yet they are typical of the incremental cost of irrigation water in regions where farmers must pump groundwater from substantial depths purchase water in market transactions or obtain surface water from the state water project demand for water has increased substantially over time with increasing development of major cities including phoenix and tucson the federally funded central arizona project was constructed in part to relieve pressure on aquifers serving those cities by delivering surface water from the colorado river in conjunction with development of the central arizona project the state passed a groundwater management act in s that requires urban areas to achieve safeyield management of aquifers by bolin et al