Abstract The Indian subcontinent today houses about one-third of the global population and is one of the most vulnerable regions to future climate variability. This region has seen changes in civilizations, kingdoms and more recently political regimes, that were intricately linked to the changing environment over the mid–late Holocene. A comparative analysis of human–environment interaction within different regions at different time scales of the Quaternary is, however, lacking. In this paper we discuss the human–environment interactions taking case studies from two diverse time periods and geographically different regions from the Indian subcontinent. First, we review and analyse the role of environmental change in the evolution of Indus civilization on the northwestern Indian subcontinent during the mid–late Holocene and secondly, we discuss the role of both the anthropogenic activities and environmental change during the Anthropocene in shaping up the Bengal Delta. Overall, during the mid–late Holocene, Indus cultural transformations were driven by natural environmental changes, whereas the anthropogenic activities in the last few centuries have modified the Bengal deltaic landscape, which has intensified the impacts of natural disasters – in both cases a change in socio-political scenarios occurred. Such studies can be used as benchmarks to understand the future response of societies to environmental changes.

Abstract River Ichamati, the major provider of freshwater to the Sundarbans mangrove ecosystem flowing along the India- Bangladesh border now stands disconnected from its freshwater source. This study estimates the run-off volume of the river basin through a SWAT model to consider it’s rejuvenation. A hypothetical channel-form for the disconnected part of Ichamati has been constructed using existing and regenerated cross-sections. The flow availability in the river channel under both present and restored conditions has been estimated using HEC-RAS model. The study indicates the average freshwater flow in the river at Kalanchi to be less than 1 cumec during the lean period and up to 100 cumec in monsoon. Hydrological Tennant method, Flow Duration Curve (FDC) and the holistic Building Block method (BBM) have been used to assess the environmental flows for the non-tidal part of the river. Comparable flow values of around 188 cumec during monsoon and little over 30 cumec in the lean months have been assessed after the proposed restoration using all methods. The authors advocate trans-boundary collaboration between India and Bangladesh for the revival of the decayed channel to ensure environmental flows and sustenance of the Sundarbans, a World Heritage and Ramsar site shared by the two neighbouring countries.

Abstract West Bengal (88,752 km 2) is the only Indian state that extends from the Himalaya to the Bay of Bengal. It can be divided into nine physiographic provinces of which the Himalayas, the western plateaus, the northern and western alluvial fans and the Ganga delta are the most important. The development of the river system of the state was largely governed by tectonic evolution of the eastern Himalaya and western edges of the Bengal basin. The characteristics of the rivers as well as a number of aspects of water resources of the state can be linked to its physiographic regions. The principal issues associated with water in West Bengal include river degeneration, channel shifting, flood, urban waterlogging, drought, pollution, groundwater depletion and inland navigation. The management of water is practised by river impoundment projects in various scales and by drainage schemes. It is estimated that the western and eastern parts of the state are the most water stressed regions due to climatic and human factors respectively. The solutions for many of the water-related problems of West Bengal, progressive or cyclic, can be achieved by putting emphasis on participatory management besides organisational intervention.