By Jean-Jacques Segalen (jjacques) February 29, 2012
After a general view of French Guiana we went for a stroll in the forest, then climbed up some trees. Today we will today relax on rivers--you can either paddle or just enjoy the scenery.
Living by the riverside....
As we, discussed here, the very name "Guyane" means "land of abundant waters" in local Indian tongue and this part of the world gets about 4m (12 feet) per year of rain per square meter, so it is no wonder there are quite a few rivers! Now, an interesting result of measuring by hydrologists has shown that only 45% of rains reach rivers as a large part goes back in the atmosphere through plant perspiration; the physiology of trees implies that the leaves evaporate water in order to create an osmotic pressure allowing sap to reach the top of plants culminating at some 50m (150 feet high). Indeed, the hydrographical network is extremely dense and branched. The center part of Guiana is considered as the water tower and many rivers start from there while large ones such as the Oyapock start in Brazil. All rivers follow the natural declivity and go from South to North, ending in the Atlantic Ocean. Though the largest ones will be called ‘riviéres' (rivers) most rivers in Guiana are called ‘criques' although this name means creek or inlet in France, just to add some confusion! A characteristic of rivers is the color, quite different from the rather clear waters which can be found in Europe and the U.S.; rivers in the Amazonia are colored, ranging from light tea to coffee with milk which bear the generic name of ‘black waters'.
This is a common feature amongst tropical and equatorial rivers due to the high level of humic matters which are produced by the rotting leaves and other organic materials hence resulting in rather acidic waters with low levels of mineral elements. The importance of tannins is another reason for those colored waters. The very abundant organic material from the canopy such as dead leaves, fruits, dead animals, excretions, insects and other wildlife falling in the passing waters allow a food chain beginning with bacteria, followed by invertebrates, fishes and the many animals from snakes to frogs, caimans, tortoises, otters and so forth, humans interfering largely in-between. The rivers and ‘criques' are of course quite variable with the seasons, the level will be at its lowest at the end of the dry season (November-December) and at its highest level in May and June and the flow can vary from a factor one to ten, narrow parts of the rivers can even be submerged with water rising to 6 meters (18 feet) higher during the heavy rains. Nearby understory forest can be flooded for periods up to several. This explains why one can see dead trunks tangling a few meters up in the vegetation on river banks and why so many trunks poke up through the surface in the dry, a common hazard one has to be aware of.
Pirogue station on the Brazilian side
One of the many 'criques' of Guiana
Basically rivers are divided in ‘biefs' and ‘sauts'. ‘Biefs' are slow water parts, the riverbed is quite flat so current is low, depth is between half meter and several meters (one foot to ten or fifteen feet). ‘Sauts' (literally ‘jumps') consist in hard stone floor which resist water erosion and partly obstruct water flow therefore accelerating the water and often looking like successive stairs. In such places the water has a high level of oxygen due to its movements so fishes found in ‘sauts' will either be good swimmers with a cylindrical shaped body or species with a flat body and mouth acting as a sucker. Sauts can vary from small to big; the ‘saut grand canori' on the Approuague river offers a difference in height of 19 m (57 feet). Some can be crossed either going up or down while others are too dangerous, people have to step out of canoes, carry all the luggage and boats across the rapid and get back on the water. This leads us to the importance of rivers as means of travels and communication in Guiana. Roads are scarce and have been built only on coastal areas where the main towns are, trails can be difficult to use in rain season and not always safe. So rivers are widely used and there are probably more boats, canoes, dug-outs and pirogues than cars and bikes! One can very often see a gang of hunters zooming up the Maroni on a speed-boat while Indians dressed in traditional out-fits slowly paddle down to trade freshly caught fish for tools or ammunitions. Larger pirogues even carry concrete bags and corrugated metal sheets to build a school upstream. The busiest rivers are unsurprisingly the ones forming borders with the two surrounding countries, the Oyapock river with Brazil and the Maroni with Surinam. People who live by the river use it to pop from one village to the other, take a short boat ride to go hunting, fishing, visit friends, reach the clearing where they grow food or cross the river to go abroad. As Guiana is a relatively rich place compared to its neighbors it obviously attracts many inhabitants of both countries who hope to get a part of this wealth. This results in a large number of illegal aliens staying more or less time in Guiana and who are the prey of passers and traffickers. Many are involved in illegal gold washing which is nowadays causing serious problems; those folks often have criminal backgrounds and will not hesitate in attacking or ransoming people, they hunt and fish widely, destroy riverbeds, and provoke very serious pollution using mercury. This liquid metal is used to separate gold from dirt and then eliminated by evaporating it through heating; it will of course soon fall down in soil and water, be fixed by fishes and end in fish-eating people giving rise to various cancers and malformed babies.
Aymara fish (Hoplias aimara)
Quite waters and pristine forest...
We cannot navigate on the Oyapock river, not to mention the bridge. The bridge is quite stunning when viewed from a small pirogue. You're admiring pristine jungle on both sides of the river when all of a sudden this huge thing appears spanning across the river. It is 378m (1134 feet) long and has pylons 83m (249 feet) high. The idea of a bridge between Brazil and Guiana was decided in 1997 and the final junction made on May 28, 2011, making it technically usable. But while on the French side there is a large, well-maintained road linking the bridge to Cayenne, on the Brazilian side, the 600km journey to the city of Macapa is mainly a track unfit for most of the year. Even if the road were completed on the Brazilian side, lorries could not cross because the European regulations that apply in Guiana would not allow Brazilian trucks to enter. Official pirogue drivers who ensure the crossing between the two countries will probably have work for some more years!
The bridge on the Oyapock river
People fishing with a net
Besides communication and fishing, the rivers also provide drinking water. and 98% of tap water comes from river (after careful treatment of course!). Three power plants built so far produce 18% of the electricity to the area. It is also an access to the Ocean where small boats go daily to catch shrimps and sea fishes. The rather low elevation of the land allows for tidal effects to be felt as far as 70km inland with both a raising water level and an inversion of water flow.
We are back at the pier now, watch your steps while getting off the pirogue, I hope you enjoyed the day and will share another visit with us soon!
About Jean-Jacques Segalen
I am a Parisian born professional horticulturist specialized in tropical seeds producing, living on Reunion island (just between Mauritius and Madagascar) since 20 years . I spend a lot of time gathering seeds in the wild, the ones I do not grow that is. Also a dedicated Tai-Chi practitioner and fully certified arborist-tree surgeon
Just released my first book on tropical plants and fruits, check it at http://www.barbadine.com/pages/livrejjGB.html