CHALLENGES ON DAM SAFETY UNDER CHANGING CLIMATE IN INDIA MANOHAR - - PowerPoint PPT Presentation
CHALLENGES ON DAM SAFETY UNDER CHANGING CLIMATE IN INDIA MANOHAR ARORA NATIONAL INSTITUTE OF HYDROLOGY, ROORKEE The most common causes of failure of large dams over the world are overtopping accounting for 32% failures followed by
CHALLENGES ON DAM SAFETY UNDER CHANGING CLIMATE IN INDIA
MANOHAR ARORA NATIONAL INSTITUTE OF HYDROLOGY, ROORKEE
dams
the world are
accounting for 32% failures followed by internal erosion accounting for 27% failures.
73% are due to inadequate spillway capacity and 27% due to spillway gate failure.
There are currently about 4839 completed large dams in India, with another 348 under construction (CWC, 2013). The total storage capacity of these dams, 76% of which are more than 20 years old, is about 283 billion cubic meters.
Temperatures increase significant changes in seasonal and annual rainfall patterns and
M ost of the world's dams have not been built to allow for the erratic hydrological patterns that climate change is bringing. M ore extreme storms and increasingly severe floods will have major implications for dam safety.
FLOOD ESTIMATION/DESIGN FLOOD CALCULATIONS IN INDIA
The Bureau of Indian standard guidelines IS: 5477 (Part IV) recommends that the Inflow Design Flood (IDF) of a structure, depending on its importance or risk involved, may be chosen from either one of the following:
Probable M aximum Flood (PM F) Standard Project Flood (SPF) Flood of a Specific Return Period
SEASONAL AND REGIONAL FLOOD CHARACTERISTICS / PROCESS TYPES PROPOSED
Process Type Long Rain Floods Short- Rain Floods Flash Floods Rain- On-Snow Floods Snowmelt Floods Timings of floods No pronounced seasonality No pronounced seasonality Floods and extreme rainfall mainly in summer
Often occur during transition between cold and warm periods Floods in spring to summer Storm duration Long duration (> 1- day) Duration of several hours to 1 day Short duration (< 90 min), high intensities Moderate rainfall events can cause large floods Rainfall unimportant Rainfall depths, snow melt Substantial rainfall depths Moderate to Substantial rainfall Small to moderate rainfall depths Snow melt and rainfall Snowmelt, no or minor rainfall Catchment state (SWE, soil moisture) Wet due to persistent rainfall Wet for large flood event Any Wet , snow covered Wet , snow covered Runoff response dynamics Slow response Fast response Flashy response Responses range from fast to slow Medium or slow response Spatial coherence Large spatial extent
( >104 km2) Local or regional extent Limited spatial extent of storms and floods (< 30 km2) Limited to areas of snow cover Medium spatial extent of floods
NEW CLIMATE CHANGE PROJECTIONS FOR INDIA
based climate projections are now available.
climate projections at global scale
(1-2.8°) than the previous CMIP3 models
AN INTRODUCTION TO THE RCP SCENARIOS
30 25 20
GtC/Yr
RCP 8.5
936 ppm
RCP 6.0
670
15 10 5
ppm
RCP 4.5 RCP 2.6
538 ppm 421 ppm
LIST OF CMIP 5 GCMs
No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Model Modeling Center (or Group) CCSM4 National Center for Atmospheric Research, USA Commonwealth Scientific and Industrial Research Organization in CSIRO-Mk3.6 collaboration with Queensland Climate Change Centre of Excellence, Australia GISS-E2-R NASA Goddard Institute for Space Studies, USA HadGEM2-ES Met Office Hadley Centre, UK IPSL-CM5A-LR Institut Pierre-Simon Laplace, France Japan Agency for Marine-Earth Science and Technology, The MIROC-ESM University of Tokyo), and National Institute for Environmental Studies Japan Agency for Marine-Earth Science and Technology, The MIROC-ESM-CHEM University of Tokyo), and National Institute for Environmental Studies The University of Tokyo, National Institute for Environmental MIROC5 Studies, and Japan Agency for Marine-Earth Science and Technology MRI-CGCM3 Meteorological Research Institute, Japan NorESM1-M Norwegian Climate Centre BCC-CSM1.1 Beijing Climate Center, China Meteorological Administration CESM1(CAM5) Community Earth System Model Contributors FIO-ESM The First Institute of Oceanography, SOA, China GFDL-CM3 NOAA Geophysical Fluid Dynamics Laboratory GFDL-ESM2G NOAA Geophysical Fluid Dynamics Laboratory GFDL-ESM2M NOAA Geophysical Fluid Dynamics Laboratory HadGEM2-AO Met Office Hadley Centre, UK NorESM1-ME Norwegian Climate Centre Resolution (lat) - Resolution (lon) deg
0.942 1.250 1.895 1.875 2.022 2.517 1.250 1.875 1.895 3.750 2.857 2.813 2.857 2.813 1.417 1.406 1.132 1.125 1.895 2.500 2.812 2.812 0.937 1.250 2.812 2.812 2.000 2.500 2.000 2.500 2.000 2.500 1.241 1.875 1.875 2.500
MULTI-MODEL APPROACH TO CAPTURE UNCERTAINTIES IN TEMPERATURE AND PRECIPITATION PROJECTIONS OVER INDIA
Baseline = 1961-1990 Chaturvedi et al., (2012)
CMIP5 model ensemble mean temperature change (°C) relative to the pre-industrial period
Chaturvedi et al., 2012
CMIP5 model ensemble mean precipitation change (%) relative to the pre-industrial period
Chaturvedi et al., 2012
LIMITATIONS OF THE CMIP5 BASED CLIMATE PROJECTIONS
For the whole India, the projections of maximum temperature from all the six models showed an increase within the range 2.5°C to 4.4°C by end
climate simulations. The annual rainfall projections from all the six models indicated a general increase in rainfall being within the range 15-24%.
RCP8.5) scenario, mean warming in India is likely to be in the range 1.7-2 degrees C by 2030s and 3.3 - 4.8 degrees C by 2080s relative to pre-industrial times;
scenario is projected to increase from 4% to 5% by 2030s and from 6% to 14% towards the end of the century (2080s) compared to the 1961-1990 baseline;
extreme precipitation days (e.g. > 40 mm/ day) for decades 2060s and beyond.
Assumptions
Pyramid of uncertainties in climate models (GCM ’s)
Conclusions for water management M odels (e.g. climate scenarios) Theory Data
Result:
“ Climate is changing, the risk is unacceptable! “
Scientist Water manager
(Hans M iddelkoop, ~1995)
How certain are the changes ?
Scientist Water manager “ How much.. ? “
Hans M iddelkoop, ~1995)
Dam function Climate variable Potential impact Flood detention High rainfall Increased flow into reservoirs increases flood risk: increased storage requirements or less well managed floods. Increase in sedimentation during flood events could lead to reduction in flood storage capacity and/ or blockage of spillways due to increased mobilisation of vegetation in flood flows High temperature Increase in vegetation growth
reduction in reservoir capacity and/ or blocking of spillways
‘Short List’ of potential vulnerability of reservoir function
to climate change
Dam function Climate variable Potential impact Storage for seasonal use High rainfall High rainfall events leading to increased peak flows into impounding reservoirs can lead to overtopping. Dams may need to be operated at lower
more variable levels to mitigate against this risk, potentially reducing available storage. Increase in sedimentation during flood events could lead to a reduction in water storage capacity. Increase in turbidity during flood events could lead to water clarity & quality issues with resultant increased treatment requirements. Water may no longer be suitable for some uses at certain times of year
Dam function Climate variable Potential impact Storage for seasonal use Low rainfall Lower rainfall will lead to lower flows, decreasing reservoir levels and less water will be available for use. Reduced yields. Low rainfall will increase demand for water for irrigation and environmental uses. For reservoirs with secondary purposes, management conflicts can
when draw down is required for primary function (e.g. recreational use
water supply reservoirs; environmental flow releases). Lower water levels leading to increased concentration of pollutants, lower water quality and higher treatment requirements.
Dam function Climate variable Potential impact Storage for seasonal use High temperature Increase in water temperature leading to increased vegetation growth and eutrophic conditions. Increased duration and frequency
Algal
and increase in treatment requirements. Water may not be suitable for some purposes (e.g. environmental releases). Increase in evaporation
stored water, and transpiration from vegetation and soils - lower water levels in reservoirs and less available for use.
Dam function Climate variable Potential impact Electricity generation High rainfall Damage caused to HEP auxiliary infrastructure (power houses etc) by flooding could be very costly - damage to assets and electricity supply outage. Flood risk may require reduced operating levels, reducing availability or flexibility of power generation. Increase in water available for release during winter
Dam function Climate variable Potential impact Electricity generation Low rainfall Decrease in water available for release/ flush during summer High temperature Change in demand for electricity – milder winters reduce power demand, hotter summers increased demand. Opposite to seasonal water availability.
The following functions related to Dam Safety aspects need to be strengthened:
and future dams.
State Govts / Organisations
Way Forward
structural behavior
Dams with special reference to implemented instrumentation systems in the dams
dams in efficient manner
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