Unprecedented drought in South India and recent water scarcity

Peninsular Indian agriculture and drinking water availability are critically reliant on seasonal winter rainfall occurring from October to December, associated with the northeastern monsoon (NEM). Over 2016-2018, moderate-to-exceptionally low NEM rainfall gave rise to severe drought conditions over much of southern India and exacerbated water scarcity. The magnitude and dynamics of this drought remain unexplored. Here, we quantify the severity of this event and explore causal mechanisms of drought conditions over South India. Our findings indicate that the 3-year cumulative rainfall totals of NEM rainfall during this event faced a deficit of more than 40% - the driest 3-year period in ∼150 years according to the observational record. We demonstrate that drought conditions linked to the NEM across South India are associated with cool phases in the equatorial Indian and Pacific Oceans. Future changes in these teleconnections will add to the challenges of drought prediction. © 2021 The Author(s). Published by IOP Publishing Ltd.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Drought and famine in India, 1870?2016

Millions of people died due to famines in India in the 19th and 20th centuries; however, the relationship of historical famines with drought is complicated and not well understood. Using station?based observations and simulations, we reconstruct soil moisture (agricultural) drought in India for the period 1870?2016. We show that over this century and a half period, India experienced seven major drought periods (1876?1882, 1895?1900, 1908?1924, 1937?1945, 1982?1990, 1997?2004, and 2011?2015) based on severity?area?duration (SAD) analysis of reconstructed soil moisture. Out of six major famines (1873?74, 1876, 1877, 1896?97, 1899, and 1943) that occurred during 1870?2016, five are linked to soil moisture drought, and one (1943) was not. The three most deadly droughts (1877, 1896, and 1899) were linked with the positive phase of El Nino Southern Oscillation (ENSO). Five major droughts were not linked with famine, and three of those five non?famine droughts occurred after Indian Independence in 1947. Plain Language Summary India witnessed some of the most famous famines during the late 19th and early 20th century. These famines caused millions of deaths primarily due to widespread crop failure. However, the role of agricultural drought in these famines remains unrecognized. Using station based observations and simulations from a hydrological model, we reconstructed agricultural droughts and established a linkage between famines and droughts over India. We find that a majority of famines were caused by large?scale and severe soil moisture droughts that hampered the food production. However, one famine was completely resulted due to the failure of policy during the British Era. Expansion of irrigation, better public distribution system, rural employment, and transportation reduced the impact of drought on the lives of people after the independence.by Vimal Mishra, Amar Deep Tiwari, Saran Aadhar, Reepal Shah, Mu Xiao, D. S. Pai and Dennis Lettenmaie

In Situ UV Disinfection of a Waveguide-Based Photobioreactor

Compact waveguide-based photobioreactors with high surface area-to-volume ratios and optimum light-management strategies have been developed to achieve high volumetric productivities within algal cultures. The light-managing strategies have focused on optimizing sunlight collection, sunlight filtration, and light delivery throughout the entire bioreactor volume by using light-directing waveguides. In addition to delivering broad-spectrum or monochromatic light for algal growth, these systems present an opportunity for advances in photobioreactor disinfection by using germicidal ultraviolet (UV) light. Here, we investigated the efficacy of in situ, nonchemical UV treatment to disinfect a heterotrophic contaminant in a compact photobioreactor. We maintained a >99% pure culture of <i>Synechocystis</i> sp. PCC 6803 for an operating period exceeding 3 weeks following UV treatment of an intentionally contaminated waveguide photobioreactor. Without UV treatment, the culture became contaminated within only a few days (control). We developed a theoretical model to predict disinfection efficiency based on operational parameters and bioreactor geometry, and we verified it with experimental results to predict the disinfection efficiency of a <i>Bacillus subtilis</i> spore culture

Hydroclimatological perspective of the Kerala flood of 2018

Flood is among the deadliest disasters in India, and the frequency of floods and extreme precipitation events is projected to increase under the warming climate. The frequency of floods in India varies geographically as some regions are more prone to floods than the others. The Kerala flood of 2018 caused enormous economic damage, affected millions of people, and resulted in the death of more than 400 people. Here we provide a hydroclimatological perspective on the Kerala flood of 2018. Using the observations and model simulations from the Variable Infiltration Capacity (VIC) model, we show that the 2018 extreme precipitation and runoff conditions that caused flooding were unprecedented in the record of the past 66 years (1951–2017). Our results show that mean monsoon precipitation has significantly declined while air temperature has significantly increased during 1951–2017 in Kerala. The drying and warming trends during the monsoon season resulted in a declined total runoff in large part of the state in the last 66 years. Apart from the mean hydroclimatic conditions, extreme precipitation, and extreme total runoff have also declined from 1951 to 2017. However, 1 and 2-day extreme precipitation and extreme runoff conditions in August 2018 exceeded substantially from the long-term 95th percentiles recorded during 1951–2017. Since there is no increase in mean and extreme precipitation in Kerala over the last six decades, the extreme event during August 2018 is likely to be driven by anomalous atmospheric conditions due to climate variability rather anthropogenic climate warming. The severity of the Kerala flood of 2018 and the damage caused might be affected by several factors including land use/land cover change, antecedent hydrologic conditions, reservoir storage and operations, encroachment of flood plains, and other natural factors. The impacts of key drivers (anthropogenic and natural) on flood severity need to be established to improve our understanding of floods and associated damage.by Vimal Mishra and Harsh L. Sha

Projected increase in Hydropower production in India under climate change

Hydropower is a valuable renewable energy resource in India, which can help in climate change mitigation and meet the increasing energy demands. However, the crucial role of climate change on hydropower production in India remains unexplored. Here using the observations and model simulations, we show that seven large hydropower projects experienced a significant (p-value < 0.05) warming and a decline in precipitation and streamflow during the observed period of 1951–2007. However, all the hydropower projects are projected to experience a warmer and wetter climate in the future. Multimodel ensemble mean annual average temperature (precipitation) is projected to rise up to 6.3 ± 1.6 °C (18 ± 14.6%) in the catchments upstream of the other reservoirs by the end of the 21st century under representative concentration pathway (RCP) 8.5. Due to the projected increase in precipitation, mean annual streamflow (up to +45%) and hydropower (up to +25%) production are projected to rise under the future climate. However, significant warming (6.25 ± 1.62 °C) is projected to result in a decline in streamflow and hydropower production in May- June for snow-dominated Nathpa Jhakri and Bhakra Nangal hydropower projects. Our results provide insights into the development and planning of hydropower projects in India under the current projected future climate.by Syed Azhar Ali, Saran Aadhar, Harsh L. Shah and Vimal Mishr