COLLABORATORS

Recent Results

Recent research results from SAHRA's interdisciplinary research teams working at new state-of-the-art ecoyhdrological research facilities in northern New Mexico include:

Vegetation controls on Snow Accumulation and Melt

This tree spacing balances the effects of vegetation shading, which reduces sublimation (the transition of snow and ice directly to water vapor), and the interception of snow by the tree canopy, which increases sublimation. Shaded areas with increased snowpack also have greater infiltration and potentially more groundwater recharge; however, this may be balanced in part by the greater root density found in these areas. Results of models simulating these processes find that a canopy cover of about 60 percent results in the greatest snow accumulation.

Modeling of seasonal snowpack using forest density, solar radiation, and measured snow accumulation suggests that moderate tree densities limit sublimation and increase net water input.

Soil Moisture Field Campaign

During the summer of 2005 SAHRA researchers and students, primarily from NMT, undertook a coordinated field campaign to examine the spatial variability of soil moisture. At each location three sites spanning a transition from forest to open grassland to wetland were measured for soil moisture content. The first half of the field campaign featured several precipitation events, resulting in increased soil moisture. The second half of the campaign was largely dry and resulted in decreasing soil moisture at most site.

(L-R) Luis Mendez, Rob Wyckoff (NMT), Bart Forman (UCLA), Gautam Bisht (MIT), Alex Rinehart (NMT)

Transpiration above the Mountain Front

SAHRA researchers are investigating the hypothesis that tree transpiration is an important component of the water balance in snow-dominated, sub-alpine terrain even during winter. Specific objectives include characterizing tree transpiration at the mixed conifer and pine sites (DRI) through replicated sap flow measurements and linking these transpiration measurements to environmental conditions (e.g., meteorology, snow cover & depth, soil moisture & temperature (UC-Merced, UA, CU, NCAR). This understanding will then be used to up scale tree measurements using flux tower measurements, ultimately linking to modeling efforts.

SAHRA researchers have installed 2 sap flow sensors in each of 8 trees at the mixed conifer & pine sites.

Soil water variability in the forest

Measurements to understand the controls on soil moisture variability must account for spatial variability in both horizontal and vertical directions as well as temporal variability cover both wet and dry conditions. To examine horizontal variability sites are divided into open areas, canopy areas and edge locations at the boundary between the two. Vertical variability is examined using soil profiles measure soil texture, hydraulic properties as well as root patterns, both density (g root / kg soil) and count (number / area)

TDR probe to measure vertical variability in soil moisture

Digging a soil pit

A typical soil pit after profiling and sampling for soil hydraulic properties and root density

Rainfall-Runoff Modeling

SAHRA researchers are investigating how vegetation and other land surface characteristics influence rainfall-runoff relationships. Modeling is focusing on the Jemez River as well as the neighboring Rio Puerco. Terrain characteristics are similar, however there are distinct differences in vegetation and soil properties as well as hydrologic response. Modeling efforts are also looking at nested catchments within the Jemez River to examine how store response changes with basin scale.
©2006. SAHRA - NSF Science and Technology Center