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Robin  Glas

Robin Glas

PhD Student Earth Sciences

304 Heroy GL

Robin's CV

PhD Student Earth Sciences

Advisor: Laura Lautz

Robin Glass

My research serves to answer questions surrounding climate change and the hydrologic cycle, integrating the fields of hydrology, hydrogeology, and geophysics. Specifically, I am interested in groundwater as a buffer for changing meteorological patterns, as evidenced by both geophysical and more traditional hydrologic data. I use spatial and time series analysis to shed light on preferential flow of water through the subsurface that is contributing to water availability for downstream communities. International and interdisciplinary collaboration play an important role in my work in order to contribute globally to questions of shifting water resources.

Proglacial aquifer structure in the Cordillera Blanca, Peru

Inverted resistivity model

Geological and depositional conditions of the glaciated Cordillera Blanca in Peru have given way to proglacial aquifer systems that contribute substantially to regional streams and rivers, particularly during the dry season.  As glacial retreat accelerates, the dry season water budget will be increasingly dominated by groundwater inputs, although predictions of future groundwater quantities require estimations of groundwater storage capacity, aquifer extents, and groundwater residence time.  We present a characterization of the sediment structure in a prototypical proglacial valley in the central portion of the range, the Quilcayhuanca Valley.  Northern and Central valleys of the Cordillera Blanca feature ubiquitous talus deposits that line the steep granite walls, and have become partially buried beneath lacustrine sediments deposited in proglacial lake beds.  The portion of the talus still exposed near the valley walls provides recharge to deeper portions of the valley aquifers that underlie lacustrine clay, resulting in a confined aquifer system that is connected to the surface via perennial springs.  Seismic refraction surveys reveal an interface separating relatively slow (~400-800 m/s) and fast (~ 2500 m/s) p-wave velocities. The depth of this refractor coincides with the depth to buried talus observed in drilling records.  Electrical resistivity tomography profiles of the same transect show depths near the buried talus to be relatively conductive (10-100 Ωm).  At these depths, we hypothesize that electrical conductance is elevated by saturated clay particles in the sediment matrix of the talus deposit.  The resistivity models all show a more resistive (~700 Ω m) region at depth, likely corresponding to a more hydraulically conductive material. The resistive zone is interpreted to be a deeper portion of a buried talus deposit that did not accumulate clay in the matrix.  Other possibilities include a thick deposit of gravelly glacial outwash, or a relatively clay-poor glacial till. We present a groundwater modeling framework to resolve the nature of the sediments in deeper layers, where geophysical data become less certain.  Sediment permeability estimates will allow for more refined predictions of groundwater storage volume in buried talus aquifers, which are likely prevalent throughout the range.

Changing streamflow regimes in New York State:  trends, change points, and attribution

Results from hierarchal clustering analysis for seasonal average streamflow from 1975-2016. Clustering provides insight into spatial correlation, and crosses subregion basin divides, indicating climatic controls on spatial clustering.

Results from hierarchal clustering analysis for seasonal average streamflow from 1975-2016.  Clustering provides insight into spatial correlation, and crosses subregion basin divides, indicating climatic controls on spatial clustering.

New York (NY) is among the first states in the US to sign a law, the Community Risk and Resiliency Act, aimed at requiring state agencies to consider climate change-associated risks and extreme weather events in regulatory decision-making. Hydrologic risks, including increased flooding, storm surges, and sea level rise, must be considered when designing infrastructure, such as bridges, highways, and culverts. An in-depth evaluation of hydrologic trends in NY can assist planning efforts associated with implementation of this law. Spatial and temporal patterns in streamflow magnitude, flood frequency, and timing were examined for 100 USGS stream gages in NY and adjacent areas from 1961 to 2015.  Stream gages were clustered hierarchically based on similarities in inter-annual trends in mean seasonal streamflow.  Clusters and spatial correlations vary seasonally, with the fewest spatial clusters occurring during spring and winter.  Trend and change point analyses were performed on a suite of flow statistics including low, median, and high flow regime magnitudes, monthly mean discharge, peak flow frequency, and spring snowmelt timing.  Increasing step changes in most variables occurred in the early 1970s, coincident with the end of a millennial drought. After 1975, low and median flow regimes show increasing trends in magnitude throughout the state, while the highest annual flow magnitudes remain relatively unchanged.  Throughout NY and surrounding areas, flow magnitudes are increasing significantly in the month of January, consistent with increasing rain-on-snow events. For all spatial clusters, the timing of floods are transitioning away from spring and towards a more even distribution throughout the rest of the year. This could be due to a diminished influence of spring snowmelt on the annual hydrologic regime, along with increased precipitation events during other seasons. The trends in magnitude, timing, and frequency of high flows in NY are weakly correlated with increasing precipitation and temperature, and future analyses will explore the connections of flow patterns with large-scale climatic oscillations and land use changes. These results will improve our understanding of statewide hydrologic temporal and spatial patterns, and inform policy and decision-making related to vulnerable infrastructure