Rapid Urbanization, and other anthropogenic activities, have amplified the change in land-use transition from green space to heat emission in built-up areas globally. As a result, there has been an increase in the land surface temperature (LST) causing the Urban Heat Island (UHI) effect, particularly in large cities. The UHI effect poses a serious risk to human health and well-being, magnified in large developing cities with limited resources to cope with such issues. This study focuses on understanding the UHI effect in Kathmandu Valley (KV), Delhi, and Dhaka, three growing cities in South Asia. The UHI effect was evaluated by analyzing the UHI intensity of the city with respect to the surroundings. We found that the central urban area, of all three cities, experienced more heat zones compared to the peri-urban areas. The estimated average surface temperature ranged from 21.1 ${}^{\circ }$C in March 2014 to 32.0 ${}^{\circ }$C in June 2015 in KV, while Delhi and Dhaka experienced surface temperature variation from 29.7 ${}^{\circ }$C in June 2017 to 40.2 ${}^{\circ }$C in June 2019 and 23.6 ${}^{\circ }$C in March 2017 to 33.2 ${}^{\circ }$C in March 2014, respectively. Based on magnitude and variation of LST, highly built-up central KV showed heat island characteristics. In both Delhi and Dhaka, the western regions showed the UHI effect. Overall, this study finds that the UHI zones are more concentrated near the urban business centers with high population density. The results suggest that most areas in these cities have a rising LST trend and are on the verge of being UHI regions. Therefore, it is essential that further detailed assessment is conducted to understand and abate the impact of the temperature variations.

Drought is an environmental disaster related to the extremes (on a drier side) in hydrometeorology. The precipitation amount modulates drought in Nepalese river basins. It is vital for efficient water resources management to quantify and understand drought. This paper aims to characterize the droughts in Nepal based on standard precipitation index (SPI) and rainfall anomaly index (RAI) using daily precipitation data and assess their impacts on annual crop yields. We used 41 years (1975–2015) of daily precipitation data to compute monthly means and then the drought indices, namely, SPI and RAI, at 123 stations across Nepal. Results showed that the northwest and eastern regions experienced drought compared to other regions, although the severity and duration were shorter. For stations 101 and 308, we found extreme drought events after 2005 for SPI-1, SPI-3, and SPI-6. However, for SPI-6, extreme drought was also observed in 1989 and 1994 at both stations. The year 1992 was one of the severest drought years for the western and northwest regions, where the severity crossed more than −2.0 for all SPI months. Similar to SPI, RAI also revealed a similar degree of drought in the country. RAI showed that the eastern region depicted a higher degree of severity of drought compared to other areas beyond 2004. The lesser severity is also seen in the far west part beyond 2005. The results showed that SPI and RAI could equally be used to analyze drought severity. More frequent drought incidents have been observed after 2010 at all the considered precipitation stations. With the increase in the drought severity, the crop yield (such as paddy, maize, barley, millet, and wheat) has been directly impacted. These results might be significant for planning water resource and irrigation water management systems.

It is unambiguous that climate change alters the intensity and frequency of precipitation and temperature distribution at the global and local levels. The rate of change in temperature in the northern latitudes is higher than the worldwide average. The annual distribution of precipitation over the Himalayas in the northern latitudes shows substantial spatial and temporal heterogeneity. Precipitation and temperature are the major driving factors that impact the streamflow and water availability in the basin, illustrating the importance of research on the impact of climate change on streamflow by varying the precipitation and temperature in the Thuli Bheri River Basin (TBRB). Multiple climate models were used to project and evaluate the precipitation and temperature distribution changes in temporal and spatial domains. To analyze the potential impact of climate change on the streamflow in the basin, the Soil and Water Assessment Tool (SWAT) hydrological model was used. The climate projection was carried out in three future time windows. The result shows that the precipitation fluctuates between approximately +12% and +50%, the maximum temperature varies between −7% and +7%, and the minimum temperature rises from +0.7% to +5% in intermediate- and high-emission scenarios. In contrast, the streamflow in the basin varies from −40% to +85%. Thus, there is a significant trend in the temperature increase and precipitation reduction in the basin. Further, the relationship between precipitation and temperature with streamflow shows a substantial dependency between them. The variability in precipitation and streamflow is successfully represented by the water yield in the basin, which plays an important role in the sustainability of the water-related projects in the basin and downstream to it. This also helps quantify the amount of water available for hydropower generation, agricultural production, and the water ecosystem in the TBRB.

The Sittaung river basin (SRB) remains one of the least studied basins of Myanmar in terms of the assessment of the impact of climate change. As several reservoirs already exist in the basin, much research is needed to understand how projected climate change impacts rainfall, temperature, flows, domestic and agricultural demands, and hydropower generation. Given the limitation in observed data on the ground, a combination of satellite-derived meteorological data and digital elevation data is used to generate inputs to a Water Evaluation and Planning (WEAP) model. Five CMIP5 GCMs are used in the WEAP to assess the impact of climate change on the water, food, and energy production of the SRB for the baseline (BL: 1985–2014), near future (NF: 2021–2050), and far future (FF: 2051–2080) periods. The results indicate that the average temperature and rainfall are likely to increase in the future for the SRB. December and January are expected to be drier and warmer, whereas rainy months are expected to be wetter and warmer in the future. The BL flows (1091 m³/s) are expected to increase by 7–10% during NF and by 16–19% during FF at the basin outlet. Meanwhile, the unmet domestic demand during BL (1.3 MCM) is expected to decrease further by approximately 50% in the future. However, the unmet agricultural demand (667 MCM) for food production is estimated to increase from the BL by 11–15% during NF and by 14–19% during FF. Similarly, the total energy generation of nine hydropower projects (4.12 million MWh) is expected to increase by 9–11% during NF and by 16–17% during FF. Thus, the riverine flows are expected to increase in the future, thus positively impacting the domestic and hydropower sectors, whereas the unmet demands in the agricultural sector likely remain unsatisfied. These results will help the water, agriculture, and energy sectors to develop strategies to maximize benefits and cope with the impacts of climate change in the near and long-term future.