Climate change impact on water resources and seawater intrusion in the Bang Pakong River Basin, Thailand | |
| Author | Thundorn Okwala |
| Call Number | AIT Diss. no.WM-21-01 |
| Subject(s) | Climatic changes--Thailand--Bang Pakong River Basin Water resources development--Thailand--Bang Pakong River Basin Saltwater encroachment--Thailand--Bang Pakong River Basin |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Water Engineering and Management, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. WM-21-01 |
| Abstract | Climate change can affect water resources in several ways. Water shortage and seawater intrusion are the main problems experienced by the Bang Pakong Basin. This study investigates the impact of climate change on water resources in the Bang Pakong River Basin and seawater intrusion in the Lower Bang Pakong River. Three Regional Circulation Models (RCMs) and two General Circulation Models (GCMs) are used to project future climate conditions, including maximum and minimum temperatures, rainfall, and sea surface level under two climate change scenarios (RCP4.5 and RCP8.5). This study compares the biases in historical data with observed data and projects future climate conditions using the linear scaling method. Future climate conditions are divided into three future periods: the 2020s (2011–2040), 2050s (2041–2070), and 2080s (2071–2100). The Soil and Water Assessment Tool (SWAT) is used to simulate the future streamflow under climate change scenarios. The calibration and uncertainty program for SWAT (SWAT-CUP) was used to calibrate and validate the SWAT model. This study uses extreme value type I distribution (EVI) to analyse extreme streamflow and investigate the impact of climate change on seawater intrusion in the Lower Bang Pakong River, while MIKE11 is employed to simulate water salinity in the river. The results of future climate projections indicate an increasing trend in both maximum and minimum temperatures. The current annual maximum temperature is 31.7 ºC (1980–2005), and the annual maximum temperature is expected to increase by 0.9 ºC (1.1 ºC), 1.5 ºC (2.1 ºC), and 1.9 ºC (3.6 ºC) in the 2020s, 2050s, and 2080s, respectively under RCP4.5 (RCP8.5). The current annual minimum temperature is 31.7 ºC (1980–2005), and the annual minimum temperature is expected to increase by 0.7 ºC (0.9 ºC), 1.2 ºC (1.9 ºC), and 1.6 ºC (3.3 ºC) in the 2020s, 2050s, and 2080s, respectively under RCP4.5 (RCP8.5). However, annual rainfall tends to fluctuate and a slight decrease is indicated in the future. The annual rainfall is expected to decrease by -4.5% (-8.3%), -6.8% (-8.5%), and -4.2% (-11.0%) in the 2020s, 2050s, and 2080s, respectively under RCP4.5 (RCP8.5). Moreover, the results indicate that the annual sea surface level in the Inner Gulf of Thailand will gradually rise until the end of the twenty-first century. In the 2080s, the sea surface level is expected to increase by 5.4 cm and 3.4 cm for RCP4.5 and RCP8.5, respectively. This study uses the SWAT model to simulate the hydrological conditions in the Bang Pakong River Basin, especially streamflow. To project annual discharge in the Bang Pakong River, two changing trends are used for simulation. Under RCP4.5, the annual discharge is expected to increase by 13.5%, 12.0% slightly, and 12.9% in the 2020s, 2050s, and 2080s, respectively. However, under RCP8.5, the annual discharge tends to fluctuate in the future and may increase slightly by 3.6 and 7.6% in the 2020s and 2050s, respectively, and decrease by 0.2% in the 2080s. The monthly discharge in seasonal streamflow tends to increase during the wet season (June to September) but slightly decreases in the dry season under both RCP4.5 and RCP8.5. The 90 and 50% exceedance discharges (Q95, Q90, and Q50) tend to decrease throughout the twenty-first century under RCP4.5 and RCP8.5. On the other hand, the 10 and 5% exceedance discharges (Q10 and Q5) tend to increase. Moreover, the extreme event analysis shows an increase in extreme discharge in every return period, indicating that the Bang Pakong River Basin might face more significant floods and drought in the future. Under RCP4.5 and RCP8.5 scenarios, seawater is projected to intrude further into the Lower Bang Pakong River in the future. During a period of high concentration (December to May), water salinity is expected to increase throughout the river, especially upstream. The most significant change in water salinity in January might increase to 13.53 g/l (15.57 g/l) in the 2080s under RCP4.5 (RCP8.5). The result indicates that seawater intrusion is likely to affect several water use sectors, especially water supply, rice cropping, and other agriculture. The potential for seawater intrusion tends to increase in the future. Water cannot be directly extracted from the river for off-season rice cropping in the dry season, and the yield for in-season rice cropping might be affected by increased concentration. Although a clear impact is indicated on water supply, seawater intrusion remains a severe problem for tap water production in the Bang Pakong River Basin. |
| Year | 2021 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. WM-21-01 |
| Type | Dissertation |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Shrestha, Sangam; |
| Examination Committee(s) | Sundaram, S. Mohana;Datta, Avishek; |
| Scholarship Donor(s) | Faculty of Engineering at Kamphaeng Saen Kasetsart University, Thailand; |
| Degree | Thesis (Ph. D.) - Asian Institute of Technology, 2021 |