Inter basin water transfer under climate change conditions a case study of Bheri-Babai River Basins, Nepal | |
| Author | Mishra, Yogendra |
| Call Number | AIT Diss. no.RS-18-07 |
| Subject(s) | Water transfer--Nepal--Case studies Climatic changes--Nepal--Case studies Water-supply--Remote sensing |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Remote Sensing and Geographic Information Systems |
| Publisher | Asian Institute of Technology |
| Abstract | Streamflow alteration is one of the most noticeable effects of climate change. Modification of streamflow reflects on environmental flow. Irrigation water demand also changes due to climate change. All three components are associated with the interbasin water transfer. This study investigated the interbasin water transfer considering the present and future climatic condition in Bheri-Babai rivers in Nepal. It analyzed the water budget in Bheri and Babai river basin under present and climate change condition and recommended the optimize quantity of the transferable water between candidate basins in present and future. This study explored the effects of climate change on streamflow in the Bheri and Babai River using the Soil and Water Assessment Tool model. Three General Circulation Models (MIROC-ESM, BCC-CSM1.1, and CCSM4) under two Representative Concentration Pathways (RCPs; 4.5 and 8.5) for the periods of 2020-2044, 2045- 2069, and 2070-2099 were used to investigate the impact of climate change. CROPWT8.0 was used to fmd the irrigation water demand. The environmental flow was calculated by using the "software package for global assessment of environmental flow" developed by IWMI. In daily calibration, the SWAT model performed good performance in the Bheri river basin. The indices (NSE and R2 greater than 0.7 for both calibration and validation and PBIAS -4.4% for calibration and -8.9% for validation) showed a good performance at the daily timescale. In monthly calibration in Babai basin, the SWAT model performed well with the indices (NSE and R2 around 0.9 for both calibration and validation and PBIAS 14.5 % for calibration and 10.9 % for validation). The calibrated model represents the hydrological processes of both basin and reliably predicts future streamflow. The result from an ensemble of the three GCMs showed an armual streamflow rise in Bheri river by 6.2-7.3% under RCP 4.5, and 6.0-12.5% under RCP 8.5. However, the prediction was different for every GCM and scenario. On a monthly scale, all the models under all scenarios (except the RCP 4.5 in the 80 s and RCP 8.5 in the 80 s) predicted that the streamflows would decrease in July and August, relative to the baseline flow. The average monthly flow in spring and winter would also increase significantly. The ensemble's results showed that the monthly increment could go up to 70% in February and March. The hydrological processes of streamflows for each GCM presented similar trends when compared to the baseline. The environment flow in Bheri river varies from 21 to 79% of mean armual runoff in different environment management class. Irrigation water demand was calculated in the present climatic condition and future climate condition under the cropping intensities of 116, 170 and 258%. Total water demand in a year in RCP4.5 and RCP 8.5 under CI 170% was 674 and 741 Mm3 for scheme efficiency 30%. And the value was 1035 and 1015 Mm3 for CI 258%. In all case, maximum water demand is in July and no water demand in August. All analysis showed that water could be excess in Bheri river under the highest cropping intensity of258% and environmental management class type C. The ensemble of the three GCMs showed that annual streamflow in Babai river could rise in future by 24 - 27 % under RCP 4.5 and 28 to 37 % under RCP 8.5. The average monthly flow in dry period could increase significantly. The ensemble's results show that the monthly increment could rise to 75 % in February and March. The study showed that the irrigation water demand in this basin would increase in future. This is not only by climate change but also rise in cropping intensity. The rainfall could increase in the future, but the increment rainfall is not sufficient to accomplish the incremental water demand. Under current condition, water deficit in four months November, February, April and May. Water available in the river is just enough III in January and March. Under RCP4.5 ofthe 30s and present cropping intensity, irrigation water demand could decrease by around 5%. However, for cropping intensity of 250%, all scenario predicted that water could be a deficit in five months of the year; from January to May. Hence, all these results indicate that water available in Babai river is not sufficient now and future so to supply the year-round-irrigation system and run the fresh eco-system, the alternative source of water is essential at earliest. Hence from this study, it can be concluded that Babai river basin is a water deficit basin under present and future condition. So, to supply the year-round-irrigation system and run the fresh eco-system, the alternative source of water is essential at earliest. Bheri river may be the donor basin for Babai river, but in some cases, environmental flow in Bheri river will be reduced to EMC type F. |
| Year | 2018 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Remote Sensing (RS) |
| Chairperson(s) | Nakamura, Tai;Babel, Mukand S. |
| Examination Committee(s) | Sarawut Ninsawat;Ochi, Shiro; |
| Scholarship Donor(s) | Japanese Government;Asian Institute of Technology |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2018 |