Martha A Scholl
Martha Scholl is a research hydrologist in the Earth System Processes Division, Water Cycle Branch of the USGS Water Resources Mission Area. Her work includes synthesizing stable isotope tracer methods with precipitation and land cover characteristics to determine climate patterns that control groundwater recharge and streamflow.
Biography
M.S. 1989 University of Virginia, Environmental Sciences (Hydrology)
B.S. 1985 University of Minnesota Duluth, Geology
Research topics:
Water availability in forested mountain watersheds: Mountain forests provide a steady, sustainable supply of high-quality water, and our research aims to improve understanding of the geologic, land cover and atmospheric interactions that affect this important resource.
Ecohydrology of cloud forests and coastal fog systems: Cloud water and fog inputs sustain important coastal and mountain ecosystems on six continents. Our research aims to quantify this unmeasured precipitation source in the water balance, including contributions to soil moisture, transpiration suppression, recharge and streamflow.
Science and Products
A 42 year inference of cloud base height trends in the Luquillo Mountains of northeastern Puerto Rico
The Luquillo Mountains of eastern Puerto Rico are home to the only tropical rainforest managed by the United States Forest Service, with cloud-immersed forests historically occupying the highest elevations. However, within the past 50 yr, studies of the Luquillo cloud forest have suggested an increase in cloud base heights (CBH), although the CBH...
Miller, Paul W.; Mote, Thomas L.; Ramseyer, C.A.; Van Beusekom, Ashley E.; Scholl, Martha A.; Gonzalez, Grizelle Seasonality of stable isotope composition of atmospheric water input at the southern slopes of Mt. Kilimanjaro, Tanzania
To understand the moisture regime at the southern slopes of Mt. Kilimanjaro, we analysed the isotopic variability of oxygen (δ18O) and hydrogen (δD) of rainfall, throughfall, and fog from a total of 2,140 samples collected weekly over 2 years at 9 study sites along an elevation transect ranging from 950 to 3,880 m above sea level....
Otte, Insa; Detsch, Florian; Gutlein, Adrian; Scholl, Martha A.; Kiese, Ralf; Appelhans, Tim; Nauss, Thomas A method for quantifying cloud immersion in a tropical mountain forest using time-lapse photography
Quantifying the frequency, duration, and elevation range of fog or cloud immersion is essential to estimate cloud water deposition in water budgets and to understand the ecohydrology of cloud forests. The goal of this study was to develop a low-cost and high spatial-coverage method to detect occurrence of cloud immersion within a mountain cloud...
Bassiouni, Maoya; Scholl, Martha A.; Torres-Sanchez, Angel J.; Murphy, Sheila F. Reassessing rainfall in the Luquillo Mountains, Puerto Rico: Local and global ecohydrological implications
Mountains receive a greater proportion of precipitation than other environments, and thus make a disproportionate contribution to the world’s water supply. The Luquillo Mountains receive the highest rainfall on the island of Puerto Rico and serve as a critical source of water to surrounding communities. The area’s role as a long-term research site...
Murphy, Sheila F.; Stallard, Robert F.; Scholl, Martha A.; Gonzalez, Grizelle; Torres-Sanchez, Angel J. Analyzing cloud base at local and regional scales to understand tropical montane cloud forest vulnerability to climate change
The degree to which cloud immersion provides water in addition to rainfall, suppresses transpiration, and sustains tropical montane cloud forests (TMCFs) during rainless periods is not well understood. Climate and land use changes represent a threat to these forests if cloud base altitude rises as a result of regional warming or deforestation. To...
Van Beusekom, Ashley E.; González, Grizelle; Scholl, Martha A. Noble gas signatures in the Island of Maui, Hawaii: Characterizing groundwater sources in fractured systems
Uneven distribution of rainfall and freshwater scarcity in populated areas in the Island of Maui, Hawaii, renders water resources management a challenge in this complex and ill-defined hydrological system. A previous study in the Galapagos Islands suggests that noble gas temperatures (NGTs) record seasonality in that fractured, rapid infiltration...
Niu, Yi; Castro, M. Clara; Hall, Chris M.; Gingerich, Stephen B.; Scholl, Martha A.; Warrier, Rohit B. Tropical river suspended sediment and solute dynamics in storms during an extreme drought
Droughts, which can strongly affect both hydrologic and biogeochemical systems, are projected to become more prevalent in the tropics in the future. We assessed the effects of an extreme drought during 2015 on stream water composition in the Luquillo Mountains of Puerto Rico. We demonstrated that drought base flow in the months leading up to the...
Clark, Kathryn E.; Shanley, James B.; Scholl, Martha A.; Perdrial, Nicolas; Perdrial, Julia N.; Plante, Alain F.; McDowell, William H. Insights into plant water uptake from xylem-water isotope measurements in two tropical catchments with contrasting moisture conditions
Water transpired by trees has long been assumed to be sourced from the same subsurface water stocks that contribute to groundwater recharge and streamflow. However, recent investigations using dual water stable isotopes have shown an apparent ecohydrological separation between tree-transpired water and stream water. Here we present evidence for...
Evaristo, Jaivime; McDonnell, Jeffrey J.; Scholl, Martha A.; Bruijnzeel, L. Adrian; Chun, Kwok P. High mercury wet deposition at a “clean Air” site in Puerto Rico
Atmospheric mercury deposition measurements are rare in tropical latitudes. Here we report on seven years (April 2005 to April 2012, with gaps) of wet Hg deposition measurements at a tropical wet forest in the Luquillo Mountains, northeastern Puerto Rico, U.S. Despite receiving unpolluted air off the Atlantic Ocean from northeasterly trade winds,...
Shanley, James B.; Engle, Mark A.; Scholl, Martha A.; Krabbenhoft, David P.; Brunette, Robert; Olson, Mark L.; Conroy, Mary E. Stable-isotope and solute-chemistry approaches to flow characterization in a forested tropical watershed, Luquillo Mountains, Puerto Rico
The prospect of changing climate has led to uncertainty about the resilience of forested mountain watersheds in the tropics. In watersheds where frequent, high rainfall provides ample runoff, we often lack understanding of how the system will respond under conditions of decreased rainfall or drought. Factors that govern water supply, such as...
Scholl, Martha A.; Shanley, James B.; Murphy, Sheila F.; Willenbring, Jane K; Occhi, Marcie; González, Grizelle
Stable isotope (δ18O and δ2H) data for precipitation, stream water, and groundwater in Puerto Rico
Puerto Rico is located in the northeastern Caribbean Sea (18.2 °N, 66.3 °W), with the Atlantic Ocean on its northern coast. The U.S. Geological Survey’s Water, Energy, and Biogeochemical Budgets (WEBB) program study area in which most of these data were collected comprises the El Yunque National Forest and surrounding area of eastern Puerto Rico....
Scholl, Martha A.; Torres-Sanchez, Angel; Rosario-Torres, Manuel Precipitation isotopes link regional climate patterns to water supply in a tropical mountain forest, eastern Puerto Rico
Like many mountainous areas in the tropics, watersheds in the Luquillo Mountains of eastern Puerto Rico have abundant rainfall and stream discharge and provide much of the water supply for the densely populated metropolitan areas nearby. Projected changes in regional temperature and atmospheric dynamics as a result of global warming suggest that...
Scholl, Martha A.; Murphy, Sheila F.