Freshwater quality in urban areas: a case study from Rome, Italy

Mapping Urbanization and Evaluating Its Possible Impacts on Stream Water Quality in Chattanooga, Tennessee, Using GIS and Remote Sensing

Impervious surfaces (IS) produced by urbanization can facilitate pollutants’ movement to nearby water bodies through stormwater. This study mapped and estimated the IS changes in Chattanooga, Tennessee, using satellite imagery acquired in 1986 and 2016. A model was developed utilizing the Normalized Difference Vegetation Index coupled with density slicing to detect and map urbanization through IS growth. Urban growth was quantified at USGS HUC12 watershed level including stream riparian areas. The obtained results show a net growth of 45.12 km2 of IS with a heterogeneous distribution. About 9.96 km2 of this growth is within 90 m of streams, about 6% of the study site’s land cover. The Lower South Chickamauga Creek watershed experienced the largest urban growth with a change from 24.2 to 48.5 km2. Using the riparian zone percent imperviousness, a stream risk assessment model was developed to evaluate potential stream impairment due to this growth. Approximately 87, 131, and 203 km lengths of streams identified as potentially at high, very high, and extreme risks, respectively, to be impaired due to urban growth from the last 30 years. These findings would benefit to proactively implement sustainable management plans for the streams near rapidly urbanizing areas in the study site.

Defining nutrient and biochemical oxygen demand baselines for tropical rivers and streams in São Paulo State (Brazil): a comparison between reference and impacted sites

Determining reference concentrations in rivers and streams is an important tool for environmental management. Reference conditions for eutrophication-related water variables are unavailable for Brazilian freshwaters. We aimed to establish reference baselines for São Paulo State tropical rivers and streams for total phosphorus (TP) and nitrogen (TN), nitrogen-ammonia (NH(4) (+)) and Biochemical Oxygen Demand (BOD) through the best professional judgment and the trisection methods. Data from 319 sites monitored by the São Paulo State Environmental Company (2005 to 2009) and from the 22 Water Resources Management Units in São Paulo State were assessed (N = 27,131). We verified that data from different management units dominated by similar land cover could be analyzed together (Analysis of Variance, P = 0.504). Cumulative frequency diagrams showed that industrialized management units were characterized by the worst water quality (e.g. average TP of 0.51 mg/L), followed by agricultural watersheds. TN and NH(4) (+) were associated with urban percentages and population density (Spearman Rank Correlation Test, P < 0.05). Best professional judgment and trisection (median of lower third of all sites) methods for determining reference concentrations showed agreement: 0.03 & 0.04 mg/L (TP), 0.31 & 0.34 mg/L (TN), 0.06 & 0.10 mg-N/L (NH(4) (+)) and 2 & 2 mg/L (BOD), respectively. Our reference concentrations were similar to TP and TN reference values proposed for temperate water bodies. These baselines can help with water management in São Paulo State, as well as providing some of the first such information for tropical ecosystems.

Watershed influence on fluvial ecosystems: an integrated methodology for river water quality management

The EU Water Framework Directive 2000/60 (Integrated River Basin Management for Europe) establishes the importance of preserving water quality through policies applied at watershed level given the strong links existing among ecological, hydrological, and hydrogeological systems. Therefore, monitoring campaigns of river water quality should be planned with multidisciplinary approaches starting from a landscape perspective. In this paper, the effects of the basin hydrology on the river water quality and, in particular, the impacts caused by the runoff production coming from agricultural areas are investigated. The fluvial segments receiving consistent amount of pollutant loads (due to the runoff routing over agricultural areas) are assumed more critical in terms of water quality and thus, they require more accurate controls. Starting from this perspective, to evaluate the runoff productions coming from agricultural areas, we applied a semi-distributed hydrological model that adopts satellite data, pedological and morphological information for the watershed description. Then, the river segments receiving critical amount of runoff loads from the surrounding cultivated areas were identified. Finally, in order to validate the approach, water quality for critical and non critical segment was investigated seasonally, by using river macroinvertebrates as indicators of water quality because of their effectiveness in preserving in time a memory of pollution events. Biomonitoring data showed that river water quality strongly decreases in correspondence of fluvial segments receiving critical amount of runoff coming from agricultural areas. The results highlight the usefulness of such a methodology to plan monitoring campaigns specifically devoted to non-point pollution sources and suggest the possibility to use this approach for water quality management and for planning river restoration policies.

Temporal variations of surface water quality in urban, suburban and rural areas during rapid urbanization in Shanghai, China

As the economic and financial center of China, Shanghai has experienced an extensive urban expansion since the early 1980s, with an attendant cost in environmental degradation. We use an integrated pollution index to study the temporal variations of surface water quality in urban, suburban and rural areas between 1982 and 2005. Data on monitored cross-sections were collected from the Shanghai Environmental Monitoring Center. The results indicated that the spatial pattern of surface water quality was determined by the level of urbanization. Surface water qualities in urban and suburban areas were improved by strengthening the environmental policies and management, but were worsening in rural areas. The relationship between economic growth and surface water quality in Shanghai showed an inversed-U-shaped curve, which reflected a similar pattern in most developed countries. This research suggests that decision makers and city officials should be more aware of the recent pollution increases in Shanghai.