Urban stream syndrome in a small, lightly developed watershed: a statistical analysis of water chemistry parameters, land use patterns, and natural sources

Inland navigation and land use interact to impact European freshwater biodiversity

Inland navigation in Europe is proposed to increase in the coming years, being promoted as a low-carbon form of transport. However, we currently lack knowledge on how this would impact biodiversity at large scales and interact with existing stressors. Here we addressed this knowledge gap by analysing fish and macroinvertebrate community time series across large European rivers comprising 19,592 observations from 4,049 sampling sites spanning the past 32 years. We found ship traffic to be associated with biodiversity declines, that is, loss of fish and macroinvertebrate taxonomic richness, diversity and trait richness. Ship traffic was also associated with increases in taxonomic evenness, which, in concert with richness decreases, was attributed to losses in rare taxa. Ship traffic was especially harmful for benthic taxa and those preferring slow flows. These effects often depended on local land use and riparian degradation. In fish, negative impacts of shipping were highest in urban and agricultural landscapes. Regarding navigation infrastructure, the negative impact of channelization on macroinvertebrates was evident only when riparian degradation was also high. Our results demonstrate the risk of increasing inland navigation on freshwater biodiversity. Integrative waterway management accounting for riparian habitats and landscape characteristics could help to mitigate these impacts.

Empirical evidence of climate change and urbanization impacts on warming stream temperatures

Climate change and urbanization threaten streams and the biodiversity that rely upon them worldwide. Emissions of greenhouse gases are causing air and sea surface temperatures to increase, and even small areas of urbanization are degrading stream biodiversity, water quality and hydrology. However, empirical evidence of how increasing air temperatures and urbanization together affect stream temperatures over time and their relative influence on stream temperatures is limited. This study quantifies changes in stream temperatures in a region in South-East Australia with an urban-agricultural-forest landcover gradient and where increasing air temperatures have been observed. Using Random Forest models we identify air temperature and urbanization drive increasing stream temperatures and that their combined effects are larger than their individual effects occurring alone. Furthermore, we identify potential mitigation measures useful for waterway managers and policy makers. The results show that both local and global solutions are needed to reduce future increases to stream temperature.

Ecological River Health Assessment Using Multi-Metric Models in an Asian Temperate Region with Land Use/Land Cover as the Primary Factor Regulating Nutrients, Organic Matter, and Fish Composition

This study was performed to determine the ecological health of a temperate river over nine years (2011−2019); it also analyzed the trophic structure and linkage of nutrients (nitrogen [N] and phosphorus [P]), sestonic chlorophyll-a (CHL-a), and the top trophic fish in the Asian monsoon region. Water chemistry, trophic indicators, and tolerance guilds were primarily influenced by land use and land cover (LULC); the magnitude of variation was also related to geographic elevation, artificial physical barriers (weirs), and point sources. Levels of nutrients, organic matter, and CHL-a largely influenced by the intensity of the monsoon seasonality for a particular LULC and stream order. Mann−Kendall tests based on a long-term annual dataset showed that annual organic matter and CHL-a increased over time because of longer hydraulic residence time after weir construction. The results of empirical nutrient models suggested that P was the key determinant for algal growth (CHL-a); the strong P-limitation was supported by N:P ratios > 17 in ambient waters. Linear regression models and canonical correspondence analysis (CCA) were used to determine the influences of LULC and water quality on the trophic/tolerance linkages, fish community compositions and structures, and river health. Tolerant species had a positive functional relationship with nutrient enrichment through total phosphorus (TP) (R2 = 0.55, p < 0.05) and total nitrogen (TN) (R2 = 0.57, p < 0.05), organic pollution in terms of biological oxygen demand (BOD) (R2 = 0.41, p < 0.05) and chemical oxygen demand (COD) (R2 = 0.49, p < 0.05), and algal growth (R2 = 0.47, p < 0.05); sensitive species exhibited the opposite pattern. The degradation of river health, based on the multi-metric index of biotic integrity (IBI) model, was evident in the downriver region (“fair−poor” condition) and was supported by the quantitative fish community index (QFCI) model. The outcomes suggested that the degradation and variation of ecological river health, trophic linkages of water chemistry (N, P)-algal biomass-fish, were largely controlled by the land use pattern and construction of physical barriers in relation to the Asian monsoon.

Characterizing the Chemical Profile of Biological Decline in Stormwater-Impacted Urban Watersheds

Chemical contamination is an increasingly important conservation issue in urban runoff-impacted watersheds. Regulatory and restoration efforts typically evaluate limited conventional parameters and pollutants. However, complex urban chemical mixtures contain hundreds to thousands of organic contaminants that remain unidentified, unregulated, and poorly understood. This study aimed to develop broadly representative metrics of water quality impairment corresponding to previously documented biological degradation along gradients of human impacts. Stream samples (n = 65, baseflow/rainfall conditions, 2017-2018) were collected from 15 regional watersheds (Puget Sound, WA, USA) across an urbanization gradient defined by landscape characteristics. Surface water chemical composition characterized via non-targeted high-resolution mass spectrometry (7068 detections) was highly correlated with landscape-based urbanization gradient (p < 0.01) and season (p < 0.01). Landscape-scale changes in chemical composition closely aligned with two anchors of biological decline: coho salmon (Oncorhynchus kisutch) mortality risk (p < 0.001) and loss of stream macroinvertebrate diversity and abundance (p < 0.001). We isolated and identified 32 indicators for urban runoff impacts and corresponding receiving water ecological health, including well-known anthropogenic contaminants (e.g., caffeine, organophosphates, vehicle-derived chemicals), two related environmental transformation products, and a novel (methoxymethyl)melamine compound. Outcomes support data-directed selection of next-generation water quality indicators for prioritization and evaluation of watershed management efforts intended to protect aquatic ecosystems.

The Effectiveness of an Artificial Floating Wetland to Remove Nutrients in an Urban Stream: A Pilot-Study in the Chicago River, Chicago, IL USA

Ever expanding urbanized landscapes are increasingly impacting streams that run through them. Among other stressors, urban streams often are host to elevated concentrations of nutrients, salts, and heavy metals. The pollutants, coupled with high temperatures, are drivers of ecosystem degradation in urban streams. The installation of artificial floating wetlands (AFWs) has been successful in mitigating the effects of urbanization in lakes and wastewater treatment ponds, but rarely have they been tested in streams. This pilot-study examined the ability of an AFW to improve water quality in an urban stream. The small, 90 m2 AFW was installed to improve the aquatic habitat and aesthetics of a small section of the Chicago River, Chicago, IL USA. Water samples and in-situ measurements were collected from the surface and at 0.3 m depth of upstream and downstream of the AFW. Samples were analyzed for nitrate-as-nitrogen, phosphate, chloride, and heavy metals. Comparison of upstream and downstream waters showed that the AFW lowered the concentrations of nitrate-as-nitrogen and phosphate during the growing season by 6.9% and 6.0%, respectively. Nitrate was also removed during the dormant season; however, phosphate was not removed during that time. Plant or microbial uptake of the nutrients are believed to be the dominant mechanisms in the growing season with denitrification serving as the primary pathway in the dormant season. Despite not having a measurable effect on the water temperature, the AFW was an effective means to reduce concentrations of nitrate and phosphorus, decreasing the potential for eutrophication.

Stream sediment bacterial communities exhibit temporally-consistent and distinct thresholds to land use change in a mixed-use watershed

Freshwater ecosystems are susceptible to biodiversity losses due to land conversion. This is particularly true for the conversion of land from forests for agriculture and urban development. Freshwater sediments harbor microorganisms that provide vital ecosystem services. In dynamic habitats like freshwater sediments, microbial communities can be shaped by many processes, although the relative contributions of environmental factors to microbial community dynamics remain unclear. Given the future projected increase in land use change, it is important to ascertain how associated changes in stream physico-chemistry will influence sediment microbiomes. Here, we characterized stream chemistry and sediment bacterial community composition along a mixed land-use gradient in West Virginia, USA across one growing season. Sediment bacterial community richness was unaffected by increasing anthropogenic land use, though microbial communities were compositionally distinct across sites. Community threshold analysis revealed greater community resilience to agricultural land use than urban land use. Further, predicted metagenomes suggest differences in potential microbial function across changes in land use. The results of this study suggest that low levels of urban land use change can alter sediment bacterial community composition and predicted functional capacity in a mixed-use watershed, which could impact stream ecosystem services in the face of global land use change.

Trophic state and limiting nutrient evaluations using trophic state/level index methods: a case study of Borçka Dam Lake

The relationships between nutrients and the trophic state of Borçka dam reservoir in the Çoruh River Basin, which is located in the Eastern Black Sea region of Turkey, were evaluated using the trophic state index (TSI), trophic level index (TLI), and statistical analysis. The samples data were analyzed for chlorophyll-a (Chl-a), total phosphorus (TP), total nitrogen (TN), and secchi disk (SD). In the evaluation, according to the TSI' TLI and Turkish legislation, the reservoir is assessed as mesotrophic in terms of TP, TN data of the water quality. The measurement results of these parameters are higher at the depth points and lower on the surface. The Chl-a parameter is evaluated mesotrophic with 2013 data at the depth, and oligotrophic with 2016 data. The result of TSI (Chl-a) < TSI (SD), TSI (Chl-a) < TSI (TP), and TSI (TN) indicate non-algal turbidity. At the same time, this was verified by calculating the non-algal turbidity coefficient (Kna). It is observed that there is a low correlation between Chl-a and Kna, however a low correlation with TN, and a high correlation with TP. Non-algal particles in the dam lake may occur due to surface runoff and soil erosion from the agricultural area and human settlements. Regression analysis was conducted to determine the relationship between nutrients and Chl-a. The relationship of Chl-a concentration with TN, TP, and TN/TP concentrations is weak. This supports that there are inorganic suspended solids (non-volatile suspended solids) with high underwater light availability.Graphical abstract.

Considerations on the monitoring of water quality in urban streams: a case study in Portugal

Monitoring water quality in urban stream is of utmost importance for water resources managers, who are pressured to optimize monitoring schemes in order to reduce costs. The present study aims to use the results of a 2-year-long water quality monitoring program of an urban stream in Portugal to identify improvement opportunities. The urban stream under study was subjected to wastewater treatment plants effluent discharges, leachates from a major sealed landfill, low-class housing effluents, and nonpoint sources of pollution. Contributing watersheds are mostly artificial surfaces and agricultural land, which irrigate directly from the river. River water quality was evaluated on 11 sampling locations for 24 months from October 2013 to September 2015. The present paper describes statistical analysis of the results obtained for 12 physicochemical parameters in order to optimize the monitoring scheme. Cluster analysis detected a seasonal variation in the water quality and a spatial pattern based on the major point sources of pollution. A factor analysis showed that the parameters that mostly contribute to water quality assessment in this urban river are alkalinity, ammonia, electrical conductivity, pH, temperature, and dissolved oxygen. Results suggest that the monitoring efforts-and associated costs-may be reduced by decreasing monitoring frequency, sampling points, and monitored parameters. The statistical analysis described in this study may be replicated in other water quality monitoring programs, providing useful and important information for the systematic and iterative assessment of the adequacy of water quality sampling programs towards a sustainable management of water quality surveillance.

Geochemical signature of urbanisation in Blue Mountains Upland Swamps

Urbanisation leaves a geochemical signature on the environment, as weathering of urban materials such as concrete contributes to elevated levels of major ions including calcium, bicarbonate and potassium. However, there is limited research that addresses the ecological consequences of this signature on the biotic community. Blue Mountains Upland Swamps (BMUS), an endangered ecological community with high conservation values, are vulnerable to urban degradation. Chemical properties of water, sediment and foliage from native and exotic species were assessed within two urbanised and two naturally vegetated swamp catchments. Water in urban swamps exhibited elevated pH and electrical conductivity. Non-urban swamps were sodium and chloride dominated, with higher calcium and bicarbonate in urban swamps. Water from urban swamps also exhibited 32 times higher levels of strontium. Calcium concentrations were elevated by 14 times in urban swamp sediment. Foliage from urban catchments exhibited six times greater potassium, and three times higher calcium and bicarbonate compared to foliage in non-urban catchments. Calcium, bicarbonate, potassium and strontium were key parameters that were enriched in the urbanised swamps. However, the ecological implications of these findings for urban wetland communities, including BMUS, remain unclear. Interestingly, the chemical signature of water did not fully represent the signatures of sediment and foliage, highlighting the need to further explore sources and forms of major ions within these ecosystems, particularly in sediment. In an increasingly urban world, enhancing knowledge of drivers of change in endangered ecosystems such as BMUS is crucial to promote conservation and guide the development of sustainable management practices.

Effects of urbanization on water quality in a watershed in northeastern Brazil

Changes to land use generate imbalances in the natural dynamics of aquatic ecosystems. These changes can vary according to the specific characteristics of each environment and due to seasonal factors, reinforcing the importance of studies in this area in different regions of the globe. Thus, the aim of this study was to analyze the effects of land use change on the rivers and streams of the Cachoeira River Basin in the Northeast of Brazil. Samples were collected bi-monthly at 16 points along the basin over 1 year and analyzed for physical and chemical parameters (temperature, pH, conductivity, and percentage saturation of dissolved oxygen), inorganic nutrients (NO₃^-, NO₂^-, NH₄⁺/NH₃, PO₄^3-, SiO₄) and dissolved major ions (Ca²⁺, K⁺, Mg²⁺, Na⁺, HCO₃^-). The highest concentrations of NO₃^-, NO₂^-, NH₄⁺/NH₃, and PO₄^3- occurred at the points with the highest percentage of urban areas and population density. The major ions Ca²⁺, K⁺, Mg²⁺, Na⁺, and HCO₃^- were positively correlated with the percentage of pasture coverage; however, the high concentrations of these ions and the strong correlation between them revealed that other factors besides land use, such as soil cover, geological formation, and water deficit, may be jointly contributing to increases in their concentrations. Thus, the results show that urbanization represents the type of land use with the greatest negative effect on water quality since it alters the concentrations of inorganic nutrients dissolved in the Cachoeira River Basin.

Land cover impacts on storm flow suspended solid and nutrient concentrations in southwest Ohio streams

Impacts between urban and agricultural land cover on storm flow water quality are poorly understood for the Eastern Corn Belt Ecoregion in SW Ohio. Storm flow water samples were collected from May 2017 to October 2017 across seven SW Ohio watersheds which ranged in urban land cover from 6% to 92% and in agricultural land cover from 4% to 70%. Two watersheds contained water resource recovery facilities (WRRFs). Percent agricultural land cover in a watershed and storm magnitude were primary explanatory variables for total suspended solid and total phosphorus concentrations. Total nitrogen, nitrate, and phosphate concentrations were primarily explained by the presence of WRRFs and percent agricultural land cover. Increased dissolved nutrient concentrations in watersheds with WRRFs indicate that WRRFs in the study area are ineffectively removing nitrate and phosphate from effluent. Results suggest that to improve water quality during storm flows, additional management efforts need to be focused on agricultural watersheds and WRRFs. PRACTITIONER POINTS: Storm flow water quality in the study area is significantly affected by land cover, WRRF Q, and storm Q. TSS and TP concentrations are best explained by percent of agricultural land cover in a watershed and magnitude of storms. TN, NO₃ -N, and PO 4 3 -P concentrations are best explained by WRRF Q, followed by the percent agricultural land cover. This study shows that agricultural land cover and WRRFs play a significant role in water quality degradation in SW Ohio.

An Integrated Approach for Evaluating Water Quality between 2007–2015 in Santa Cruz Island in the Galapagos Archipelago

Water quality in Galápagos has been deteriorating by increased human impacts over the past few decades. Water quality is a key environmental component and issue in need to be evaluated in the Pelican Bay Watershed, the biggest urban and economic development of Santa Cruz Island, for better management and regulation of water resources. This study assesses coastal and ground water bodies of Pelican Bay by employing a 9-year dataset obtained during a local water quality monitoring program conducted by the Galápagos National Park. Physical-chemical and microbial parameters were evaluated with respect to national and international water quality standards. A statistical integrated approach was performed to calculate environmental background levels of water quality parameters and to explore their seasonal and spatial variation. In addition, a sensitivity analysis was conducted to evaluate the impact of changes in tourism and residents in San Cruz Island in the degradation of water sources. Results highlighted are: (a) water is not suitable for drinking and domestic use at some inland sites; (b) saline water is used for irrigation in the highlands; (c) the presence of parameters of concern at coastal sites represent a risk for human and ecosystem health; (d) background levels may serve for defining site-specific limits to control water quality, and; (e) the influence of population change on water quality conditions varied at each site with a higher effect at coastal sites relatively to inland sites. This study provided valuable information of the water quality status in Santa Cruz Island and can serve as a baseline for effective water management and control of pollution.

Diel changes in aquatic biogeochemistry of a pristine stream receiving untreated urban sewage at Brazilian rainforest

Freshwater bodies experience diel variations in aquatic chemistry, driven by natural processes. However, changes in land use, like urbanization, can modify the natural dynamics of such systems. This article describes changes in biogeochemistry of a pristine stream after receiving untreated sewage of an urban nucleus. Water samples were collected and field parameters measured, during low flow period. Temperature, pH, dissolved oxygen, electric conductivity, turbidity, total suspended solids, silicate, N-NO₃, N-NO₂, N-NH₄, dissolved and particulate organic nitrogen, PO₄, and dissolved and particulate organic phosphorus were measured hourly during a diel cycle. Upstream hydrochemistry resembles pristine watersheds in tropical rainforest, and results are restricted to a narrow range of values during the entire sampling period. Conversely, values downstream varied widely and, for some analytes, presented differences between day and night. Dissolved oxygen and electric conductivity showed the effect of the urban pulse, varying according to the routine of the population. Other field parameters did no presents a pattern that could distinguish up- and downstream stations. All the nutrients, but silicate, increased in concentration downstream. Particulate organic phosphorus, N-NO₂, and N-NH₄ were the nutrients that highlight the magnitude of the changes driven by urban effluents. These three nutrient species, and dissolved organic phosphorus, revealed a remarkably pattern that reflects the routine of the urban population, with low concentrations at night and a progressive increase starting at the early morning.

Influence of land use on trophic state indexes in northeast Brazilian river basins

Eutrophication is a natural process within the ecological succession of aquatic ecosystems that results from nutrient inputs to water bodies, especially limiting elements such as phosphorus and nitrogen. However, the anthropogenic activities in river basin influence areas accelerate the eutrophication process of water bodies. Eutrophication is a global problem and considered one of the most relevant reasons of aquatic environments' degradation. In this context, watercourses that make up the Eastern Water Planning and Management Region (RPGA) receive high pollutant contributions due to release of wastewater and agriculture diffuse sources from cities located in influence area. The present study aims to evaluate the land use effect in trophic state of the water bodies in Eastern RPGA basins. The Carlson Trophic State Index in 1977, adjusted by Lamparelli 2004, was used to determine the eutrophication degree of the three river basins (Almada, Cachoeira, and Una) located in the Eastern RPGA. The nutrient and chlorophyll a data were obtained from the Monitoring Program (Monitora) of Environment and Water Resources Institute of Bahia (INEMA), covering the period from 2008 to 2015, at thirteen (13) sampling sites, with quarterly collections. The results showed that, among three basins analyzed, Cachoeira River basin presented the worst values for trophic state index (TSI) due to the high level of anthropization, while best results were found in Una basin. It was verified that land use exerted a significant influence on the water quality of bodies of water evaluated.

Holistic approach for quantification and identification of pollutant sources of a river basin by analyzing the open drains using an advanced multivariate clustering

Global scarcity of freshwater has been gearing towards an unsustainable river basin management and corresponding services to the humans. It needs a holistic approach, which exclusively focuses on effective river water quality monitoring and quantification and identification of pollutant sources, in order to address the issue of sustainability. These days, rivers are heavily contaminated due to the presence of organic and metallic pollutants released from several anthropogenic sources, such as industrial effluents, domestic sewage, and agricultural runoff. It is astonishing to note that even in many developing countries, most of these contaminants are carried through open drains, which enter river premises without proper treatment. Such practice not only devastates riverine ecosystem but also gives rise to deadly diseases, such as minimata and cancer in humans. Considering these issues, the present study develops a novel approach towards simultaneous identification of major sources of pollution in the rivers, along with critical pollutants and locations using an advanced hierarchical cluster and multivariate statistical analysis. A systematic approach has been developed by agglomerating both R-mode and Q-mode analysis, which develops monoplots, two-dimensional biplots, rotated component matrices, and dendrograms (using "SPSS" and "Analyse It" software) to reveal relationships among various quality parameters to identify the pollutant sources along with clustering of critical sampling sites and pollutants. A case study of the Ganges River Basin of India has been considered to demonstrate the efficacy and usefulness of the model by analyzing 85 open drains. Both organic and metallic pollutants are analyzed simultaneously as well as separately to get a holistic understanding of all the relationships and to broaden the perspective of water characterization. Results provide a comprehensive guidance to the policy makers and water managers to optimize corrective efforts, minimize further damage, and improve the water quality condition to ensure sustainable development of the river basin.

The Distribution of Road Salt in Private Drinking Water Wells in a Southeastern New York Suburban Township

We used a GIS analysis of sodium and chloride concentrations in private water wells in a southeastern New York township to describe the pattern of distribution of road salt in aquifers tapped for drinking water. The primary source of road salt was sodium chloride, and sodium and chloride concentrations were significantly correlated ( = 0.80, < 0.01). Chloride concentrations in wells increased as the percentage of impervious surface cover (ISC) within a 250-m radius around wells increased ( = 0.87, < 0.01) and declined with increasing distance to the nearest road ( = 0.76, < 0.01). Wells that were located lower in elevation than the nearest road had higher concentrations of chloride than wells that were higher than the nearest road, but this occurred only when the nearest road was >30 m from the wells ( < 0.01). Chloride concentrations were not affected by well depth or adjacent road type (major or minor roads). Surface geology and hydrologic soil class had significant effects ( < 0.01) on chloride concentrations in wells, with porous surface geology types and well-drained soils having higher concentrations; these effects may be confounded by the fact that ISC was more likely to occur on these permeable surface geology and soil types. Hot and cold spot analysis revealed substantial unevenness in chloride concentrations. Results for sodium were similar to those for chloride. Overall, these results indicate that road salt contamination of groundwater is unevenly distributed and is affected by landscape factors that can be used to guide well testing and best management practices of deicing salt distribution.

Driver detection of water quality trends in three large European river basins

This study analyses how indicators of water quality (thirteen physico-chemical variables) and drivers of change (i.e., monthly aggregated air temperature and streamflow, population density, and percentage of agricultural land use) coevolve in three large European river basins (i.e., Adige, Ebro, Sava) with different climatic, soil and water use conditions. Spearman rank correlation, Principal Component Analysis, and Mann-Kendall trend tests were applied to long-term time series of water quality data during the period 1990-2015 in order to investigate the relationships between water quality parameters and the main factors controlling them. Results show that air temperature, considered as a proxy of climatic change, has a significant impact, in particular in the Adige and Ebro: positive trends of water temperature and negative of dissolved oxygen are correlated with upward trends of air temperatures. The aquatic ecosystems of these rivers are, therefore, experiencing a reduction in oxygen, which may exacerbate in the future given the projected further increase in temperature. Furthermore, monthly streamflow has been shown to reduce in the Ebro, thereby reducing the beneficial effect of dilution, which appears evident from the observed upward patterns of chloride concentrations and electrical conductivity. Upward trends of chloride and biological oxygen demand in the Adige and Sava, and of phosphate in the Adige appears to be related to increasing human population density, whereas phosphates in the Sava and biological oxygen demand in the Ebro are highly correlated with agricultural land use, considered as a proxy of the impact of agricultural practises. The present study shows the complex relationships between drivers and observed changes in water quality parameters. Such analysis can represent, complementary to a deep knowledge of the investigated systems, a reliable tool for decision makers in river basin planning by providing an overview of the potential impacts on the aquatic ecosystem of the three basins.

Spatial Regression and Prediction of Water Quality in a Watershed with Complex Pollution Sources

Fast economic development, burgeoning population growth, and rapid urbanization have led to complex pollution sources contributing to water quality deterioration simultaneously in many developing countries including China. This paper explored the use of spatial regression to evaluate the impacts of watershed characteristics on ambient total nitrogen (TN) concentration in a heavily polluted watershed and make predictions across the region. Regression results have confirmed the substantial impact on TN concentration by a variety of point and non-point pollution sources. In addition, spatial regression has yielded better performance than ordinary regression in predicting TN concentrations. Due to its best performance in cross-validation, the river distance based spatial regression model was used to predict TN concentrations across the watershed. The prediction results have revealed a distinct pattern in the spatial distribution of TN concentrations and identified three critical sub-regions in priority for reducing TN loads. Our study results have indicated that spatial regression could potentially serve as an effective tool to facilitate water pollution control in watersheds under diverse physical and socio-economical conditions.

Evaluation of nutrients and major ions in streams-implications of different timescale procedures

Small watersheds are characterized by a high degree of sensitivity to changes observed in their environment, making them important sampling and management units. Due to this high sensitivity, several studies have shown that intensive collecting may be more effective in these systems compared to other timescale procedures. The aim of this study was to evaluate the concentration of organic and inorganic nutrients and major ions dissolved in two small watersheds with different land uses to determine whether there are differences between these watersheds with different levels of impact and to identify the most appropriate timescale procedure for the variables under analysis. Therefore, monthly, daily, and hourly samples were taken in the two streams in the northeast of Brazil. One of the streams is located in an undisturbed area (environmental protected area) (S1) and one in a disturbed area (S2). The results showed significant differences for conductivity, temperature, pH, dissolved oxygen (%), sodium (Na(+)), and chloride (Cl(-)) ions and higher values presented in the anthropogenic stream. Dissolved inorganic nitrogen (DIN) in S2 mainly comprised ammonium (NH4 (+)), while nitrate (NO3 (-)) predominated in S1. The considerable increase in the concentration of NO3 (-) and dilution of Na(+) and Cl(-) after rain in April in S1 shows how precipitation may change the chemical composition of the water in a 1-day period. No changes were observed in the concentrations of major ions and nutrients that could be related to the cyclical variation of the hours during the day in both small watersheds. Daily collections allow better monitoring of the dynamics of streams and greater robustness of the data.

Water quality changes in response to urban expansion: spatially varying relations and determinants

Urban expansion is an important stressor to water bodies, and the spatial variations of their relations are increasingly highlighted by recent studies. What remain unclear, however, are the underlying drivers to the spatial variability. The paper was not limited to modeling spatially varying linkages but also drew attention to the local anthropogenic influential factors that shape land-water relations. We employed geographically weighted regression to examine the relationships between urban expansion (measured by land use change intensity) and water quality changes (focusing on six water quality indicators) in a recently fast-growing Chinese city, Lianyungang. Specifically, we analyzed how the local characteristics including urbanization level, environmental management, industrial zone expansion, and land use composition, attributed to the varying responses of water quality changes. Results showed that urbanization level significantly affects land-water linkages. Remarkable water quality improvement was accompanied by urbanization in highly developed watersheds, primarily due to strong influence from extensive water management practices (particularly for COD, BOD, NH3-N, and TP). By contrast, water qualities of less-urbanized watersheds were more sensitive and negatively responsive to land use changes. Clustering industrial activities acted as distinct contributor to Hg contamination, while boosted organic pollution control in highly urbanized areas. The approach proposed in the study can locate and further zoom into the hot-spots of human-water interactions, thereby contributing to better solutions for mitigating undesirable impacts of urbanization on water environment.

Quantification of phytoplankton bloom dynamics by citizen scientists in urban and peri-urban environments

Freshwater ecosystems are severely threatened by urban development and agricultural intensification. Increased occurrence of algal blooms is a main issue, and the identification of local dynamics and drivers is hampered by a lack of field data. In this study, data from 13 cities (250 water bodies) were used to examine the capacity of trained community members to assess elevated phytoplankton densities in urban and peri-urban freshwater ecosystems. Coincident nutrient concentrations and land use observations were used to examine possible drivers of algal blooms. Measurements made by participants showed a good relationship to standard laboratory measurements of phytoplankton density, in particular in pond and lake ecosystems. Links between high phytoplankton density and nutrients (mainly phosphate) were observed. Microscale observations of pollution sources and catchment scale estimates of land cover both influenced the occurrence of algal blooms. The acquisition of environmental data by committed and trained community members represents a major opportunity to support agency monitoring programmes and to complement field campaigns in the study of catchment dynamics.

Spatial and temporal analysis of land cover changes and water quality in the Lake Issaqueena watershed, South Carolina

Monitoring changes in land cover and the subsequent environmental responses are essential for water quality assessment, natural resource planning, management, and policies. Over the last 75 years, the Lake Issaqueena watershed has experienced a drastic shift in land use. This study was conducted to examine the changes in land cover and the implied changes in land use that have occurred and their environmental, water quality impacts. Aerial photography of the watershed (1951, 1956, 1968, 1977, 1989, 1999, 2005, 2006, and 2009) was analyzed and classified using the geographic information system (GIS) software. Seven land cover classes were defined: evergreen, deciduous, bare ground, pasture/grassland, cultivated, and residential/other development. Water quality data, including sampling depth, water temperature, dissolved oxygen content, fecal coliform levels, inorganic nitrogen concentrations, and turbidity, were obtained from the South Carolina (SC) Department of Health and Environmental Control (SCDHEC) for two stations and analyzed for trends as they relate to land cover change. From 1951 to 2009, the watershed experienced an increase of tree cover and bare ground (+17.4 % evergreen, +62.3 % deciduous, +9.8 % bare ground) and a decrease of pasture/grassland and cultivated land (-42.6 % pasture/grassland and -57.1 % cultivated). From 2005 to 2009, there was an increase of 21.5 % in residential/other development. Sampling depth ranged from 0.1 to 0.3 m. Water temperature fluctuated corresponding to changing air temperatures, and dissolved oxygen content fluctuated as a factor of water temperature. Inorganic nitrogen content was higher from December to April possibly due to application of fertilizers prior to the growing season. Turbidity and fecal coliform bacteria levels remained relatively the same from 1962 to 2005, but a slight decline in pH can be observed at both stations. Prior to 1938, the area consisted of single-crop cotton farms; after 1938, the farms were abandoned, leaving large bare areas with highly eroded soil. Starting in 1938, Clemson reforested almost 30 % of the watershed. Currently, three fourths of the watershed is forestland, with a limited coverage of small farms and residential developments. Monitoring water quality is essential in maintaining adequate freshwater supply. Water quality monitoring focuses mainly on the collection of field data, but current water quality conditions depend on the cumulative impacts of land cover change over time.