Rivermatics

USGS Streamgage 13127000

Big Lost River below Mackay Reservoir near Mackay, ID

Big Lost River below Mackay Reservoir near Mackay, ID is USGS streamgage 13127000 in Idaho, monitoring river discharge in hydrologic subbasin 17040218. It sits on the Big Lost River, alongside 8 other gauges Rivermatics tracks on the same river. It drains a watershed of about 801 square miles. Discharge records at this site go back to 1903. Typical flow runs near 607.1 cfs in July and 123.4 cfs in April, with the higher of the two arriving in July. Rivermatics issues a daily machine-learned flow outlook for this gauge, reaching 14 days ahead.

View live conditions & forecast →

Gauge details

State
Idaho
Drainage area
801 sq mi
Subbasin (HUC-8)
17040218
Coordinates
43.93917, -113.64833
USGS site number
13127000
Records begin
1903-12-01 (123 years)
Rivermatics forecast
14-day flow outlook

14-day flow forecast

Based on observations through for Big Lost River below Mackay Reservoir near Mackay, ID. Each day carries a median estimate and the band the model expects the flow to fall within — not a single number to plan against. Forecasts are re-issued daily; see the live screen for the current outlook.

Forecast daily mean discharge in cubic feet per second, by date
Date Low p10 Expected p50 High p90 Range
266 291 300
244 287 300
226 283 301
205 277 302
185 268 300
182 264 301
168 258 303
158 253 299
153 250 298
148 246 297
139 242 298
133 239 297
132 238 297
130 238 298

All values in cubic feet per second (cfs). Estimates only — do not use them for navigation or for any safety, rescue, or emergency decision.

Typical flow by month

Long-term daily discharge percentiles from the USGS record (up to 122 years of data), averaged within each month. These describe the historical normal range — they are not a forecast and not today's reading.

Historical monthly discharge percentiles in cubic feet per second
Month Low p10 Typical p50 High p90 Range
January 75.9 103.6 190.8
February 86.9 113.6 184.2
March 94 122 202.7
April 95.7 123.4 284.5
May 157.2 380.9 907.6
June 406.1 800 1,662
July 290.8 607.1 1,017.5
August 156.7 386.4 649.5
September 136.1 208 371.9
October 77 145.4 270.4
November 50.4 76.4 201.8
December 59.7 87.6 192.7

All values in cubic feet per second (cfs).

Common questions

When does Big Lost River below Mackay Reservoir near Mackay, ID normally run highest?
June, on the long-term record. The median daily flow that month is about 800 cfs, against 76.4 cfs in November, the lowest month. These are historical normals for the date, not a forecast and not today's reading.
What is a normal flow for Big Lost River below Mackay Reservoir near Mackay, ID?
It depends on the month. In January, half of days historically fall near 103.6 cfs, with the middle 80% of days between 75.9 and 190.8 cfs. The month-by-month table on this page gives the full range.
How long has Big Lost River below Mackay Reservoir near Mackay, ID been measured?
Discharge records at USGS site 13127000 begin in 1903, about 123 years, covering roughly 9,200 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.
Is there a flow forecast for Big Lost River below Mackay Reservoir near Mackay, ID?
Yes. Rivermatics trains a machine-learned model — a temporal-fusion transformer — on this basin's observed flows, weather, and snowpack, and issues a daily flow outlook reaching 14 days ahead: a median estimate inside a confidence band, not a single number to bet on. Every forecast is scored against days the model never trained on, and that track record is published on the live gauge screen. Open live conditions to see the current outlook.
Where is Big Lost River below Mackay Reservoir near Mackay, ID?
The gauge sits at 43.93917, -113.64833, in Idaho, in hydrologic subbasin 17040218, draining roughly 801 square miles.
Can I use Big Lost River below Mackay Reservoir near Mackay, ID data for flood or safety decisions?
No. Rivermatics provides estimates, not guarantees, and the readings and forecasts here may be delayed, inaccurate, or wrong. Do not use them for navigation or for any safety, rescue, or emergency decision. Check the National Weather Service and USGS directly, and use your own judgment.

Upstream and downstream on the Big Lost River

Every gauge Rivermatics tracks on this river, ordered by drainage area — upstream first. See the Big Lost River in full.

Other gauges in this subbasin