Set Up and Calibration of a Spatial Tool for Simulating River Discharge of Western Java in Recent Decades: Preliminary Results and Assessments

This paper discusses a study of the application of global spatiotemporal climate datasets and the hydrological model STREAM (Spatial Tools for River Basin Environmental Analysis and Management Options). In the study, set up and calibration of STREAM for the reconstruction of monthly discharge for several locations in the western part of Java, Indonesia, for the period 1983 -2002 are carried out. The set up includes the preparation of monthly precipitation and temperature datasets, a digital elevation model of the domain being studied, and maps of land cover and soil water holding capacity. Discharge observations from six stations located mostly in the upper parts of major watersheds in the domain are used to calibrate the model by comparing simulated and observed discharge variables. The model performs reasonably well. Comparison between computed and observed mean monthly discharges yield correlation coefficients ranging from 0.72 to 0.93. The computed mean annual discharge in five out of six observation stations ranges between -8 and 5% with respect to the mean annual observed discharge. This study offers a tool which can be used for reconstructing historical discharg

Assessment of Different Real Time Precise Point Positioning Correction Over the Sea Area

In a global scale, the accuracy of Real Time Precise Point Positioning (RT-PPP) method in Global Navigation Satellite System (GNSS) point positioning is within cm to dm level. Unlike other conventional method in GNSS point positioning which used differential data to minimize the error sources, RT-PPP used additional orbit correction, clock correction and other atmospheric correction to minimize the error since RT-PPP is an absolute point positioning method. Currently, there are several providers who give the orbit correction and clock correction in real-time. Not only in the land area, this service can be also used in sea area. Thus, this research aims to analyse the differences in point determination derived from RT-PPP method by using several service providers in sea area. The RT-PPP data acquisition used three different receivers with unique service correction, namely RTX correction from Trimble Net R9 receiver, ATLAS correction from Hemisphere receiver and Veripos correction from Hemisphere receiver. All these antennas were set up on the ship with a controlled distance and the point coordinates were estimated from Seribu Island to Ancol, Jakarta with a different time interval for each receiver due to the technical limitations. To assess the point positioning stability, the distance between each antenna derived from point positioning then evaluated by comparing to its controlled distance. The results indicate that a time lag is found in Trimble Net R9 compared with the others, and it should be corrected first before applying the further analysis. In general, after removing the outliers, the distance and the precision between each antenna between Veripos-ATLAS is 4.472 ± 0.040 m, RTX-ATLAS is 2.054 ± 0.077 m and RTX-Veripos is 3.947 ± 0.060 m. Therefore, RT-PPP method can be used as an alternative in precise point positioning in sea area

How land use/land cover changes can affect water, flooding and sedimentation in a tropical watershed: a case study using distributed modeling in the Upper Citarum watershed, Indonesia

[EN] Human activity has produced severe LULC changes within the Upper Citarum watershed and these changes are predicted to continue in the future. With an increase in population parallel to a 141% increment in urban areas, a reduction of rice fields and the replacement of forests with cultivations have been found in the past. Accordingly, LCM model was used to forecast the LULC in 2029. A distributed model called TETIS was implemented in the Upper Citarum watershed to assess the impact of the different historical and future LULC scenarios on its water and sediment cycles. This model was calibrated and validated with different LULCs. For the implementation of the sediment sub-model, it was crucial to use the bathymetric information of the reservoir located at the catchment's outlet. Deforestation and urbanization have been shown to be the most influential factors affecting the alteration of the hydrological and sedimentological processes in the Upper Citarum watershed. The change of LULC decreases evapotranspiration and as a direct consequence, the water yield increased by 15% and 40% during the periods 1994-2014 and 2014-2029, respectively. These increments are caused by the rise of three components in the runoff: overland flow, interflow and base flow. Apart from that, these changes in LULC increased the area of non-tolerable erosion from 412 km(2) in 1994 to 499 km(2) in 2029. The mean sediment yield increased from 3.1 Mton -yr(-1) in the 1994 LULC scenario to 6.7 Mton-yr(-1) in the 2029 LULC scenario. An increment of this magnitude will be catastrophic for the operation of the Saguling Dam.This study was partially funded by the Spanish Ministry of Economy and Competitiveness through the research projects TETISMED (CGL2014-58,127-C3-3-R) and TETISCHANGE (RTI2018-093717-B-I00). The authors are also thankful to the Directorate General of Higher Education of Indonesia (DIKTI) for the Ph.D. funding of the first author.Siswanto, SY.; Francés, F. (2019). How land use/land cover changes can affect water, flooding and sedimentation in a tropical watershed: a case study using distributed modeling in the Upper Citarum watershed, Indonesia. Environmental Earth Sciences. 78(17):1-15. https://doi.org/10.1007/s12665-019-8561-0S115781

Jakarta Climate Adaptation Tools (JCAT)

Historical records show that flooding per se is not a new problem in Jakarta, and that flooding has occurred throughout the city’s history. However, the impacts of flooding have increased in recent decades, as a result of changes in both physical (e.g. land subsidence and erosion) and socioeconomic (e.g. population growth and urban expansion) drivers. Moreover, the future flood problems in Jakarta may potentially be exacerbated due to climatic change. The project JCAT was set up to contribute to scientific knowledge and the development of methods and tools to assess flood risk in Jakarta. This report summarises the main findings