Natural and anthropogenic effects on spatio-temporal variation in sediment load and yield in the Godavari basin, India

Abstract

River sediment, the most crucial component of the land-ocean interaction, is enduring substantial changes worldwide because of anthropogenic alterations and climate change. Our study assesses the interaction of sediment load variability and yield to the rainfall, land-use, and dam constructions at both spatial and temporal scales in the Godavari and its major tributaries. The most important river basin in Peninsular India, the Godavari, has witnessed a dramatic decline (p-value <0.001) in sediment load over the past five decades, with average annual rates of 2 million tonnes (Mt) yr−1. Sediment load in the Godavari reduced from 150 Mt between 1970 and 1979, to 115 Mt in 1980–1989, 98 Mt in 1990–1999, 48 Mt in 2000–2009, and 47 Mt in 2010–2019, respectively. While sediment load in the Godavari and its major tributaries is declining significantly, the rainfall showed an overall insignificant increasing trend barring the Sabari sub-catchment, where the rainfall is increasing at a significant rate of 7 mm yr−1 (p-value = 0.001). Twenty-five sub-basins in the Godavari showed a large variation in sediment yield (28 to 3404 t km−2 yr−1). Our results revealed that spatial variability in sediment yield is primarily associated with both rainfall and land-use pattern. The temporal variation in sediment load in the Godavari and Pranhita is associated with intensified human activities during the most recent decades, while climate is the primary controlling factor in Indravati and Sabari sub-catchments. Sediment entrapment under a high rate of siltation by reservoirs in the Godavari has sharply reduced the sediment flux to the Bay of Bengal, causing aggravated delta erosion by wave actions. The findings of this study have significant implications for understanding the complex interrelationship between the management of reservoirs, land use, sediment loads, denudation, and coastal erosion in the Godavari catchment.