Climate change impacts on water resources of the Ganges : Suitable adaptation options for agriculture in the Indian-Himalayan region

Sammanfattning: Climate change is affecting several environmental factors and together with socio-economic changes put high pressure on water resources. Climate change manifest itself through increasing temperatures and changes in precipitation patterns and intensities, with knock-on effects on hydrologically-relevant parameters such as water flows, evapotranspiration rates, glacial melt etcetera, all of which have already been observed in the recent past and are predicted to continue in the future. India has the world’s second largest population. The majority of the population live in rural areas and are dependent on climate sensitive sectors such as agriculture, forestry and fishery. The Indian-Himalayan region supplies 600 million people with water, thus future climate change impacts on the hydrological cycle in the area are of great interest and concern. In order to cope with these predicted impacts, there is a need to adapt to the changing climate. This study combines data analyses from a hydro-climatic modelling campaign (carried out externally to this thesis), a literature review on climate change effects on agriculture and opportunities to adapt to these effects and participatory methods bringing stakeholders and scientists together in order to co-create adaptation options that are suitable to minimise short- and long-term climate change impacts on the water flows of the Ganges and hence agriculture in the region. The study concentrates on two districts in the Indo-Gangetic Plain that are characterised by their high dependency on the farming sector: Uttarkashi (upstream Ganges, Uttarakhand) and Patna (downstream Ganges, Bihar). The analysis of hydro-climatic data based on a modelling campaign focussed on three climate variables that are of significance for agriculture: precipitation, temperature, and evapotranspiration. To characterise future climates, four climate change projections based on IPCC’s representative concentrations pathways (RCPs) have been chosen: RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5. The impacts of these scenarios on the above listed three climate variables are analysed over three time periods: 2011-2040, 2041-2070, and 2071-2100, with a special focus on the monsoon months from June to October, as this is the main crop (rice) growing season. The results from the hydro-climatic modelling indicate that the maximum, minimum, and average temperature will be increasing over the next century in both districts. An increase in evapotranspiration can be seen for both districts, with a few exceptions for RCP scenarios 2.6, 6.0 and 8.5 in April and May in Patna, and for all RCP scenarios in April, May and June in Uttarkashi. An increase in maximum and average precipitation can be seen for most RCP scenarios and future time periods (e.g. of exceptions in average precipitation: RCP 4.5 and 8.5 in June and July in the period 2011-2040) during the monsoon period in Patna. Similarly, in Uttarkashi maximum and average precipitation increases for all three time periods and RCP scenarios during the monsoon months of September and August (only for RCP scenarios 2.6 and 8.5). For the remaining months, the precipitation patterns show great variability for all scenarios and both regions. The literature review resulted in a table of adaptation options, where nine out of 63 were considered as transformational adaptation, and enabled identification of possible climate change impacts on agriculture in the two districts. The minimum temperature could result in more severe and intense hailstorms in the future for both districts. The increase in temperature could lead to a prolonged growing season in Uttarkashi, whilst the increase in average and maximum temperature in Patna could lead to heat-stress for the crops. Furthermore, the increase in average and maximum precipitation could lead to more severe and intense natural disasters e.g. landslides in Uttarkashi and floods in Patna. Moreover, the increase in average evapotranspiration combined with the decrease in average precipitation during some months could lead to an increasing need of irrigation. Two workshops were held in the region with the aim to bring together researchers and stakeholders (e.g. famers) in order to jointly discuss 1) the suitability of hydrological modelling data for preparing the agriculture sector to a changing climate, and 2) suggest suitable adaptation options based on researchers’ and stakeholders’ knowledge and experience. Information from the first workshop was obtained by a workshop report, whilst information from the second workshop was obtained from the author’s own participation. The result from the workshop showed that the farmers had several suggestions of suitable adaptation options e.g. implementation of irrigation system and improved access to credit. It also showed that the farmers already adapted to climate change e.g. usage of short- and long duration variations of rice and sowing date adjustment. The combination of these results informed the suggestions for adaptation options for the two districts, namely the development of disaster reduction plans and early warning systems for weather extremes, as well as a diversification of agriculture and more generally livelihoods. In addition, indirect adaptation measures suggested for both districts included insurance schemes against yield failure, improved access to credit schemes, and right/fair market prices. Specific measures for each district were also suggested e.g. heat-tolerant crops in Patna and implementation or irrigation systems in Uttarkashi.