Overview:

The Valles Caldera, a volcanic collapse feature located in the Jemez Mountains in northern New Mexico, is a large (19-24 km) circular depression with many internal domes. These domes create a diverse topography from lower elevation meadows, or "Valles", to densly forested domes, whose summits are sometimes more than 1,000 m above the surrounding caldera floor. The largest of these, the central resurgent dome called Redondo Peak (3,432 m), is the focus area for much of our research. In particular, we are interested in studying the affect that aspect (slope direction) has on the hydrologic response of a series of headwater streams that emerge near the top of Redondo Peak. The streams vary in both physical size and extent, ranging from the small 3.7 km² La Jara Creek catchment on the east side of Redondo Peak, to the larger 13.4 km² Redondo Creek valley on the west side of the mountain. Vegetation in the Valles Caldera consists of meadow and Ponderosa Pine at the lower elevations and Mixed Conifer and Aspen at the higher elevations. The climate is temperate and montaine, with slightly over half of the annual 476 mm falling as snow during the winter months, with the remainder falling as rain primarily during summer thunderstorms.

Hypothesis and Research Questions:

Because there are streams that drain every major aspect of Redondo Peak (along with the relatively homogenous climate and internal geology), we have a unique opportunity to determine how aspect affects soil formation and hydrological processes. These different aspects receive, on average, different amounts of solar energy, which might considerably influence hydrologic variables such as groundwater recharge, snow sublimation, timing of snowmelt, evaporation, and transpiration. Therefore, aspect might be a useful metric for categorizing different hydrological properties and processes.

Site Map and Instruments:

Hydrological research at Redondo Peak relies on the monitoring of physical (i.e., amount, intensity, timing) and chemical (i.e., biogeochemical, cations/anions, isotopic) signals present in both hydrologic inputs and outputs.

• We have installed temperature/light sensors (Onset HOBO Pendant) to monitor the hydrologic state both in terms of streamflow and snow cover around Redondo Peak. These gauges will help us determine recession of the water table in the entire dome of Redondo Peak.
• There are two snowmelt lycemeters to determine the timing, intensity, and stable isotopic signature of the snowmelt input into the hydrologic system.
• There are pressure transducers in free bodies of water so that we can monitor when the system is in a 'wet' state vs. a 'dry' state.
• In addition to the equipment shown, there is also extensive manual and automatic sampling of the chemical and isotopic signatures of stream waters across the site. This sampling is used for a number of purposes including determining water source, deducing its residence time (that is, how long it remains in the system) and tracing flowpaths.