USE OF CONTINUOUS WATER QUALITY SENSORS TO EXAMINE HEADWATER RESPONSE TO SNOWMELT: VALLES CALDERA, JEMEZ MOUNTAINS, NM

Many hydrological factors contribute to changes in stream water quality, including variations in annual snowpack, monsoonal precipitation, forest fires, and forest management practice. In this study, we examine two years (2018-2019) of water quality time-series data from streams located in the Valles Caldera National Preserve, Jemez mountains, New Mexico. These two years represent significant differences in snowpack in an area recently affected by fire and forest treatment. SNOTEL data show that 2018 was well below average, and 2019 well above average. This study is part of a long-term monitoring effort to gain a better understanding of the hydrological factors of the Jemez river, an alpine snowmelt-dominated system. Previous work has shown that biological activity in the form of primary production in stream reaches on the valley floor is dominated by submerged aquatic macrophytes.

Measurements of temperature, dissolved oxygen (DO), pH, and turbidity were taken using Yellow Springs Instruments model 6920 V2 sondes. We report on two consecutive years at 15 minute intervals between May and October in 2018 and 2019. Reference stream discharge data are from the USGS Jemez River gauge and SNOTEL data are from the Quemazon site. Data analysis was performed using the AQUARIOUS (Aquatic Informatics) data platform.

In 2018, a year with minimal snowpack, dissolved oxygen levels were consistently high throughout the year, with strong DO amplitude driven by photosynthesis/respiration. Increases in snowmelt for 2019 increased turbidity to maximum measurable levels (1200 NTU) during the snowmelt pulse, with evidence from multiple sondes. The dissolved oxygen levels from the sites were considerably lower than 2018. The pH values from the sites ranged between 7-8. The temperatures were consistent at 5-19°C.

The strong snowmelt-runoff in spring 2019 resulted in high turbidity, suppressing in-stream photosynthetic productivity as evidenced by high turbidity, relatively low and constant dissolved oxygen, and attenuated diurnal pH variations relative to conditions in 2018, where strong diurnal variations are noted. Further observations will allow comparisons of discrete flow events following the snowmelt pulse.