Headwater streams play a crucial role in arid and semiarid regions. They provide freshwater to adjacent lowlands and temporarily store water as snowpack and groundwater. Downstream users – both humans specifically and ecosystems more broadly – depend on the delayed release, particularly during dry seasons. Headwater streams are highly vulnerable to climate change through shifts in snowmelt dynamics, changes in precipitation patterns, evapotranspiration, and wildfire prevalence, among other factors. Monitoring headwater streams in dryland areas over time is therefore of critical importance.

Each year, graduate students enrolled in the Water Resources Program at the University of New Mexico monitor hydrological, chemical, and biological characteristics of two headwater streams in central New Mexico as part of a field methods class. This dataset contains measurements from the 2022 field campaign. At each stream site, measurements were repeated for two or three separate transects.

Las Huertas Creek (LH), the first monitoring site, is the only perennial stream in the Sandia Mountains along spring-fed reaches. The stream drains north from the northeastern slope of the Sandias towards the town of Placitas, running through a narrow and heavily forested canyon. Three transects range in elevation from 2190 m – 2320 m above sea level and were sampled on October 1, 2022. The second monitoring site is on the East Fork of the Jemez River (JR) within the Valles Caldera National Preserve. The primarily spring-fed stream runs through the montane grasslands of the caldera, a 20 km circular depression formed by a large volcanic eruption and subsequent land subsidence approximately 1.2 million years ago. Three transects are located at an elevation of approximately 2560 m above sea level and were sampled on October 22, 2022.

Discharge and Sediment

Discharge at each transect was estimated using two methods: (1) the velocity-area method, with velocity measured using a Marsh-McBirney Flo-Mate Model 2000 flow meter, and (2) the salt dilution (or slug injection) method after Hudson and Fraser (2005). Electrical conductivity (EC) for the salt dilution method was monitored in 10-second increments using a YSI Professional Plus multiparameter meter. Particle size distribution of the channel bed surface was characterized based on the pebble count method (Wolman, 1954) by randomly selecting 100 pebbles along a zig-zag pattern (Bevenger and King, 1995) and measuring them with a gravelometer.

Water Chemistry

The following water chemistry parameters were measured at three points (right bank, center, left bank) along a transect: water temperature (°C), specific conductivity (µS/cm at 25 degrees C), conductivity (µS/cm), (dissolved oxygen (% saturation and mg/L) and pH. The parameters were measured with a YSI Professional Plus multiparameter meter. Data are averaged across the three points. Turbidity (NTU) was also measured at three locations per transect using a LaMotte 2020e portable turbidimeter and averaged.

Water samples were taken to measure alkalinity in a lab environment; one liter of unfiltered water was collected at two locations per transect and placed in a HPDE collection bottle, which was stored under refrigeration until lab testing. Alkalinity was determined by using endpoint titration; the titrant was 0.02 N sulfuric acid, while indicator solutions used were phenolphthalein (for carbonate) and bromocresol green (for bicarbonate). Reported alkalinity data represent the average of two samples for each transect. 

Additional water samples were collected to test the anion and cation concentrations in a lab environment. One anion and one cation sample were collected near the right bank and near the left bank at the transect. Approximately 50 mL of water was collected, filtered through a 0.45 µm glass fiber filter, and stored in a 50 mL centrifuge tube. A few drops of diluted nitric acid were added to only the cation samples, while nothing was added to the anion samples. All samples were stored under refrigeration until lab analysis. Cation concentrations were analyzed using inductively coupled plasma-optical emission spectroscopy (ICP-OES) with a Perkin Elmer Optima 5300DV instrument. Anion concentrations were analyzed using ion chromatography (IC) with a Dionex 1100 IC instrument. Cation and anion data represent the average of two samples for each transect.

Organic Matter and Benthic Macroinvertebrates

Organic matter was qualitatively sampled from three points (right bank, center, left bank) at each transect.  Substrate was collected with a trowel while samples from the water column were collected in one liter Nalgene bottles.  In the lab, water and substrate samples were processed for Ash Free Dry Mass (AFDM) (Steinman et al., 2017). The water samples were filtered through a 1.5 µm glass fiber filter. The filters and substrate samples were dried for 24 hours at 60°C, weighed, ashed at 500°C for 2 hours in a muffle furnace, and reweighed. The difference in weights was calculated as the % organic matter as AFDM. Reported AFDM data represent the average of three samples for each transect. 

Aquatic macroinvertebrates were collected from a known area (measured in m²) at each transect using a D-frame net. Samples were preserved in 70% ethanol and stored in Whirlpak bags.  In the lab, invertebrates were separated from organic/inorganic matter using forceps and a dissecting microscope, enumerated, and identified to Order (in most cases), using taxonomic references including Voshell (2002). Macroinvertebrate densities were calculated from raw counts as individuals/m².

References

Bevenger, G.S. and R.M. King, 1995. A pebble count procedure for assessing watershed cumulative effects (Vol. 319). US Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO.

Harrelson, C.C; Rawlins, C.L., and Potyondy, J.P., 1994. Stream channel reference sites: an illustrated guide to field technique. Gen. Tech. Rep. RM-245. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 61 pp.

Hudson, R. and Fraser, J., 2005. The mass balance (or dry injection) method. Streamline Watershed Management Bulletin, 9(1), pp.6-12.

Steinman, A.D., Lamberti, G.A., Leavitt, P.R., and Uzarski, D.G., 2017. Biomass and pigments of benthic algae, pp. 223-241 in (Hauer, F.R. and G.A. Lamberti eds) Methods in Stream Ecology: Vol. 1 Ecosystem Structure, Third Edition. Academic Press, Cambridge, MA.

Voshell, J.R., 2002. A Guide to Common Freshwater Invertebrates of North America. University of Nebraska Press, Lincoln, NE. 422 pp.

Wolman, M.G., 1954. A method of sampling coarse river‐bed material. EOS, Transactions American Geophysical Union, 35(6), pp. 951-956.