| Summary: | A review of global water demand projections (WDPs) show substantial overpredictions or under-predictions. The pre-1990 WDPs, with population as the main driver of change, overpredicted current water use by 20 to 130%. The post-1990 WDPs, with sophisticated modeling frameworks, show substantial underestimation under the ‘business-as-usual’ scenarios and are more downward biased under sustainable scenarios. Overall, the value of long-term country-level projections in global WDPs is inadequate for local water resource planning. To increase the accuracy and value of global WDPs, future WDPs should take into account the spatial variation and influence of rapidly changing key exogenous and endogenous drivers of water demand in different sectors across and within countries, and provide a sensitivity analysis of projections.
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