That is, water demand measures the total amount of water withdrawn from the environment (gross demand) rather than the amount of water withdrawn after accounting for the volumes returned (net demand). Gross measures of water use include consumptive and non-consumptive uses of water. By contrast, net water demand only measures consumptive uses of water, so is a measure of water consumption rather than water demand. Because only a part of what is withdrawn is effectively consumed (Table B.5), most of the flow is returned - usually at a lower quality - to the water systems, where it can be reused. Water withdrawals for energy generation - hydropower and thermo-cooling - are on the rise, but energy is one of the economic sectors that consume the least water and it returns most of the water withdrawn back to the water system. Withdrawal per capita ranges from 20 m3 a year in Uganda to more than 5 000 m3 in Turkmenistan, with a world average of 600 m3 (WWAP, 2009).