INTERANNUAL VARIABILITY OF NORTH AMERICAN MONSOON HYDROCLIMATE AND APPLICATION TO WATER MANAGEMENT IN THE PECOS RIVER BASIN by KATRINA AMELIA GRANTZ B.A., Grinnell College, 1997 M.S., University of Colorado, 2003 A thesis submitted to the faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirement for the degree of Doctor of Philosophy Department of Civil, Environmental, and Architectural Engineering 2006 i This thesis entitled: Interannual Variability of the North American Monsoon Hydroclimate and Application to Water Management in the Pecos River Basin written by Katrina A. Grantz has been approved for the Department of Civil, Environmental, and Architectural Engineering __________________________________________ Balaji Rajagopalan __________________________________________ Edith Zagona __________________________________________ Kenneth Strzepek Date ______________ The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline. ii Grantz, Katrina A. (Ph.D., Civil, Environmental, and Architectural Engineering) Interannual Variability of the North American Monsoon Hydroclimate and Application to Water Management in the Pecos River Basin Thesis directed by Professor Balaji Rajagopalan The North American Monsoon (NAM) is the large-scale atmospheric circulation system responsible for up to 55% of the annual precipitation in the southwestern U.S. These summer thunderstorms, however, are highly variable and predicting the variability in the strength, location, and timing of monsoonal precipitation and streamflow is understandably very important for efficient water resources management. This research, comprised of three main components, analyzes the spatial and temporal variability of NAM precipitation and streamflow; and using this information it develops a statistical forecasting framework which is then integrated with a decision support system to evaluate water management strategies on the Pecos River Basin. First, the interannual variability of precipitation and streamflow in the NAM region of southwest U.S. is studied and large-scale and local climate features that drive the variability are diagnosed using robust Spearman rank correlation analysis and Kendall Theil slope estimators. These analyses led to the proposal of the following hypothesis: antecedent Pacific sea surface temperatures (SSTs) modulate the winter/spring hydroclimatology and land conditions of the NAM region, thus playing an important role in setting up the land-ocean temperature gradient (the key driver of the NAM), and, consequently, in modulating monsoonal rainfall and precipitation. This offers increased hopes of long-lead forecasts of summer iii hydrologic conditions in the NAM region. The second component of this study develops a framework for generating ensemble forecasts of spring and summer streamflow at five lead times using the large-scale climate information obtained from the diagnostics. In the third, and final, component of this study, streamflow exceedance probabilities calculated from the ensemble forecasts are used in a decision support system, modeled with RiverWare, to evaluate various water management options for reservoir releases, irrigation diversions and inter-state spill in the Pecos River Basin. The Pecos River receives a significant portion of its annual streamflow in the summertime from monsoon thunderstorms, however operations on the river do not utilize forecasts of this important moisture source. The research framework developed here demonstrates significant improvements to water management though decreased reservoir spills and increased irrigation water delivery. iv ACKNOWLEDGEMENTS This thesis would not have been possible without the support of many people. I would like to thank my advisors, Balaji Rajagopalan, Edith Zagona, and Martyn Clark. Each provided a unique perspective and invaluable guidance to this work. Their wisdom, encouragement, and time investment are very much appreciated. I also thank my committee members Kenneth Strzepek and Subhrendu Gangopadhyay for their insightful comments and suggestions. I would like to acknowledge the NOAA Office of Global Program's GWEX America’s Prediction Project for funding this study (project number NA03OAR4310063). Logistical and technical support provided by the Center for Advanced Decision Support for Water and Environmental Systems (CADSWES) is also thankfully acknowledged. Many people provided technical advice and support throughout this project. I would like to thank Craig Boroughs of BH and H Engineering for assistance with the water management application of this research. Useful discussions with David Gochis of the National Center for Atmospheric Research and Bruce Anderson of Boston University are also greatly appreciated. I would also like to thank my husband, Matt, my son, Talon, and my family and friends for their constant encouragement and emotional support. Finally, I thank my parents for instilling in me this love and appreciation of learning. v CONTENTS CHAPTER 1: INTRODUCTION............................................................................. 1 MOTIVATION.............................................................................................................. 1 NAM BACKGROUND ................................................................................................. 1 OUTLINE OF THE STUDY ............................................................................................. 6 CHAPTER 2: PRECIPITATION ANALYSIS ....................................................... 9 INTRODUCTION .......................................................................................................... 9 DATA ......................................................................................................................... 9 Climate Division Data .......................................................................................... 9 NWS COOP Data................................................................................................ 10 NCEP/NCAR Re-analysis Data .......................................................................... 10 METHODOLOGY ....................................................................................................... 10 RESULTS .................................................................................................................. 14 Monsoon Cycle.................................................................................................... 14 Monsoon Rainfall................................................................................................ 17 Hypothesis........................................................................................................... 19 Antecedent Land Conditions............................................................................... 20 Antecedent Ocean Conditions............................................................................. 25 SUMMARY AND CONCLUSIONS................................................................................. 28 CHAPTER 3: STREAMFLOW ANALYSIS ........................................................ 30 INTRODUCTION ........................................................................................................ 30 vi STUDY AREA ........................................................................................................... 33 DATA ....................................................................................................................... 33 HCDN Streamflow Data ..................................................................................... 33 Climate Division Data ........................................................................................ 34 NCEP/NCAR Re-analysis Data .......................................................................... 34 METHODOLOGY ....................................................................................................... 34 RESULTS .................................................................................................................. 36 Streamflow Classification ................................................................................... 36 Winter / Spring Streamflow Analysis .................................................................. 38 Summer Streamflow Analysis: Volume Trends.................................................. 43 Summer Streamflow Analysis: Timing Trends................................................... 48 SUMMARY AND CONCLUSIONS................................................................................. 53 CHAPTER 4: STREAMFLOW FORECAST....................................................... 55 INTRODUCTION ........................................................................................................ 55 PECOS RIVER BASIN ................................................................................................ 56 Selection Criteria................................................................................................ 56 Physical Description........................................................................................... 57 Operations and Policies...................................................................................... 58 FORECASTING REQUIREMENTS ................................................................................. 61 DATA ......................................................................................................................