Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Climate Change Impact Assessment on Hydrological Regime of Kali Gandaki Basin

501 views

Published on

The presentation focuses on the findings of the impact of climate change on the hydrological regime and water balance components of the Kali Gandaki basin in Nepal. The Soil and Water Assessment Tool (SWAT) has been used to predict future projections.

Published in: Environment
  • Login to see the comments

Climate Change Impact Assessment on Hydrological Regime of Kali Gandaki Basin

  1. 1. Climate change impact assessment on hydrological regime of Kali Gandaki basin in Nepal using RCP scenarios Ajay Ratna Bajracharya Sagar Ratna Bajracharya Arun Bhakta Shrestha 8th Nepal Geological Congress Geoscience in National Development and Disaster Management November 27-29, 2016 Kathmandu, Nepal
  2. 2. Study Area  Sub-basin of Narayani basin  Total Area 11,830 sq km  Elevation 188 m to 8143 m  14 Rainfall Stations  9 Temperature Stations  1 Hydrological stations Kali Gandaki Basin Fig 1 Location map of Kali Gandaki basin of Nepal (left) and Spatial distribution of Hydrological, Precipitation and Temperature Stations (Right)
  3. 3. Data Description Source Hydro-meteorological data of Kali Gandaki basin Department of Hydrology and Meteorology, Nepal Land use/ cover data European Space Agency (ESA), 300 m Digital Elevation Model (DEM) Shuttle Radar Topography Mission (SRTM) DEM (90 m), NASA Soil Data Soil and Terrain Database Programme (SOTER), FAO, 1:1 million scale Future Projected Climate Data Lutz et al ( 2016), 10km X 10km (IGB) Table 1 Data Sources and Type used in study Data Collection
  4. 4. Data collection 0 20 40 60 80 100 0 2000 4000 6000 8000 %AreaBelowElevation Elevation (m) Fig 2 DEM, Land Use and Soil map for Kali Gandaki basin used in SWAT model
  5. 5. Methodology Table 2 Ensemble of GCM runs with projected change in mean temperature and precipitation during 2090s for IGB basin (Lutz et al., 2016). Fig 3 Mean annual precipitation and mean temperature from 1981-2010 for IGB basin (Lutz et al., 2016) Climate Change Analysis
  6. 6. Methodology Projection WGS 84 UTM Zone 45N (EPSG: 32645) Extent xmin: -1600000 ymin: 2300000 xmax: 160000 ymax: 420000 Spatial resolution 10000 x 10000 meter Temporal resolution Daily Time step, 1 Jan 2011 - 31 Dec 2100 Variables and units prec Daily precipitation sum mm tavg Daily mean air temperature °C tmax Daily maximum air temperature °C tmin Daily minimum air temperature °C Data format Netcdf (1 file per year and per variable per GCM) Table 3 Total IGB dataset (Lutz et al., 2016) Climate Change Analysis
  7. 7. Methodology Model Interface: ArcSWAT 2012 Total Year of Study: 1995 - 2004 Warm up period: 1997 – 1999 (3 years) Calibration Period: 2000 - 2004 (5 years) Validation Period: 1995 – 1999 (5 years) Time Step: Daily Average Model Evaluation: Statistical Evaluation (NSE, PBIAS, R2, RSR) Hydrological Modeling (SWAT) Model Setup Fig 4 Sub-basins delineated from SWAT model
  8. 8. Methodology Hydrological Modeling (SWAT) • Semi distributed hydrological model • Computationally efficient and capable of simulating long periods • Suitable for modeling of ungauged catchment Statistical Evaluation Criteria Equation Nash and Sutcliffe Efficiency (NSE) NSE = 1 - 𝑖=1 𝑛 (𝑄 𝑖−𝑄𝑖 ′ )2 𝑖=1 𝑛 (𝑄 𝑖− 𝑄𝑖)2 Coefficient of Determination (R2) R2= 𝑛 𝑥𝑦− 𝑥 𝑦 𝑛( 𝑥2)−( 𝑥)2 × 𝑛( 𝑦2)−( 𝑦)2 Percent bias (PBIAS) PBIAS = 𝑖 𝑛 𝑌𝑖𝑜𝑏𝑠−𝑌𝑖𝑠𝑖𝑚 ∗100 𝑖 𝑛 𝑌𝑖𝑜𝑏𝑠 RMSE Observations standard deviation ratio (RSR) RSR = 𝑅𝑀𝑆𝐸 𝑆𝑇𝐷𝐸𝑉 𝑜𝑏𝑠 = 𝑖=1 𝑛 (𝑌𝑖𝑜𝑏𝑠−𝑌𝑖𝑠𝑖𝑚)2 𝑖=1 𝑛 (𝑌𝑖𝑜𝑏𝑠−𝑌𝑚𝑒𝑎𝑛)2 Table 4 Evaluation of SWAT model Model Setup Future Timeline  2030s (2011 – 2040)  2060s (2041 – 2070)  2090s (2071 – 2100)
  9. 9. Results and Discussion -6 -4 -2 0 2 4 6 8 10 12 ∆Tmax(C) 2090s RCP 4.5 inmcm4 BNU-ESM CMCC CMS CSIRO-Mk3-6-0 -6 -4 -2 0 2 4 6 8 10 12 ∆Tmax(C) 2090s RCP 8.5 inmcm4 bcc-csm1-1 CMCC CMS CanEsm2 Projection of Temperature  Both minimum and maximum temperature of the basin is projected to increase in the future.  The maximum annual average temperature is projected to increase by 2.22 °C and by 4.16 °C by the end of the century for RCP 4.5 and RCP 8.5 scenarios respectively.  The minimum annual average temperature could increase by 2.54 °C and 4.18 °C . Fig 5 Future projected average temperature of the basin (left) and box plot diagram of maximum projected temperature during 2090s under RCP scenarios for different GCMS (right)
  10. 10. Results and Discussion Projection of Precipitation  Precipitation is projected to increase for all seasons, timelines (2030s, 2060s, 2090s) and scenarios (RCP 4.5 and RCP 8.5).  Large Difference in precipitation between wet and dry seasons could be projected.  The difference is even more pronounced in case of RCP 8.5 scenario during 2090s.  The average annual precipitation of Kali Gandaki basin is projected to increase maximum by 19.67% during 2090s under RCP 4.5 scenario.  Under RCP 8.5 scenario, the maximum increase in average annual precipitation is projected to occur during 2090s, by 26.14% Fig 6 Future projected average precipitation of Kali Gandaki basin under RCP scenarios
  11. 11. Results and Discussion 0 2000 4000 6000 Jan-00 Dec-00 Dec-01 Dec-02 Dec-03 Dec-04 Discharge(m3/s) 0 2000 4000 6000 8000 Jan-95 Jan-96 Dec-96 Dec-97 Dec-98 Dec-99 Discharge(m3/s) Simulated Observed Parameter Value NSE 0.78 PBIAS -4.01% R2 0.78 RSR 0.52 Parameter Value NSE 0.8 PBIAS 9.6% R2 0.82 RSR 0.49 Calibration and Validation Fig 7 Calibration (2000-2004) and Validation (1995-1999) of SWAT model at the outlet of Kali Gandaki basin Table 5 Model performance during calibration (2000-2004) Table 6 Model performance during validation (1995-1999)
  12. 12. Results and Discussion Impact on Water Balance (RCP 4.5) Fig 8 Seasonal separation of climate change impacts on key water balance components of Kali Gandaki basin during 2030s, 2060s and 2090s under RCP 4.5 scenarios  Figure 8 shows significant impact on seasonal water balance components leading to increase in precipitation, snowmelt, evapotranspiration and water yield for future period.  In terms of percentage change, snowmelt of the basin is mostly affected by increase in precipitation and temperature.  Snowmelt is maximum during the monsoon season for all timelines for RCP 4.5 scenario.  Increase in snowmelt could be projected to increase more than 80% during 2090s under RCP 4.5 scenario
  13. 13. Results and Discussion Fig 9 Seasonal separation of climate change impacts on key water balance components of Kali Gandaki basin during 2030s, 2060s and 2090s under RCP 8.5 scenarios Impact on Water Balance (RCP 8.5)  Snowmelt is also the most affected component of water balance under RCP 8.5 scenarios during the future period.  Both winter and monsoon precipitation are projected to increase, which could be observed maximum during 2090s under RCP 8.5 scenario.  The seasonal change in evapotranspiration ranges from 1% to 29%.  Increase in water yield is maximum during the dry season, and is expected to increase more than 50% during 2090s under RCP 8.5 scenario.
  14. 14. Results and Discussion 0 500 1000 1500 2000 2500 3000 Precip Snowmelt PET ET SurQ Wyield Unit(mm) RCP 4.5 0 500 1000 1500 2000 2500 3000 Precip Snowmelt PET ET SurQ Wyield Unit(mm) Water Balance Components Historical 2030s 2060s 2090s RCP 8.5  Compared to 1980s, The average annual precipitation of Kali Gandaki basin is projected to increase maximum by 19.67% during 2090s under RCP 4.5 scenario.  Snowmelt is projected to be maximum during 2090s under RCP 8.5 scenario, and is expected to increase more than 80%.  Annual average evapotransipiration is projected to increase by 6.9% and 14.3% during 2090s under RCP 4.5 and RCP 8.5 scenario respectively.  Maximum increase in water yield could be observed during 2090s by 41% and 51% under RCP 4.5 and RCP 8.5 scenario respectively. Fig 10 climate change impacts on annual average water balance components of Kali Gandaki basin during 2030s, 2060s and 2090s under RCP scenarios Impact on Water Balance
  15. 15. Results and Discussion  The percentage increase in discharge at the outlet of Kali Gandaki basin is projected to be maximum during the pre- monsoon season under RCP 4.5 scenario.  The percentage increase in discharge at the outlet of Kali Gandaki basin is projected to be maximum during monsoon season under RCP 8.5 scenario.  Maximum increase in discharge could be observed during 2090s by 41% and more than 50% under RCP 4.5 and RCP 8.5 scenario respectively. Impact on DischargeRCP 4.5 RCP 8.5 Fig 11 Impact of climate change on discharge of Kali Gandaki basin during 2030s, 2060s and 2090s under RCP scenarios RCP 4.5 RCP 8.5
  16. 16. Fig 12 Spatial distribution of historical and future projected change in snowmelt (mm) Kali Gandaki basin for RCP 4.5 scenario  The spatial distribution of snowmelt shows minimum or no snowmelt at lower elevations and are not affected by climate change.  Snowmelt is maximum at the higher elevation sub- basins and is expected to increase in the future.  Maximum increase in snowmelt up to 30 mm at higher elevation could be projected during 2090s under RCP 4.5 scenario Impact on Snowmelt (RCP 4.5) Results and Discussion
  17. 17. Fig 13 Spatial distribution of historical and future projected change in snowmelt (mm) of Kali Gandaki basin for RCP 8.5 scenario  Lower basin shows minimum effect of climate change on snowmelt under RCP 8.5 scenario  Significant increase in snowmelt could be observed during the future scenarios for individual sub-basins  Maximum increase in snowmelt ranging from 20 mm to 30 mm could be projected in the upper basins and mid-basins. Impact on Snowmelt (RCP 8.5) Results and Discussion
  18. 18. Fig 14 Spatial distribution of future projected change in Evapotranspiration (%) of Kali Gandaki basin for RCP 4.5 (top) and RCP 8.5 scenario (bottom)  Increase in temperature is projected to increaser the evapotranspiration of the basin.  Increase in evapotranspiration is higher at upper and mid- basins during 2090s ranging from 10% to 15% increase under RCP 4.5 scenario and from 25% to 40% under RCP 8.5 scenario. Impact on Evapotranspiration Results and Discussion
  19. 19. Results and Discussion Impact on Water Yield Fig 15 Spatial distribution of future projected change in Water Yield (%) of Kali Gandaki basin for RCP 4.5 (top) and RCP 8.5 scenario (bottom)  Increase in water yield is relatively higher at the upper and mid basins.  The water yield is expected to increase by no more than 30% at lower basins during future period.  Maximum increase in water yield could be observed at upper basin ranging from 60% to 100%.
  20. 20. Conclusions  Both temperature and precipitation of Kali Gandaki is projected to increase affecting the annual averaged water balance components of the basin.  Large Difference in precipitation between wet and dry seasons could be projected.  Maximum increase in discharge could be observed during 2090s by 41% and more than 50% under RCP 4.5 and RCP 8.5 scenario respectively.  The water balance component of the upper and mid-basin are largely affected compared to lower basins.  In terms of percentage change, snowmelt of the basin is mostly affected by increase in precipitation and temperature. Average annual snowmelt is projected to increase more than 80% during 2090s.
  21. 21. THANK YOU !!!! Dr. Arun Bhakta Shrestha Regional Programme Manager River Basin Management arun.shrestha@icimod.org Ajay Ratna Bajracharya Water Resources Modeler-SSA Water and Air bajracharya.aj@gmail.com Acknowledgement: This work was carried out by the Himalayan Adaptation, Water and Resilience (HI-AWARE) consortium under the Collaborative Adaptation Research Initiative in Africa and Asia (CARIAA) with financial support from the UK Government’s Department for International Development and the International Development Research Centre, Ottawa, Canada. Sagar Ratna Bajracharya Hydrometeorological Analyst Water and Air Sagar.Bajracharya@icimod.org

×