Oroville Dam Forecast – 14.2.17 – 10.24GMT

Oroville Dam and the our forecast for the next week. Raw data is included at the bottom.

Data Sources

Dam Data: https://cdec.water.ca.gov/cgi-progs/queryF?s=ORO&d=14-Feb-2017+00:18&span=12hours

Weather Data: https://www.wunderground.com/US/CA/Oroville.html?MR=1

Oroville Dam Forecast Summary

If the forecast from Wunderground is accurate, there is a good chance emergency  spillway will be required at some point, possible as soon as 17.2.17

Oroville Dam – Analysis

oroville_dam
Top graph – Low effect of ground saturation Middle graph – Average effect of ground saturation Bottom graph – Dynamic ground saturation, increasing saturation on consecutive rainy days. All 3 graphs use Wunderground rainfall forecasts If main spillway cannot operate at more than 100,000 cubic feet per second, real possibility of emergency spillway coming into play.

 

In our opinion the data shows that the closing of the main spillway is what triggered the events/situation we have today.

It is also our opinion that the emergency spillway is just that. Only to be used in an emergency, the definition of emergency being when the main spillway was no longer capable of flowing enough water, damaged or not.

The situation will reach its peak severity on the 21st or 22nd of February

Or alternatively, if the Wunderground figures are over estimating the rainfall and ground saturation plays no part in future flows through the dam, the worst is behind us.

Oroville Dam – Our Opinion/Forecast

We think Wunderground is probably over estimating rainfall.

As long as the main spillway does not suffer unforeseen erosion issues which limits it flow capability, the worst should be behind us.

However if Wunderground rain forecast is correct, it does not look like the main spillway will have the required capactity, assuming it is running at max capacity now, ie 100,000 cubic/feet/per second. If there is excess capacity in the main spillway ie it is able to operate at more than 100,000cfs, this analysis becomes irrelevant.

The key issue is ensuring that the emergency spillway does not need to be used, as that we have been told is the whole problem ie erosion on emergency spillway.

We recommend following the advice of authorities in the area they have all the information, we do not.

Oroville Dam Forecast Data

The key column is the 3 day rolling rainfall total:lake inflow ratio. Ratio referred to as λ

λ factors in the effect of ground saturation on rainfall and in turn, what effect rainfall will have on inflows into lake Oroville

λ is calculated by adding the previous 3 days rainfall together and dividing by the inflow volume on the 3rd day.

This λ figure ramps up a lot if rain falls for consecutive days due to the ground becoming saturated

Using a flat λ ratio of 2000 and forecast rainfall, the worst is behind us

Using a flat λ ratio of 3000 and forecast rainfall, the situation is touch and go

Using a rising λ ratio to reflect ground saturation, the situation does not look good, as the forecast is for 7 days of consecutive rain with rolling 3 days total over 38mm.

The lake height predictions are assuming net outflow of 80,000 CFS leads to a 12 feet change in lake level for the day.

Please note the “Record/Forecast Column”

 

 

Day Rainfall 3 Day Roll Rainfall Lake Level Outflow In Flow Inflow Net 3 Day Rolling Rfall mm:inflow λ
1 1.52 Record
2 0 Record 1.52
3 19.3 Record 20.82
4 1.52 Record 20.82
5 Record 20.82
6 Record 1.52
7 21.34 Record 21.34 788.14 1720 7483 5763 #DIV/0!
8 41.4 Record 62.74 789.4 1709 14782 13073 1043.345829
9 8.89 Record 71.63 805.22 1645 150609 148964 2636.133248
10 22.86 Record 73.15 820.67 1616 72395 70779 3113.27656
11 0.25 Record 32 834.62 1607 99114 97507 2344.620643
12 Record 23.11 844.75 4314 44982 40668 4503
13 Record 0.25 849.33 13216 20360 7144 2827.434011
14 Record 0 851.31 19733 18137 -1596 153988
15 Record 0 851.64 19826 6003 -13823 #DIV/0!
16 Record 0 851.34 19836 3406 -16430 #DIV/0!
17 Record 0 850.75 19754 2598 -17156 #DIV/0!
18 24.38 Record 24.38 849.86 19798 5311 -14487 #DIV/0!
19 2.79 Record 27.17 849.66 14403 6249 -8154 474.1591468
20 23.11 Record 50.28 850.56 14271 5133 -9138 418.9179242
21 10.16 Record 36.06 851.67 11071 12725 1654 355.1710422
22 12.7 Record 45.97 852.76 11098 8712 -2386 594.4814199
23 Record 22.86 854 11013 9403 -1610 394.0613444
24 Record 12.7 855 10984 3234 -7750 552.79965
25 Record 0 855 11201 2025 -9176 414.0944882
26 Record 0 855 9891 -1199 -11090 #DIV/0!
27 Record 0 855 7974 -2312 -10286 #DIV/0!
28 Record 0 855 9732 -6956 -16688 #DIV/0!
29 Record 0 854 9795 -3131 -12926 #DIV/0!
30 Record 0 854 13071 -3987 -17058 #DIV/0!
31 Record 0 853 14800 5421 -9379 #DIV/0!
1 Record 0 852 19955 -480 -20435 #DIV/0!
2 18.03 Record 18.03 850 20274 -3272 -23546 #DIV/0!
3 11.18 Record 29.21 849 20414 5583 -14831 128.1752634
4 0 Record 29.21 848 30305 26590 -3715 1101.437864
5 9.9 Record 21.08 849 29766 30668 902 1960.219103
6 26.16 Record 36.06 849 29732 29559 -173 2857.068311
7 10.67 Record 46.73 850 47787 67298 19511 2685.995563
8 13.2 Record 50.03 862 5113 83933 78820 3236.272202
9 28.96 Record 52.83 874 32663 123681 91018 4149.790126
10 1 Record 43.16 890 45139 179625 134486 5741.16979
11 2.5 Record 32.46 899 55068 103772 48704 6566.195551
12 0 Record 3.5 902 55070 61754 6684 5099.383857
13 0 Record 2.5 899 98832 44890 -53942 30469.71429
14 0 Record 0 891 98832 34966 -64922 31942.4
15 18 Forecast 18 881.4 98832 36000 -9.6 2000
16 26 Forecast 44 879.6 98832 88000 -1.8 2000
17 20 Forecast 64 883.8 98832 128000 4.2 2000
18 6 Forecast 52 884.4 98832 104000 0.6 2000
19 14 Forecast 40 881.4 98832 80000 -3 2000
20 22 Forecast 42 879 98832 84000 -2.4 2000
21 11 Forecast 47 878.1 98832 94000 -0.9 2000
22 5 Forecast 38 874.5 98832 76000 -3.6 2000
23 0 Forecast 16 864.3 98832 32000 -10.2 2000
No Issues -26.7
15 18 Forecast 18 884.1 54000 -6.9 3000
16 26 Forecast 44 888.9 132000 4.8 3000
17 20 Forecast 64 902.7 192000 13.8 3000
18 6 Forecast 52 911.1 156000 8.4 3000
19 14 Forecast 40 914.1 120000 3 3000
20 22 Forecast 42 918 126000 3.9 3000
21 11 Forecast 47 924.15 141000 6.15 3000
22 5 Forecast 38 926.25 114000 2.1 3000
23 0 Forecast 16 918.45 48000 -7.8 3000
27.45
Required Dam Level 872
15 18 Forecast 18 880.05 27000 -10.95 1500
16 26 Forecast 44 878.25 88000 -1.8 2000
17 20 Forecast 64 887.25 160000 9 2500
18 6 Forecast 52 895.65 156000 8.4 3000
19 14 Forecast 40 898.65 120000 3 3000
20 22 Forecast 42 908.85 168000 10.2 4000
21 11 Forecast 47 929.1 235000 20.25 5000
22 5 Forecast 38 948.3 228000 19.2 6000
23 0 Forecast 16 944.1 72000 -4.2 4500
53.1
Required Dam Level 846.9

 

 

 

 

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