The Brzanka Mountain Range in the Ciężkowickie Foothills has a dense river network. Unfortunately the contemporary maps contain only the names of some main rivers of the Brzanka Mountain Range. Local communities use the same set of names of rivers as cartographers, while studies in the historical geography of the Brzanka Mountain Range reveal a wealth of local hydronyms that have seemingly been forgotten. The article attempts both to reconstruct a set of hydronyms of the Brzanka Mountain Range and to explain their etymology. It shows that hydronyms change over time and that studies on local hydronyms can help restore the collection of the names of rivers in the Brzanka Mountain Range and provide interesting information related to the past of this region. Moreover, they reveal contemporary unknown facts related to the natural environment and settlement processes in the Middle Ages. A visual summary of the article is a map showing the Brzanka Mountain Range with its river network and associated hydronyms.