Kevin A. Dressler

A Comparison of Snow Telemetry and Snow Course Measurements in the Colorado River Basin

Temporal and spatial differences in snow-water equivalent (SWE) at 240 snow telemetry (SNOTEL) and at 500 snow course sites and a subset of 93 collocated sites were evaluated by examining the correlation of site values over the snow season, interpolating point measurements to basin volumes using hypsometry and a maximum snow extent mask, and variogram analysis. The lowest correlation at a point (r 0.79) and largest interpolated volume differences (as much as 150 mm of SWE over the Gunnison basin) occurred during wet years (e.g., 1993). Interpolation SWE values based on SNOTEL versus snow course sites were not consistently higher or lower relative to each other. Interpolation rmse was comparable for both datasets, increasing later in the snow season. Snow courses correlate over larger distances and have less short-scale variability than SNOTEL sites, making them more regionally representative. Using both datasets in hydrologic models will provide a range of predicted streamflow, which is potentially useful for water resources management.

A Synthesis of Community Data and Modeling for Advancing River Basin Science: The Evolving Susquehanna River Basin Experiment

Our WATERS test-bed project seeks to link our Penn State Integrated Hydrologic Model (PIHM) development efforts and our Real-Time Hydrologic Monitoring Network (RTH_Net, http://www.engr.psu.edu/rth_net) initiative to begin to resolve how predictive and experimental hydrologic science can be combined to characterize the “active zone”. This effort represents the first phase of a long-term adaptive observation and characterization strategy for the Penn State Experimental Forest. We define the term “active zone” as the local watershed control volume divided into three partitions: (1) the atmosphere from land surface to the atmospheric boundary layer, (2) a transition sub-volume that includes the land-surface and near surface processes (canopy, root system, snow, frost, etc.) and (3) the regolith from land surface to the depth of the subsurface boundary layer (SBL). By analogy with the atmosphere, we are proposing the SBL represents an “effective depth” which also feels the direct influence of the overlying surface fluxes and energy fluxes, and operates at time scales significant to the water cycle and climate over the watershed domain. Our proposed concept of the SBL will be an active topic of research in our WATERS project.

Comparing AVHRR and hydrologically modelled discontinuous alpine snow-covered area estimates

Snowcover and snowpack information are used extensively by water resources managers to estimate peak streamflows and seasonal runoff volumes. In the southwestern US, the NASA EOS Southwestern Regional Earth Science Applications Center is providing these data to users, such as the Salt River Project, to improve hydrologic predictions. Snowpack water volumes are derived from the combination of snow covered area estimates and snow water equivalent estimates. NOAA Advanced Very High Resolution Radiometer imagery are used to generate a daily fractional SCA product on a 1 km grid. These data are compared to modelled SCA generated from the USGS Precipitation Runoff Modelling System. The meteorological data driving the PRMS model are sparse across the study area (White River Basin in Arizona). Overall, the PRMS-modelled SCA is greater than AVHRR-derived SCA at higher elevations and lesser at lower elevations, predicting too much snowmelt streamflow too early in the winter season.