Megacities are facing serious water pollution problems due to urbanization, rapid population growth and economic development. Water is an essential resource for human activities and socio-economic development and water quality in urban settings has important implications for human and environmental health. Urbanization and lack of sewerage has left the water in Jakarta, Indonesia in a heavily polluted condition. Rigorous assessment of urban water quality is necessary to understand the factors controlling water quality conditions. We use trend analysis to assess the current water quality conditions in Jakarta, focusing on Biochemical Oxygen Demand (BOD), Dissolved Oxygen (DO), and Total Suspended Solids (TSS). In most monitoring stations analyzed, BOD and TSS concentrations have decreased over time, but from large starting concentrations. DO in most monitoring stations has increased. Although Jakarta’s water quality has shown some improvement, it remains heavily impaired. The average value of BOD is low in upper stream stations compared to middle and lower stream stations. BOD and TSS trends of some water quality stations in middle and lower streams show increasing trends. Cluster analysis results suggest three groups for BOD and TSS, and four groups for DO. Understanding water quality conditions and factors that control water quality suggest strategies for improving water quality given current trends in climate, population growth and urban development. Results from this study suggest research directions and management strategies to address water quality challenges.

Plastic waste generation has been increasing over the last decades. Rivers represent complex environments where plastics may be stored and remobilized. Studies on riverine plastic, including riverbank contamination, are still lacking. Riverbank surveys were carried out in the Citarum River, Indonesia, at three river sections in Purwakarta, Karawang, and Muara Gembong in March-April 2021. The aim was to quantify the abundance of plastic waste at different points in the riverbank zone. The sample ‘monolith’ was taken by digging a quadrat of 30x30x10 cm3. All material was then weighed. Three replicates along the length of the bank and three replicates across the bank were taken. The non-plastic fraction was weighed and its composition was estimated. Plastic fraction was classified into categories, counted, and weighed. The result show that plastic litter was found in all monolith ranging from 0.7-301 g of plastic litter per monolith. The largest proportion of plastic contaminant was found in Karawang with 2.85% of plastic in a single monolith and the largest average plastic contaminant was about 0.78% of the total monolith weight, showing that plastic contamination is prevalent. Enhancing waste management, reducing single-use plastics, and plastic recycling are recommended to tackle plastic contamination in the study area.

<strong>Evaluation of Riparian Rehabilitation in River River Usingthe Macrozoobenthos Community Indicator. </strong>Macrozoobenthos organism is one of aquatic biota which is often used to assess the ecosystems health of river.The evaluation of riparian habitat rehabilitation using benthic macroinvertebrates has been commonly used in many countries. The purposes of this study were to evaluate the impact of Ranggeh river riparian rehabilitation and to determine environmental parameters that influenced benthic macroinvertebrate communities in Ranggeh River. This research was conductedfrom February to September 2019. Benthic macroinvertebrate Benthic macroinvertebrates, river, evaluation, EPT, rehabilitationsamples were collected using Hess Sampler in a sampling area of 0.2 m². This evaluation was carried out after two months since the rehabilitation of riparian habitat completed. The results show that rehabilitation of the riparian habitat has changed the community, in the aspects of biological metrics of taxa number, abundance, and taxa numbersof Ephemeroptera, Plecoptera, and Trichoptera (EPT). Furthermore, the taxa number and EPT metrics increased after habitat rehabilitation, however the abundance decreased slightly. In addition, the taxa number metric was positively correlated with conductivity parameter (r = 0.8), but negatively correlatedto turbidity (r = -0.91) and pH (r = -0.77). Meanwhile, the EPT metric was negatively correlated with turbidity parameters (r = -0.76) and  %<em>embeddedness</em> (r = -0.94). The total abundance metric was not sensitive to the parameters measured in this study. Meanwhile, biological metrics for taxa number and EPT can be used to assess rehabilitation success of river ecosystem habitats

<strong>Spatial and Temporal Distribution of Nutrient in Lake Tempe, South Sulawesi.</strong> The concentration of nutrients in the process of eutrophication have an important role in the freshwater productivity. Lake Tempe constitutes a conservation area for water resources that has been degraded, indicated by high sedimentation and abundant water weeds. This resulted in the lowered carrying capacity of the lake. This study aimed to determine the concentration and spatiotemporal distribution of nutrients in Lake Tempe as the basis for the management of the lake. Water samples were taken using Kemmerer water sampler in April, July, and October 2013 from seven stations. Dissolved oxygen, pH, temperature, and transparency were measured in situ, while the N-Nitrite, N-Nitrate, N-Ammonium, TN, orthophosphate, and TP as well as supporting parameters such as COD, TOM, and chlorophyll-a were analyzed in the laboratory using methods according to the Standard Method. The study showed the concentrations of N and P were varied at all observation sites. The concentrations of N-Nitrate, TN, and TP tended to be high in October, while the concentrations of N-Nitrite, N-Ammonium, and orthophosphate tended to be high in April. PCA analysis showed the water quality conditions in Lake Tempe were characterized by the N and P compounds. The high average concentrations of TN and TP in Lake Tempe with respective values of 1.386 mg/L and 0.198 mg/L indicated that the lake was a productive lake, classified as eutrophic with nitrogen as limiting factor of lake fertility. If the nutrient enrichment continues, it will have a negative impact on the water quality of the lake<br /><br />

The bottom substrate is one of the main ecological factors that influence the structure of the aquatic organism. Macrozoobenthos are the organisms living either in the bottom waters or the bottom surface of the waters. The presence of macrozoobenthos in the water is strongly influenced by various environmental factors such as temperature, salinity, dissolved oxygen, pH, and substrate of the bottom water. This study aimed to analyze the characteristics of the physico-chemical of waters and the substrate bottom of River Ranggeh, as well as their relationship to macrozoobenthos abundance. Samples were taken in 2019 for five times (February, March, April, July, and August). Survey method was used in this study. Purposive random sampling was carried out at four stations based on the environmental factors and land use. Insect class was the most dominant class found at all study area with the diversity index value of H’> 1 (high diversity). Type of the bottom substrate of River Ranggeh is argillaceous sand with high organic carbon concentration values. The results of the Canonical Correspondence Analysis showed that the abundance of macrozoobenthos was positively correlated with temperature, TSS, P-organic and C-organic, but it was negatively correlated with pH, water flow, DO, Total N, and substrate type.

Ciliwung is the river that flows from upstream in the Puncak area of Bogor Regency to Jakarta Bay. Water quality parameters have been monitored each month at three stations in the Ciliwung River watershed by the Indonesian Ministry of Environmental and Forestry and Meteorological, Climatological, and Geophysical Agency. The data analyzed in this study are rainfall and water quality data for the period 2017-2020 with water quality variables including pH, temperature, Dissolved Oxygen (DO), electrical conductivity (EC), Turbidity, Total Dissolved Solids (TDS), and Nitrate-N. This paper aimed to analyze the time series data using statistical methods and describes certain chemical parameters and rainfall data, that show Ciliwung water quality during 2017-2020. Descriptive analysis was used to determine the mean, skewness, and kurtosis values based on time and location. Histogram and boxplot graphs were used to describe distribution of the data set. Test of Kolmogorov-Smirnov was used to evaluate the normality of the data set. The descriptive analysis resulted in the mean of each water quality parameter showing a value that did not show a significant difference between observation locations except for the TDS parameter. From the histogram and boxplot graphs, it can be seen that the data shows an abnormal distribution and there are many outliers. Kolmogorov-Smirnov test resulted in better normality of data distribution. The main problem of pollution is the use of oxygen by organic matter contained in river water. Ciliwung River downstream was changed into open accumulator wastewater from the food industry, livestock, and settlements.

Small lakes are important freshwater resources to support the quality of human life. However, small lakes in the watershed are becoming threatened ecosystems because of increasing land-use changes and anthropogenic activity. The study aimed to determine characteristic physical-chemical parameters and trophic status some small lake in Ciliwung Watershed to support the sustainable management of small lakes in the Ciliwung watershed in preventing eutrophication effects.  The data was collected in April and June 2021. Measurement and analysis of water quality parameters were conducted by insitu and Laboratory. Some parameters were not in accordance with the Government Regulation number 22/2021 for class II water quality criteria (WQC), including TSS (>50 mg.L-1)., TP (>0.03 mg.L-1), COD (>25 mg.L-1) and DO (<3 mg.L-1), especially for Lake Sunter and Lake Cincin.There are two groups of lakes based on water quality and trophic status. Lake Telaga Warna Lake Cikaret, and Lake Cilodong were classified as eutrophic while lake Sunter and Lake Cincin were classified as hypereutrophic lake Lake Telaga Warna, Lake Cikaret, and Lake Cilodong, located at the upper and middle watershed, are eutrophic, characterized by deeper bottom and higher Secchi depth. At the lower watershed, Lake Sunter and Lake Cincin are hypereutrophic characterized by higher nutrients (TN and TP), COD, temperature, conductivity, salinity, and TDS. The downstream area was a densely populated area that contributed high pollution from upstream and middle of Ciliwung watershed.

Small lakes are critical freshwater resources to support the quality of human life. Small lakes in the watershed are becoming threatened ecosystems because of increasing land-use changes and anthropogenic activity. We determine the trophic status, phytoplankton community, and environmental factors in Lake Telaga Warna, Lake Cikaret, Lake Sunter, and Lake Cincin. The data was collected from primary and secondary data in 2000, 2007, 2008, 2016, and 2021. There are two groups of lakes based on water quality and trophic status. Lake Telaga Warna and Lake Cikaret, located at the upper and middle watershed, are eutrophic characterized by lower nutrient temperature, pH, conductivity, and Total Dissolved Solids (TDS). Lake Sunter and Lake Cincin, located at lower watersheds, are hypereutrophic characterized by higher nutrients, temperature, pH, conductivity, and TDS. Cyanobacteria dominance was recorded in Lake Telaga Warna and Lake Sunter, where Microcystis aeruginosa; Cylindrospermosis raciborskii; and Planktotrhix agardhii are the dominant species. Hypereutrophic status in Lake Sunter was characterized by the bloom of Planktothrix agardhii with total abundance (1,038x103 individualL-1 x 103), chlorophyll-a (431 µgL-1), low diversity index and species richness index. Cyanobacteria dominance in Lake Telaga Warna was under phosphorous limitation, while Cyanobacteria bloom in Lake Sunter was under nitrogen limitation.