Big Lost HUC8 17040218
A 6,355 km² sub-basin of the Pacific Northwest region in ID. Drought coverage is from the US Drought Monitor (map of 2026-09-01); streamflow classes place each USGS gauge's latest reading against its own day-of-year record.
Health score
55
Moderate
Drought index
278
Severe
Area in D2+
50.78%
0% exceptional (D4)
Gauges below normal
40%
of 5 reporting
Median flow
78%
p30 of record
Water assets
1,868
43 springs · 1,346 wells
USGS gauges (15)
- BIG LOST RIVER NR ARCO ID131325000 cfsp10 · below normal
- NF BIG LOST RIVER AT WILD HORSE NR CHILLY ID1312000030 cfsp20 · below normal
- BIG LOST RIVER AT HOWELL RANCH NR CHILLY ID13120500100 cfsp30 · normal
- LOWER CEDAR CREEK AB DIVS NR MACKAY ID1312890014 cfsp42 · normal
- BIG LOST RIVER BL MACKAY RES NR MACKAY ID13127000312 cfsp75 · above normal
- THOUSAND SPRINGS CREEK NR CHILLY ID131220003 cfsno long-term record
- WARM SPRINGS CREEK BELOW DIVERSION NR MACKAY ID1312426526 cfsno long-term record
- BIG LOST RIVER NR LESLIE ID13130300240 cfsno long-term record
- ANTELOPE CREEK NR DARLINGTON, ID1313100019 cfsno long-term record
- BIG LOST RIVER BELOW MOORE DIV NR MOORE ID131321000 cfsno long-term record
- BIG LOST RIVER AT ARCO AT SUNSET ROAD ID131323730 cfsno long-term record
- INL DIVERSION AT HEAD NEAR ARCO ID13132513no readingno long-term record
- BIG LOST RIVER BL INL DIV NEAR ARCO ID13132520no readingno long-term record
- BIG LOST R AT LINCOLN BLVD BRIDGE NR ATOMIC CITY13132535no readingno long-term record
- BIG LOST RIVER AB BIG LOST RIVER SINKS NR HOWE ID13132565no readingno long-term record
Recent conditions
| Date | DSCI | D2+ % | Gauges low | Flow pct |
|---|---|---|---|---|
| 2026-09-07 | 278 | 50.78 | 2/5 | p30 |
Top water assets
- 69Warm Springs Creek Below Diversion Nr Mackay Idriver
- 69Big Lost River At Howell Ranch Nr Chilly Idriver
- 69Big Lost River Nr Leslie Idriver
- 69Antelope Creek Nr Darlington, Idriver
- 69Lower Cedar Creek Ab Divs Nr Mackay Idriver
- 69Nf Big Lost River At Wild Horse Nr Chilly Idriver
- 69Thousand Springs Creek Nr Chilly Idriver
- 69Big Lost River Bl Mackay Res Nr Mackay Idriver
- 69Kane Creekriver
- 69Rock Creekriver