Total Nitrogen Load Research Articles

Modelling nutrient fluxes into the Mediterranean Sea

Study regionMediterranean River Basins. Study focusHuman activities and consequent pollution have put the freshwater and marine ecosystems of the Mediterranean region under pressure, with high risk of eutrophication phenomena. In this study, an extended version of the Geospatial Regression Equation for European Nutrient losses model (GREEN), originally developed for estimating nutrient loads from diffuse and point sources in Europe, was extended to include additional nutrient sources using a grid cell discretization. The spatial resolution is 5 arc minute and the model inputs consist of the latest and best available global data. New hydrological insights for the regionThe results of this study show that during 2003–2007 (baseline), 1.87 Tg/y of total nitrogen (TN), 1.22 Tg/y of nitrates (N-NO3), 0.11 Tg/y of total phosphorus (TP) and 0.03 Tg/y of orthophosphate (P-PO4) were discharged in the Mediterranean Sea. The source apportionment analysis showed that the main contributor to total nitrogen and nitrate loads is agriculture followed by natural background, while for orthophosphate dominant sources include wastewater and scattered dwellings. Two scenarios were investigated to assess sustainable water and nutrient management options, showing that the reduction of 50% of nitrogen surplus leads to a significant reduction of nitrogen emission in regions characterized by high intensity agriculture, while the upgrading of wastewater treatment plants to tertiary level was more efficient for TP reduction.

Tannery wastewater: Organic load and sulfide removal dynamics by electrochemical oxidation at different anode materials

Abstract The electrochemical oxidation of a real tannery effluent with very high organic load and sulfide content was assessed by galvanostatic electrolysis, utilizing different electrode materials, Ti/Pt/PbO2, Ti/Pt/SnO2 – Sb2O4 and BDD. Assays were run for 8 h, under a current density of 30 mA cm−2, in a batch with stirring electrochemical cell. The efficiencies of the electrodes were tested by evaluating variations in chemical oxygen demand (COD), total carbon (TC), dissolved organic carbon (DOC), N-containing compounds, sulfide and sulfate. Although all the tested materials have proved to be very effective in organic load and sulfide abatement, BDD electrode showed the best performance in the removal of COD and TC, with similar behavior to the other two electrodes in DOC removal. Ti/Pt/SnO2 – Sb2O4 was the least efficient in the oxidation of N-containing compounds to NO 3 − , despite providing considerable production of gaseous nitrogen compounds, which reduces the total nitrogen load present in the treated effluent. Sulfide removal was more intense at BDD, being Ti/Pt/SnO2 – Sb2O4 the most effective in the oxidation of S 2 − to SO 4 2 − . Regarding specific charge and energy consumptions, BDD showed the best results, even when compared to other studies from the literature. These results show that electrochemical oxidation can be an effective treatment to tannery wastewater, regarding COD, N-containing compounds and sulfide removals.

Societal decisions about climate mitigation will have dramatic impacts on eutrophication in the 21st century

Excessive nitrogen runoff leads to degraded water quality, harming human and ecosystem health. We examine the impact of changes in land use and land management for six combinations of socioeconomic pathways and climate outcomes, and find that societal choices will substantially impact riverine total nitrogen loading (+54% to −7%) for the continental United States by the end of the century. Regional impacts will be even larger. Increased loading is possible for both high emission and low emission pathways, due to increased food and biofuel demand, respectively. Some pathways, however, suggest that limiting climate change and eutrophication can be achieved concurrently. Precipitation changes will further exacerbate loading, resulting in a net increase of 1 to 68%. Globally, increases in cropland area and agricultural intensification will likely impact vast portions of Asia. Societal and climate trends must therefore both be considered in designing strategies for managing inland and coastal water quality.

Water quality characterization of storm and irrigation runoff from a container nursery

Commercial nurseries grow specialty crops for resale using a variety of methods, including containerized production, utilizing soilless substrates, on a semipervious production surface. These “container” nurseries require daily water application and continuous availability of mineral nutrients. These factors can generate significant nutrients [total nitrogen (TN), and total phosphorus (TP)] and sediment [total suspended solids (TSS)] in runoff, potentially contributing to eutrophication of downstream water bodies. Runoff is collected in large ponds known as tailwater recovery basins for treatment and reuse or discharge to receiving streams. We characterized TSS, TN, and TP, electrical conductivity (EC), and pH in runoff from a 5.2 ha production portion of a 200-ha commercial container nursery during storm and irrigation events. Results showed a direct correlation between TN and TP, runoff and TSS, TN and EC, and between flow and pH. The Storm Water Management Model (SWMM) was used to characterize runoff quantity and quality of the site. We found during irrigation events that simulated event mean concentrations (EMCs) of TSS, TN, and TP were 30, 3.1 and 0.35 mg·L−1, respectively. During storm events, TSS, TN and TP EMCs were 880, 3.7, and 0.46 mg·L−1, respectively. EMCs of TN and TP were similar to that of urban runoff; however, the TSS EMC from nursery runoff was 2–4 times greater. The average loading of TSS, TN and TP during storm events was approximately 900, 35 and 50 times higher than those of irrigation events, respectively. Based on a 10-year SWMM simulation (2008–2018) of runoff from the same nursery, annual TSS, TN and TP load per ha during storm events ranged from 9230 to 13,300, 65.8 to 94.0 and 9.00 to 12.9 kg·ha−1·yr−1, respectively. SWMM was able to characterize runoff quality and quantity reasonably well. Thus, it is suitable for characterizing runoff loadings from container nurseries.

Identification of Critical Source Areas (CSAs) and Evaluation of Best Management Practices (BMPs) in Controlling Eutrophication in the Dez River Basin

Best Management Practices (BMPs) are commonly used to control pollution in the river basins. Prioritization of BMPs helps improve the efficiency and effectiveness of pollution reduction, especially in Critical Source Areas (CSAs) that produce the highest pollution loads. Recently, the Dez River in Khuzestan, Iran, has become highly eutrophic from the overuse of fertilizers and pesticides. In this basin, dry and irrigated farming produce 77.34% and 6.3% of the Total Nitrogen (TN) load, and 83.56% and 4.3% of the Total Phosphorus (TP) load, respectively. In addition, residential, pasture, and forest land uses together account for 16.36% of the TN and 12.14% of the TP load in this area. The Soil and Water Assessment Tool (SWAT) was implemented to model the Dez River basin and evaluate the applicability of several BMPs, including point source elimination, filter strips, livestock grazing, and river channel management, in reducing the entry of pollution loads to the river. Sensitivity analysis and calibration/validation of the model was performed using the SUFI-2 algorithm in the SWAT Calibration Uncertainties Program (SWAT-CUP). The CSAs were identified using individual (sediment, TN, TP) and combined indices, based on the amount of pollution produced. Among the BMPs implemented, the 10 m filter strip was most effective in reducing TN load (42.61%), and TP load (39.57%).

A coupled model system to optimize the best management practices for nonpoint source pollution control

Agricultural nonpoint source pollution (NPS) is the main water-use impairment in the upper watershed of the Miyun Reservoir in Beijing, China. Selection and placement of best management practices (BMPs) in heterogeneous watersheds, requires a multi-objective optimization framework to identify the most cost-effective conservation strategy to achieve desired water quality goals. In this paper, a novel optimization methodology was developed, utilizing a BMP database that includes BMP reduction efficiencies and costs, using a multi-objective sorting genetic algorithm (NSGA-II, nondominated sorting genetic algorithm-II) combined with the Soil Water and Assessment Tool (SWAT) served as the NPS watershed model. Cost-effectiveness curves (optimal fronts) between pollutant reduction and total net cost input were obtained for the upper watershed of Miyun Reservoir. The optimal combination of BMP, which include a combination of conservation tillage, careful timing of 30% less fertilizer application, contour planting, and use of a 10-m edge-of-field buffer strip, indicate that the least costly scenario reduced total nitrogen (TN) and total phosphorus (TP) loads by 33% at a cost of 1.02 × 106 China Yuan. The cost-effective scenario reduced TN and TP loads 44% and 68% at a cost of 2.52 × 107 and 5.64 × 107China Yuan. The greatest reduction scenario reduced TN and TP loads 55% and 76%, respectively, at a cost of 2.01 × 108 and 2.48 × 108 China Yuan. Watershed with poultry operations, required a 30% reduction in number of birds, along with a 30% reduction in the amount of manure applied was needed to achieve water quality goals. Use of the coupled BMP optimization model can assist the policy makers achieve a cost-effective implementation of best management practices to mitigate agricultural nonpoint sources at a watershed scale.

Treatment and valorization of a primary municipal wastewater by a short rotation willow coppice vegetation filter

The objective of this study was to evaluate the treatment efficiency of a short rotation willow coppice (SRWC) vegetation filter for the treatment of wastewater from a municipal primary effluent in a humid continental climate context. The experimental work was carried out at pilot scale on a willow plantation located in Québec, Canada. The experimental design included nine plots that were irrigated with groundwater (L0 = 14 mm/d) or two primary effluents (L1 = 10and L2 = 16 mm/d) for 111 days. This research showed that SRWCs operated on coarse-textured soils allow efficient removal of organic matter (91% of COD for L1 and L2) and nitrogen (98% of TKN for L1 and L2) from wastewater. It was also shown, in this case, that the total nitrogen loading should be used as the limiting design parameter to minimize the risk of contaminating underground drinking water sources with nitrates. Almost complete removal of total phosphorus was observed during this experiment (98% for L1 and L2). However, a significant increase in soil available phosphorus was observed following the L2 treatment, which suggests an eventual phosphorus soil profile saturation in the event of continued wastewater irrigation. Avoiding such a saturation would require chemical phosphorus removal upstream of SRWC vegetation filters. Finally, an imbalance between irrigation and willows needs was observed as a result of irrigating plots at a constant hydraulic loading rate. Thus, irrigation of an SRWC with wastewater should be modulated according to willow seasonal transpiration trends to allow a better allocation of water and nutrients according to plant needs, and in doing so, increase treatment efficiency and resources valorization.

Wastewater discharge with phytoplankton may favor cyanobacterial development in the main drinking water supply river in Uruguay

The main drinking water source supplying Uruguay (Santa Lucía River, SLR) was threatened in 2013 by a cyanobacterial bloom transported downstream to the water treatment plant that provides water to half of this country population. Several eutrophic reservoirs and stabilization ponds located in the river basin may have been the source of cyanobacterial populations. Such conditions may be common in productive basins; however, few studies have evaluated the impact of microalgae from wastewater stabilization ponds on rivers and its viability downstream. The effect of a dairy wastewater effluent on SLR was studied by means of nutrient and chlorophyll a loads, phytoplankton composition, and effluent incubation in river water in order to evaluate the potential development of cyanobacteria. Total phosphorus and nitrogen loads of the effluent reached up to 25% and 17% of SLR, respectively, while chlorophyll a was up to 37%. The upstream-downstream evaluation showed an increase in dissolved phosphorus and chlorophyll a. The effluent phytoplankton (14.16mm3L-1) was dominated by organisms <10μm and diatoms (91%), and 3% of cyanobacteria. Cyanobacteria were not detected in SLR, though it appeared downstream of the effluent discharge. At the end of the bioassay, cyanobacterial biomass became the dominant group (37%). This study shows the potential development of cyanobacteria present in industrial effluents when diluted in river water. The effect of phytoplankton discharge from stabilization ponds is not generally considered in monitoring assessments and environment management, despite representing a particular risk if the water body is used as a drinking water source.

Biological Nitrogen Removal Process in a Microbubble-aerated Biofilm Reactor Treating Low C/N Wastewater

The microbubble-aerated biofilm reactor as a new treatment process combines microbubble aeration technology with aerobic biological treatment. A microbubble aerated biofilm reactor was used in this study to treat low C/N ratio wastewater at a low air/water ratio. The process and performance of biological nitrogen removal were investigated, and the functional bacterial populations for nitrogen removal in the biofilm were analyzed. The results showed that the biological nitrogen removal process was converted from simultaneous nitrification-denitrification to simultaneous partial nitrification, ANAMMOX and denitrification (SNAD) processes when DO concentration was controlled by an air/water ratio of lower than 1:2 and the influent C/N ratio was reduced. As a result, the efficient biological nitrogen removal performance was achieved when treating low C/N ratio wastewater. When the DO concentration was lower than 1.0 mg·L-1 and the influent C/N ratio was 1:2.8, the SNAD process became dominant for biological nitrogen removal. In this case, the average total nitrogen (TN) removal efficiency was 76.3%, and the average TN loading rate removed was 1.42 kg·(m3·d)-1. In addition, it was estimated that 86.0% of TN removal was attributed to the ANAMMOX process. The relative abundances of ammonia-oxidizing bacteria populations and ANAMMOX bacteria populations in the biofilm increased gradually, while the relative abundances of nitrite-oxidizing bacteria populations and denitrifying bacteria populations decreased gradually, with a decrease in influent C/N ratio. The variation of functional bacterial populations for nitrogen removal was consistent with the conversion of nitrogen removal process to SNAD process.

Pelagic contribution to gross primary production dynamics in shallow areas of York River, VA, U.S.A.

AbstractThe pelagic contribution to total gross primary production (GPP) is often used to evaluate the assemblages of primary producers in shallow estuarine and coastal ecosystems that shift between benthic‐dominated and pelagic‐dominated status as a response to nutrient loading change. This study investigated the spatial and temporal variability of the pelagic contribution to ecosystem GPP for the years 2003–2015 in shallow areas of the York River. The monthly average values of ecosystem GPP and pelagic GPP were estimated by using 15‐min observational data of dissolved oxygen and chlorophyll a, respectively. A larger pelagic contribution, generally, corresponded to a higher pelagic GPP, while pelagic GPP showed significant positive correlations to riverine discharge and total nitrogen loading at mesohaline and polyhaline stations. The interannual variability in benthic GPP (ecosystem GPP – pelagic GPP), however, exhibited a non‐monotonic relationship to the increase in pelagic GPP. A conceptual model with four ecosystem stages in response to nutrient loading changes is proposed based on changes in the relationship between benthic GPP and pelagic GPP, and that between pelagic contribution and pelagic GPP. The model can explain the different responses of an ecosystem to nutrient loading observed in various estuaries and can be used to evaluate the status of an ecosystem undergoing the eutrophication/oligotrophication process. The stages of York River ecosystems during the study period were quantitatively examined. Results suggest that benthic GPP shows negative correlations to pelagic GPP in the downstream York River over most months of the year, indicating a gradual degradation of the benthic community.

Nitrogen removal potential of shellfish aquaculture harvests in eastern Canada: A comparison of culture methods

Bivalve farming can contribute to nutrient removal in coastal and estuarine systems, as bivalves directly incorporate nutrients into their tissues and shells. We conducted a meta-analysis to compare the nitrogen removal potential (NRP; i.e., percentage of nitrogen in tissues and shells) of mussels, Mytilus edulis, and oysters, Crassostrea virginica. We then used species-specific NRPs to determine and compare the total and per-hectare NRPs for four shellfish aquaculture methods used in two Atlantic Canadian provinces – New Brunswick (NB) and Prince Edward Island (PEI) – based on current harvest biomasses. Finally, we determined the contribution of current shellfish farming to nitrogen load mitigation for a subset of bays in NB and PEI. Results revealed that on a per-weight basis, NRP was similar for the tissues of mussels and oysters, while mussel shells had a significantly higher percentage of nitrogen than oyster shells. Collectively, shellfish harvesting has the capacity to remove a mean annual total of 99088 kg and 204571 kg of nitrogen from NB and PEI, respectively. Given current harvesting practices for four culture methods employed in the region, suspended mussel culture provides the greatest NRP per hectare of farm area, followed in sequence by suspended mussel and oyster mixed culture, suspended oyster culture, and bottom oyster culture. Preliminary analysis suggested that harvests in the region typically remove <10% of the total nitrogen load on the bay scale, with the exception of bays where nitrogen loads are low and farming intensity is high (where shellfish harvesting can remove higher percentages of nitrogen loads). Ultimately, harvests from shellfish farming in NB and PEI have the capacity to remove substantial amounts of nitrogen from local bays. Future studies assessing the influence of shellfish farming on full nutrient budgets across bays with varying physicochemical conditions will enhance our understanding the role of shellfish farms in nearshore nutrient dynamics, both regionally and globally.

An innovative approach to identifying agricultural pollution sources and loads by using nutrient export coefficients in watershed modeling

Agricultural nonpoint source (ANPS) pollution has become a major reason for eutrophication in many regions of the world. However, it is still difficult to identify the relative contributions of different ANPSs to the nutrient export flux at the watershed outlet due to a lack of effective methods. The export coefficient approach (ECA) and the Soil and Water Assessment Tool (SWAT), which is a process-based watershed simulation model with aquatic nutrient retention simulation modules, were implemented to identify the ANPS and its associated quantitative contributions in the Three Gorges Reservoir Region, China. By using the SWAT-ECA framework, nutrient loadings to the river reaches in the subbasin and the export flux at the outlet of the watershed, which were derived from individual agricultural sources in each subbasin, were quantified accordingly. The primary goal of this study is to quantify the pollutant loads from different agricultural sources by using SWAT-ECA. The proposed work was conducted in the Xiangxi River Watershed of the Three Gorges Reservoir Region, Hubei Province, China. The total nitrogen (TN) and total phosphorus (TP) loads that were generated from the agricultural sources were 1299.1 t a−1 and 97.4 t a−1, respectively. Livestock production was the main source of the TN load, accounting for 82% of agricultural TN load. Livestock production and crop cultivation were the main sources of the TP load, accounting for 52% and 42%, respectively. The delivery ratios of N and P from the source areas to the watershed outlet were relatively high in the study watershed. TN (1234 t a−1) and TP (87.1 t a−1) from agricultural sources were ultimately released to the reservoir area, which accounted for 40.2% and 37.6%, respectively, of the total fluxes from the whole watershed. The comprehensive approach that is proposed in this study can be useful for identifying the contributions of individual agricultural sources to the nutrient export flux at the watershed outlet.

Deciphering the evolution characteristics of extracellular microbial products from autotrophic and mixotrophic anammox consortia in response to nitrogen loading variations

Extracellular microbial products (EMP) in biological wastewater treatment systems vary with operational conditions and in turn indicate the metabolic status of functional bacteria. In this study, the response of EMP from autotrophic and mixotrophic anammox consortia (AAC and MAC) to the variation of total nitrogen loading rates (TNLR) were investigated as well as their correlations with the community evolution. The variation of TNLR showed a significantly negative correlation with the production of bound microbial products (BMP) but a significantly positive correlation with the production of soluble microbial products (SMP). The presence of organic matters with COD/TN ratio of 0.15 limited the abundance of anammox bacteria in MAC at the full-load phase and suppressed their proliferation at the restart phase. Due to the improved abundance of carbohydrate metabolism genes, MAC with lower abundance of anammox bacteria produced lower soluble polysaccharides than AMC at the full-load phase. Furthermore, four components (C1–4) were identified on the excitation–emission matrix fluorescence spectra of SMP using parallel factor analysis. C1 exhibited a relative higher proportion at the full-load phase, whereas C4 was generated only at the light-load phase or empty-load phase. At the restart phase, C2 and C3 appeared simultaneously and accounted for a high proportion. The information of four components also suggested the metabolic status of AC as revealed by the specific anammox activity, which therefore provided a novel complementary but direct approach for monitoring the operation status of anammox bioreactors.

The supply of total nitrogen and total phosphorus from small urban catchments into the Gulf of Gdańsk

The main goal of work was to quantify the nitrogen and phosphorus loads transported by small streams to the Gulf of Gdańsk. The research aims to determine wastewater release volumes over time, instead of focusing only on spatial distributions. Another aim is to identify the main determinants potentially affecting water quality in rivers flowing across the city of Sopot. The study area consists of six small river catchments located in the city of Sopot, each with an open flow channel, which lies along the bay. Studies were conducted 12 times per year in the period from March 2014 to February 2015. Laboratory analyses were performed to determine the concentration of both total nitrogen and total phosphorus. In order to calculate pollutant loads, discharge was also measured in each of studied rivers. Conducted research has shown that all analyzed streams were characterized by low total nitrogen and total phosphorus concentrations. The mean annual values ranged from 0.60 to 1.28 mg·dm-3 in case of total nitrogen and from 0.066 to 0.100 mg·dm-3 in case of total phosphorus. In 2012, the total nitrogen load from Poland to the Baltic Sea was 210.768.000 kg N while the total phosphorus load was 15.269.000 kg P, which means that streams analyzed in this paper supplied barely 0.002 % of the biogenic load supplied to the Baltic Sea by Poland as a whole.

Spatial Distribution Assessment and Source Apportionment of Land-Based Pollutant Yield from Qingdao, China

The spatial distribution of chemical oxygen demand (COD) and total nitrogen (TN) yield from Qingdao are studied by comparing pollutant yield amount, densities and spatial aggregation (Getis-Ord indexes) among the land-based pollutant source regions (PSRs) entering the three sub-seas (i.e. the Jiaozhou Bay (JZB), other coastal area in the Yellow Sea (OCAYS) and Laizhou Bay (LZB), respectively). Industrial composition of the loads are also studied by comparing pollutant yield among the sources of agriculture, rural domesticity, industry, urban domesticity and service, and calculation of Gini coefficient. Results show that spatial distribution of COD and TN yield from Qingdao are extremely unbalanced. The JZB, with less than 3% of the total coastal sea area of Qingdao, received 62% COD load and 65% TN yield from Qingdao, while the OCAYS, with more than 97% area, only received 23% COD and 20% TN, which consist with the much worsen water quality of JZB than that of OCAYS. On the other hand, the source apportionment of COD and TN loads in the PSRs entering JZB and the OCAYS was similar. The agricultural and domestic sources with high pollution intensity account for more than 80%, while the industrial and service sources with low pollution intensity account for less than 20%. While Gini coefficients, COD 0.81 and TN 0.84 which are much higher than the ‘imbalance’ threshold of 0.4, show the uneven industrial structure of Qingdao. These results may be useful in the determination of land-based pollution total amount control at the PSR level.

The reduction effects of riparian reforestation on runoff and nutrient export based on AnnAGNPS model in a small typical watershed, China.

The continuous deterioration of the aquatic environment in rivers and streams is increasingly causing social and political tensions. To alleviate aquatic environmental problems, especially for the nonpoint source pollution, establishment of riparian forest buffers has been demonstrated as an effective control measure. However, few comprehensive studies of the reduction effects of riparian reforestation on the aquatic environment have been performed, particularly in identifying the suitable widths of reforestation projects. In this paper, the Annualized Agricultural Non-Point Source (AnnAGNPS) model was used to simulate the reduction effects of riparian reforestation on runoff and nutrient loads in Wucun watershed, China. The results showed that 20-m, 40-m, and 60-m widths of riparian buffer reforestation had significant effects on the yearly loads of total nitrogen (TN) and total phosphorus (TP), with reduced rates of 23.21 to 56.2% and 18.16 to 52.14%, respectively. The reduction effect on annual runoff varied from 2.8 to 5.4%. Furthermore, the reduction effect of nutrients performed best during the transition period, while the best runoff reduction was found during the dry period. These distinct reductions indicated that the implementation of riparian forest buffers was capable of reducing the risk and frequency of flooding and eutrophication, especially during the wet and transition periods. Additionally, the 20-m width of riparian buffer reforestation achieved the highest reduction efficiency for runoff, and the 40-m width was the most suitable reforested riparian buffer width for TN and TP. Therefore, 40m may be the optimum buffer width for the implementation of riparian reforestation in the Wucun watershed. These research results provided scientific information on selecting the optimum buffer width for aquatic environmental regulators and managers as the reduction effects of different widths of riparian buffers on runoff and nutrients were different when considering buffer reforestation.

Analysis of urban water quality trends for effective reservoir sedimentation management in Cameron Highland

Water quality in Cameron Highlands has significantly diminished due to agricultural activities. This research aims to analyse water quality in the urban and agricultural area by conducting water sampling and in situ analysis. Water quality index (WQI), total nitrogen (TN) and total phosphorus (TP) were calculated and compared among different areas. Results for WQI shows that water quality at W7 deteriorates at class IV (33.5) compared to class II for another agriculture area. Meanwhile, another results showed that the WQ_02_AG transported significantly higher (14.9 mg/L) loads of TN than the urban area, but the phosphorus load was considerably lower (1.58 mg/L). Results for the urban area are slightly polluted and unsuitable for recreational purpose. In agricultural areas, water quality deteriorates due to sediment transport and nutrient infusion caused by agricultural activities. Therefore, powerful agricultural management practices for effective reservoir sedimentation management as one of the non-structural measures are recommended.

Evaluating the factors responsible for post-fire water quality response in forests of the western USA

Wildfires commonly increase nutrient, carbon, sediment and metal inputs to streams, yet the factors responsible for the type, magnitude and duration of water quality effects are poorly understood. Prior work by the current authors found increased nitrogen, phosphorus and cation exports were common the first 5 post-fire years from a synthesis of 159 wildfires across the western United States. In the current study, an analysis is undertaken to determine factors that best explain post-fire streamwater responses observed in those watersheds. Increased post-fire total nitrogen and phosphorus loading were proportional to the catchment extent of moderate and high burn severity. While post-fire dissolved metal concentrations were correlated with pre-fire soil organic matter. Total metal concentration increased where post-fire Normalised Difference Vegetation Index, a remote sensing indicator of live green vegetation, was low. When pre-fire soil field capacity exceeded 17%, there was a 750% median increase in total metals export to streams. Overall, the current analysis identified burn severity, post-fire vegetation cover and several soil properties as the key variables explaining extended post-fire water quality response across a broad range of conditions found in the western US.

Green infrastructure practices simulation of the impacts of land use on surface runoff: Case study in Ecorse River watershed, Michigan

As an urban fringe district, the Ecorse River watershed is faced with increased impervious area caused by urban expansion. Effects of Green Infrastructure (GI) practice implementation were simulated with the Long-Term Hydrologic Impact Assessment-Low Impact Development 2.1 model (L-THIA-LID 2.1). Suitable locations of each GI practice were identified, based on construction condition requirements and demand on GI practices in the study area. Using the data of 2011, various GI practice combination scenarios were explored according to the cost-efficiency of each GI practice. GI practice implementation scenarios in 2050 were also simulated based on projected land use and rainfall data. Results show that grassed swales, rain barrels (residential areas) and dry ponds were the top three most cost-efficient GI practices, with the cost at $1.5/m³/yr, $3.0/m³/yr and $3.4/m³/yr, respectively. Green roofs with rain cisterns (industrial and commercial area) were the most expensive GI practices, with the cost at $92.9/m³/yr. With the increase of investment in GI practices, the changing curves of the annual runoff volume, Total Nitrogen (TN) load and Total Phosphorus (TP) load reduction ratios match the law of diminishing marginal utility. The scenario with grassed swales, rain barrels, dry ponds and porous pavement would be the most cost-efficient scenario for runoff water quantity reduction. In addition, the scenario with additional wet ponds would be the most cost-efficient one for TN load and TP load reduction. GI practices in each scenario for expected 2050 conditions show better effectiveness on water quantity and quality management.

Water Quality Control Options in Response to Catchment Urbanization: A Scenario Analysis by SWAT

Urbanization poses a challenge to sustainable catchment management worldwide. This study compares streamflows and nutrient loads in the urbanized Torrens catchment in South Australia at present and future urbanization levels, and addresses possible mitigation of urbanization effects by means of the control measures: river bank stabilization, buffer strip expansion, and wetland construction. A scenario analysis by means of the Soil and Water Assessment Tool (SWAT) based on the anticipated urban population density growth in the Torrens catchment over the next 30 years predicted a remarkable increase of streamflow and Total Phosphorous loads but decreased Total Nitrogen loads. In contrast, minor changes of model outputs were predicted under the present urbanization scenario, i.e. urban area expansion on the grassland. Scenarios of three feasible control measures demonstrated best results for expanding buffer zone to sustain stream water quality. The construction of wetlands along the Torrens River resulted in the reduction of catchment runoff, but only slight decreases in TN and TP loads. Overall, the results of this study suggested that combining the three best management practices by the adaptive development of buffer zones, wetlands and stabilized river banks might help to control efficiently the increased run-off and TP loads by the projected urbanization of the River Torrens catchment.