ABSTRACT
B. Garcia-Fresca The John A. and Katherine G. Jackson School of Geosciences – The University of Texas at Austin P.O. Box B, University Station – Austin, TX 78713-8902
ABSTRACT: Cities and urban populations are growing at a high pace and as consequence, so are the local scale anthropic impacts on the hydrologic cycle. The shallow urban underground is an intricate network of tunnels, conduits, utilities, and other buried structures comparable to a natural karstic system, except that the “urban karst” is generated much more rapidly. Urbanisation also introduces new sources of water that increase groundwater recharge. These sources include irrigation of parks and lawns, leakage from water mains and sewers, and infiltration structures. Geologic, land use, and utilities information for the city of Austin, Texas, was compiled and processed by means of a GIS in order to make a water balance for the city. The areal extent of Austin, has increased five-fold since the 1960s. Direct recharge from rainfall has decreased, due to impervious pavements, from 53 mm/a under pre-urban conditions to 31 mm/a in the year 2000. However, 85 mm/a of treated tap water never reaches wastewater treatment plants and potentially contributes to recharge. A conservative estimate yields 63 mm/a of recharge from urban sources and a total recharge rate that nearly doubles that of pre-urban conditions.
