Deciphering the Water-Forest-Climate nexus through long-term hydro-climatic trends in watersheds of Narmada River

Water availability and quality is essential for natural ecosystems and sustainable societies, due to its central position in all living and natural interactions, which is ultimately linked to the socio-economic-ecological health of a region. Water and forests are intertwined as their interactions along with climatic, topographical, ecological and edaphic factors play an essential part in water regulation between land and atmosphere. Rising deforestation and degradation have diminished the climate and water regulatory functions of forests threatening the water quality and quantity in forested watersheds. Given the growing global concerns over water security and climate change, understanding these interlinkages have become imperative for sustainable water management. Therefore, exploring water dynamics in conjunction with vegetation and climatic indicators is crucial for a comprehensive assessment of the forest-water-climate nexus. Forest-fed streams and rivers predominantly spanning the southern and central parts of India are dependent on the rainfall and groundwater flows but changing climate and forest patterns have negative connotations for perennial water flows. The largest west-flowing Central Indian River, the Narmada has high ecological, economic, social, religious, cultural importance and dependence. With more than 30% of the basin being forested, the basin comprises 150 watersheds in different agro-ecological zones with varied climatology and hydrology. Other dominant land use is agriculture covering almost 57% of the basin, closely tied to the economy of 17,493 villages and the livelihood of residents. This necessitates a deeper understanding of long-term patterns of eco-hydro-meteorological variables in differently forested watersheds for planning holistic forest-water-climate adaptation and management strategies. Therefore, varying trends in stream discharge, climate and vegetation were assessed for two distinctly forested watersheds of Narmada River. This study examines the forest-water linkages and the changing climate patterns of Dindori (Tropical Moist Deciduous-Sal dominant) and Barwani (Tropical Dry Deciduous-Teak dominant) watersheds with different forest types and cover. Long-term trend analysis (2001-2020) was conducted at annual, monthly and seasonal time scale for selected climate, forest, soil and water variables through appropriate indicators (minimum and maximum temperature, rainfall, evapotranspiration, Normalized Difference Vegetation Index, Enhanced Vegetation Index, Modified Soil Adjusted Vegetation Index, forest cover, soil moisture, and water discharge). The study followed an integrated approach combining station data supplemented by remotely sensed proxy indicators, secondary literature and trend analysis using Mann-Kendall statistical test. The results indicate shifting rainfall patterns, increasing minimum and maximum temperature with expanding agriculture area and reduction in forest cover in both watersheds. Declining patterns of stream discharge, increased drought frequency and evapotranspiration losses were also observed. These findings reiterate the need for integrated forest-water management for a climate resilient future of the Narmada basin. A comprehensive perspective for water variations should involve associated parameters which can inform integrated water management for developing countries like India.