University of Twente Student Theses
An impact assessment of human interventions on the hydrological regime of the Black River Basin in Vietnam
Winkel, W. (2022) An impact assessment of human interventions on the hydrological regime of the Black River Basin in Vietnam.
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| Abstract: | Measurements of water levels and streamflow show reduced flow in the Vietnamese part of the Black River basin from 2008 onwards. It is expected that human interventions in the Chinese part of the Black River basin play a large role in this. This study aims to assess impacts of human interventions on the hydrological regime of the Black River qualitatively by a water balance and quantitatively by using a hydrological model, the VIC-model. Two observed streamflow timeseries were derived by using rating curves and measurement data and validated by comparison to other independent station data. A global and regional gridded precipitation data product were acquired and compared to measurement data. It was concluded that the regional data product is more accurate than the global data product, also after correction of the global data product. A water balance was created to assess impacts of climate variability on streamflow and literature research was used to identify impacts of land use and land cover changes and water storage reservoirs on streamflow. The VIC-model was used to quantify and separate the impacts of human interventions on streamflow and calibrated and validated for the Black River basin by means of a split-sample test and a proxy-basin test. Streamflow has spontaneously reduced in 2008 in the Vietnamese part of the Black River basin by 21%. The water balance showed that a precipitation decrease could account for up to 50% of this discharge reduction. The VIC-model showed that water storage reservoirs account for 53% of this discharge decrease. Between 1992 and 2012, 5% of the basin area was subject to reforestation and the urban areas tripled during this period. The streamflow has been reduced by 3% due to changes in land use and land cover between 1992 and 2019. Between 2003 and 2018, 15 dams were constructed in the Chinese part of the Black River basin. The average streamflow has been reduced by 14% when comparing the period 1980-2007 with the period 2008-2018 due to the impacts of reservoirs. The wet season is responsible for 88% and the dry season for 12% of this average streamflow reduction. This suggests that the water storage reservoirs are mainly being filled during the wet season. The discussion treats the potential, limitations and generalization of this project. The largest limitation of this project is the reliability on and availability of data. Much input data is uncertain or estimated, thereby increasing the degree of output uncertainty. A second limitation is the VIC-model calibration and validation part. The observed data series that are used for these processes have a certain degree of uncertainty in them as well, thereby weakening the calibration and validation of the VIC-model. Lastly, the method that is used for human intervention impact assessment. The methods that are used to assess impacts of Land Use and Land Cover changes and water storage reservoirs might not cover all aspects of these human interventions, i.e. seepage below dams is not considered. The main conclusion from this thesis is that water storage reservoirs have a large impact on the hydrological regime in the downstream area of the Black River basin. Land use and Land cover changes also affect the streamflow, however in a small degree. Lastly, natural climate variation has a large direct impact on the hydrology of the Black River. The recommendations focus on improving the accuracy of this research by using and establishing more precise and more detailed data (series). Next to that, a module could be added to the VIC-model to represent the Black River basin better in its current state. |
| Item Type: | Essay (Bachelor) |
| Faculty: | ET: Engineering Technology |
| Programme: | Civil Engineering BSc (56952) |
| Link to this item: | https://purl.utwente.nl/essays/93485 |
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