It is worded strangely, and confluent is the culprit. As the flu part suggests, confluent refers to flows and movement. While it can be used to describe the place where ships or streams of thought converge, its most common use is in respect of rivers, referring to the point where a river and one of its tributaries meet.

Bassin here means 'catchment' or 'catchment area', i.e. the area which drains surface runoff to a single point. It is thus an area surrounded by high points from which water flows in two directions, on each side of the high point (a ridge). As such, in the UK this continuous line of high points is called the 'watershed' (it sheds water on both sides). In the US, however, 'watershed' means 'catchment' (the area into which water is shed from one side of that continous ridge) and 'divide' is used to refer to the [UK] watershed.

To play safe, you can do the usual thing of talking down to Americans and call the watershed a divide since the word is understood that way in UK English too.

You can say 'head of the catchment/watershed' for tête de bassin, but this refers to but one side of the watershed/divide, while your confluent, used bizarrely, seems to refer to the place where several catchments meet.

"Burgundy is drained by rivers or all sizes and lies across the divides of three catchments/watersheds."


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Note added at 45 mins (2023-03-13 11:30:06 GMT)
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They should probably have said ligne(s] de partage des eaux (=divide, watershed) rather than confluent.

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Note added at 50 mins (2023-03-13 11:34:52 GMT)
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https://www.bourgogne-tourisme.com/sites-naturels/point-de-p...

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Note added at 4 hrs (2023-03-13 14:52:00 GMT)
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catchment area In British usage the term refers to the total area from which a single river collects surface runoff. In the USA the term watershed is used this context, and the term catchment area is reserved to describe both the intake area and all areas which contribute surface water to the intake area of an aquifer. In the UK the term catchment area has been used loosely by river authorities that are responsible for the water supply, drainage and flood control, since the statutory boundaries of their catchment boards sometimes extend beyond a single river basin.

divide The area of high ground which separates two different drainage systems. In the UK, but not in the USA, it is synonymous with watershed, interfluve.

drainage basin That part of the land surface which is drained by a unitary river system. Its perimeter is marked by a drainage divide or watershed (English [read 'British'] usage only ...

interfluve The area of higher ground separating two rivers which flow in the same drainage system.

watershed (1) In Britain watershed is used synonymously with divide, i.e. to mean a water-parting from which headstreams flow to separate river systems. (2) In the USA, the term refers to the entire catchment area of a single drainage basin.
[all the above from the Penguin Dict. of Physical Geography. I also grew up reading the books of my father, a civil engineer who worked for the Severn River Board, the NZ Ministry of Works, the South Canterbury Catchment Board (responsible for several catchments), and the Christchurch Drainage Board, and for many years I myself translated texts concerning hydro and irrigation dams for a French dam designer - which involved catchment and river flow analysis, etc].

It is because Burgundy lies across the watersheds/divides of three major rivers (or in one case, of one of its tributaries) that in 'La Billebaude', Burgundy writer Henri Vincenot refers repeatedly to his home region, specifically Le Morvan, as le toit du monde.

Another way to look at it is to consider that tête de bassin refers to the 'headwater streams' (see https://en.wikipedia.org/wiki/River_source) of a catchment. In French, tête de bassin can refer to streams with a particular Strahler number (see https://en.wikipedia.org/wiki/Strahler_number): the SDAGE Loire Bretagne, for example, defines têtes de bassins versants as les bassins versants des cours d'eau dont le rang de Strahler est inférieur ou égal à 2 et dont la pente est supérieure à 1 %.. https://www.sevre-niortaise.fr/tetes-de-bassin-versant-sage-...
But this is a notion récente au regard des politiques d’amélioration de la qualité de l’eau et des milieux https://layonaubancelouets.fr/toutes-nos-actions/tetes-de-ba... i.e. the term is more associated with environmental concerns than physical geography.
Moreover, since the headwater streams are those closest to the divides/watersheds, I see little point in going down the 'watery' path since the writer has already screwed up with confluent. So I'd go for the firm, dry (mostly) ground option.
In addition, the real headwater streams of the Loire and Saône/Rhône catchments, i.e. those near the source of the river, miles away, as can be seen in the map below. Sure, there are headwater streams all around the perimeter of a catchment, i.e. on the tributaries flowing in the main river, but 'headwaters' tends to make one think of the head of the main river, not the heads of its tributaries.
headwaters The upper parts of a river drainage system, the source or sources of a river at the head of its catchment area. [Penguin as above].

As inferred above, none of this makes any sense of confluent which logically would refer to the downstream end of a river system, as has been suggested here. However the downstream ends of the 3 systems referred to are a long way from Burgundy, being the mouths of the Seine in Normandy, the Saône/Rhône in Provence, and the Loire in Loire-Atlantique.



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Note added at 4 hrs (2023-03-13 14:53:09 GMT)
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Note added at 5 hrs (2023-03-13 15:45:07 GMT)
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I've just spotted - oops - that you say it's about environmental matters, so I take back my negative opinion of 'headwater streams' which, if we are not talking geography, need not suggest 'headwaters of the main river giving its name to the catchment', so my Answer heading should be:
[gen.] head of catchment; watershed [UK], divide [UK, US]; [env.] headwater streams.

"Headwater streams are the smallest parts of river and stream networks, but make up the majority of river miles in the United States. They are the part of rivers furthest from the river's endpoint or confluence with another stream. Many headwater streams have been lost or altered due to human activities such as urbanization and agriculture, and this can impact species and water quality downstream.
Watershed [catchment] managers have had little guidance to help protect headwaters or assess their condition. Because there are so many headwater streams, monitoring all of them for health and permanence is impractical. Therefore, other methods are needed." https://www.epa.gov/water-research/headwater-streams-studies

Still, I'm having trouble working that around La Bourgogne ... est au confluent [sic] de trois têtes de bassin without including the notion of divide/watershed or catchment/watershed:
Burgundy lies across many of the headwater streams of three [US] watersheds / [UK] catchments.