An assessment of the Colombian water resources is presented that uses the water withdrawal and water availability ratio as an indicator of the anthropogenic pressure on limited water resources. In this work water availability is defined as the modal value of the annual runoff measured by the Colombian hydrological network. The environmental water requirements are considered as additional water demand and a statistical approach is proposed to define their magnitude. The mentioned approach leads to a variation of the UNESCO water pressure index that is known as the Colombian water scarcity index and allowed to determine places with heavy anthropogenic pressure over the local water resources in Colombia. Finally, the scale issues are touched upon and a regional case and a climate change outlook for the scarcity index are also presented.