Waterbud: A spreadsheet-based model of the water budget and water management systems of the Upper San Pedro River Basin, Arizona

Abstract

Spreadsheet programming is used to model the water budget and water management systems of the Upper San Pedro River Basin, Arizona, to examine how hydrologic, demographic, climatic, and economic conditions affect this budget; and how water management policies may affect the budget over the next twenty years. The model represents relationships among urban and rural population and median incomes; urban and rural domestic water consumption; agricultural and industrial consumption; domestic, agricultural, and industrial return flows; phreatophyte and other evapotranspiration losses; natural surface and ground-water recharges and discharges; head-dependent flow between a floodplain aquifer and the river; head-dependent flow between a regional aquifer and the floodplain aquifer; and changes in aquifer storage. Applications indicate that stringent conservation measures and reductions in irrigation are necessary to significantly reduce ongoing losses to storage in both aquifers, which also threaten river discharges and the viability of riparian habitat in the basin.