Ron Loehman, Conservation Chairman
Water temperature critically affects the suitability of a given stream for health and survival of trout. Even if a stream has clean water, lots of food, and structure where fish can hide, it still cannot support trout if the water temperature is above about 72°F for large parts of the year. Coldwater streams in New Mexico (and everywhere else) are under stress from drought and long-term climate warming, which puts at risk their future as habitat for coldwater fish. Monitoring is an essential part of any restoration or management action. Availability of stream temperature profiles over multiple years can quantify long-term warming trends, as well as seasonal temperature spikes that may affect trout survivability. Temperature data also will allow a more scientific approach to any restoration or remediation efforts that might be taken.
Before he left in 2019, the Santa Fe National Forest (SFNF) fisheries biologist placed about 15 temperature loggers in streams on the west side of the Jemez. Those loggers have sealed bodies with non-replaceable, limited-life batteries that require a special device to read them. The batteries in some of them are near the ends of their lives, or possibly dead already. New Mexico Trout volunteers have been collaborating with SFNF personnel to recover the old loggers and replace them an upgraded version (Onset Corp, Pendant MX2201) that we purchased. Those loggers have replaceable batteries and can be read with a Smartphone app via a Bluetooth connection.
To be useful, the temperature data need to answer questions that can lead to an action, so their placement in streams must be carefully considered. One example of such a question is, “How has a particular restoration treatment affected stream temperature?”. Beaver Dam Analogs (BDAs or artificial beaver dams) are one such restoration treatment that we have helped implement in Jemez streams. These BDAs reduce stream velocity, trap sediment, raise the water table, and create marshy meadows that promote willow growth. One question is whether the water temperature is increased or lowered by the BDA. The shallow, turbid water ponded behind a BDA could be an effective solar collector, which should raise downstream water temperature. On the other hand, the raised water table might allow better connection and exchange with the approximately 50°F aquifer that parallels and underlies our Jemez streams. The enhanced willow growth behind BDAs will at least partly shade the water from direct sun.
So, which is it, increasing or decreasing stream temperature? Last month NM Trout volunteers replaced failing temperature loggers above and below BDAs on the Rio Cebolla south of where the creek flows under FR 376. We also replaced loggers on the Rio San Antonio in the segment from just above the San Antonio hot spring north to the Valles Caldera boundary. That reach of the San Antonio contains more than a dozen BDAs. Comparison of temperatures over time on the two stream segments will show the effect, if any, of BDAs on two streams with different hydrogeomorphologies (I like that word!).
There are lots of other questions that temperature monitoring could answer. Some examples are: Is my favorite stream getting too hot in summer for trout survival? Has extensive cattle grazing along a particular stream segment raised water temperatures to dangerous levels for aquatic organisms? (Actual data in such cases will carry weight with the USFS if we plan to object to the action.). Has some change in management practice raised water temperature unacceptably? (In this case we will need to have temperature loggers in affected locations to record baseline data before the given action occurs.)
By the time you read this we will have replaced all of the loggers previously set out by the USFS. New Mexico Trout has purchased additional loggers that we can place in locations important to our interests that have not been instrumented by the USFS. Examples are above and below other beaver ponds or BDAs; sites on the Rio Guadalupe (the FS has none there and no plans to install any); comparing paired stream reaches that have extensive cattle impacts with those free from grazing.
We are soliciting proposals from members that can answer a scientific question or (and) that can lead to some restoration action. We also want to hear from members who want to be involved as idea generators, installers, or as an adopter of a particular logger (by agreeing to upload its data at least twice a year). With sufficient interest, we will hold a half-day workshop on installation and use of these instruments on an easily accessible part of the Rio Guadalupe. The following are some important sources for background and more detail.
- Stream Temperature Monitoring; A Trout Unlimited guide for volunteers: https://www.tu.org/wp-content/uploads/2019/05/Water-Temperature-Monitoring-v3-5Sept2018.pdf
- Monitoring stream temperatures—A guide for non-specialists; USGS comprehensive guide, lots of detail; https://pubs.er.usgs.gov/publication/tm3A25
- Data Logger Basics, a general introduction from the manufacturer of the MX 2201 logger that we are using; https://www.onsetcomp.com/files/data-logger-basics.pdf
If you want to be part of this project, send a message by email to firstname.lastname@example.org