Hjälmaren (Swedish pronunciation: [ˈjɛ̂lːmarɛn] or [ˈjɛ̂lːmaɳ]), also spelled Jälmaren, is Sweden's fourth largest lake. It is situated in the Central Swedish lowland and drains through Eskilstunaån into the adjacent Lake Mälaren, which in turn drains into the Baltic Sea, west of Stockholm. It is connected by waterway with Stockholm by the 13 kilometres long Hjälmare kanal.
It is bounded by the provinces of Södermanland, Närke, and Västmanland.
Svartån is a river in Örebro County, Sweden, approximately 100 kilometers long with a drainage basin area of 1410 km. The river has its source at lake Ölen in Degerfors Municipality and flows south through the lakes Storbjörken and Lillbjörken and the mill town of Svartå. At lake Toften it joins with several streams from the south, flowing through Hasselfors to lake Teen, joining with Stavån. From Teen the river flows northeast over the Närke plain to the city of Örebro, passing Örebro Canal on its way east. East of Örebro the river passes through Skebäck and Oset, joining with Lillån before ending in Lake Hjälmaren.
Svartån is the main tributary of Lake Hjälmaren and Eskilstunaån, which in turn is the largest tributary of Lake Mälaren and Norrström in Stockholm, the main outlet into the Baltic Sea.
Eskilstuna (Swedish pronunciation: [ˈɛ̂sːkɪlsˌtʉːna] ) is a city and the seat of Eskilstuna Municipality, Södermanland County, Sweden. The city of Eskilstuna had 69,948 inhabitants in 2020, with a total population of 107,806 inhabitants in Eskilstuna municipality 2023. Eskilstuna has a large Sweden Finn population. The town is located on the River Eskilstunaån, which connects Lake Hjälmaren and Lake Mälaren.