U.S. Department of the Interior U.S. Geological Survey SIMULATION OF STREAMFLOW AND WATER QUALITY IN THE CHRISTINA RIVER SUBBASIN AND OVERVIEW OF SIMULATIONS IN OTHER SUBBASINS OF THE CHRISTINA RIVER BASIN, PENNSYLVANIA, MARYLAND, AND DELAWARE, 1994-98 by Lisa A. Senior and Edward H. Koerkle Water-Resources Investigations Report 03-4193 In cooperation with the DELAWARE RIVER BASIN COMMISSION, DELAWARE DEPARTMENT OF NATURAL RESOURCES AND ENVIRONMENTAL CONTROL, and the PENNSYLVANIA DEPARTMENT OF ENVIRONMENTAL PROTECTION New Cumberland, Pennsylvania 2003 U.S. DEPARTMENT OF THE INTERIOR GALE A. NORTON, Secretary U.S. GEOLOGICAL SURVEY Charles G. Groat, Director Any use of trade, product, or firm names in this report is for identification purposes only and does not imply endorsement by the U.S. Geological Survey. For additional information Copies of this report may be write to: purchased from: District Chief U.S. Geological Survey U.S. Geological Survey Branch of Information Services 215 Limekiln Road Box 25286, Federal Center New Cumberland, Pennsylvania 17070 Denver, Colorado 80225-0286 Email: [email protected] Telephone 1-888-ASK-USGS Internet Address: http://pa.water.usgs.gov ii CONTENTS Page Abstract . 1 Introduction . 2 Purpose and scope . 5 Previous studies . 5 Acknowledgments . 5 Description of study area . 5 Physical setting . 5 Climate . 6 Geology . 6 Soils. 6 Hydrology . 6 Land use. 8 Water use . 8 Description of model . 9 Data for model input and calibration . 11 Model-input data . 11 Meteorologic data . 11 Water-use data . 15 Spatial data. 15 Model-calibration data. 18 Hydrologic data. 18 Water-quality data. 18 Simulation of streamflow . 31 Assumptions . 33 Calibration . 33 Sensitivity analysis . 42 Model limitations . 44 Simulation of water quality . 45 Calibration . 45 Water temperature . 46 Sediment. 47 Dissolved oxygen and biochemical oxygen demand. 56 Nitrogen . 61 Phosphorus . 75 Sensitivity analysis . 79 Model limitations . 83 Overview of Christina River Basin models . 84 Calibration . 84 Simulated sediment and nutrient yields . 85 Model applications . 89 Limitations and uncertainty . 94 Summary and conclusions . 98 References cited . 101 Appendixes . 105 Contents iii ILLUSTRATIONS Page Figure 1-3. Maps showing: 1. Location of the Christina River Basin and its four major subbasins and nonpoint-source water-quality monitoring sites, Pennsylvania, Delaware, and Maryland. 3 2. Mapped soil associations in the Christina River subbasin, Pennsylvania, Maryland, and Delaware. 7 3. National Oceanic and Atmospheric Administration meteorologic stations and calculated Thiessen polygons in the vicinity of the Christina River subbasin, Pennsylvania, Maryland, and Delaware . 12 4-5. Graphs showing: 4. Monthly precipitation measured at the Wilmington Airport National Oceanic and Atmospheric Administration and Porter Reservoir meteorologic stations near the Christina River subbasin in Delaware. 13 5. Monthly estimates of potential evapotranspiration for Wilmington Airport, Delaware . ..