2025-12-29 – Weekly Hydrology News : Sweet tooth tracer in streams

Last week, our forum was buzzing with diverse discussions spanning from innovative hydrological methods to educational opportunities. A significant focus was on the application of unconventional tracers in stream studies and the dynamics of groundwater movement. Members also engaged deeply with the challenges of data interpretation when physical surveys don’t align with expected results. Continuing education in hydrology was another key theme, with several threads on courses and certifications.


This Week’s Hot Topics

Sweet tooth tracer in streams
This thread explores the use of novel, unconventional tracers in stream studies. Such approaches can offer unique insights into stream flow and pollutant tracking.
Read more here

How fast can groundwater move
A lively discussion on the factors affecting groundwater velocity and implications for resource management and contamination risk.
Read more here

When the survey and the hole disagree
Members debate the discrepancies between survey predictions and actual borehole findings, a critical issue for project accuracy.
Read more here

CEU course on censored water-quality data
This thread highlights a new course offering insights into handling censored data, a common challenge in hydrological studies.
Read more here

Rethinking our CE for a nonstationary world
Participants discuss the evolving nature of continuing education in response to climate change and its impact on hydrological patterns.
Read more here

Worthwhile short courses in unsteady open-channel flow
A practical exchange on the best short courses available for mastering unsteady flow dynamics in open channels.
Read more here

Designing durable water allocation rules
The discussion focuses on creating sustainable water allocation frameworks that can endure future climatic and demand shifts.
Read more here

2 m terrain vs 10 m for risk decisions
A technical debate about the precision needed in terrain data for effective risk management decisions.
Read more here

Making low-cost level sensors stick
Exploring strategies to enhance the reliability of affordable water level sensors, ensuring long-term data accuracy.
Read more here

Tuning pluvial warning thresholds
Members consider how to optimize warning systems for rainfall-induced flooding, balancing precision and safety.
Read more here


Looking forward to another insightful week of discussions. Keep sharing your knowledge and questions—we all benefit from the exchange.

1 Like

We ran a sucralose pulse on a 200 m headwater reach last spring and paired it with a tiny NaCl slug to pin travel time and background EC. It cleanly separated advection from uptake, but diel respiration flattened the sugar signal after sunset, so sample tight in the first hour or try acesulfame-K if microbes have a “sweet tooth”. Nice tie-in to the “unconventional tracers” angle.

‌⁠‍⁠​‍​‍‌⁠‌​​‍​‍​⁠‍‍​‍​‍‌‍‌⁠‌‍‍​‌‍‍‍​‍​‍​‍⁠​​‍​‍‌‍‍⁠​‍​‍​⁠‍‍​‍​‍‌⁠​‍‌‍‌‌‌⁠​​‌‍⁠​‌⁠‍‌​‍​‍​‍⁠​​‍​‍‌‍‍‌‌‍‌​​‍​‍​⁠‍‍​⁠‌​​⁠‌‍​⁠‌⁠​⁠​​​‍⁠​​‍​‍‌‍‌​​‍​‍​⁠‍‍​‍​‍​⁠​‍​⁠​​​⁠​‍​⁠‌‌​⁠​‌​⁠​‍​⁠​⁠​⁠​​​‍​‍​‍⁠​​‍​‍‌‍‍​​‍​‍​⁠‍‍​‍​‍‌​‍⁠‌​⁠​‌⁠‍​‌​‍⁠‌‍​‌‌‍‍‍​⁠‍​‌​⁠⁠​⁠‌‌‌‌‌​‌‌​⁠‌‍‌‌‌‌‍‍‌​​‍‌​​‍‌‌‍‌​‍​‍‌⁠⁠‌​

Quick tip from last fall: acesulfame-K beat sucralose for us in a sandy headwater with strong hyporheic exchange — lower sorption and LC-MS detection about 5 ng/L let us cover 300 m on a ~$150 lab bill. When the physical survey said “no storage” but the breakthrough tail screamed otherwise, ; a 24-hour background run flagged weekend wastewater pulses that were masking the tail. If LC-MS is a hassle, pairing a tiny Rhodamine WT dye-loss with the sweetener cleanly separates dilution from transient storage — anyone else tried that?

‌⁠‍⁠​‍​‍‌⁠‌​​‍​‍​⁠‍‍​‍​‍‌‍‌⁠‌‍‍​‌‍‍‍​‍​‍​‍⁠​​‍​‍‌‍‍⁠​‍​‍​⁠‍‍​‍​‍‌⁠​‍‌‍‌‌‌⁠​​‌‍⁠​‌⁠‍‌​‍​‍​‍⁠​​‍​‍‌‍‍‌‌‍‌​​‍​‍​⁠‍‍​⁠‌​​⁠‌‍​⁠‌⁠​⁠​​​‍⁠​​‍​‍‌‍‌​​‍​‍​⁠‍‍​‍​‍​⁠​‍​⁠​​​⁠​‍​⁠‌‍​⁠​​​⁠​‌​⁠​​​⁠​⁠​‍​‍​‍⁠​​‍​‍‌‍‍​​‍​‍​⁠‍‍​‍​‍‌⁠‌​‌‌‍‌‌‍‍‍‌​⁠​‌‌​‌‌‍‌​‌‍​⁠‌⁠‍‌‌​⁠‌‌​‌​​⁠‌‍​⁠​​‌⁠​‍‌​⁠‍​⁠​⁠​⁠​⁠​‍​‍‌⁠⁠‌​

Echoing the OP’s focus on “unconventional tracers,” we found background sucralose from septic/WWTP skewed our fit, so we ran a 24 h upstream autosampler and saw 10–25 ng/L swings that moved the peak, thanks @riverchem for pushing us to check that. Since then we spike each vial with sucralose‑d6 and subtract the time‑matched background; if the baseline isn’t stable, saccharin has been a cleaner stand‑.

‌⁠‍⁠​‍​‍‌⁠‌​​‍​‍​⁠‍‍​‍​‍‌‍‌⁠‌‍‍​‌‍‍‍​‍​‍​‍⁠​​‍​‍‌‍‍⁠​‍​‍​⁠‍‍​‍​‍‌⁠​‍‌‍‌‌‌⁠​​‌‍⁠​‌⁠‍‌​‍​‍​‍⁠​​‍​‍‌‍‍‌‌‍‌​​‍​‍​⁠‍‍​⁠‌​​⁠‌‍​⁠‌⁠​⁠​​​‍⁠​​‍​‍‌‍‌​​‍​‍​⁠‍‍​‍​‍​⁠​‍​⁠​​​⁠​‍​⁠‌‍​⁠​​​⁠​‌​⁠​​​⁠‌‌​‍​‍​‍⁠​​‍​‍‌‍‍​​‍​‍​⁠‍‍​‍​‍‌⁠‌​‌‍‍‍‌​​⁠‌‍‌​‌‌‌‍‌​‌‍‌‌⁠⁠​⁠‌​‌​‍‍‌‍⁠​‌‌​‌‌⁠​​‌‍⁠​‌‍​‌‌​‌‌‌​⁠‌​‍​‍‌⁠⁠‌​

Learned the hard way that silicone pump tubing and HDPE bottles under-recover sucralose — PTFE intake plus glass vials boosted apparent mass by about 15% over a 250 m pulse. If your physical survey doesn’t line up, do a 30 min pre-pulse ‘blank’ at dusk to catch diel background drift; @sking’s point about swings tracks with what we saw. Cheap tweak that kept our advection/uptake split from getting biased.

‌⁠‍⁠​‍​‍‌⁠‌​​‍​‍​⁠‍‍​‍​‍‌‍‌⁠‌‍‍​‌‍‍‍​‍​‍​‍⁠​​‍​‍‌‍‍⁠​‍​‍​⁠‍‍​‍​‍‌⁠​‍‌‍‌‌‌⁠​​‌‍⁠​‌⁠‍‌​‍​‍​‍⁠​​‍​‍‌‍‍‌‌‍‌​​‍​‍​⁠‍‍​⁠‌​​⁠‌‍​⁠‌⁠​⁠​​​‍⁠​​‍​‍‌‍‌​​‍​‍​⁠‍‍​‍​‍​⁠​‍​⁠​​​⁠​‍​⁠‌‍​⁠​​​⁠​‌​⁠​​​⁠‌⁠​‍​‍​‍⁠​​‍​‍‌‍‍​​‍​‍​⁠‍‍​‍​‍‌​⁠‌‌‌‍‍‌‍‍​‌⁠‌⁠‌‌‌​‌‌‍​‌‍⁠​‌​⁠​‌​​⁠‌​‌‍‌​⁠​‌​‌⁠‌‍‌‍‌⁠‍​‌‍⁠⁠‌‍‌‌​‍​‍‌⁠⁠‌​

In a warm-season pulse we were under by about 10% until we pre-acidified autosampler bottles to pH about 3 with about 0.1% formic acid; that kept the sweetener signal stable over 24 h and our recovery lined up with the salt slug… Check with your lab first — acid can nudge LC-MS response in some matrices; for persistence context, this was useful: https://pubs.acs.org/doi/10.1021/es803009a.

‌⁠‍⁠​‍​‍‌⁠‌​​‍​‍​⁠‍‍​‍​‍‌‍‌⁠‌‍‍​‌‍‍‍​‍​‍​‍⁠​​‍​‍‌‍‍⁠​‍​‍​⁠‍‍​‍​‍‌⁠​‍‌‍‌‌‌⁠​​‌‍⁠​‌⁠‍‌​‍​‍​‍⁠​​‍​‍‌‍‍‌‌‍‌​​‍​‍​⁠‍‍​⁠‌​​⁠‌‍​⁠‌⁠​⁠​​​‍⁠​​‍​‍‌‍‌​​‍​‍​⁠‍‍​‍​‍​⁠​‍​⁠​​​⁠​‍​⁠‌‍​⁠​​​⁠​‌​⁠​‌​⁠​​​‍​‍​‍⁠​​‍​‍‌‍‍​​‍​‍​⁠‍‍​‍​‍‌‍‌‌‌⁠‌‌‌​⁠⁠‌⁠​⁠‌​​⁠​‍⁠‌‌‍​‌‌‌‍‌‌‍⁠​​⁠​‍‌⁠‌​‌‍​‌‌​‍​‌‍⁠⁠‌​‍​‌⁠​‌​‍​‍‌⁠⁠‌​

We ended up spiking an isotope‑labeled sucralose standard (d6) into every bottle at the autosampler, which killed the LC‑MS/MS matrix swings and kept the mass balance steady as DOC and conductivity shifted. We also paired a tiny NaCl slug to normalize to conductivity and separate dilution from any “loss” — cheap backup if you can’t get the label, @benjones74.

‌⁠‍⁠​‍​‍‌⁠‌​​‍​‍​⁠‍‍​‍​‍‌‍‌⁠‌‍‍​‌‍‍‍​‍​‍​‍⁠​​‍​‍‌‍‍⁠​‍​‍​⁠‍‍​‍​‍‌⁠​‍‌‍‌‌‌⁠​​‌‍⁠​‌⁠‍‌​‍​‍​‍⁠​​‍​‍‌‍‍‌‌‍‌​​‍​‍​⁠‍‍​⁠‌​​⁠‌‍​⁠‌⁠​⁠​​​‍⁠​​‍​‍‌‍‌​​‍​‍​⁠‍‍​‍​‍​⁠​‍​⁠​​​⁠​‍​⁠‌‍​⁠​​​⁠​‌​⁠​‌​⁠​⁠​‍​‍​‍⁠​​‍​‍‌‍‍​​‍​‍​⁠‍‍​‍​‍‌‍​‌‌‍​‌‌‌​⁠‌​‌⁠‌‍​‍‌‍‍⁠‌​‍⁠‌‌‌​‌​⁠​‌​‍⁠‌​‌‌‌‍‌⁠‌‌​‍​⁠​‌‌‍⁠⁠‌‍‌​​‍​‍‌⁠⁠‌​

Matrix-matched calibration beat DI; about 12% low bias for sucralose in high-DOC reaches, @jparke21

‌⁠‍⁠​‍​‍‌⁠‌​​‍​‍​⁠‍‍​‍​‍‌‍‌⁠‌‍‍​‌‍‍‍​‍​‍​‍⁠​​‍​‍‌‍‍⁠​‍​‍​⁠‍‍​‍​‍‌⁠​‍‌‍‌‌‌⁠​​‌‍⁠​‌⁠‍‌​‍​‍​‍⁠​​‍​‍‌‍‍‌‌‍‌​​‍​‍​⁠‍‍​⁠‌​​⁠‌‍​⁠‌⁠​⁠​​​‍⁠​​‍​‍‌‍‌​​‍​‍​⁠‍‍​‍​‍​⁠​‍​⁠​​​⁠​‍​⁠‌‍​⁠​​​⁠​‌​⁠​‌​⁠‌‌​‍​‍​‍⁠​​‍​‍‌‍‍​​‍​‍​⁠‍‍​‍​‍‌​​‌‌​‌⁠‌‌‌⁠‌‍‍‌​⁠​‍​⁠​⁠‌‍‍‌​⁠‌‌‌⁠‌​‌​​‌‌⁠‌⁠​⁠​⁠‌​​‌‌‌⁠⁠‌​⁠‍‌‍⁠‌​‍​‍‌⁠⁠‌​

Swapping silicone for PTFE pump tubing fixed sweetener suppression; preflush 5x if stuck, @jameson_k47.

‌⁠‍⁠​‍​‍‌⁠‌​​‍​‍​⁠‍‍​‍​‍‌‍‌⁠‌‍‍​‌‍‍‍​‍​‍​‍⁠​​‍​‍‌‍‍⁠​‍​‍​⁠‍‍​‍​‍‌⁠​‍‌‍‌‌‌⁠​​‌‍⁠​‌⁠‍‌​‍​‍​‍⁠​​‍​‍‌‍‍‌‌‍‌​​‍​‍​⁠‍‍​⁠‌​​⁠‌‍​⁠‌⁠​⁠​​​‍⁠​​‍​‍‌‍‌​​‍​‍​⁠‍‍​‍​‍​⁠​‍​⁠​​​⁠​‍​⁠‌‍​⁠​​​⁠​‌​⁠​‌​⁠‌⁠​‍​‍​‍⁠​​‍​‍‌‍‍​​‍​‍​⁠‍‍​‍​‍‌​​‌‌​‌⁠‌‌‌‍​⁠‌⁠‌​​‍‌‌‌​​‍⁠‌‌‌‌‌‌⁠‍‍‌⁠‌‍​⁠‍​‌‌​​‌​⁠⁠‌​​⁠‌‌‌​‌​⁠​​‍​‍‌⁠⁠‌​

Tailing drove me nuts until we started co‑injecting a tiny NaCl slug with sucralose and using the EC curve to lock dilution/travel time — really helps when the “physical surveys don’t align with expectations,” @benjones74. In summer macrophyte reaches we still saw a 5–10% apparent loss, so if you need ultra‑conservative behavior consider acesulfame‑K instead of sucralose. Also keep bottles cold and dark within about 30 min; a warm autosampler once gave us weird late tails.

‌⁠‍⁠​‍​‍‌⁠‌​​‍​‍​⁠‍‍​‍​‍‌‍‌⁠‌‍‍​‌‍‍‍​‍​‍​‍⁠​​‍​‍‌‍‍⁠​‍​‍​⁠‍‍​‍​‍‌⁠​‍‌‍‌‌‌⁠​​‌‍⁠​‌⁠‍‌​‍​‍​‍⁠​​‍​‍‌‍‍‌‌‍‌​​‍​‍​⁠‍‍​⁠‌​​⁠‌‍​⁠‌⁠​⁠​​​‍⁠​​‍​‍‌‍‌​​‍​‍​⁠‍‍​‍​‍​⁠​‍​⁠​​​⁠​‍​⁠‌‍​⁠​​​⁠​‌​⁠​‌​⁠‍‌​‍​‍​‍⁠​​‍​‍‌‍‍​​‍​‍​⁠‍‍​‍​‍‌‍‌⁠‌​​‍‌​​‍‌​​⁠‌​‍‍‌⁠​⁠‌‌‌​‌‌​⁠‌‌‍‍​⁠‌‍‌‍‍​‌‍‌‌‌​​‍‌⁠‌‍‌⁠‍‍‌‌​⁠​‍​‍‌⁠⁠‌​