On Earth water is an irreplaceable asset, and an estimate of its resource capacity is necessary. The improper selection of indicators of water resources can lead to the underestimation or overestimation of the actual resources present. Incorrect assessments of water resources contribute to the improper completion of necessary water management tasks, thereby failing to satisfy the needs of different water users such as industry, agriculture and forestry, inland water navigation, tourism and recreation and the general population for the purposes of municipal water use. This article discusses the advantages of utilizing Earth Observation technology for estimating water resources in Poland. Despite the large amount of water on Earth, decades of wrongly pursued water management have lead to a critical point in maintaining this valuable resource. According to actual estimations, there are enough fresh water resources in the world; the problem is the uneven distribution and pollution of these resources, especially in the case of surface water. Currently, Poland, in comparison with other European countries, is classified as a country with very little water resources. It is important, however, that a thorough evaluation using the latest measurement technologies is conducted, particularly for groundwater resources in deep layers of the lithosphere. The proper assessment of water resources requires knowledge of the hydrogeological conditions within each of the catchments of the analyzed area. International data sets are mostly incomplete and heterogeneous, which makes the comparison of data of several years difficult and often leads to mistakes. While analyzing Polish water resources several factors should be taken into account including: the amount of rainfall, the amount of water in rivers, lakes and groundwater, and the above-mentioned factors affecting the measurement of the amount of disposable water resources. This article is an introduction to the broader analysis of water resources in Poland and an explanation of the issue from a different perspective.