Since 1993, through Law 99, the “Ministerio de Ambiente, Vivienda y Desarrollo Territorial” has published “decretos” with the end of implementing tools for economic water resources “sustainability”. This work performs an analysis of “aplicability” of “Decreto 155 de 2004” which declares Article 43 de la Law 99 de 1993, about Water Using Costs (Tasa por Utilizacion del Agua, TUA). An analysis of actual legislation related with Water Resources is described. A technical analysis about each one of the parameters used in TUA estimation is performed, some technical “inconsistencies” for TUA estimation have been found, and some suggestions for this failures are proposed. This work concludes that there are many conceptual inconsistencies in TUA estimation methodology and economic water resoures procedures in