Discharge and sediment transport in the Kapuas river

Abstract: Deteriorating water quality is a challenge which affects people of the entire world, with a growing population and increased industrialization worldwide. The problem is especially apparent in many developing nations where water resource management must be improved to secure a future sustainable supply. This study was undertaken as a bachelor degree within the MFS-program funded by SIDA. The study took place in two small rivers which are a part of the Kapuas river basin in the Indonesian province of West Kalimantan on the island of Borneo. This province has a population of 4.5 million (SI:1, 2010) and many people are dependant of water from the river system for drinking and hygiene. There is a lack of water resources management in the area such as monitoring changes in hydrology and sediment content due to industrial activities such as logging, palm oil plantation and mining. Because of this situation, the purpose of this study was to advance the data collection of sediment content and discharge. The field work was undertaken in between may 7th and july 19th 2013 which is at the end of the rainy season in the region. Two rivers were studied, river 1 with high water velocities and high sediment contents and river 2 with low water velocities and lower sediment contents. The study resulted in stage-discharge and stage-sediment relationships for daily measurements using a flow meter and lab analysis of TSS-content in water samples. Four simple methods were tested and with varying results, two methods for measuring discharge(float method and disc method) and two methods for measuring TSS by determining the turbidity (turbidity tube and turbidity by photos). The float method proved successful in river 1 with an average error of 13% and a maximum error of 26%. In river 2 with lower water velocities the average error was 46% and the maximum error 136%. The disc method was only able to produce results in river 1 with an average error of 35% and a maximum error of 65%. However the errors were, with one exception, all larger than the true value (obtained by using a flow meter). This suggests that the accuracy could be improved by adding a correcting constant to the calculations, which would be obtained through more extensive testing and calibrating. Neither the turbidity tube nor the turbidity by photos was able to produce any accurate results of determining the sediment content. However the turbidity tube has shown trends in the results and might be improved through more testing to be able to roughly determine the sediment content of water.