2. Assessment of Water Resources in Poland

The paper analyzes the size of water resources in Poland, which are among the lowest in Europe. Water resources are very variable, both temporally and spatially, which results from the temporally and spatially variable distribution of atmospheric precipitation, whose course is random. The average annual total outflow from Poland in the years 1951–2015 was about 61 km³, ranging from 37.5 km³ in 1954 to 89.9 km³ in 1981. The average unit outflow from the years 1951–2015 was 5.4 dm³/s·km² in the Vistula basin, and 4.7 dm³/s·km² in the Oder basin. One way to reduce excesses and deficits of water may be to undertake small-retention reservoir projects within agricultural catchments and in urban areas. Such works have been implemented in Poland as part of a small-retention programme by Lasy Państwowe (State Forest Holding) in mountainous and lowland areas. A separate problem related to the use of water resources is the level of water intake and consumption by various sectors of the national economy. The reduction of water consumption can be achieved in various ways. One of the simplest, but also the most severe for all users, is to increase the price of water. However, the most practical solution is to invest in the most modern water recovery and reuse technology in industrial plants, agriculture, and newly built residential buildings. Nowadays, technical solutions using rainwater in single-family houses are becoming increasingly popular in Poland. This water is most often used for watering gardens. However, there is little interest in the construction of purification and reuse systems for previously used water (“grey water”), mainly due to high installation costs. Grey water recycling or rainwater management not only significantly reduces operating costs, but also has tangible environmental benefits.