Integrated assessment of climate and landuse change impacts on hydrology and water resources of the Koshi River Basin, Nepal | |
| Author | Agarwal, Anshul |
| Call Number | AIT Diss. no.WM-14-02 |
| Subject(s) | Land use--Evaluation--Koshi River Basin (Nepal) Climatic changes--Evaluation--Koshi River Basin (Nepal) Water resources--Evaluation--Koshi River Basin (Nepal) |
| 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-14-02 |
| Abstract | Global changes are creating enormous pressure on the Himalayan region. Changing climate and land cover patterns are expected to intensify the hydrological cycle and consequently affect average water availability as well as extreme situations. For sustainable planning and management of water resources, the assessment of climate change and its impacts on the hydrological processes is important. This study investigated the impacts of climate change and land cover change on the hydrology and water resources of the Koshi river basin. The lack of hydro-meteorological data in the Koshi basin is a major constraint in understanding the system’s dynamics and in analyzing climate change and its impacts. To overcome this limitation, climate data from global sources was analyzed and used in this study. Projections of climate from ten General Circulation Models (GCMs) for three Intergovernmental Panel on Climate Change, Special Report on Emission Scenarios (IPCC SRES)–B1, A1B and A2–were used to estimate the range. Low resolution future climate data, obtained from the GCMs, was downscaled using the statistical downscaling model—the Long Ashton Research Station Weather Generator (LARS-WG)—for 10 temperature stations and 77precipitation stations. The analysis in this study focuses on three periods over the 21stcentury: an early-century period of 2011 to 2030 (the 2020s), a mid-century period of 2046 to 2065 (the 2055s), and a late-century period of 2080 to 2099 (the 2090s). The extremes in baseline climate and future periods’ climate were analyzed using indices recommended by the Expert Team on Climate Change Detection, Monitoring and Indices (ETCCDMI). The impacts of climate change and land cover change on the hydrology and water resources of the basin were analyzed using the Soil and Water Assessment Tool (SWAT) model. The impacts of land cover change were analyzed by using land cover data from MODIS for the period of 2001-2010. Land cover change scenarios were developed keeping in view the projected changes in temperature and also the rate of change of various land cover types in the basin in the past. The calibration and validation results show that the downscaling model LARS-WG and the hydrological model SWAT performed well for the Koshi basin. The results show that temperature will increase in the basin in all three future periods. All temperature indices show an increase in the three future periods, although differences exist in the magnitude of change. The cold years in the periods 2055s and 2090s may become warmer than the hottest yearsin the baseline period in terms of mean annual temperature. The projections for precipitation are not unidirectional and vary with the GCM and the SRES scenarios. The amount of precipitation in dry years may remain the same but the amount is expected to increase significantly during the wet years in the future periods. A majority of the precipitation indices show large differences in both, magnitude and direction of change. The mean monthly flow in the Koshi basin is expected to increase as projections of a majority of the GCMs and the mean value of all the GCMs indicate. The GCMs do not agree on the direction of change of flow. The difference in the projection of flow varies as high as -35 to 51% under A1B scenario during the 2055s. The changes in high flow and the differences among GCM projections for high flows are much higher than the projections for changes in low flow. The range of projections for all water balance components is very large. The water balance components: surface flow, base flow and water yield may decrease or increase in future period, as GCMs do not agree on the direction of change. Evapotranspiration (ET)and potential evapotranspiration (PET)are projected to increase under all the scenarios, although uncertainty exists in the magnitude of change. An analysis of Climate Moisture Index (CMI) values for the GCMs under the three scenarios for all three future periods shows that IPCM has the driest projections for all three periods while INCM shows the wettest projections in most cases. Land cover change in the Koshi basin is not significant as indicated by the past records and its impact on the hydrology of the basin is minimal. The maximum change of 3.5% was observed in the flow considering the land cover change during 2001-2010. In case of hypothetical scenario when all forests are expected to change to grasslands flow will increase by 10%. The changes in climate will play a dominant role in changing streamflow and water balance components in the Koshi and its tributaries. The effect of land cover change analyzed through various scenarios and, even some extreme land cover changes, is secondary when compared to the effect of climate change. |
| Year | 2014 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. WM-14-02 |
| 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) | Babel, Mukand S.; |
| Examination Committee(s) | Shrestha, Sangam;Oki, Taikan;Kawasaki, Akiyuki;Tripathi, Nitin K.;Maskey, Shreedhar; |
| Scholarship Donor(s) | Adaptation to Global Change in Agricultural Practices (AGloCAP Project);UNESCO-IHE;Asian Institute of Technology Fellowship; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2014 |