Climate Change and its Impacts on Selected Indian Hydrological Systems using Earth System and High-Resolution Modeling

Due to its diversified socio-economic and climatic regions, India is prominently vulnerable to the ensuing climate changes and related impacts. An increase in temperature and changes in the overall precipitation patterns have a profound impact on the water availability. The advent of climate change and its impact on glacier melt may lead to abrupt floods in regions neighboring the Himalayas. Hence, understanding the monsoon variability and the hydrological cycle in the baseline and future time scales would enrich the information available for policy makers and stakeholders for informed decision making - this is the objective of the NORINDIA project. The NORINDIA Project draws its research activities on an existing partnership between Norway and India with five Norwegian and three Indian collaborators. The project is coordinated by Dr. Michel Mesquita (Uni Research Climate/BCCR); the Norwegian collaborators are: the University of Bergen and Oslo, the Norwegian Institute for Air Research (NILU) and Statkraft. The Indian partners are: the Indian Institute of Tropical Meteorology (IITM), the Centre for Mathematical Modelling and Computer Simulation (C-MMACS) and The Energy and Resources Institute (IITM). The project also brings contribution from the National Center for Atmospheric Research (NCAR) in the United States, thus drawing on their expertise in hydrological modelling. NORINDIA is therefore a multi-disciplinary and unique project, not only due to the gamut of participant institutions, but also for the state-of-the-art science it develops. This project has five Work Packages (WP), which deal with large-scale atmospheric processes down to smaller scales. WP1 studies the effect of climate change on the Indian monsoon. WP2 quantifies the role of snow and surface processes on the Indian summer monsoon. WP3 quantifies the role of snow and glacier melt on water resources. WP4 develops dynamical downscaled model output. WP5 studies changes in the hydrological cycle in the present and future climate. Hence, all of the WPs in NORINDIA work together to integrate results across spatial and temporal scales to produce a unified understanding on how climate change may affect the monsoon and water availability in India. Results from WP1, using the RCP8.5 scenario, indicate an increase of around 10% in summer rainfall during the period 2076-2096 compared to recent climate in the Indo-Pacific region. In WP2, we show that high snow depth over the Himalayan-Tibetan Plateau (HTP) region influences the meridional tropospheric temperature gradient reversal that marks the monsoon onset. Composite differences reveal that, in high snow years: i) the onset is delayed by about 7 days, and ii) negative precipitation anomalies, as well as persisting dry and warm surface conditions prevail over India. About half of this delay can be attributed to the realistic initialization of snow over the HTP region. WP3 shows that increasing temperatures may reduce annual snowfall in the Himalaya/Hindu Kush/Karakoram region, despite a likely increase in precipitation. With the RCP 8.5 scenario, the reduction in annual snowfall is estimated to be 30-50% in the Indus Basin, 50-60% in the Ganges Basin, and 50-70% in the Brahmaputra Basin. In WP4, we show that for the RCP4.5 scenario, we have a robust increase in surface temperature, compared with the present climate, for the Beas and Brahmaputra basins on the order of 1.8°C in 2039-2080, and 3°C in 2079-2100. For the Indus basin, the data suggest a significant increase on the order of 3°C in 2079-2100, and not in earlier decades. Also, we show a weakening trend of the monsoon circulation and precipitation decline over South Asia during the recent few decades, which is largely due to anthropogenic influence. In addition to that, the surface-warming trend over the Indian region is accompanied by decline in precipitation and soil moisture starting from the mid-1950s and continuing into the 21st century. In WP5, our hydrological modelling results show that the precipitation may increase 0.5% (RCP45) and 8.8% (RCP85) around 2050, and increase 0.8% (RCP45) and 6% (RCP85) at the end of 2100 over the Beas river basin. The glacier area loss is about 47% (RCP45) and 49% (RCP84) around 2050 and 73% (RCP45) and 80% (RCP85) at the end of 2100, which gives a reduction in runoff of 34% around 2050 and 46% at the end of the century. In summary, the anticipated significance of the results include: a) improved scientific understanding of the monsoon hydroclimatic response to climate change; b) development of human resources (two PhD students and a post-doc) and capacity building in Climate Science (through the workshops and use of novel models, such as WRF-Hydro); and c) the generation of knowledge base for long-term planning and policy development. Thus, we hope that this project may make a significant contribution to stakeholders and policy-makers, with respect to the future of water resources in India.

Climate change, though global in nature, may affect regional scales in different ways. The severity of regional impacts is dependent on the awareness and preparedness of the country in concern. Due to its diversified socio-economic and climatic conditions , India is prominently vulnerable to the ensuing climate change and related impacts. The regulation and availability of water supply over the north-Indian region depends on both seasonal and perennial rivers. The glacial melt regions surrounding Himalayas are also prone to abrupt floods and riverine changes. These are, in turn, dependent on the monsoon variability there. Global climate change and its impact on regional monsoonal variability has been a focal concern in the past years. However, key gaps sti ll exist in the regional monsoon prediction with appropriate representation. An integrated assessment of climate change and its impact on water resources needs a hierarchical model configuration, which involves the representation of glob al and regional processes with reasonable accuracy for the present climate. These models could then be considered appropriate tools for future climate projections over a region. The present project aims to address an integrated climate modeling assessment involving Earth-system, regional-climate and hydrological models to address climate change and its impact on the hydrological cycle of surface water availability over India. The uniqueness of this multidisciplinary project is due to the gamut of particip ant institutions, and the state-of-art science put together for this proposal. There are five work packages: the first four contribute to the central themes on the assessment of global and regional climate models and monsoon variability for baseline and f uture RCP scenarios over the Indian region; the final work package (WP5) provides the hydrological estimation of water availability for selected water sheds over the North Indian region.