REGIONAL FLOW ESTIMATION USING A HYDROLOGIC MODEL By ZORAN MICOVTC B.Sc.(Eng.), The University ofNovi Sad, Yugoslavia, 1994 A THESIS SUBMITED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF CIVIL ENGINEERING We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA July 1998 ©ZoranMicovic, 1998 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia Vancouver, Canada DE-6 (2/88) ABSTRACT The twelve watersheds analyzed in this study are heterogeneous in terms of drainage area, climate, topography, soil type, vegetation, geology and hydrologic regime, which indicates that any attempt at a statistical regionalization of streamflow characteristics for these watersheds would be unreliable unless based on a very large number of watersheds. Therefore, the hydrological behavior of these watersheds was analyzed using the UBC Watershed Model. The watersheds were calibrated until a maximized efficiency was achieved. A sensitivity analysis showed that the model was most sensitive to precipitation parameters and thus, precipitation was the most important factor. Given good precipitation data, the next most important parameter was found to be the fraction of impermeable area in the watershed. Therefore, several methods for estimating this parameter were examined and surficial geology maps gave the best results. Analysis of all the parameters for each watershed revealed that there was quite a consistent set of parameters for everything except the precipitation gradients and the fraction of impermeable area. Lack of variability of the parameters affecting the time distribution of runoff with watershed size supports the idea that the land phase controls the runoff process and the channel phase is secondary and appears almost negligible even for the watersheds larger than 1000 km2 in size. Thus, the watersheds were re-run using the fixed set of parameters and inputting precipitation and fraction of impermeable area for each watershed. The results obtained by this simplified method were then compared with the results of the original calibration for each watershed. The comparison showed that this fixed parameter set provided reliable flow estimates, because the reduction in overall model efficiency ranged from 0 to 10%, and in most cases stayed within 5%. In addition, this set of parameters considerably simplifies model calibration, and is an excellent first step in obtaining a full calibration. Therefore, this method is very useful for estimating runoff from an ungauged watershed, provided meteorological input is available. ii TABLE OF CONTENTS ABSTRACT ii LIST OF TABLES vi LIST OF FIGURES vii LIST OF SYMBOLS ix ACKNOWLEDGEMENTS xi 1. INTRODUCTION 1 1.1 General Introduction 1 1.2 Regional Flow Estimates 2 1.3 Objectives 3 1.4 Study Outline 5 2. LITERATURE REVIEW 7 2.1 Introduction 7 2.2 Land Phase Routing 8 2.3 Channel Phase Routing 11 2.4 Previous Studies 13 2.5 Summary 20 iii 3. STUDY WATERSHEDS 21 3.1 General Information 21 3.2 Physical Description of the Watersheds 21 3.2.1 Barlow Creek 21 3.2.2 Bone Creek 23 3.2.3 Bridge River 24 3.2.4 Campbell River 25 3.2.5 Coquihalla River 27 3.2.6 lllecillewaet River 28 3.2.7 Jordan River 30 3.2.8 Littie Swift River 31 3.2.9 Naver Creek 32 3.2.10 Stitt Creek 33 3.2.11 Tabor Creek 34 3.2.12 Watching Creek 35 4. MODEL CALIBRATION 51 4.1 The Watershed Model 51 4.1.1 The conceptual design 52 4.2 Calibration of the Watershed Model to Study Watersheds 54 4.2.1 Introduction 54 4.2.2 Sensitivity of precipitation parameters 57 4.2.3 Fraction of impermeable area 66 iv 4.2.4 Parameters affecting the time distribution of runoff 76 4.3 Calibration Results 77 5. AVERAGING OF THE PARAMETERS 84 5.1 Parameters Variability Among the Study Watersheds 84 5.2 Reliability of the Results Obtained by Averaged Set of Parameters 95 6. CONCLUSIONS 98 6.1 General Conclusions 98 6.2 Implications for the Watershed Behavior 102 REFERENCES 104 APPENDIX - Calibration Statistics and Verification 107 v LIST OF TABLES 3.1 Physical characteristics of the study watersheds 38 4.1 Calibrated periods for the study watersheds 56 4.2 Analysis of sensitivity of impermeable fraction for the Bone Creek watershed 72 5.1 Calibration values for the parameters affecting the time distribution of runoff 84 5.2 Averaged values for the parameters affecting the time distribution of runoff 88 5.3 Statistical measures of the model performance for both runs (Illecillewaet River) .... 95 5.4 Average statistical differences between flows calculated with calibrated and those with averaged parameters 96 vi LIST OF FIGURES 2.1 Derivation of the time-area diagram 10 2.2 Channel reach storage 12 2.3 The relation between drainage area and peakedness index for Scottish basins 18 3.1 Locations of the study watersheds 37 3.2 Barlow Creek watershed and its area-elevation distribution curve 39 3.3 Bone Creek watershed and its area-elevation distribution curve 40 3.4 Bridge River watershed and its area-elevation distribution curve 41 3.5 Campbell River watershed and its area-elevation distribution curve 42 3.6 Coquihalla River watershed and its area-elevation distribution curve 43 3.7 Illecillewaet River watershed and its area-elevation distribution curve 44 3.8 Jordan River watershed and its area-elevation distribution curve 45 3.9 Little Swift River watershed and its area-elevation distribution curve 46 3.10 Naver Creek watershed and its area-elevation distribution curve 47 3.11 Stitt Creek watershed and its area-elevation distribution curve 48 3.12 Tabor Creek watershed and its area-elevation distribution curve 49 3.13 Watching Creek watershed and its area-elevation distribution curve 50 4.1 Relationship between mean annual flood and drainage area for 12 study watersheds 57 vii 4.2 Relationship between mean annual flood and mean annual precipitation for 12 study watersheds 58 4.3 Mean annual water yield versus mean annual precipitation for 12 study watersheds . 58 4.4 Sensitivity of the precipitation adjustment factors for study watersheds 60 4.5 Sensitivity of the fraction of impermeable area for study watersheds 66 4.6 Starting estimates of impermeable fraction versus calibrated values 73 4.7 Surficial geology of the Watching Creek watershed near Kamloops, B.C 75 4.8 Improved estimates of impermeable fraction versus calibrated values 76 4.9 Observed and calculated hydrographs for the 12 studied watersheds 78 5.1 Routing time constants versus drainage area for 12 studied watersheds 85 5.2 Flows calculated with calibrated (Qcal) and averaged parameters (Qcal(avr)) 89 viii LIST OF SYMBOLS a = coefficient in Eq. 4.6 A = drainage area of the watershed b = coefficient in Eq. 4.6 B = channel width c = wave celerity C = Chezy's resistance coefficient Dj = drainage density D! = coefficient of determination E! = coefficient of efficiency g = gravitational acceleration i = local inflow into the reach / = inflow into the reservoir K = storage time constant L = length of the channel reach L0 = length of overland flow L5 = sum of the stream lengths for the watershed n = Manning's resistance coefficient = number of days for daily runs or hours for hourly runs O = outflow from the reservoir ix PODZSH = deep zone share PODZTK = deep zone groundwater time constant POFRTK = rainfall fast runoff time constant POFSTK = snowmelt fast runoff time constant POIRTK = rainfall interflow runoff time constant POISTK = snowmelt interflow time constant POPERC = groundwater percolation POUGTK = upper groundwater time constant Q = discharge R = hydraulic radius s2 = variance S = storage Sf = friction slope S0 = bed slope / = time v = flow velocity W = water input to the first linear reservoir in Eq. 2.24 x = distance in the flow direction X = weighting factor in Eq. 2.9 y = flow depth r = Gamma function cW - volume error X = ratio of the stream equilibrium time to the catchment equilibrium time ACKNOWLEDGEMENTS I would like to express my sincere appreciation and gratitude to my research supervisor, Dr. Michael Quick, who has a very positive impact on my academic as well as personal attitude. I am particularly grateful to my wife Sandra who contributed her time and knowledge in helping me to set up all watershed files. I appreciate the assistance I received from Mr. Edmond Yu in the computer works. I am also thankful to Drs Barbara Lence and Dennis Russell for their comments and suggestions which improved the quality of this thesis. This research has been partly funded by the Walter C. Koerner Graduate Fellowship. Finally, I would like to thank my daughter Natasa for being a constant source of joy in my life and Don Pigone for being my role-model. xi CHAPTER 1 INTRODUCTION 1.1 General Introduction Water resource management implies a good knowledge of the hydrological regimes of the basins and understanding of the physical processes involved in streamflow generation, especially for low-flow or flood periods. Problems for which design floods must be determined include flood protection works, dams, river crossings, urban drainage, floodplain delineation, culverts, channel restoration, river diversions and impoundments. Design low flow is often used as the minimum flow required for favorable water quality conditions and preservation of fish and wild life habitat.