Past and future trends in nutrient export by 19 rivers to the coastal waters of Indonesia

Abstract

This article analyzes past and future trends in nutrient export of dissolved and particulate nitrogen and phosphorus by rivers into the coastal waters of Indonesia. The focus is on 19 rivers included in the Global Nutrients Export from WaterSheds model. In the past, export of dissolved inorganic nitrogen by rivers doubled, while export of other forms of nitrogen and phosphorus by rivers did not change largely. For future trends of four Millennium Ecosystem Assessment scenarios, the largest increases are calculated for river export of dissolved inorganic phosphorus by rivers caused by increased inputs from sewage systems. The export of other nutrient forms is relatively constant in time, which is surprising, given the growing population and the associated increasing inputs of nitrogen and phosphorus to the land. Changes in export by rivers are the net effect of human activities and changes in hydrology. The results indicate that future increases in nitrogen and phosphorus inputs on land are partly counterbalanced by decreases in basin discharge as a result of climate change and consumptive water use. These results differ from other Asian regions, for which large increases in nitrogen and phosphorus inputs to coastal waters are calculated. This can be explained by population growth, gross domestic product increase, and sewage system development.

Modeling increased riverine nitrogen export: Source tracking and integrated watershed-coast management

“…Implementing these models requires detailed, high quality input data which is often not available for large watersheds. Global NEWS-2 (Nutrient Export from WaterSheds) is a spatially explicit watershed scale model which has been applied at the global (Dumont et al, 2005;Mayorga et al, 2010;Seitzinger et al, 2010) and regional scales (Bowes et al, 2005;Qu and Kroeze, 2010;Suwarno et al, 2013). Global NEWS-2 is an ideal tool for management purposes in data-poor regions such as China's coastal watersheds because it requires mainly social-economic input data and simple model parameters.…”

Fast increases in urban sewage inputs to rivers of Indonesia

“…1 and 2 summarize the results for the 19 selected Indonesian rivers. These 19 rivers are the same rivers as we used in an earlier analysis using Global NEWS (Suwarno et al 2013). Our results are in all cases higher than the Global NEWS estimates (see Tables 4, 5, 6).…”

“…In an earlier study (Suwarno et al 2013), we compared N and P measurements at the mouths of 19 selected rivers in Indonesia with the modeled values from the Global NEWS model. In general, we concluded that the fit is reasonable, considering that the model was not originally developed for Indonesia.…”

Modeling sources of nutrients in rivers draining into the Bay of Bengal—a scenario analysis

“…Global NEWS was validated for rivers worldwide ) and for all regional applications, including parts of the Bay of Bengal and Indonesia (Sattar et al 2014;Suwarno et al 2013). In all studies, the model performance has been evaluated as acceptable, with a similar performance for BOB LME in this study (Online Resource 2).…”

“…We investigated model uncertainties by comparing our results to earlier studies for the Bay of Bengal (Naeema and Kroeze, 2014;Sattar et al 2014;Suwarno et al 2013) and for other world regions. We learn from this comparison that we may be missing sources of nutrients, including point sources from human and animal waste (e.g.…”