RIVER GAUGES
Real-time streamflow data is readily available online and through the use of mobile apps:
National Weather Service (NWS) River Observations and Forecasts (Iowa)
Iowa Flood Center (Iowa Flood Information System or IFIS) (IFIS Gauges also appear on the NWS Website)
RiverApp (One of several available Apple and Android Apps.)
The NWS and USGS pages display stream status (high, low, flood, etc.) as colored, clickable icons. Those can be useful for a quick assessment, but for more detail you'll want to click on each gauge of interest. Guidance on interpretation is provided below.
Terms to Know:
Gauge Height (a.k.a. Stage) as provided by the NWS, USGS and USACE indicates the measurement of the water surface above a locally established reference point (e.g. the top of a bridge pier footing), NOT the stream depth as is often assumed. IFIS Gauges report the water surface elevation above sea level, from which stream depth at the gauge can be determined.*
Discharge (a.k.a. Flow or Streamflow), in cubic feet per second (cfs) is a calculated value that that can be useful when comparing values to other streams, but it isn't available at all gauge sites. The calculation involves measurements of stream velocity and of the cross-sectional area of the stream (see How Streamflow is Measured for an explanation).
(You may find that the USGS doesn't publish discharge data in winter, while it may be available on the NWS and USACE pages.)
Before you read on:
It's important to remember that there can be hazards on the river even at normal and low flows. Most are easily avoided by skilled boaters, but river reading and boat handing skills become increasingly important as streamflow increases, and rescues and recoveries become increasingly difficult with increased velocity and depth.
Read more about Flows and Float Times here.
Know the flow before you go, and if you're unsure, it might be wise to postpone your trip!
Keep Notes!
By noting the relevant gauge reading(s) after each trip, paddlers establish a range of stream levels that suit their personal preferences. Lacking that knowledge, or specific guidance from trusted sources (e.g. Paddling Iowa), they might choose to avoid anything above or below normal, depending on their skill level, that of their paddling partner(s), current conditions, etc. (Read on to get a sense of what might be "normal.")
Digging Deeper:
There's a wealth of information available within these online resources. For example, on many of the USGS "Legacy" Pages (such as the South Skunk above Ames) you'll see a table comparing the current discharge (the Most Recent Instantaneous Value) with historical data for that gauge and day of the year. Here's a table clipped from the South Skunk above Ames Gauge some years ago.
This table indicates that the median value over 80 years of records is 209 cfs, and that happens to be a really nice level for most paddlers. At the 25th percentile value of 81 cfs one would want to have the skills to stay in deep water - and be willing to walk a few of the riffles. The mean value for July 23rd was 535 cfs, and 75% of all daily mean values were under 499 cfs.
For the South Skunk above Ames, those historical numbers represent a range of what one might consider to be normal, and persons lacking the skills or ability to safely navigate around obstacles (e.g. strainers and sweepers) should use caution at higher than normal levels.
Realize that these historical numbers will vary with the seasons, so once you've found the table of your gauge of interest, click on "more" to open a table of Mean of Daily Mean Values for the entire year.** For the South Skunk above Ames the historical data indicates that mean flows are highest during the month of June (typical for Iowa), and one could assume that those numbers are also normal for that part of the Skunk.
* The IFIS gauges report the water surface elevation above sea level along with the elevation of the gauge sensor, so you can determine (or select to display) actual stream depth at the gauge site. IFIS Gauges don't include discharge data but are often useful when there are no USGS, NWS or USACE Gauges nearby.
**A Mean of Daily Mean Values table can also be created (and customized) from a drop-down box on the Legacy Page. Select "Available Data For This Site" and then "Time-Series: Daily statistics."