Tirziņa - the left tributary of the Gauja in Gulbene and Alūksne districts. Length 18 km, swimming pool 125 km2. Annual runoff 0.029 km3, drop 15 m (0.8 m / km). Tirziņa is formed by the confluence of Svārbe (7 km) and Zellenė (5 km). The river basin is located on the Trapene Plain. The flow flows in the D - Z direction, its bed is regulated along its entire length. The basin is mostly forests, wider fields only at the mouth of the Ilgupīte.

Largest tributaries: Dzelzupite (9 km), Ilgupite (7 km). The road from Lizuma to Vidzeme highway crosses the river near the estuary.

The list of information source can be found here .