[citation needed] Another theory is that it is derived from Proto-Balto-Slavic *teišus meaning still, quiet, silent to describe the river.

Since plains can cause a river to flow very slowly, the Tisza used to follow a path with many curves and turns, which led to many large floods in the area.

[8] In the 1970s, the building of the Tisza Dam at Kisköre started with the purpose of helping to control floods as well as storing water for drought seasons.

The first, in January 2000, occurred when there was a release of sludge containing cyanide from a Romanian mine and killed 2000 tons of fish.

The second, from a mine pond at Baia Borsa, northern Romania, resulted in the release of 20,000 m3 (710,000 cu ft) of sludge containing zinc, lead and copper occurred in early March 2000.

A week later, the third spill occurred at the same mining site at Baia Borsa, staining the river black, possibly including heavy metals.

Usage of river water for any purpose was temporarily banned and the Hungarian government pressed the Romanians and the European Union to close all installations that could lead to further pollution.

The Tisza water system is shared by five countries: Ukraine (8%), Slovakia (10%), Hungary (29%), Romania (46%) and Serbia (7%).

The western - southwestern reach of the watershed is comparatively low in some places – on its Hungarian and Serbian parts it is almost flat.

The area is divided roughly along the centreline by the Carpathians Mountains, east of which lies the 400–600 m high plateau of the Transylvanian Basin, and the plains to the west.