Green River Basin New Verification Tool 7 Forecast

Green River Basin New Verification Tool ¡ 7 Forecast Points Selected ¡ Five Major Inquires ¡ William B. Reed Green River Basin November 2008

Five Major Inquires Climate Indices ¡ ESP Distributions ¡ Anomalous Years ¡ l Basic Hydrology ESP vs. SWS ¡ Joes Valley ¡

Green River Basin ü WBRW 4 (Green – Warren Bridge ü GBRW 4 (Green – Fontenelle Res)

Green River Basin GBRW 4 • GBRW 4 (Green – Fontenelle Res) ü MBLC 2 (Yampa nr Maybell) ü LILC 2 (Little Snake nr Lily ü GRVU 1 ( Green at Green River)

Green River Basin ü USTU 1 (Upper Stillwater Res) ü JOVU 1 (Joes Valley Res) • GRVU 1 ( Green at Green River)

Climate Indices ¡ Is there a Signal? l l Answer 1: Looking at 3 El Nino indices there were no significant correlations. Answer 2: Best correlation was with PDO but still likely not significant.

Climate Indices: Green – Fontenelle Reservoir. Looked at SST, MEI and ONI with essentially the same results: no significant correlation.

Climate Indices: Green – Fontenelle Reservoir. Best R*2 = 0. 0679 but still likely not significant.

Climate Indices: Green - Warren Bridge No Improvement Further North, essentially the same results: Best R*2 = 0. 0229.

ESP Distributions ¡ Is there a major difference between using one ESPADP distribution over the others. l Answer: For the Green River at Green River the Normal and Wakeby distributions may be best to use in January. However, on average there is really no difference between the top six. ¡ Never use the Loglogistic distribution. ¡

Looking at Categories Contingency Table for January Green River – Green River, UT Bad News Normal & Wakeby - slightly better?

Contingency Table for April (All Distributions OK) Green River – Green River, UT In April these five all look okay categorically.

RMSE for Distributions On the average, all distributions are OK with the exception of Loglogistic (not used in previous plots). This is true regardless of the lead time.

Anomalous Years Contingency Table ¡ Historical Plot ¡ Cause of Forecast Error Due To Seasonal Change ¡ Basic Hydrology ¡ l l Low to High/High to Low Above Record

Looking at Categories Contingency Table for January Green River – Green River, UT 1993, 1995, & 1998

Historical – GRVU 1 1993: under then over forecasted 1995: under forecasted then caught up 1998: never caught up

1993: under then over forecasted Late season snow starting in mid-March and continuing thru May.

1995: under forecasted then caught up Late season snow staring in mid-April with late seasonal peak. 1993 happened two years prior.

1998: never caught up Dry thru late January. Then peaks slightly above average.

Basic Basin Hydrology Time series Can go from below normal to above normal Can go from above normal to below normal

Time series Can go from below normal to above normal But I was still surprised by the size of this jump.

ESP vs. SWS ¡ Is One Better? l ¡ Answer: In the Green Basin for the 6 Forecast Points investigated, on average ESP was better. Is it Always Better? l Answer: Yes, on average, for the sites investigated.

RMSE (lead time) – 1991 -2008 On average ESP is better than SWS.

RMSE (lead time) – 1991 -2008 On average ESP is better than SWS.

RMSE (lead time) – 1991 -2008 On average ESP is better than SWS.

Joes Valley is consistently underforecasted. ¡ Low flows are forecasted okay but high flows are a problem. ¡

Rank histogram (1993 -2008) General Tendency To Be Under-Forecasted.

Rank histogram by LT (1993 -2008) General Tendency To Be Under-Forecasted regardless of Month.

Historical – JOVU 1 Forecast have tended to be below blue lines (Observed). Have ESP for only one year.

POD below mean Good Job of Detecting Volumes Below Mean.

POD above mean Poor Job of Detecting Volumes Above Mean. Very Little Improvement Thru Season.

Error Doesn’t Improve

Time series (short time series 2002 missing) Further Investigation Required.

SUMMARY With regard to climate indices, no significant signals were found. • With regard to ESPADP distributions, on average there is really no difference between the top six. However, never use the Loglogistic distribution. • Anomalous forecasts can often be explained by looking at what climate occurred within the basin during the anomalous year. • For the sites investigated within the Green Basin, on average ESP is better than SWS as a tool. • Joes Valley requires further investigation. •