The territory embraces the basin of the River Salaca with its tributaries including Lake Burtnieku, as well marine area of the Gulf of Riga up to depth of 10 m stretching 60 km along Vidzeme coast. The boundaries of the Reserve lie within Limbaži, Valmiera and Valka districts with the total area of 4500 sq. km and 167.5 sq. km marine area, which amounts to almost 6% of Latvia's total area.