Domestic and industrial diversions for the base year 1995 are taken from international databases published by the World Resources Institute. The growth in domestic and industrial diversions is computed as follows: First the relationships of 1995 per capita GDP and 1995 per capita domestic and industrial diversions are established. The per capita GDP projections of each country are calculated using the GDP growth rates of the 18 regions for the World Water Vision scenarios (following results from the Polestar model, chapter 11 of this book). The projections of per capita GDP and the per capita diversions and GDP relationships of 1995 are used in estimating the 2025 domestic and industrial diversions.

A distinction is made between diversions and evaporative use: not all water that is diverted for domestic and industrial purposes is actually consumed but a large portion flows back into the system and is potentially available for reuse. As explained earlier this is accounted for by the "evaporation factor" (EF). The Evaporation Factor for cities and industry is often between 10 to 20 percent. In some cases this can be considerably higher. Where industries are required to keep water clean the factor can be quite high as industries recycle the water internally, and require less deliveries of water. If much domestic water is used by vegetation such as lawns or trees, the factor can be higher.

We assumed the evaporation factor for the domestic sector (EF_dom) at 20 percent (i.e., 20% of the water diverted is evaporated while 80% flows back to the system). For industrial use (EF_ind) we assumed 10 percent. These factors remain constant in the year 2025^ind1.
Resource: World Water Scenarios: Analysis chapter 15: world water Supply and Demand: 1995 to 2025