Geohydrology, water quality, and estimation of ground-water recharge in San Francisco, California, 1987-92

Abstract

Introduction 1 Purpose and scope 2 Description of study area 2 Previous studies 4 Acknowledgments 4 Geohydrology 4 Geology 4 Geometry of groundwater basins 5 Hydrologic characteristics 6 Water levels 6 General trends 6 Seasonal variation 7 Comparison of shallow and deep groundwater levels Aquifer properties 9 Water quality 11 Sample collection and analysis 11 Factors affecting water quality 11 Variation of water-quality characteristics 12 General conditions 12 Comparison of shallow and deep ground water 14 Characterization of nitrate sources 15 Fertilizers 15 Sewage 16 Distribution of nitrate and tritium near Lake Merced 18 Seawater contamination 18 Estimation of groundwater recharge 21 Climate 22 Temperature 22 Rainfall 23 Land and water use 24 Land use 24 Water use 25 Sources of recharge 26 Infiltration of rainfall 26 Infiltration of irrigation water 29 Leakage from water and sewer pipes 29 Recharge interception 30 Rainfall runoff 30 Evapotranspiration 30 Calibration and sensitivity of hydrologic routing model 32 Sewer flow 33 Monthly calibration 35 Simulation of storms 36 Sensitivity analysis and limitations of the model 37 Estimated groundwater recharge 39 Summary and conclusions 40 References cited 41 Appendix 1. Description of variables used in hydrologic routing model 65 Appendix 2. Equations used in hydrologic routing model 67 Contents