Goa: before the monsoon, the sea travels sixty-five kilometres up its rivers

01 A coast seen from the inside

Goa is India's smallest state: 3,702 square kilometres, about sixty kilometres across at its widest, between the Arabian Sea and the Western Ghats. Almost everyone knows it by its sandy edge. But look carefully at the map and something else appears: seven main rivers, the Terekhol, Chapora, Mandovi, Zuari, Sal, Talpona and Galgibaga, coming down from the hills and opening into estuaries, with 253 navigable kilometres in total.

Between those rivers lie more than forty estuarine islands and some ninety river islands. The Mandovi and the Zuari, the two largest, are joined inland by a natural channel, the Cumbarjua canal, so that the centre of the state is in fact a web of brackish water lined with mangroves. Divar, Chorão and other islands in that maze are whole villages reached by boat.

That changes how the place reads. Arrive by plane and you see coconut palms and beaches; travel the interior and you spend the day crossing water: bridges over river arms, dykes between rice fields, jetties where a ferry is waiting. In Goa the coast is only the last of many edges between land and water.

02 The salt that climbs and the rain that pushes it back

The finding that explains the rest is a classic measurement from Indian oceanography. In the early 1980s, S. Z. Qasim and R. Sen Gupta described the Mandovi-Zuari system as a tide-dominated estuary and recorded something striking: in the dry season, before the monsoon, salt-water intrusion is felt as far as about 65 kilometres upstream in both rivers. In a state sixty kilometres wide, that means the sea reaches, through meanders and channels, almost to the foot of the hills.

Then the rain arrives. Goa receives in the order of 3,000 millimetres between June and September, around 90 per cent of its annual total. With that flood of fresh water the rivers stratify and the salt wedge retreats to about 10 kilometres from the mouth in the Mandovi and 12 in the Zuari. The same river is almost sea in May and almost only river in August.

This breathing of the salt, advancing for eight months and retreating for four, explains how people farm, how they fish and even how they cross from one bank to the other. Recent studies of the estuary have also observed that between 2002 and 2022 the mangroves have been migrating inland along the Mandovi, the Zuari and the Cumbarjua canal: the brackish edge is not standing still.

03 Fields that open to the sea

On the low banks of the estuaries, Goans have for centuries been winning land from the tide with a system known here as khazan. It covers some 18,000 hectares, close to 5 per cent of the territory, and works with three parts: an outer dyke of stone and mud, often shielded by mangroves; inner dykes of mud, straw and poles; and a sluice gate of wood or concrete, the manos, which controls how much river water comes in and goes out with each tide.

At the end of the field, at the lowest point, a depression called the poim collects excess water and protects the paddies at high tide. Fish come in there with the brackish water and are caught there: the right to fish by the sluice gates has traditionally been auctioned among villagers, and during the monsoon access is restricted to protect the poim. It is a rice field that is also a fish trap and a defence against the sea.

In the rainy season, salt-tolerant rice varieties such as korgut are sown; in the dry season, when the river turns saltier, the fields that stay fresh yield vegetables, pulses and onions. For centuries management was collective, in the hands of village associations, and today it rests with tenants' associations. The system is fragile: a broken dyke lets the salt in, and an estimated 4,000 hectares of khazan have been lost in three decades. When you see a flooded paddy next to a mangrove, you are looking at a daily negotiation with the tide.

04 Ferries where others would build a bridge

A territory split by so many arms of water solves the crossing from bank to bank with boats. The state's River Navigation Department runs ferries on 19 routes, with a fleet of 38 vessels, linking islands and banks that have no bridge. For anyone on foot or on a motorbike the trip costs little or nothing; the ferry is an ordinary part of the day, like a bus.

The ferry sets a different pace. You wait at the jetty, cross in a few minutes with the water at eye level and arrive on islands such as Divar or Chorão, where the villages keep a scale that bridges would have changed. On the western tip of Chorão, 178 hectares of mangrove have formed the Salim Ali Bird Sanctuary since 1988, with herons, kingfishers and mudskippers among the roots. What elsewhere would be a commute here becomes a way of understanding that water is not an obstacle but the fabric of the land.

05 Where the water begins

The water the tide pushes upstream begins at the state's other edge. The Western Ghats, known here as the Sahyadri, cover around a fifth of Goa: a band of humid forest to the east, with summits around or above a thousand metres, much of it protected in sanctuaries such as Netravali, Bhagwan Mahavir, Mhadei and Cotigao. Netravali, for instance, is where one of the Zuari's tributaries rises.

On the upper Mandovi, Dudhsagar Falls drops about 310 metres in four tiers, and its flow depends entirely on the monsoon. Between the hills and the coast stretch laterite plateaus, the reddish rock from which many of the state's houses and walls have been built. For most of the year they look dry and brown; three months after the rains begin, around September, they are covered in ephemeral flowers that complete their life cycle within the rainy season. It is the same logic as the rivers: the land changes its face according to how much water runs through it.

06 A tree planted to hold the ground

On those laterite slopes grows a tree that now seems to have always been Goan and was not. The cashew arrived with the Portuguese in the sixteenth century, and its first job was practical: to hold the soil and slow erosion on the slopes. It adapted so well that today it is part of the hill landscape and of the economy of many villages.

Feni is distilled from the pulp of the cashew apple, not from the nut. The traditional process takes place in a bhatti: the fermented juice boils in a pot, once earthenware and now often copper, and the vapour condenses in a clay vessel sitting in water. In 2009 cashew feni received geographical indication status, the first granted in India to a distilled spirit. It is Goa's story in miniature: something brought by sea to hold the land in place that ended up becoming its own signature.

07 Two coasts in one

The coast, finally, is not one coast. The north, between the Chapora and the Mandovi, holds the most built-up and lively strip: beaches such as Calangute, Baga and Anjuna, with villages that have grown around the winter season. The south, above all the Canacona area, keeps longer and less crowded beaches, closed off by headlands and river mouths, with casuarinas and coconut palms behind.

What is interesting is that both coasts share a visitor who arrives in the same season as travellers: the olive ridley turtle, which nests in winter. The forest department protects four nesting beaches, two in the north and two in the south: Morjim and Mandrem, Agonda and Galgibaga. Official figures show that nests on the Morjim-Mandrem stretch rose from 8 in 2014-15 to 276 in 2024-25, and that Agonda recorded 181 in 2024. Even on the busiest beach, Goa's edge is still a place where something arrives from the water and room has to be made for it.

08 What a few days here feel like

The first adjustment is one of direction. You arrive thinking about the sea and end up looking at the rivers: a jetty early in the morning, the ferry crossing with motorbikes and bicycles, a heron standing still on the mud left by the low tide. The second is one of calendar. The Goa of the dry season, with brackish rivers and khazan fields lying fallow, looks nothing like the Goa of the monsoon, when the paddies are green, the plateaus bloom and the waterfalls swell.

The third is subtler. After a few days you start noticing the tide without looking for it: the water higher or lower against a bridge pillar, the mangroves with their roots exposed, a sluice gate open or closed by the side of the road. Goa teaches that a coast does not end at the beach, but where the sea stops reaching.

What tends to stay in the memory is not a single image but that back-and-forth: the salt that climbs the rivers for months and the rain that returns it to the sea in a few weeks, and between the two, generations of dykes, sluice gates, ferries and trees planted so that the land would not wash away. Goa is not understood from the sand; it is understood from a riverbank, waiting for the ferry while the tide comes in.