Godavari estuary

• Category: Marine and Oceanic Biomes.
• Geographic Location: India.
• Summary: The globally significant, biodiversity-rich Godavari estuary and its species-rich mangrove forests are threatened because of anthropogenic stressors.

The Godavari, a perennial river in southern India, is considered to be one of the seven sacred rivers in India and is popularly known as the Ganga of the South. At 910 miles (1,465 kilometers) long, it is the second-longest river after the Ganga (as the Ganges is sometimes called), extending its catchment over an area of 120,777 square miles (312,812 square kilometers), which is nearly 9.5 percent of the total area of the country. It originates in the Trayambak, or Western Ghats, near Nasik, northeast of Mumbai in the state of Maharashtra, at an elevation of 3,501 feet (1,067 meters). The Godavari meets the Bay of Bengal on the east coast of India in the state of Andhra Pradesh.

The river bifurcates at Dowlaiswaram into two principal distributaries, the Vasishta and the Gautami, which give rise to a sprawling estuarine deltaic system fringed with tidal creeks and dense mangrove forests, before reaching the Bay of Bengal. The Vasishta-Godavari further divides at Gannavaram into two branches known as Vasishta Proper and Vainatheyam, both of which open separately into the Bay of Bengal. The Gautami-Godavari is also connected to Kakinada Bay by two channels: Coringa, arising at Yanam, and Godern, arising at Bhairavapallam.

The Godavari River has an average depth of 39 feet (12 meters), and the maximum width of the estuary is 0.6 mile (1 kilometer). The tidal influence extends up to 28 miles (45 kilometers) from the mouth. Average salinity is 34 parts per thousand. The temperature ranges from 84 to 95F (29 to 35C).

The southwest monsoon in early July brings a heavy influx of freshwater to the estuary, resulting in freshwater flowing in the upper layer toward the sea, with the seawater moving at the bottom in the opposite direction. This circulation prevents vertical mixing and disrupts the prevailing estuarine salinity, resulting in a complete scouring of the entire system. This condition generally exists from mid-July to September. The recovery phase begins in October, when the estuarine condition stabilizes. Less freshwater flow in the system results in the establishment of a vertical salinity gradient at sea, progressively shifting toward the estuary. The tidal range is about 3 feet (1 meter).

Flora and Fauna

The Godavari estuarine delta is characterized by dense mangrove forests and associated floral and faunal species. It is the second-largest mangrove forest in India. Part of this area has been preserved as Coringa Wildlife Sanctuary. The mangrove community in the Godavari estuarine delta is represented by thirty-five species of mangroves, of which sixteen are true mangroves and the rest are associated species. The dominant species in other mangrove forests, Rhizophora spp., is poorly represented here. This area is the only place in India where three species of Avicennia are found together: Avicennia officinalis, A. marina, and A. alba.

The Godavari estuarine system supports prawn aquaculture throughout the year. A total twenty-three species of Penaeid prawn contribute to the aquaculture industry. Dominant species are Metapenaeus monoceros, Penaeus indicus, and P. Monodon.

One dominant sessile faunal element, a wood-boring mollusk, is common to this biome. The estuary also provides an important habitat for fish, reptiles, amphibians, birds, and mammals that need a coastal ecosystem to survive. Animals such as otters, fisher cats, jackals, and sea turtles are found in creeks here. Birds such as snipes, ducks, seagulls, and flamingos are common. There is a recorded population of 119 bird species, of which fifty are migrants from eastern Europe and central and northern Asia. The relatively rare winter migrant species include the golden plover (Pluvialis apricaria), woodcock (Scolopax rusticola), common snipe (Gallinago gallinago), and long-billed ringed plover (Charadrius placidus).

Many sea turtle species, like the leatherback turtle (Dermochelys coriacea) and the green turtle (Chelonia mydas), are found in the estuary during feeding and breeding seasons. The Krishna-Godavari basin is the main nesting site of the endangered olive Ridley turtle (Lepidochelys olivacea).

Also documented in the estuary are a full range of microbethos, including 137 species of phytoplankton and eight-one species of zooplankton; thirty-seven groups of meiobenthos, such as nematodes and copepods; and 114 species of macrobenthos, featuring worms, sponges, and crustaceans. Dinoflagellates, blue-green algae, red algal species, and many foraminiferal species (dominated by fourteen species) are found throughout the year in the Godavari estuary.

Environmental Threats

Mangroves not only provide shelter to many species, but also protect the nearby villages and the coastal area by acting as a barrier against tropical storms, tidal waves, cyclones, and other natural calamities. Over the years, much of the dense mangrove forest has been destroyed for fuel wood and feral cattle grazing.

Additional threats come from anthropogenic stresses from the adjacent rural and urban areas, including nearby Kakinada City. These stresses include habitat conversion for real estate development, subsidence, maritime traffic, the discharge of heavy effluents in the estuary, unsustainable fisheries and other aquacultural activities, overexploitation of biological resources, nonadherence to seasonal fishing bans, pollution, eutrophication, and siltation. Such events are contributing to the degradation and loss of mangrove forest stands here, directly affecting the health of the Godavari estuarine ecosystem. Rising sea levels have also caused erosion, leading to flooding along with a reduction of natural beaches and shorelines.

The Godavari mangroves also play important roles as carbon sinks. Therefore, maintaining the extent and ecosystem functionality of the mangrove forests and preventing any further retrogression is an important strategy for mitigating the effects of climate change.

Bibliography

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Naidu, T. Appala. "Godawari, Krishna Estuaries Provide a Safe Ground." The Hindu, 23 Nov. 2020, www.thehindu.com/news/national/andhra-pradesh/godavari-krishna-estuaries-provide-a-safe-ground/article33156092.ece. Accessed 23 Jan. 2025.

R., Mani M., et al. "Land Subsidence Studies in the Godavari Delta Regions of the East Coast of India Using ALOS and Sentinel 1 Data." Ecological Informatics, vol. 78, 2023. doi.org/10.1016/j.ecoinf.2023.102373. Accessed 23 Jan. 2025.

Sen Gupta, R. and E. Desa, eds. The Indian Ocean—A Perspective, Vol. 1. CRC Press, 2001.

Sharma, N. S. Godavari Estuarine Processes. National Institute of Oceanography, 2007.

Tiwari, Samakshi. “On-Ground Monitoring Set to Shore Up Mangrove Resilience in Coringa Wildlife Sanctuary.” Forest News, 28 Aug. 2024, forestsnews.cifor.org/89131/india-on-ground-monitoring-set-to-shore-up-mangrove-resilience-in-coringa-wildlife-sanctuary?fnl=. Accessed 23 Jan. 2025.

Wikramanayake, Eric. “Godavari-Krishna Mangroves.” One Earth, 23 Sept. 2020, www.oneearth.org/ecoregions/godavari-krishna-mangroves/. Accessed 23 Jan. 2025.