Lotic surface waters
Freshwater ecosystems play an important role, especially in the landscape, with no water supply to the populations and as a source of water for the production of energy and the permanence of the canals of the water mills.
The hydrology of the Azores is characterized by lagoons, streams, transitional waters, coastal waters and groundwater. The hydrological specificities result from the geographic, climatic and geological specificities of the archipelago. A biometric the means is a high end to the water of water having a large massage in the water of permanent was to the type in temporary.
In the Azores, loamy surface waters of permanent regime (rivers) only exist in the islands of Santa Maria, São Miguel, São Jorge, Faial and Flores. The streams are fed by ponds or by higher flow springs, located in the interior of the islands and, in the case of São Jorge, by the springs of the North coast.
A total of 736 river basins have been identified. Most of the streams have a drainage area of less than 10 km2, with a non-permanent flow rate and a torrential regime. For example, the main permanent water courses on the island of São Miguel integrate the river basins of Ribeira Grande, Ribeira do Guilherme, Ribeira do Faial da Terra, Ribeira do Purgar and Ribeira Quente.
The most important levadas (irrigation water channels or aqueducts that generally radiate from the highest and central points of the island) are located in Faial and São Miguel (e.g., Lagoa do Fogo). The aqueducts or “stone walls” of the Coal and Nine Windows (Sete Cidades) are testimony to the architecture associated with the water supply. On the other hand, water reservoirs are monumental on Graciosa Island.
Waterfalls, waterfalls due to the natural layout of the terrain or human action are common in the islands (eg, Santa Maria, São Miguel and Flores).
Lentic surface waters
The 88 lagoons constitute water masses very important for the hydrological dynamics of the islands, since they function as a reserve and as a source of water for feeding the streams. They are distributed by the islands, namely of São Miguel, Terceira, Pico, Flores and Corvo. The lacustrine surface of the Azores occupies 0.4% of the regional territory (about 9.5 Km2), about 90% of this value in São Miguel.
The lagoons of the Azores are water bodies of relatively small dimensions, varying between 0.5 and 10 km2 of area. The largest lagoons are all located on the island of São Miguel: Lagoa das Sete Cidades (one of the seven wonders of Portugal), Furnas and Fogo. The ponds are even smaller than one hectare. Ponds are permanent or temporary stands of standing water, smaller in size than a pond and larger than a puddle (a small mass of ephemeral water, which it is usually possible to cross in one step).
Transitional waters are water bodies in the transitional situation between the terrestrial environment and the marine environment, with intermediate characteristics between inland and coastal waters being influenced by freshwater. They are unique coastal ecosystems, including lagoons and marshes. Examples are the lagoons of the Fajãs dos Cubres and Santo Cristo, on the island of São Jorge. The cases of Juncus marshes in the Lajes do Pico and the Pântano do Paul in Praia da Vitória (Terceira) are excellent resting places for some migratory birds, waders of the Azores.
In the archipelago, artificial water bodies find correspondence in artificial ponds, created by human activity and used in supplying the population (as reinforcement in summer seasons) and agricultural activity. Three artificial lagoons are identified for the agricultural activity (São Miguel island – artificial lagoon of Contendas, Terceira island – artificial lagoon of the Altares / Raminho, Faial island – artificial lagoon of Faial) and one as reinforcement to the public supply (Corvo Island – artificial pond of the Crow).
Livestock drinkers across the pastures of the Azorean islands also play an important role in the reproduction of Odonates (dragonflies), especially in the islands and regions where water is scarce (eg, Graciosa). Public sources for water supply have abounded in the population centers of the Azores for a long time.
The Laurissilva forest and the peat bogs play an important role in the water balance of the islands. This forest, due to its hydrological characteristics, is considered a “water-producing” forest.