Project Summary

HELIX assesses potential climate change impacts and adaptation for global warming above 20C. Development of coherent, internally-consistent global scenarios of the combined natural and human world at 1.5, 2, 4 and 60C global warming, including reaching this level early (2060s) or later (after 2100) has been carried out under WP3.

The study is aimed at quantifying uncertainties from multiple climate model data derived impacts on the water resources of the Ganga Basin using Specific Warming Levels (SWL) under Helix objectives. The hydrological model SWAT has been deployed to generate scenarios for assessing implications on quantity of water on account of multiple regional climate model climate data.

The outputs of these scenarios have been analyzed to evaluate the possible impacts on some of the important hydrological entities such as the runoff, baseflow, soil moisture, ground water recharge and actual evapotranspiration. The impacts have been expressed as change in the future periods with respect to the baseline.

Study Objective

This study aims to quantifying uncertainties from multiple climate model data derived impacts on the water resources of the Ganga Basin, including:

• Change in climate: The key parameters of precipitation and temperature have been taken up to explore their variation across the models at the temporal and spatial scale;
• Change in water balance components: Two important water balance components i.e., water yield and evapotranspiration have been taken to quantify the change in these components;
• Change in extremes: The outputs from the hydrological models have been used to assess the impact of the climate change on the river basins in terms of occurrence of droughts and floods;
• Change in crop growth: has been analysed based on average crop yield, evapotranspiration and amount of irrigation applied;
• CO2 ferilization: Sensitivity analysis has been carried out for a pilot basin to assess the impact of CO2 concentration on crop yield and water requirement.

Findings

Higher warming is projected for some parts of Ganga basin than average temperature global warming for SWL1.5, SWL2 and SWL4 levels both in minimum and maximum temperatures. In case of precipitation, most of the models show marginal increase/decrease in annual precipitation (see figure below).

Figure: Projected change in annual minimum temperature and annual precipitation for the Ganga basin for RCP8.5 Scenario at specific global warming levels of SWL1.5, SWL2 and SWL4

Two important water balance components i.e., water yield and evapotranspiration have been taken to quantify the change in these components under RCP8.5 scenario for SWL1.5, SWL2 and SWL4 scenarios with respect to the baseline scenario for each of the 11 identified models of RCP8.5 and have been presented in the figure below.

Figure: Projected change in annual stream flow and evapotranspiration for the Ganga basin

Linkage to the SDGs

Goal 6: Clean water and sanitation
Ensure availability and sustainable management of water and sanitation for all.

The study was to provide information on the climate change implications at different warming levels to the water resources of the Ganga basin. This is very important for sustainable management of the present water resources.

Goal 13: Climate action
Take urgent action to combat climate change and its impacts.

The assessment has provided very detailed information on potential impacts of climate change, water quantity, magnitude and frequency of floods and droughts, sediment erosion, as well as impacts on agriculture, at different warming levels.