The Gola de Marchamalo is one of the five canals, along with El Charco, La Torre, Ventorrillo and Estacio, which connect the waters of the Mar Menor with the Mediterranean. As the Mar Menor lacks important tides, the function of this gorge, as the The rest is the compensation of rainwater that dumped into the pond and agreed level exchange with atmospheric pressure or the wind regime. Is this communication mechanism which as a consequence the intense evaporation of the Mar Menor, gives rise to the supersalination which in turn generates migratory movements of the fish between the two seas, what has given origin to the fishing system for encañizadas designed in times of Arab domination.

In 1762 the construction license of the Gola de Marchamalo was granted, for its fishing exploitation under the name of Encañizada de Calnegre, to the Royal Hospital de la Caridad de Cartagena. This work constitutes the only totally artificial communication between the Mar Menor and the Mediterranean, which causes a certain difficulty in maintenance to keep it free of the sand sediments that tend to block it.

Because of its shallow depth, the Marchamalo channel does not allow transit except for pirogues or shallow draft boats. Despite being an entirely artificial construction channel, it maintains its function of regulating levels between the seas.