Balancing water supply demand is vital for sustaining livelihoods. Spatial mapping and calculating water yield dynamics due to land use changes over decades are needed to manage land resources and formulate ecological protection policies. This study mapped the supply, demand, and matching status of water product service using the Integrated Valuation of Ecosystem Service and Tradeoff (InVEST) biophysical models in the Citarum Watershed (CW) in 2000, 2010, and 2020. Moreover, this study used Exploratory Spatial Data Analysis (ESDA) and Geographic Information System (GIS) techniques to study the agglomeration characteristics and evolutionary trajectories of supply–demand over two decades. The results showed that between 2000–2010 and 2010–2020, the water supply decreased by 19.01 × 10⁸ m³ (18.28%) and 12.97 × 10⁸ m³ (15.27%), respectively. However, the water demand in the same period increased by 6.17 × 10⁸ m³ (23%) and 15.74 × 10⁸ m³ (47%), respectively. Over the decades, the contribution of land use land cover (LULC) changes to variations in water supply has yielded values ranging from 2.87% to 6.37%. The analysis of the water supply–demand imbalance indicated that the entire CW experienced water shortage, and the type of spatial matching for supply and demand is dominated by a high supply and high demand class (16.09% of the total area). Based on the level of water deficit calculation, the upstream and downstream areas were identified as zones that require ecological conservation, while the middle CW area requires ecological restoration or ecological improvement.

The application of remote sensing data has been significant in modeling soil erosion. However, previous studies have fallen short in elucidating and lacked an understanding of the multifactor influencing erosion. This study addresses these limitations by employing the InVEST and the Geodetector models. Specifically, it aims (1) to delineate both spatial and temporal variations in soil erosion within the Citarum watershed from 2010 to 2020, (2) to identify the key drivers of soil erosion and unravel the underlying mechanisms, and (3) to identify the high-risk zones for soil erosion. Both models consider a range of natural predictors, including topography (slope factor), climate (precipitation factor), and vegetation cover (vegetation factor). In addition, they incorporate social parameters such as income per capita and population density, which interact with the watersheds position in the downstream, middle, and upper streams. The results reveal that, over a decade, the average soil erosion increased by 15.50×10⁶ tons, marking a 16.65 surge. The impact of factors varies significantly across different subwatershed areas. For example, fraction vegetation cover interactions influence upper- and middle-stream regions, while the downstream area is notably affected by precipitation interactions. The high-risk erosion areas in the watershed are primarily influenced by slope, precipitation, and fractional vegetation cover. In these areas, factors causing high erosion risks include slope, precipitation, and other environmental variables categorized into strata. The study highlights the varying influential factors in different watershed areas.

Lake Batur’s water quality on Bali Island has significantly declined, leading to massive annual fish mortality rates. The suspected reason is the expansion of aquaculture using floating net cages (FNC) beyond their capacity. The study aims to assess the impact of FNC-based aquaculture on water quality and organic matter distribution, specifically total organic matter, TSS, and chlorophyll a. The result states that Lake Batur has exceeded its carrying capacity of 10,047 plots since 2018 and currently holds 18,768 plots as of 2022. Within the last five years (2018-2022), the FNC discharged 5,947 tons of organic waste into Lake Batur, containing 1,779 quintals of nitrogen and 430 quintals of phosphorus. Consequently, each liter of Lake Batur water accrues 7.29 mg of organic waste annually, including 2.18 mg of nitrogen and 0.53 mg of phosphorus. Organic waste in Lake Batur has led to a reduction in water transparency, an increase in total organic matter (TOM), a decrease in dissolved oxygen (DO), and an increase in chlorophyll-a (Chl-a) concentrations. Its changes serve as indicators of eutrophication and degradation of water quality. The distribution of organic matter across the euphotic zone did not correlate with FNC distribution, suggesting that FNC distribution no longer influences organic matter distribution. Environmental factors surrounding the SL have emerged as the primary driver of differences in organic matter distribution. It demonstrates the dissemination of organic matter in the euphotic zone of Lake Batur due to the constant discharge of effluent by the long-standing FNC, which has surpassed its maximum capacity.

National Institute for Environmental Studies (NIES) has been implementing a joint monitoring project of greenhouse gases (GHGs) and air pollutants in Indonesia with Bogor Agricultural University (IPB), Agency for the Assessment and Application of Technology (BPPT), and Meteorological, Climatological, and Geophysical Agency (BMKG). To estimate the amount of anthropogenic emissions from Jakarta megacity (Jabodetabek) and compare with city activities, we developed a ground-based comprehensive monitoring system of GHGs and air pollutants and installed it at Bogor (center of Bogor city) in March 2016, Serpong (Jakarta suburb) in August 2016, and Cibeureum (mountainous area, background-like site) in March 2017. The monitoring system consists of data acquisition/control units and the instruments for continuous measurements of CO₂, CH₄, CO, NO_x, SO₂, O₃, aerosol concentrations (PM_2.5, PM₁₀, BC) and the chemical components, and meteorological parameters. Flask sampling of air is also done to analyze N₂O, SF₆, and carbon isotopes (¹³C, ¹⁴C) in CO₂ and to validate the continuous measurement data. The result shows that CO₂ mole fractions observed at three sites have clear diurnal variations representing the minimum values from 12 to 15 local time while the values at Bogor and Serpong are 6.8 and 7.1 ppm higher than Cibeureum, respectively.

Exploring the drivers of changes in ecosystem services is crucial to maintain ecosystem functionality, especially in the diverse Central Citarum watershed. This study utilises the integrated valuation of ecosystem service and trade-offs (InVEST) model and multiscale geographically weighted regression (MGWR) model to examine ecosystem services patterns from 2006 to 2018. The InVEST is a hydrological model to calculate water availability and evaluate benefits provided by nature through simulating alterations in the amount of water yields driven by land use/cover changes. Economic, topographic, climate, and vegetation factors are considered, with an emphasis on their essential components. The presence of a geographical link between dependent and explanatory variables was investigated using a multiscale geographic weighted regression model. The MGWR model is employed to analyse spatial impacts. The integration of both models simplified the process and enhanced its understanding. The findings reveal the following patterns: 1) decreasing land cover and increasing ecosystem services demand in the watershed, along with a decline in water yield, e.g. certain sub-districts encounter water scarcity, while others have abundant water resources; 2) the impact of natural factors on water yield shifts along vegetation > climate > topography (2006) changes to climate > vegetation > topography (2018).

Center for Climate Risk and Opportunity Management of Bogor Agricultural University in collaboration with National Institute for Environmental Studies-Japan developed an on-line system to monitor real time air quality and greenhouse gases for three sites surrounding Jakarta area, i.e. Bogor (Center of Bogor city), Serpong (Jakarta suburb) and Cibeureum (mountainous area, background-like site). The system uses standards air-quality monitoring equipped with an array of gaseous and meteorological sensors. The system records data every minute and stores in local storage and sent automatically to a Dropbox every 6 hours. The data in the Dropbox is accessed using API and being processed and analysed using several modules to be converted into useful information and presented in a website. The website will display real time air quality for ozone (O₃) and particulate matters (PM_2.5 and PM₁₀) and greenhouse gas data (CO₂, CH₄), Carbon monoxide (CO) Nitrogen Oxide (NO_x), and Sulfur Dioxide (SO₂), in the past 30-day including local weather data for the past 7 days. These data are then converted into an index indicating the status of the quality of the air surrounding the stations. The index is divided into five categories based on EPA air quality standard, namely good, moderate, unhealthy for sensitive group, unhealthy and very unhealthy. The system can provide the status of air quality index on a six hours basis and easy to be accessed by any stakeholder. The system allows local authorities, communities and industries to easily access and use the information for air quality management purposes and early warning.