Post on 29-Jan-2016
description
Manoa Watershed Runoff
By: Mari Doi, Travis Voeller, Kiku Mochimaru, Victor Lee, Boyd Mackenzie, Rebecca Mierzejewski, Daniel Mehrez, Will Couture
Objectives
Calculate runoff for Manoa watershed (60 grids) using Curve # Method and base flow
RO-the amount of precipitation that is unavailable for groundwater recharge
Model Runoff using the Curve Number Method
•Each grid assigned a CN number based on the dominant current land cover.
•Soil properties and hydrologic condition were taken into consideration.
Grid
Land Cover Level I Land Cover Level II
% Land Cover Level II
CN Value II
CN Value I
CN Value III
1 3 Rangeland32 Shrub and Brush Rangeland 100% 86 71 95
2 4 Forest Land 42 Evergreen Forest land 1% 83 67 93
2 3 Rangeland32 Shrub and Brush Rangeland 99% 79 62 90
3 3 Rangeland32 Shrub and Brush Rangeland 100% 79 62 90
4 4 Forest Land 42 Evergreen Forest land 100% 77 59.5 89.5
5 4 Forest Land 42 Evergreen Forest land 100% 77 59.5 89.5
6 4 Forest Land 42 Evergreen Forest land 100% 77 59.5 89.5
7 4 Forest Land 42 Evergreen Forest land 25% 77 59.5 89.5
7 3 Rangeland32 Shrub and Brush Rangeland 75% 79 62 90
8 3 Rangeland32 Shrub and Brush Rangeland 100% 79 62 90
9 3 Rangeland32 Shrub and Brush Rangeland 100% 79 62 90
10 4 Forest Land 42 Evergreen Forest land 100% 77 59.5 89.5
11 4 Forest Land 42 Evergreen Forest land 100% 60 40 78
12 4 Forest Land 42 Evergreen Forest land 100% 60 40 78
13 4 Forest Land 42 Evergreen Forest land 89% 60 40 78
13 3 Rangeland32 Shrub and Brush Rangeland 11% 69 50 84
14 4 Forest Land 42 Evergreen Forest land 49% 66 46 83
14 3 Rangeland32 Shrub and Brush Rangeland 51% 69 50 84
Model Runoff
CN for Antecedent Moisture conditions (I & III) assigned.
ROMatrix program used to determine model runoff for each grid using:
-CN-Actual Rainfall
Total Runoff (mm)
1
2 3 0-100mm
4 5 6 7 8 9 100-200mm
10 11 12 13 14 15 16 200-300mm
17 18 19 20 21 22 23 300-400mm
24 25 26 27 28 29 400-500mm
30 31 32 33 34 35 500-600mm
36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51
52 53 54
55 56 57
58 59
60
Calculate estimated stream flow
Find the average runoff of all 60 grid squares for each day
Multiply by area of the watershed to get volume of discharge
USGS 16242500 Manoa Str at Kanewai Field, Honolulu, Oahu, HIStream Discharge Datahttp:/ / nwis.waterdata.usgs.gov/ nwis/ nwisman/ ?site_ no=16242500&agency_ cd=USGS
Discharge, Discharge,
date ft3/ s m3/ sMeasured (cu
m per day)8/29/2010 18 0.509703239 440388/30/2010 5.6 0.158574341 137018/31/2010 5.1 0.144415918 124789/1/2010 5.9 0.167069395 144359/2/2010 8 0.226534773 195739/3/2010 8.3 0.235029827 203079/4/2010 5.2 0.147247602 127229/5/2010 4.8 0.135920864 117449/6/2010 5.7 0.161406026 139459/7/2010 24 0.679604318 587189/8/2010 6.8 0.192554557 166379/9/2010 5.1 0.144415918 124789/10/2010 8.4 0.237861511 20551
Determining Baseflow•Look at the average minimum stream flow on days with no rainfall•From the runoff found from ROmatrix, get average and multiply it by the area of the watershed to get volume of runoff•Look at difference of the measured and modeled stormflow
Adjust curve numbers to optimize runoff estimates
0
100000
200000
300000
400000
500000
600000
700000
800000
900000
1000000
8/20/2010 8/30/2010 9/9/2010 9/19/2010 9/29/2010 10/9/2010 10/19/2010 10/29/2010 11/8/2010 11/18/2010 11/28/2010
Measured (cu m per day)
Model stormflow plusBaseflow
Calculate weighted base flow
o Find average rainfall for each grido Find average rainfall for all gridso Base flow for grid= (average rainfall
per grid)/ (average rainfall for all grids * average base flow)
Conclusion
Adjusted curve #’s & added base flow provided us with the most efficient results of basin RO
RO results can then be plugged into water balance equation as an output of water
Runoff was calculated by obtaining precipitation data and utilizing the curve number method. By adjusting the curve numbers and adding base flow, the data was a close representation the model data from the USGS results.