The average rainfall in a small watershed (total area: 1.271 km2) is 50 inches per year over the recent ten years; the average annual net surface stream flow (inflow minus outflow) is 432 mm (total volume divided by the watershed area); the average annual net groundwater crossing the watershed boundary (inflow minus outflow) is 0.3 ft. The average change in storage each year is (+) 16551 acre-in. On an annual average basis, what fraction of rainfall is evapotranspiration? Start your solution with the general form of water budget.