Assessment of alterations in hydrologic regime using a machine learning technique and water quality changes due to hydropower dam development in the Lancang-Mekong River Basin | |
| Author | Ishankha, Wickramaarachchi Colambage Achini |
| Call Number | AIT Thesis no.WM-22-11 |
| Subject(s) | Hydrology--Mekong River Basin Hydroelectric power plants--Mekong River Basin Water quality--Mekong River Basin |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Water Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | Large-scale hydropower dam development in the mainstream of Lancang-Mekong basin led in significant flow regime alterations in past few decades. In this research, the Indicators of Hydrologic Alteration (IHA) was utilized to determine statistical characteristics of observed and predicted streamflow. The natural streamflow was predicted using Random Forest (RF) model at four hydrological stations along the mainstream in the pre-impact period (1961-1991), the transition period (1992-2008), and post-impact period (2009-2021). The streamflow alteration was more significant particularly in the post-impact period in comparison to both pre-impact period and forecasted non-regulated flow at the stations. The trend of annual high flow threshold magnitudes decreased significantly whereas that of annual low flow thresholds increased over 1961-2021 at the gauging stations at the 0.05 significance level. Furthermore, the highest overall hydrological alteration of observed flow compared to pre-impact period was at upstream Chiang Saen station (77.3%) and it decreased towards the downstream. The median monthly flow, the annual extreme water conditions, the rate, and frequency of flow change groups of IHA were found to be highly altered in the post-impact period compared to natural flow condition in the same period. It is investigated that the human activities contributed more to the total streamflow changes than climate variability in post-impact period compared to pre impact period particularly in Chiang Saen (68.3%) and Stung Treng (76.4%). The contribution of human activities on streamflow change in Chiang Saen based on 5-year analysis indicated clear relationship with hydropower dam commissions in the Upper Mekong Basin (UMB). Overall, the Water Quality Index for Protection of Aquatic Life (WQIal) was varied “Good” to “High” (1986-2017) at the stations. However, long-term water quality data is required to clearly assess alterations in water quality due to recent hydropower dam developments in the basin. Identifying historical hydrological and water quality changes due to hydropower dam development will facilitate basis for future hydropower dam development and reservoir operation in the basin as well as to enhance the transboundary cooperation. |
| Year | 2022 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Shrestha,Sangam |
| Examination Committee(s) | Babel, Mukand S.;Ho Huu Loc |
| Scholarship Donor(s) | His Majesty the King's Scholarship (Thailand) |
| Degree | Thesis (M. Sc.) - Asian Institute of Technology, 2022 |