The Kalmius is a river flowing through Donetsk Oblast, Ukraine. Its source is near the Ukrainian city of Yasynuvata, and its mouth is in Mariupol. The Kalmius is one of two rivers flowing through Mariupol. The other is the Kalchyk, which flows into the Kalmius. The Kalmius flows into the Sea of Azov near the Azovstal Iron and Steel Works in Mariupol. Major citieā¦The Kalmius is a river flowing through Donetsk Oblast, Ukraine. Its source is near the Ukrainian city of Yasynuvata, and its mouth is in Mariupol. The Kalmius is one of two rivers flowing through Mariupol. The other is the Kalchyk, which flows into the Kalmius. The Kalmius flows into the Sea of Azov near the Azovstal Iron and Steel Works in Mariupol. Major cities along the Kalmius are Yasynuvata, Donetsk, Kalmiuske, and Mariupol.