The Gélise is a river of south-western France that flows through the Gers, Landes and Lot-et-Garonne departments, in the Occitanie and Nouvelle-Aquitaine regions. It is a left tributary of the Baïse river.
Geography
The Gélise has a length of , and a drainage basin with an area of approximately .
Its average yearly discharge (volume of water which passes through a section of the river per unit of time) is 4.72 cubic metres per second at Mézin.
Course
The Gélise starts in the place known as Cahuzères in the commune of Lupiac, Gers department, at an elevation of about . It flows to the northwest and then, after Castelnau-d'Auzan, turns to the northeast.
It joins the Baïse on its left bank at Lavardac, at about of altitude.
The Gélise flows through 21 communes. It passes through the following regions, departments and communes:
Occitanie region
Gers: Dému, Eauze, Labarrère, Ramouzens, Castillon-Debats, Castelnau-d'Auzan, Lupiac, Noulens Nouvelle-Aquitaine region Landes: Parleboscq, Escalans Lot-et-Garonne: Sos, Poudenas, Mézin, Barbaste, Sainte-Maure-de-Peyriac, Nérac, Lavardac, Andiran, Saint-Pé-Saint-Simon, Réaup-Lisse
Main tributaries
The main tributaries of the Gélise river are: Left tributaries Rimbez - 16.4 km; Gueyze - 17.7 km; Right tributaries Izaute - 37.5 km; Auzoue - 74.1 km; Osse - 120.2 km;