IMPACTS OF EL NIÑO AND MONSOONAL INTERACTIONS ON RIVER WATER QUALITY AND CAGE AQUACULTURE IN THE PAHANG RIVER, MALAYSIA

Zooplankton samples from the North Arabian Sea Environment and Ecosystem Research (NASEER) cruises were analyzed to determine the basic taxonomic composition, biomass (standing stock) and the total and copepod numeric abundance; these characteristics are discussed with reference to the different monsoon periods. Cruises carried out during March 1993 and May 1994, categorized as pre-southwest monsoon periods, and a cruise in December 1994, categorized as a northeast monsoon period, are discussed in detail. The biomass of January 1992 versus August 1992 and August 1992 versus March 1993 differed significantly (F = 6.44, P≤ 0.05). Ranges of highest and lowest biomass from each cruise are also given. Distinct “high” and “low” production areas of statistically significant difference (F = 12.67, P≤ 0.05) were observed. The “high” and “low” production areas were mobile and followed the surface wind circulation patterns (wind reversal pattern) during the northeast and southwest monsoon periods. Overall zooplankton showed a patchy distribution. The overall zooplankton abundance and total copepod counts differed significantly between the Cruises 3 versus 4 and 4 versus 5 (F = 15.67, P≤ 0.05 and F = 34.39, P≤ 0.05, respectively). There was no significant difference (P≥ 0.05) in biomass, between eutrophic and oligotrophic stations, suggesting no difference between near shore and offshore waters. Thirty-eight taxonomic groups were identified from the samples, with copepods being the most dominant group, followed by chaetognaths and siphonophores. Copepods constitute an average of 52.50 to 74.93% of the total zooplankton count and reach maxima of 92.14% of the total zooplankton count at the outset of the southwest monsoon (March 1993) and 91.39% at the outset of the active northeast monsoon (December 1994).

Excess nutrients from agriculture in the Mississippi River drainage, USA have degraded water quality in freshwaters and contributed to anoxic conditions in downstream estuaries. Consequently, water quality is a significant concern associated with conversion of lands to bioenergy production. This study focused on the Arkansas‐White‐Red river basin (AWR), one of five major river basins draining to the Mississippi River. The AWR has a strong precipitation gradient from east to west, and advanced cellulosic feedstocks are projected to become economically feasible within normal‐to‐wet areas of the region. In this study, we used large‐scale watershed modeling to identify areas along this precipitation gradient with potential for improving water quality. We compared simulated water quality in rivers draining projected future landscapes with and without cellulosic bioenergy for two future years, 2022 and 2030 with an assumed farmgate price of $50 per dry ton. Changes in simulated water quantity and quality under future bioenergy scenarios varied among subbasins and years. Median water yield, nutrient loadings, and sediment yield decreased by 2030. Median concentrations of nutrients also decreased, but suspended sediment, which is influenced by decreased flow and in‐stream processes, increased. Spatially, decreased loadings prevailed in the transitional ecotone between 97° and 100° longitude, where switchgrass, Panicum virgatum L., is projected to compete against alternative crops and land uses at $50 per dry ton. We conclude that this region contains areas that hold promise for sustainable bioenergy production in terms of both economic feasibility and water quality protection.

Understanding the temporal changes in river water quality is important for catchment water quality management. This study aims to detect and attribute long‐term trends and abrupt changes in river water quality. We used 26 years of water quality data (1994–2020) collected from 102 river monitoring sites across Victoria, south‐eastern Australia. We analysed six water quality constituents that are of key concerns for Australian catchment management, namely: electrical conductivity (EC), total suspended solids, nitrate‐nitrite, total Kjeldahl nitrogen, total phosphorous and filtered reactive phosphorus. To detect trends and abrupt changes in water quality at each site, a Bayesian ensemble modelling approach was applied, namely, the Bayesian estimator of abrupt change, seasonal change, and trend (BEAST). To explain water quality trends, we then built multivariate regressions to link water quality with streamflow and seasonality, and then compared alternative model structures with and without a change in the regression relationships informed by the changes detected by BEAST. Among the six constituents studied, EC shows the most distinct systematic trends, with 21 sites having a significant increase followed by a non‐significant trend; within the 21 sites, 14 had a significant change point in EC around Year 2010. The regression analyses between water quality and streamflow suggested that the observed systematic change in EC could be largely related to reduced streamflow during the Millennium drought, which greatly impacted the climate and hydrology of south‐eastern Australia over the first decade of 2000. The results of this study can help inform the design of effective mitigation strategies and avoid further degradation of water quality across Victoria. Besides, our trend analysis and attribution approaches are applicable to water quality time series in other regions for robust trend analysis and change point detection.

Impact of informal regulation of pollution on water quality in rivers in India

Transboundary spillovers may degrade environmental quality if countries free ride. This paper examines the extent of such degradation in water quality in international rivers. Using data from river monitoring stations in the UN's Global Emissions Monitoring System (GEMS), it compares pollution levels in international and domestic rivers. The results suggest that free riding may substantially increase pollution in international rivers, but the estimates are sensitive to the inclusion of country effects.

Transboundary spillovers may degrade environmental quality if countries free ride. This paper examines the extent of such degradation in water quality in international rivers. Using data from river monitoring stations in the UN's Global Emissions Monitoring System (GEMS), it compares pollution levels in international and domestic rivers. The results suggest that free riding may substantially increase pollution in international rivers, but the estimates are sensitive to the inclusion of country effects.

Suspended Particulate Matter (SPM) essentially related to the total scattering of particles in the water column. It plays the role as a transport medium for pollutants, total load of organic and inorganic substance in the water phase. In this study, we have developed empirical relationship based on a strong relationship between Landsat near infrared (NIR) band and archived SPM data. The following were the power equations:SPM NE (mg/l) = 11.68x0.666SPM SW (mg/l) = 18.61x0.493where, x (TM4) is radiance of ETM+ NIR band 4 was developed under tropical atmospheric conditions. Using the above equation, the SPM concentration for Northeast and Southwest monsoon in the Pahang River estuary as a case study was determined. The mean SPM concentration and mean reflectance value during Northeast monsoon were 131.69 mg/l and 0.135 mg/l. The mean SPMconcentration value and reflectance were 95.94 mg/l and 0.078 mg/l during the Southwest monsoon. Generally, from remote sensing archive data and above equations, the SPM concentrations of Pahang River were successfully determined from 1999 to 2012.

Pahang River (Sg. Pahang) is the longest river in Peninsular Malaysia. Flood is a common event in Pahang River Basin during wet season which triggered by monsoon season. The hydrodynamic study of Pahang River should be well understood especially when it is a target of northeast monsoon which influenced the Pahang River Basin every year (from November to March). 17 river cross section stations were selected and used to measure its drainage capacity, hydraulic parameters and estimation of flow discharge. Long term (1980 to 2009) variation of hydrologic data series comprised of river flow, river stage and rainfall data were analyzed based on the Department of Irrigation and Drainage (DID) Malaysia record. Monthly rainfall was recorded from Sg. Yap, Temerloh and Lubuk Paku Rainfall Stations. Two hydrologic sampling trips had been carried out; first sampling on January 2010 and second sampling on February 2010. The study indicates that velocity and river flow measurement during first sampling ranged from 0.308 to 0.582 m sec-1 and 153.282 to 439.684 m3 sec-1. Meanwhile, during second sampling, the velocity and river flow ranged from 0.217 to 0.484 and 52.071 to 304.485 m3 sec-1, respectively. Floods were occurred annually at Pahang River especially during northeast monsoon, these events are expected to be stimulated by the inconsistent condition of width and depth along Pahang River which finally create sedimentation and meandering characteristic.

A holistic assessment of spatiotemporal variation, driving factors, and risks influencing river water quality in the northeastern Qinghai-Tibet Plateau

Eleven physicochemical parameters of data collected from 12 stations in Daya Bay in 2003 were analyzed by multivariate statistical analysis. Cluster analysis (CA) grouped data from 4 seasons into two groups, the northeast and southwest monsoon periods, representing different natural processes. During the northeast monsoon period, principal component analysis (PCA) and CA group the 12 monitoring sites into Cluster DA1 (S1, S2 and S6) and Cluster DA2 (S3-S5 and S7-S12). During the southwest monsoon period, PCA and CA group the 12 monitoring sites into Cluster WB1 (S1, S2, S7, S9 and S11) and Cluster WB2 (S3-S6, S8, S10, S11 and S12). The spatial heterogeneity within the bay was defined by different hydrodynamic conditions and human activities. These results may be valuable for achieving sustainable use of the coastal ecosystems in Daya Bay.

A study pertaining to the seasonal variation in physicochemical properties of the coastal waters was carried out at Kalpakkam coast for a period of 1 year (February 2006 to January 2007). It revealed that the coastal water was significantly influenced by freshwater input during North East (NE) monsoon and post-monsoon periods. Concentration of all the nutrients and dissolved oxygen (DO) was relatively high during the NE monsoon, whereas, salinity and chlorophyll-a (chl-a) were at their minimum level during this period. Phytoplankton production peak was observed in summer during which a typical marine condition prevailed. The present observed values of nitrate, phosphate, silicate, and turbidity are significantly high (five to ten times) compared to that of the pre-Tsunami period from this coast. Relatively low DO and chl-a concentration was noticed during the post-Tsunami period. A notable feature of this study is that though nutrient concentration in the coastal waters during post-Tsunami period has increased significantly, turbidity, the most single dominating factor, was found to adversely affect the phytoplankton production during post-Tsunami period as reflected by relatively low chl-a concentration. Thus, the post-Tsunami period may result in a change in coastal biodiversity pattern concomitant with change in coastal water quality.

Yamuna River supplies over 70% water to the Indian capital Delhi. It has become one of the most polluted rivers globally, impacting the daily lives of over 57 million people. This study analyzes the changes in the water quality of the Yamuna River resulting from the inflow of wastewater from the Najafgarh Drain (Sahibi River) and investigates the phycoremediation potential of microalga Scenedesmus sp. Water quality parameters were assessed at the points where drains meet with the river, revealing significant degradation in water quality. Results show a 12.33 ± 0.5% decrease in pH and substantial increase in salinity (137 ± 2.2%), conductivity (155.73 ± 2.7%), total dissolved solids (TDS) (135.27 ± 3.4%), chemical oxygen demand (COD) (113.33 ± 3.6%), biochemical oxygen demand (BOD) (150 ± 4.5%), and other chemical contaminants. Heavy metal analysis of Yamuna after merging with drain using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) revealed alarming concentrations, particularly of lead (Pb, 44.33 ± 0.03µg/L) and mercury (Hg, 1.06 ± 0.02µg/L), exceeding World Health Organization (WHO) guidelines. Liquid Chromatography-Mass Spectrometry (LC-MS) analysis identified a wide range of pollutants, including herbicides, insecticides, fungicides, plasticizers, xenobiotic compounds, and persistent chemicals like perfluoropentanesulfonic acid (PFBS). Treatment with Scenedesmus sp. significantly reduced pollution in Najafgarh Drain water, with the highest reductions in manganese (Mn) at 95.86 ± 6.92% and cadmium (Cd) at 86.90 ± 2.97%. Scenedesmus sp. reduced magnesium (Mg) by 87.98 ± 7.84%, Pb by 80.12 ± 4.02% in Yamuna water, and effectively lowered nitrate and phosphate levels by 86.62 ± 8.6% and 65.53 ± 4.35%, respectively. The algae also contributed to significant reductions in salinity, conductivity, TDS, COD, and BOD. This study highlights the critical role of the Najafgarh Drain in polluting Yamuna and demonstrates the potential of Scenedesmus sp. for water quality improvement. A comprehensive approach that combines pollution source reduction and bioremediation using Scenedesmus is essential for restoring and enhancing Yamuna's water quality.

The impact of drought is intensifying due to climate change, leading to significant environmental consequences, particularly concerning river water quality. While drought is typically classified as meteorological or hydrological, studies assessing its environmental impacts remain limited. Drought-induced hydrological alterations in rivers often degrade water quality, necessitating the development of an environmental drought index. This study introduces a novel methodology for calculating an index to evaluate the effects of drought on river water quality, specifically applied to tributaries of the Nakdong River in South Korea. The index was constructed by reviewing existing water quality and drought indices, selecting relevant parameters, and weighting each factor following the National Sanitation Foundation Water Quality Index (NSFWQI) methodology. Factors integrated into the index encompass both meteorological and hydrological indicators, with priority given to variables measurable in real time. Real-time parameters—such as flow rate, cumulative precipitation, days without rainfall, and sensor-based metrics (pH, electrical conductivity [EC], dissolved oxygen [DO], and total organic carbon [TOC])—were incorporated. Additionally, for rivers with upstream dams, dam discharge data were included to reflect its influence on flow conditions. The applicability of the calculated index was assessed by comparing index values to observed water quality data. A class interval structure was implemented to enhance the index’s usability across diverse riverine conditions. Furthermore, the utility of the index was validated by comparing it to the basin’s target water quality, thereby assessing its sensitivity to drought-induced water quality deterioration. The environmental drought index proposed in this study enables the proactive and real-time monitoring of water quality under drought conditions. When applied to 10 tributaries of the Nakdong River, the index demonstrated a clear correlation between drought conditions and water quality deterioration. This index provides a practical tool for river management, facilitating early response strategies to mitigate water quality impacts associated with environmental drought.

Degradation of water quality is a major challenge in both developed and developing countries since it poses a great risk to ecological health. The Cauvery river is one of the most important rivers of southern India, where the effect of seasonal variation on the quality of river water and its adjoining groundwater on the lower part of the basin has not yet been studied. Hence, the present study was carried out to evaluate the river water and adjacent groundwater for drinking and irrigational purposes, and also to identify the sources affecting the water quality. About 118 river water and 131 groundwater samples were collected over 4 months from May 2018 to August 2019. The water samples were analyzed for electrical conductivity (EC), pH, major and minor ions, and trace elements. The major, minor, and trace elements were then compared with the Bureau of Indian Standards and World Health Organization for drinking water quality assessment. The drinking water quality was assessed, indicating that both river water and groundwater were unsuitable in the coastal regions, especially during dry seasons. Irrigation water quality was also assessed, which indicates that most of the river water and groundwater samples were unsuitable near the coastal region. The quality of river water and groundwater in the lower Cauvery Basin was found to be better during wet periods compared to the dry season. It was observed that the rock–water interactions was the major factor controlling the water quality for groundwater and surface water, followed by anthropogenic activities such as disposal of domestic sewage and effluents into the river, as runoff from irrigated lands. The study emphasizes the development of a finer observational network for water quality, along with stringent monitoring of the disposal of contaminants in the rivers and groundwater.

A perceptible degradation in water quality complicates safe water supply for drinking and irrigation purposes. Therefore, this study aims at monitoring water quality changes and effective factors in the Dez River Basin, which are required to manage water resources effectively. To this end, the common influence of flow rate changes on water quality was separated by implementing seasonal Mann–Kendall test on residuals resulting from the LOWESS test. The results show that after adjusting the effects of seasonality and streamflow fluctuations, significant positive trends in most water quality parameters are still observed. It emphasizes the role of other factors controlling river water quality in the basin. Comparison of the trends of modified quality parameter time series (residuals) in different subbasins having natural or mad-made conditions, with or without significant groundwater resources, shows almost the same presented trends in water quality. This supports that, overall, minor changes occurred in land use, groundwater table, and environmental and human factors with no important influences on presented trends in water quality. Our analyses show that overall reduction in precipitation as well as positive trends in temperature and evaporation led to intensified streamflow variations, explaining the main changes in the river water quality of the basin.