NC0069841_Rocky River Model_Low Flows_20240607

This spreadsheet includes the critical low flow calculations developed for the Rocky River QUAL2K model
Updated 6/7/2024
Hillary Yonce and Will Hicks, Tetra Tech
Tab Name Description
UnitDischarge
All 7Q10 summer and winter low flow calculations for each tributary that is gaged in the Rocky River. The source of each
estimate is provided (primarily Curtis Weaver low flow reports and NPDES permits), including drainage area based unit
discharges associated with each gage location.
7Q10 Balance
Boundary condition calculations for the summer 7Q10s, using summer-only reported 7Q10 values. Seen here is that without
normalizing or weighting the boundary flow contributions relative to known flows on the mainstem Rocky River, overall flows
along the Rocky River are underestimated slightly during summer by approxmiately 11 - 13% before weighting.
W7Q10 Balance
Same calculations as 7Q10 Balance, but using winter-only 7Q10 values. Seen here is that without normalizing or weighting the
boundary flow contributions relative to known flows on the mainstem Rocky River, overall flows along the Rocky River are
overestimated slightly during winter by approxmiately 3 - 8% before weighting.
Proposed Low Flows
This tab shows the final calculations of model inputs for each tributary during summer and winter critical low flow conditions
based on best available 7Q10 data, unit area discharges, intervening drainage areas between tributaries and downstream of
gages, and water balance information on the mainstem Rocky River.
Low Flow Conditions at USGS gages in the Rocky River model Flow (cfs)Unit Discharge (cfs/mi2)
Boundary Condition Source Report DA 7Q10 W7Q10 7Q10 W7Q10
Dye West Branch Partial Rocky River Low-Flow 4.98 0.5 0.9 0.100 0.181
RR as trib West Branch Partial Rocky River Low-Flow 4.98 0.5 0.9 0.100 0.181
West Branch West Branch Partial Rocky River Low-Flow 4.98 0.5 0.9 0.100 0.181
Clarke Clarke Partial Rocky River Low-Flow 21.9 1 2.3 0.046 0.105
Mallard Mallard upstream discharge NPDES Permit 37.5 0.64 2.1 0.017 0.056
Coddle Coddle Partial Rocky River Low-Flow 57.9 5.6 9 0.097 0.155
Back Reedy @ Rocky Partial Rocky River Low-Flow 30.9 1.6 3 0.052 0.097
Reedy Reedy @ Rocky Partial Rocky River Low-Flow 30.9 1.6 3 0.052 0.097
Irish Buffalo Irish Partial Rocky River Low-Flow 45.5 3.1 8.2 0.068 0.180
Dutch Buffalo Dutch Continuous Rocky River Low-Flow 45.1 0.7 2.2 0.016 0.049
Clear Goose Continuous Rocky River Low-Flow 24 0.3 1 0.013 0.042
Goose Goose Continuous Rocky River Low-Flow 24 0.3 1 0.013 0.042
Crooked Curtis Email N/A N/A N/A N/A 0.001 0.010
Island Curtis Email N/A N/A N/A N/A 0.001 0.010
Long Long upstream discharge NPDES Permit N/A N/A N/A 0.004 0.021
Little Long Long upstream discharge NPDES Permit N/A N/A N/A 0.051 0.302
Little Bear Little Bear Partial Rocky River Low-Flow 12.4 0 0.3 0.000 0.024
Big Bear Big Bear Continuous Rocky River Low-Flow 55.6 0 0.2 0.000 0.004
Richardson Richardson Continuous Rocky River Low-Flow 163 0.5 1.6 0.003 0.010
Cribs Richardson Continuous Rocky River Low-Flow 163 0.5 1.6 0.003 0.010
Lanes Lanes @ Marshville Continuous Rocky River Low-Flow 87.7 0 0.05 0.000 0.001
Mallard HW 0.017 0.056
Long HW 0.004 0.021
Flow (cfs)Unit Discharge (cfs/mi2)
DA 7Q10 W7Q10 7Q10 W7Q10
Long+Little 64 1.60 9.50 0.025 0.148
Long 35 0.12 0.74 0.004 0.021
Little 29 1.48 8.76 0.051 0.302
Calibration Flow (cfs)
Long HW 0.05
Little Long 0.63
SUM 0.68
Mallard Creek to Coddle Creek Mallard 41.40 0.02 131 13.20 0.59 0.98 1.31 1.65 0.59
Coddle Creek to Back Creek Coddle 74.30 0.10 215 9.70 7.19 0.72 7.22 1.21 7.25 Unweighted Sum 18.52 Weighted SUM 20.70
Back Creek to Reedy Creek Back 15.50 0.05 231 0.50 0.80 0.04 0.94 0.06 1.04 WSACC 7Q10 20.70
Reedy Creek to RRRWWTP Reedy 43.10 0.05 276 1.90 2.23 0.14 2.38 0.24 2.38 Interim Flow 2.18 11%
WSACC 7Q10 278 2.00 0.15
Norwood Unit Discharge (cfs/mi²)0.03
WSACC 7Q10 20.70 20.70
Irish Buffalo Creek to Dutch Buffalo Creek Irish Buffalo 110.00 0.07 389 1.00 7.49 0.03 8.05 0.07 8.69
Dutch Buffalo Creek to Muddy WWTP Dutch Buffalo 98.70 0.02 503 15.30 1.53 0.52 3.33 1.12 5.36
Muddy WWTP to Clear Creek
Clear Creek to Goose Creek Clear 24.50 0.01 580 52.43 0.31 1.80 0.31 3.83 0.31
Goose Creek to Crooked Creek Goose 42.30 0.01 622 0.01 0.53 0.00 0.75 0.00 0.99
Crooked Creek to Island Creek Crooked 50.40 0.00 679 6.36 0.05 0.22 1.22 0.47 2.54
Island Creek to Long Creek Island 21.90 0.00 735 34.10 0.02 1.17 1.02 2.49 2.95
Long Creek to Richardson Creek Long 201.00 0.00 965 29.00 2.67 0.99 3.04 2.12 2.67
Richardson Creek to Cribs Creek Richardson 234.00 0.00 1210 11.00 0.72 0.38 0.73 0.80 0.75 Unweighted Sum 40.99 Weighted SUM 47.27
Cribs Creek to Lanes Creek Cribs 19.50 0.00 1230 0.50 0.06 0.02 0.47 0.04 0.94 Norwood 7Q10 47.27
Lanes Creek to Plank Rd (USGS)Lanes 138.00 0.00 1380 12.00 0.00 0.41 1.37 0.88 1.37 Interim Flow 6.28 13%
Plank Rd to Norwood WWTP (US52)BC + HW SUM 47.27
Norwood WWTP to Pee Dee River
Pee Dee River Confluence 1420 40 1.37
Tributaries modeled as mainstems:
Mallard HW to Confluence Mallard HW 34.70 0.02 34.70 0.59 0.59
Mallard Confluence 41.40 6.70
Long HW to Little Long Long HW 32.00 0.00 32.00 0.11 0.16 0.16
Little Long to Little Bear Little Long 29.10 0.05 62.40 1.30 1.48 0.04 1.88 1.88
Little Bear to Big Bear Little Bear 12.50 0.00 86.60 11.70 0.00 0.40 0.39 0.39
Big Bear to Confluence Big Bear 96.10 0.00 194.00 11.30 0.00 0.39 0.24 0.24
Long Confluence 201.00 7.00 0.24 Long SUM 2.67 Weighted SUM 2.67
WSACC Unit Discharge (cfs/mi²)0.11
Dye-RRR to Mooresville WWTP Dye 3.96 0.18 3.96 0.72 0.85 0.82
Mooresville WWTP to RR-Headwaters
Dye Creek to West Branch Rocky River RR as trib 3.72 0.18 8.85 1.17 0.67 0.13 1.27 0.11 1.16
West Branch RR to Clarke Creek West Branch 22.90 0.18 37 5.25 4.14 0.60 5.44 0.49 5.19
Clarke Creek to Mallard Creek Clarke 28.10 0.11 76.4 11.30 2.95 1.30 4.47 1.05 5.09
Mallard Creek to Coddle Creek Mallard 41.40 0.06 131 13.20 1.94 1.51 3.06 1.23 1.94
Coddle Creek to Back Creek Coddle 74.30 0.16 215 9.70 11.55 1.11 11.61 0.90 11.60 Unweighted Sum 32.83 Weighted SUM 31.90
Back Creek to Reedy Creek Back 15.50 0.10 231 0.50 1.50 0.06 1.72 0.05 1.68 WSACC 7Q10 31.90
Reedy Creek to RRRWWTP Reedy 43.10 0.10 276 1.90 4.18 0.22 4.41 0.18 4.41 Interim Flow -0.93 -3%
WSACC 7Q10 278 2.00 0.23
Norwood Unit Discharge (cfs/mi²)0.06
WSACC 7Q10 31.90 31.90
Irish Buffalo Creek to Dutch Buffalo Creek Irish Buffalo 110.00 0.18 389 1.00 19.82 0.06 20.76 0.02 20.09
Dutch Buffalo Creek to Muddy WWTP Dutch Buffalo 98.70 0.05 503 15.30 4.81 0.88 7.83 0.25 5.67
Muddy WWTP to Clear Creek
Clear Creek to Goose Creek Clear 24.50 0.04 580 52.43 1.02 3.02 1.02 0.85 1.02
Goose Creek to Crooked Creek Goose 42.30 0.04 622 0.01 1.76 0.00 2.13 0.00 1.87
Crooked Creek to Island Creek Crooked 50.40 0.01 679 6.36 0.50 0.37 2.47 0.10 1.06
Island Creek to Long Creek Island 21.90 0.01 735 34.10 0.22 1.96 1.89 0.55 0.87
Long Creek to Richardson Creek Long 201.00 0.02 965 29.00 11.92 1.67 12.55 0.47 11.92
Richardson Creek to Cribs Creek Richardson 234.00 0.01 1210 11.00 2.30 0.63 2.33 0.18 2.31 Unweighted Sum 86.14 Weighted SUM 79.46
Cribs Creek to Lanes Creek Cribs 19.50 0.01 1230 0.50 0.19 0.03 0.88 0.01 0.39 Norwood 7Q10 79.46
Lanes Creek to Plank Rd (USGS)Lanes 138.00 0.00 1380 12.00 0.08 0.69 2.38 0.19 2.38 Interim Flow -6.68 -8%
Plank Rd to Norwood WWTP (US52)BC + HW SUM 79.46
Norwood WWTP to Pee Dee River
Pee Dee River Confluence 1420 40 2.30
Tributaries modeled as mainstems:
Mallard HW to Confluence Mallard HW 34.70 0.06 34.70 1.94 1.94
Mallard Confluence 41.40 6.70
Long HW to Little Long Long HW 32.00 0.02 32.00 0.67 0.75 0.75
Little Long to Little Bear Little Long 29.10 0.30 62.40 1.30 8.79 0.07 9.47 9.47
Little Bear to Big Bear Little Bear 12.50 0.02 86.60 11.70 0.30 0.67 0.95 0.95
Big Bear to Confluence Big Bear 96.10 0.00 194.00 11.30 0.35 0.65 0.75 0.75
Long Confluence 201.00 7.00 0.40 Long SUM 11.92 Weighted SUM 11.92
Interim
DA (mi2)Reach
Upstream
Boundary
Condition
Boundary
Condition
DA (mi2)
BC Unit
Discharge
(cfs/mi2)
Upstream
Mainstem
DA (mi2)
Boundary
Condition
Flow (cfs)
Interim Flow
(cfs)
Unweighted
BC + Interim
Flow (cfs)
Unweighted
Weighted
Interim
Flow (cfs)
BC + Interim
Flow (cfs)
Weighted
Proposed Low Flow Conditions for the Rocky River model
Boundary Condition Drainage Area (mi2)Calibration Model Flow (cfs)Summer 7Q10 Flow (cfs)Winter 7Q10 Flow (cfs)Summer 7Q10 Flow (cfs)Winter 7Q10 Flow (cfs)Summer 7Q10 Flow (cms)Winter 7Q10 Flow (cms)
Dye 3.96 1.06 0.40 0.72 0.54 0.82 0.015405589 0.023354323
RR as trib 3.72 0.33 0.37 0.67 1.03 1.16 0.029184945 0.032898186
West Branch 22.9 2.11 2.30 4.14 3.71 5.19 0.105159103 0.147024997
Clarke 28.1 1.26 1.28 2.95 4.15 5.09 0.117503203 0.144027718
Mallard HW 34.70 3.53 0.59 1.94 0.59 1.94 0.016769587 0.055025206
Coddle 74.3 6.72 7.19 11.55 7.25 11.60 0.205261975 0.328357138
Back 15.5 0.04 0.80 1.50 1.04 1.68 0.029461362 0.047629061
Reedy 43.1 5.15 2.23 4.18 2.38 4.41 0.067411996 0.124989291
Irish Buffalo 110 8.86 7.49 19.82 8.69 20.09 0.245965447 0.568856532
Dutch Buffalo 98.7 2.17 1.53 4.81 5.36 5.67 0.151917301 0.160455912
Clear 24.5 1.82 0.31 1.02 0.31 1.02 0.008694333 0.028911692
Goose 42.3 0.92 0.53 1.76 0.99 1.87 0.028142772 0.052835247
Crooked 50.4 2.37 0.05 0.50 2.54 1.06 0.072022605 0.029960407
Island 21.9 0.48 0.02 0.22 2.95 0.87 0.083430036 0.024604593
Long HW 32.00 0.05 0.11 0.67 0.16 0.75 0.004473784 0.021195882
Little Long 29.1 0.63 1.48 8.79 1.88 9.47 0.053285394 0.268077141
Little Bear 12.5 0.27 0.00 0.30 0.39 0.95 0.010960469 0.026987895
Big Bear 96.1 2.09 0.00 0.35 0.24 0.75 0.006789671 0.021201961
Richardson 234 7.54 0.72 2.30 0.75 2.31 0.02136068 0.065271819
Cribs 19.5 0.42 0.06 0.19 0.94 0.39 0.026536766 0.010941112
Lanes 138 1.93 0.00 0.08 1.37 2.38 0.03879812 0.067446815
SUM 49.75 27.47 68.49 47.27 79.46 1.34 2.25
Not including interim flow Including interim flow: Units CFS Including interim flow: Units CMS