Fig. 7. This graph of cumulative water availability beginning 1 May illustrates the likelihood of differing volumes of water becoming available during summer months under wet-, average-, and dry-year conditions for the Rivanna River in Virginia, USA. Estimates of water availability have been used to develop forecasts for meeting growing urban water demands whereas releasing environmental flows from storage reservoirs in the Rivanna Water and Sewer Authority's water supply system in Charlottesville, Virginia.