowed savings of between 840 and 26,000 L per month, depending on the size of the school, which has allowed the watering of gardens.

Shallow, rainfall-triggered landslides are an important catchment process that affect the rate and calibre of sediment within river networks and create a significant hazard, particularly when shallow landslides transform into rapidly moving debris flows. Forests and trees modify the magnitude and rate of shallow landsliding and have been used by land managers for centuries to mitigate their effects. We understand that at the tree and slope scale root reinforcement provides a significant role in stabilising slopes, but at the catchment scale root reinforcement models only partially explain where shallow landslides are likely to occur due to the complexity of subsurface material properties and hydrology. The challenge of scaling from slopes to catchments (from 1-D to 2-D) reflects the scale gap between geomorphic process understanding and modelling, and temporal evolution of material properties. Hence, our understanding does not, as yet, provide the necessary tools to allow vegetation to be targeted most effectively for landslide reduction. This paper aims to provide a perspective on the science underpinning the challenges land and catchment managers face in trying to reduce shallow landslide hazard, manage catchment sediment budgets, and develop tools for catchment targeting of vegetation. We use our understanding of rainfall-triggered shallow landslides in New Zealand and how vegetation has been used as a tool to reduce their incidence to demonstrate key points.

A series of flume experiments were conducted to study the hydraulic characteristics, sediment siltation mechanisms against different layouts of flexible mattresses that are gaining prominence over the traditional mattresses that are rigid and anti-scouring. The optimal layout pattern of interlacement and spacing 15 cm was found with an ecological effect of a comfortable hydraulic environment (water resistance rate of near bottom of 63%) and a proper deposition thickness (relative siltation thickness of 0.06). The ecological cavity mattress was successfully applied to the lower reach of Yangtze River in China. A stable and effective deposited layer (grain size of 25.21– 48.29 μm) was formed, which was exactly coincident to the laboratory experiment results, and where were found some organic matters (organic matter content of 1.77% ~ 3.68%) and a few of benthic fauna (abundance of 85ind./m2 and biomass of 0.62 g/m2 in flood season). A comfortable hydraulic environment was created in the inner structure in both the flood and drought seasons, just as the flume experiment presented. The sediment constituent and organic matter quantity in the inner structure were also relatively stable. Obviously, the new ecological cavity mattress exerts a positive ecological effect in the river ecosystem rehabilitation, which can be put into extensive use. In addition, design concept and optimization procedure of the new structure in this paper could also provide some reference for other relevant studies.

Metalliferous soil (MS) was collected from near an abandoned pulp and paper mill, and leachates were extracted in water to simulate natural water percolation. Metalliferous soil leachates (MSL) were added to the garden soil, and phytoremediation trials were carried out by Alternanthera sessilis and Ipomoea aquatica for 28-d in pot experiments. The aqueous leachates could extract 18–33% of the metals from the MS. The maximum accumulation of 38–43 μg Cd/g, 211–294 μg Pb/g, 199–218 μg Cr/g, 92–95 μg Ni/g, 422–511 μg Cu/g, 2366–3531 μg Zn/g, 6910–6105 μg Fe/g, and 4410–5576 μg Mn/g in the plants exceeded the respective toxic ranges, indicating their tolerance. Plants showed >50% removal efficiency for Pb, Cr, and Cu. For other metals, variable removal efficiency between 25 and 48% was also noted. The root morphology and X-ray microanalysis revealed Pb, Cr, and Fe deposits that influenced their uptake and possible interactions with other elements. The treated plants showed reduced chlorophylls, carotenoids, protein, and ascorbate, along with an increase in superoxide radical, hydrogen peroxide, and lipid peroxidation. A concomitant increase in the activities of all the vital antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidise, and guaiacol peroxidise helped to combat multi-metal stress in them. Overall, owing to their metal uptake efficiency, significant oxidative stress mitigation properties, rapid growth rate, and large biomass, A. sessilis, and I. aquatica can be recommended for use in the decontamination of multiple metals.

This paper studied the potential mechanism of form drag for emergent vegetation by combining experiments and numerical simulation. Rigid cylindrical sticks arranged in an open channel were used to simulate vegetation and experiments on flow velocity distribution near the vegetation under different vegetation density and arrangement were carried out. The new expression of hydraulic radius indicated that form drag was closely related to vortex structure near the vegetation. The relationship between vortex volume caused by vegetation and form drag was proposed and verified under different experimental conditions. The results showed that resistance form in vegetated open channels could be divided into K- and D-type resistance based on different stick arrangements within one vegetation patch. The calculated and measured form drag values were in a good agreement under different experimental conditions. Meanwhile, the numerical simulation results fit well with the experimental values and more complex experimental conditions were replicated using numerical simulation. The results provided important information for vegetation layout in open channels.

Eutrophication has emerged as one of the main threats to surface water bodies. The parameters for assessing eutrophication are not generally measured regularly from the lakes of India as part of monitoring programmes and it is necessary to express the trophic status in terms of secondary indicator variables that are included in the routine analysis by the State/Central government. In this paper, the trophic status of Ashtamudi Lake has been studied, considering its international importance and socio-economic relevance. The cause and response variables such as total phosphorus, Secchi disc depth, chlorophyll-a and the secondary indicator variables such as pH, turbidity, DO, EC, Salinity, TDS and BOD were analysed during the pre-monsoon season. The lake was predominantly classified as eutrophic, with some areas coming under a hypereutrophic state. A comparison was made among the five methods of water quality index by the use of secondary indicator variables to identify the appropriate method for simulating trophic status and the WQI based on the logarithmic method considering pH, turbidity, DO and BOD was identified to predict the trophic state very well. Further, the application of numerical strategy such as fuzzy logic was used to determine water quality indexes and trophic status, which can define the quality of a water body as a consequence of the variation of environmental parameters. The developed approach was further validated by using historical data for the years 2013–2015, which were regularly monitored by the Kerala State Pollution Control Board. The trophic state predicted by the approach was found to be in agreement with that estimated using Carlson's method. Thus the developed model, based on secondary indicator parameters that are readily available from government agencies, can be used to assess the trophic state of lakes, thereby assisting policy makers to frame regulations to minimize eutrophication.