Effect Of Watershed Changes On Streamflow

Author : Sabin Shrestha (Civil engineer)
Publisher :
ISBN 13 :
Total Pages : 148 pages
Book Rating : 4.:/5 (1 download)

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Download or read book Impact of Global Climate Change on Extreme Streamflow written by Sabin Shrestha (Civil engineer) and published by . This book was released on 2017 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is a widespread concern that climate change will lead to an increased frequency and intensity of extreme weather events in the 21st century. It is essential, from a watershed management point of view to understand how these alterations in the hydrologic regime would affect the existing water resources. This research, therefore, provides an overview of the hydrologic impacts on the Great Miami River Watershed in Ohio, USA due to projected climatic changes on both low flows and high flows. An extensively used hydrological model, the Soil and Water Assessment Tool (SWAT) was to evaluate the hydrological impacts of climate change. The multi-site model calibration and validation were performed using the SUFI-2 algorithm within SWAT-CUP. The model was calibrated (2005 - 2014) and validated (1995 - 2004) for monthly stream flows at the outlet resulting in Nash - Sutcliffe Coefficients of 0.86 and 0.83, respectively. An ensemble of ten downscaled and bias-corrected climate models from Fifth Phase Coupled Model Intercomparison Project (CMIP5) under two Representative Concentration Pathways(RCPs) 4.5 and 8.5 were used to generate a probable set of climate data (precipitation and temperature). The climate data were then fed into the SWAT model and hydrological changes in the stream in terms of daily discharge were produced for three time-frames: (2016 - 2043) as 2035s, (2044 - 2071) as 2055s, and (2072 - 99) as 2085s and compared against the baseline period (1988 - 2015). The findings from this research showed that low flows using both hydrological and biological indices would increase more than 100% in 2035s but eventually decrease slightly in the later part of the century (2085s). However, the Max Planck Institute Earth System Model (MPI-ESM-LR) used in this study predicted that the biological indices iv under RCP 8.5 would increase slightly at the beginning but decrease considerably in the middle and later part of the century. Analysis showed that the variability of the average 7-day low flows in each year would increase considerably for both emission scenarios. Furthermore, 75th percentile exceedance frequency of monthly low flows was found higher in September, October, and November during the study period. As for high flow analysis, the hydrological index for high flows (7Q10) from an ensemble of 10 climate models predicted to decrease consistently in future. When the results from the two RCPs are compared, high flows would decrease maximum by 22% in 2055s under RCP 8.5 and 21% in 2085s under RCP 4.5. However, the MIROC5 model in RCP 4.5 showed 1.2% increase in 7Q10 high flows during 2035s. The frequency of the 75th percentile non-exceedance flows was also projected to increase in the future. Under the RCP 4.5, the frequency becomes higher in 2055s whereas under the RCP 8.5 most frequent 75th percentile flow would occur in 2085s. Meanwhile, on a monthly scale, the peak would increase more on every month except January and December than that of historical records. The variability of peak discharge was also expected to increase in every other month in both scenarios. The peak would increase considerably especially in August, September, and October when compared to historical months, indicating relatively wetter months in the future years. Finally, this study has demonstrated the effects of changing climates projected by the climate models on extreme flow condition in the large agricultural watershed. The next step of the research will focus on further bias correction on simulated climate data and analysis for future.