4b. NWO Water Quality and Ecosystems

Summary

Sedimentation processes in the Mahakam Delta are governed by the discharge and sediment transport of the Mahakam River, the tide and the coastal currents. Mangroves set a natural boundary condition for theses complex processes, and human activities (especially by converting mangroves into fish ponds) express the socio-economic pressure on the delta. Remote sensing allows monitoring sedimentation processes in time and space as was demonstrated in the pilot phase of the East Kalimantan Programme.

The main objective is to quantify sediment fluxes by fluvial and tidal processes in the Mahakam delta over the last 50 years using data from aerial photographs, optical and microwave remote sensing techniques, in combination with sediment transport modelling as well as field data on sediment concentration in the delta distributaries. In this way, a reconstruction of delta development in the last fifty years can be obtained, and future trends may be predicted.

Only optical remote sensing allows the direct study of suspended sediments (TSM) in the water, but this tool fails in case of cloud cover. Microwaves penetrate clouds, but do not penetrate the water body. Therefore, an innovative synergy of the different remote sensing image types with ancillary data is planned for the reconstruction of the history of delta development.

Imaging spectrometry using bio-optical models is feasible for mapping TSM in the cloud-free periods. Spectra of water-leaving radiance are of importance to test bio-optical model closure. Therefore field measurements and laboratory analyses are needed. Based on the determination of the inherent optical properties of the water constituents a bio-optical model will be calibrated. Model inversion techniques will be used to obtain water quality parameters from remote sensing images in order to monitor water quality.

In the cloudy wet season, when most of the sediment is produced from the basin, indicators of sedimentation and the dynamics of the branches will be analysed based on microwave images, in combination with the results of sediment yield studies by in-situ measurements and sediment transport modelling. Rating of sediment transport as a function of water stage, i.e. water cover defined from radar images, will allow the assessment of sediment load in the delta even under cloudy conditions.

The results will allow the analysis of changes attributable both to natural processes (e.g. climate change) and human interactions.