The implementation of the EU Sustainable Development Strategy and Water Framework Directive and Nitrates Directive in particular by Poland requires taking actions aiming at protection of water quality against agricultural pollution, especially with nitrates. Therefore, in 2003, in the province of Western Pomerania, the area vulnerable to nitrates of agricultural origin the measures preventing their leaching into waters were undertaken. That area was located in the Płonia river basin. Despite the programme of reducing water pollution caused by nitrates from agricultural sources, in 2008 and 2012 that area was recognised again as a Nitrate Vulnerable Zone (NVZ). The studies focused on the waters of the Gowienica Miedwiańska river, from selected sections, and ground water from the piezometers located in the river basin of 63.65 km², within the Nitrate Vulnerable Zone. The concentration of NO₃^-, NH₄⁺ and PO₄^-3 as well as pH in surface and ground waters were determined. The obtained results indicated insufficient effectiveness of action programmes to reduce nitrates emission.