1. Manoa Watershed Runoff
By: Mari Doi, Travis Voeller, Kiku Mochimaru, Victor Lee, Boyd Mackenzie, Rebecca Mierzejewski, Daniel Mehrez, Will Couture

2. 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

3. 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.

4. Grid
Land Cover Level I
Land Cover Level II
% Land Cover Level II
CN Value II
CN Value I
CN Value III 1
3 Rangeland
32 Shrub and Brush Rangeland
100% 86 71 95 2
4 Forest Land
42 Evergreen Forest land 1% 83 67 93
99% 79 62 90 3 4 77
59.5
89.5 5 6 7
25%
75% 8 9 10 11 60 40 78 12 13
89%
11% 69 50 84 14
49% 66 46
51%

5. Model Runoff CN for Antecedent Moisture conditions (I & III) assigned.
ROMatrix program used to determine model runoff for each grid using:
-CN
-Actual Rainfall

6. Total Runoff (mm) 1 2 3 0-100mm 4 5 6 7 8 9 100-200mm 10 11 12 13 14
0-100mm 4 5 6 7 8 9 mm 10 11 12 13 14 15 16 mm 17 18 19 20 21 22 23 mm 24 25 26 27 28 29 mm 30 31 32 33 34 35 mm 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

7. Use ROMatrix.exe to find estimated runoff for each grid cell

8. 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

13. 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

16. Adjust curve numbers to optimize runoff estimates

17. Calculate weighted base flow
Find average rainfall for each grid
Find average rainfall for all grids
Base flow for grid= (average rainfall per grid)/ (average rainfall for all grids * average base flow)

19. % Runoff from Total Precipitation

20. % Runoff from Precipitation

21. Total Rainfall vs. Total Runoff

22. Conclusion
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.
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