Sentence:  The surface of the Balaton and the surrounding marshes is not less than 24 German square miles, or 384 English square miles; its principal <WSD>feeder</WSD> is the Szala, but all the water it receives appears inconsiderable relatively to its superficial extent, and the quantity lost in evaporation. 
Meaning of the word marked with <WSD> tags:  A tributary stream, especially of a canal.