Atmospheric influences on water quality: a simulation of nutrient loading for the Pearl River Basin, USA

Phytoplankton diversity in wastewater impacted Indian Ramsar site: a study from East Kolkata Wetland

A seasonal study was undertaken to understand the influence of wastewater on phytoplankton distribution in a water body of East Kolkata Wetland (EKW), a designated Ramsar site in Kolkata, West Bengal, India. A total of 19 different genera of phytoplankton belonging to 5 phyla were recorded. Among all the groups, Chlorophyceae was found to be dominated by 8 genera followed by Bacillariophycaeae (4 genera), Cyanophyceae (4 genera), Euglenophyceae (2 genera), and Zygnematophyceae (1 genus). Seasonal variability showed maximum dominance of phytoplankton during post-monsoon and least during pre-monsoon months. Shannon-Wiener diversity (H') indices indicated Bacillariophyceae to be most species rich (1.059) while the most dominant group (D) was observed to be Chlorophyceae (0.507). Assessment of Palmer algal pollution index (PI) revealed the water body is impacted by high organic pollution during monsoon (22) compared to the pre-monsoon (19) and post-monsoon seasons (15). The results of canonical correspondence analysis (CCA) indicated water temperature, alkalinity, total dissolved solids, dissolved oxygen, and electrical conductivity as the major influencing parameters for growth and distribution of the phytoplankton in the water body. Therefore, it can be stated that hydrological alteration of a water body fed with wastewater plays a significant role in regulating the plankton density, richness, and diversity.

Projection of Sediment Loading from Pearl River Basin, Mississippi into Gulf of Mexico under a Future Climate with Afforestation

Sediment load in rivers is recognized as both a carrier and a potential source of contaminants. Sediment deposition significantly changes river flow and morphology, thereby affecting stream hydrology and aquatic life. We projected sediment load from the Pearl River basin (PRB), Mississippi into the northern Gulf of Mexico under a future climate with afforestation using the SWAT (Soil and Water Assessment Tool)-based HAWQS (Hydrologic and Water Quality System) model. Three simulation scenarios were developed in this study: (1) the past scenario for estimating the 40-year sediment load from 1981 to 2020; (2) the future scenario for projecting the 40-year sediment load from 2025 to 2064, and (3) the future afforestation scenario that was the same as the future scenario, except for converting the rangeland located in the middle section of the Pearl River watershed of the PRB into the mixed forest land cover. Simulations showed a 16% decrease in sediment load for the future scenario in comparison to the past scenario due to the decrease in future surface runoff. Over both the past and future 40 years, the monthly maximum and minimum sediment loads occurred, respectively, in April and August; whereas the seasonal sediment load followed the order: spring > winter > summer > fall. Among the four seasons, winter and spring accounted for about 86% of sediment load for both scenarios. Under the future 40-year climate conditions, a 10% reduction in annual average sediment load with afforestation was observed in comparison to without afforestation. This study provides new insights into how a future climate with afforestation would affect sediment load into the northern Gulf of Mexico.

A REVIEW OF WATER QUALITY RESPONSES TO AIR TEMPERATURE AND PRECIPITATION CHANGES 1: FLOW, WATER TEMPERATURE, SALTWATER INTRUSION

Anticipated future increases in air temperature and regionally variable changes in precipitation will have direct and cascading effects on U.S. water quality. In this paper, and a companion paper by Coffey et al. (2019), we review technical literature addressing the responses of different water quality attributes to historical and potential future changes in air temperature and precipitation. The goal is to document how different attributes of water quality are sensitive to these drivers, to characterize future risk to inform management responses and to identify research needs to fill gaps in our understanding. Here we focus on potential changes in streamflow, water temperature, and salt water intrusion (SWI). Projected changes in the volume and timing of streamflow vary regionally, with general increases in northern and eastern regions of the U.S., and decreases in the southern Plains, interior Southwest and parts of the Southeast. Water temperatures have increased throughout the U.S. and are expected to continue to increase in the future, with the greatest changes in locations where high summer air temperatures occur together with low streamflow volumes. In coastal areas, especially the mid-Atlantic and Gulf coasts, SWI to rivers and aquifers could be exacerbated by sea level rise, storm surges, and altered freshwater runoff. Management responses for reducing risks to water quality should consider strategies and practices robust to a range of potential future conditions.

A REVIEW OF WATER QUALITY RESPONSES TO AIR TEMPERATURE AND PRECIPITATION CHANGES 2: NUTRIENTS, ALGAL BLOOMS, SEDIMENT, PATHOGENS

In this paper we review the published, scientific literature addressing the response of nutrients, sediment, pathogens and cyanobacterial blooms to historical and potential future changes in air temperature and precipitation. The goal is to document how different attributes of water quality are sensitive to these drivers, to characterize future risk, to inform management responses and to identify research needs to fill gaps in our understanding. Results suggest that anticipated future changes present a risk of water quality and ecosystem degradation in many U.S. locations. Understanding responses is, however, complicated by inherent high spatial and temporal variability, interactions with land use and water management, and dependence on uncertain changes in hydrology in response to future climate. Effects on pollutant loading in different watershed settings generally correlate with projected changes in precipitation and runoff. In all regions, increased heavy precipitation events are likely to drive more episodic pollutant loading to water bodies. The risk of algal blooms could increase due to an expanded seasonal window of warm water temperatures and the potential for episodic increases in nutrient loading. Increased air and water temperatures are also likely to affect the survival of waterborne pathogens. Responding to these challenges requires understanding of vulnerabilities, and management strategies to reduce risk.