1. Neuse River Basin – Hydrologic Model Update
Brian J. McCrodden
Casey Caldwell
Steven Nebiker
March 25, 2009

2. Agenda Project status Model overview Inflow development Calibration
Preliminary model results
Eno River system
Falls Lake
Durham
Remaining steps 2 2

3. Project Status
Two-year effort, initially projected to be complete by Feb. 2010
Project now 90% complete in terms of deliverables
Remaining project components
Finalize calibration and operating rules (if deemed necessary)
Install model on DWR server to provide stakeholder access
Provide documentation
Conduct training 3

4. Intended Uses of Model Evaluation of: Alternative operating protocols
Model Overview
Evaluation of:
Alternative operating protocols
Combined effects of water supply plans
Interbasin transfer permit applications
Development of individual water supply plans
Platform for risk-based drought plans, starting with Falls Lake
Not intended for real-time flood control 4

5. Geographic Scope of Model
Model Overview 5 5

6. Upper Basin
Model Overview 6 6

7. Middle Basin Model Overview
Added all Crabtree Creek impoundments to improve calibration with downstream flow gage 7 7

8. Lower Basin
Model Overview
Inflow from node 700 upstream 8 8

9. Inflow Development Develop daily inflow record from 1930 to present
Captures extreme drought event of 2007
Adjust gage flows for upstream impairments
Lake operations
Water withdrawals (municipal, industrial, agricultural)
Wastewater returns
Unimpaired inflows required if system is to be operated differently than in the past
Inflow data set ensures monthly unimpaired gage flow is preserved
Assumes error is embedded in the impairment data 9 9

10. Agricultural Demand Historic time series developed by county
Inflow Development
Historic time series developed by county
Basin delineated into sub-basins based on inflow reaches
Agricultural demand node placed in model for each reach of interest 10 10

11. Neuse Gage Timeline
Inflow Development 11

12. Long Term Gages Inflow Development 12 12
Gage is significantly impaired
Flat River at Bahama
Gage is moderately impaired
Eno River at Hillsborough
Gage has little to no impairment
Neuse River nr Clayton
Little River nr Princeton
Middle Creek nr Clayton
Contentnea Creek nr Hookerton
Neuse River nr Goldsboro
Neuse River at Kinston 12 12

13. Long Term Gages Inflow Development 13 13
Gage is significantly impaired
Flat River at Bahama (115, 0.05)
Gage is moderately impaired
Eno River at Hillsborough (44, 1.6)
Gage has little to no impairment
Water Year 2007 statistics:
(Avg. cfs, 7 day min avg. cfs)
Neuse River nr Clayton (994, 223)
Little River nr Princeton (176, 0.01)
Middle Creek nr Clayton (90, 6.6)
Contentnea Creek nr Hookerton (735, 35)
Neuse River nr Goldsboro (2196, 226)
Neuse River at Kinston (2710, 303) 13 13

14. Model Nodes with Inflows ( Reservoirs and Gages)
Inflow Development
010 Upstream Pond
050 WFER
060 Lake Orange
200 Little River Reservoir
250 Lake Holt
140 Lake Michie
740 Little River Reservoir (Raleigh Proposed)
080 Corp. Lake
270 Lake Rogers
100 Lake Ben Johnston
230 Beaverdam Lake
110 Hillsborough
Eno Gage
115 Durham
Eno Gage
300 Falls Lake
290 Wake Forest Lake
Needed for Eno Capacity Use requirements
750 Little River nr Princeton Gage
Needed for Teer Quarry withdrawal
500 Buckhorn Reservoir
400 Lake Crabtree
630 Clayton Gage
445 Lake Johnson
450 Lake Raleigh
780 Goldsboro Gage
560 Contentnea at Hookerton Gage
420 Lake Wheeler
440 Lake Benson
800 Kinston Gage
900 – No gage here but inflows needed for the Weyerhauser intake. Note downstream gages are tidally influenced
480 Middle Creek gage 14 14

15. Overview of Basin-wide Impairments
Inflow Development 15 15

16. Usable Storage Comparison
Inflow Development *
* Falls Lake volume includes Beaverdam sub-impoundment 16 16

17. Usable Storage Comparison – Excluding Falls Lake
Inflow Development 17 17

18. Usable Storage Comparison
Inflow Development 18 18

19. Basin Demand and WW Return Overview
Inflow Development
2004 Data * **
* Includes Raleigh WW return through Neuse River and Little Creek WWTPs
** Johnston Co. demand includes Clayton; WW return includes Clayton WWTP; Smithfield WW returned through Johnston Co. WWTP 19 19

20. Basin WW Return Comparison
Inflow Development
2004 Data
Not associated with water supply withdrawals *
* Falls Lake volume includes Beaverdam sub-impoundment 20 20

21. Agricultural Demand by County
Inflow Development
2004 Data 21 21

22. Unimpaired Gage Flow Examples
Inflow Development
Hillsborough gage (October 2007)
Gage flow = 4.5 cfs
Total impairment upstream (mainly decrease in storage in Lake Orange and West Fork Eno Reservoir) = -2.5 cfs
Unimpaired gage flow = 2.0 cfs
Clayton gage (April 2008)
Gage flow = 1080 cfs
Total impairment upstream (mainly increase in Falls Lake storage) = 703 cfs
Unimpaired gage flow = 1783 cfs 22 22

23. Unimpaired Gain
Inflow Development
Since unimpaired flow at gage is forced to match historic flow, gain between two gages also matches historic 23 23

24. Spreadsheet Showing Gage Unimpairment
Inflow Development 24 24

25. Daily Inflow Estimation
Inflow Development
Since impairment data are often only available monthly, daily variation preserved by using locally unimpaired gage
Goal: to develop a representative set of daily inflows while preserving monthly unimpaired gage flow as “ground truth” 25 25

26. Inflow Record Extends from January 1930 to April 2008
Inflow Development
Extends from January 1930 to April 2008
Fill in missing gage records based on correlations with other gages
Model equipped with inflow update provision
Since impairment data are time-consuming and costly to collect, data collection anticipated only every 5 years
In meantime, to generate real-time forecasts, use provisional inflow development approach to update inflows through present day
User only needs to input gage data and major impairment data (like Falls change in storage) 26 26

27. Calibration Required to test accuracy of inflow estimates
Possible for reservoirs where historic operating data and/or gage flow data are available
Focus on Eno River, Durham, and Falls
More calibration results shown in appendix 27 27

28. Eno River West Fork Eno Reservoir
Calibration
West Fork Eno Reservoir
Lake level and release data available since 2001 (but not always daily)
Calibration run: use estimated inflows, match release, and compare computed and historic storage
For inflows, use drainage-area adjustment of unimpaired Hillsborough gage
Unimpaired monthly, disaggregated to daily with Flat River 28 28

29. West Fork Eno Reservoir
Calibration
Dead storage 29 29

30. Eno River Lake Orange Lake level data available since 2001
Calibration
Lake Orange
Lake level data available since 2001
Release data not available
Calibration run: use estimated inflows, incorporate operating policies based on Capacity Use Area Rules, and compare computed and historic storage
Results shown at previous TRC meeting showed poor agreement
Very sensitive to release policy
Influenced to some degree by inflows from upstream agricultural ponds 30 30

31. Lake Orange (Without Adjustments)
Calibration
Dead storage 31 31

32. Adjustments Added agricultural pond upstream
Calibration
Added agricultural pond upstream
Uses cumulative storage of all ponds upstream based on Ken Terlep’s estimates
Release policy
Most of Hillsborough demand is during 8 hour periods, 5 days a week
During these periods, releases from Orange must be 2.4 times higher than the weekly average to meet instantaneous instream flow requirements
Factor = [( 5 “peak days” * 3) + (2 ”normal days” * 1 ) ] / 7 total days = 2.4 32 32

33. Lake Orange (With Adjustments)
Calibration
Dead storage 33 33

34. Eno River Hillsborough gage flow
Calibration
Hillsborough gage flow
Simulate upstream lake operations based on Capacity Use Area Rules (see Appendix)
Compare computed and historic gage flows 34 34

35. Hillsborough Gage
Calibration 35 35

36. Durham Operating data available since 2000
Calibration
Operating data available since 2000
Data on flows between reservoirs and treatment plants was often challenging to compile
Calibration run: use estimated inflows, match release, and compare computed and historic storage
For inflows, use daily drainage-area adjusted Flat River and Little River gage flows 36 36

37. Lake Michie
Calibration
Dead storage 37 37

38. Little River
Calibration
Dead storage 38 38

39. Lake Michie and Little River
Calibration
Dead storage 39 39

40. Falls/Beaverdam
Calibration
Each project is modeled explicitly so it can be evaluated independently
Operating data for Falls available since project inception (1981); data for Beaverdam available since 2000
Calibration run: use estimated inflows, match release, and compare computed and historic elevation and storage
For inflows, back-calculate from change in storage and release 40 40

41. Water Supply and Water Quality Pool Accounting
Calibration
Used Corps’ spreadsheet (developed by Terry Brown) as guidance
Corps’ calculation of Falls storage accounts includes Beaverdam accounts when elevation >= 249 feet
OASIS model breaks out storage accounts by project
Total storage = 106,322 acre feet (af)
WQ = 61,322 af
WS = 45,000 af
Elev (top of conservation pool)
Falls
Elev.249
Beaverdam
101,705 af WQ/WS
4617 af WQ/WS +
58,659 af WQ (58%)
2663 af WQ (58%)
1954 af WS (42%)
43,046 af WS (42%)
Elev (bottom of conservation pool) 41 41

42. Beaverdam
Calibration 42 42

43. Beaverdam WQ Storage
Calibration 43 43

44. Beaverdam WS Storage
Calibration 44 44

45. Falls Lake
Calibration 45 45

46. Falls Lake WQ Storage Calibration
Note: Differences due to minor adjustments to Corps’ WQ accounting 46 46

47. Falls Lake WS Storage Calibration
Note: Differences due to minor adjustments to Corps’ WS accounting 47 47

48. Falls Lake (for full period of operation)
Calibration
Note: Beaverdam data not available pre-2000, so estimated inflows to Beaverdam (which affect Falls elevation) are slightly different than those from the Corps for that period 48 48

49. Falls/Beaverdam Calibration run, but not matching historic releases
Use estimated inflows (back-calculated)
Incorporate nominal Corps operating protocols
Rule curve
Minimum Falls release (100 cfs from April to October, 60 cfs otherwise)
Minimum flow at Clayton (254 cfs from April to October, 184 cfs otherwise)
Drought management (specifying releases from Beaverdam)
Flood control rules controlling lake levels and downstream flows
Use historic Raleigh withdrawals
Compare computed and historic elevation, storage, and downstream flows 49 49

50. Falls Lake Calibration
Note: Simulation run uses current Falls rule curve adopted in 2000, resulting in some disagreement before then 50 50

51. Falls Outflow Calibration
Note: Simulation run meets Falls minimum release exactly because model has perfect foresight of inflows 51 51

52. Clayton Flow Calibration
Note: Simulation run meets Clayton target exactly because model has perfect foresight of inflows 52 52

53. Clayton Gage Flow Calibration
Note: Simulation run tries to limit Clayton flow to approximately 5300 cfs to prevent flooding. With perfect foresight, model will achieve that unless local inflow is too high. 53 53

54. Falls/Beaverdam WQ Accounting (Total Storage)
Calibration 54 54

55. Falls/Beaverdam WS Accounting (Total Storage)
Calibration 55 55

56. Crabtree Calibration
Calibration 56 56

57. Preliminary Model Results
Calibrations suggest that inflow estimates and operating protocols are properly captured
Using that information, simulate the system for full hydrologic record (1930 to present)
Focus on Eno River reservoirs, Durham reservoirs, and Falls
Use year 2004 demands and monthly demand patterns (and wastewater patterns, if significant) as starting point
Patterns need to be scrutinized (see next few slides)
Demonstrate real-time forecasting capability 57 57

58. Basin Demand Patterns 2004 * ** 58 58

59. Raleigh Demand Patterns 2002 – 2007* ** 59 59

60. Raleigh WW Return Patterns 2002 – 2007* ** 60 60

61. Lake Orange
Dead storage 61 61

62. West Fork Eno Reservoir
Dead storage 62 62

63. Durham
Dead storage 63 63

64. Falls Lake 64 64

65. Falls Lake 65 65

66. Next Steps Lake Rogers elevation-storage-area curve, operating policy?
Review monthly patterns for demand and WW return
To use inflow update, need access to gage flow data and select reservoir and demand data
Falls and Beaverdam WQ/WS storage
Elevations for West Fork Eno Res, Lake Orange, Lake Michie, Little River Res, Falls and Beaverdam Lakes
Demand for Hillsborough, Durham
Wastewater return (Middle Creek) for Cary
Representative precipitation gage for basin
Drought plan for Falls & Beaverdam
Demand and pattern for Neuse Regional WASA 66 66

67. Questions?

68. Durham Projections
Dead storage 68 68

69. Durham Projections
Dead storage 69 69

70. Falls Lake Projections70 70

71. Falls Lake Projections71 71

72. Falls/Beaverdam Projections72 72

73. Falls/Beaverdam Projections73 73

74. Falls/Beaverdam Projections74 74

75. Falls/Beaverdam Projections75 75

76. Durham Projections
Dead storage 76 76

77. Falls Lake Projections77 77

78. Falls/Beaverdam Projections78 78

79. Falls/Beaverdam Projections79 79

80. Appendix Additional calibration results
Eno River Capacity Use Area Rules 80 80

81. Additional Calibration Results81 81

82. Buckhorn
Calibration
Likely due to unrecorded upstream effects of beaver dams 82 82

83. Lake Holt Calibration – Inflows from Little River83 83

84. Knap of Reeds Creek flows – Inflows from Little River
Calibration 84 84

85. Knap of Reeds Creek flows – Inflows from Little River
Calibration 85 85

86. Swift Creek Calibration – Using area adjusted Swift Creek nr Apex flows
Other smaller discrepancies due to only having monthly averages of releases to match for calibration
Same discrepancy as previously discussed; due to issues with initial impoundment of reservoir (fixing leaks, etc) 86 86

87. Lake Wheeler Inflows
Calibration

88. Eno River Capacity Use Area Rules88 88

89. Lake Orange Minimum Release Policy89 89

90. West Fork Eno Reservoir Minimum Release Policy
Greater of A or B: A.
Flow Releases (CFS):
Tier 1 (100%-60%, ft)
Tier 2 (60%-40%, ft)
Tier 3 (40%-0%, ft)
Month
Habitat Maint.
Flow Augm.
Total Release
January
3.5
1.9
0.1
0.9
1.0
February
March
April
4.0
2.2
0.2
0.8
May
3.0
1.6
June
1.8
July
1.4
August
0.6
0.4
September
October
November
December
2.6
1.3 B. 90 90