EAR-PF: Constraining Paired Air-Water Temperature Models' Efficacy In Head and Intermediate Watersheds With Groundwater and Bedrock Assessment and Multi-Decade Temperature Records

Riddell, Jill, Morgantown WV

Investigators

Abstract

Climate change increases atmospheric temperatures, which alters temperature patterns in groundwater and streams and results in reduced water quality and ecological diversity. In parts of the eastern United States, like West Virginia, climate has already warmed 0.5º – 1.0º F over the last century and temperatures are expected to rise another 3º – 4º F by the year 2100, further warming stream and shallow groundwater temperatures and affecting the organisms that live there. Stream temperature patterns provide insight into the vulnerability of these streams and watersheds to warming temperatures. However, current models do not fully account for temperature changes caused by interactions of water on the surface and underground. Model predictions of ground and surface water temperatures in a changing climate must be informed by the factors that influence thermal signals, including climate, geology, hydrology, land use, and land cover. Data show stream temperature changes in response to changing climate are likely driven (in part) by changes in relative contributions and temperatures of discharging groundwater. The Fernow Experimental Forest (FEF) in West Virginia has been recording temperature data in at least ten headwater watersheds since 1958. Using the FEF as a well-controlled outdoor laboratory to study these temperature patterns, Riddell will generate improved models and better knowledge of these systems. Improved models can be used to estimate watershed responses to drought or high intensity precipitation events, and associated disasters such as flooding. This work will directly impact middle and high school high school students in WV through collaboration with the National Youth Science Foundation (NYSF). This proposed work is in the Monongahela National Forest where the National Youth Science Foundation has hosted its National Youth Science Camp since 1963. The FEF is close to the camp and the newly purchased National Youth Science Center (NYSCenter) in Davis, WV. During this project, collaboration with NYSF staff will result in the installation of a stream gage monitoring station on the Blackwater River, which is adjacent to the NYSCenter to deliver hydrology education to middle and high school students in WV. This collaboration will support the NYSF mission to build and maintain student interest in STEM fields and promote high school retention rates and the pursuance of post-secondary STEM education. Climate change is increasing atmospheric temperatures which alters thermal patterns in groundwater and streams, resulting in reduced water quality and ecological diversity. Thermal regimes in surface waters are highly influenced by groundwater and its connectivity to the surface, which may be discerned by comparing air and stream temperature records. Paired air-water temperature analysis via sine wave regression is a way to characterize the relationship between air temperature and surface water temperature to elucidate the groundwater contributions to watershed hydraulics, cold-water habitat refugia, and groundwater temperature response to climate change. Recent research has focused on modeling annual paired-air/water temperature signals to assess the role of groundwater in propagating air temperature to stream water from sub-watershed to continental scales. Results of these sine regression studies are focused on determining the inputs of groundwater to surface water and the eventual response of surface water to climate change by comparing the amplitude ratios (sine curve peak height) and phase lag signals (time between peaks) of air and water temperature records. Deeper groundwater signatures show little variation in annual temperature and have ambiguous amplitude ratio and phase lag whereas shallow groundwater signatures show high amplitude ratios and measurable phase lag on the order of days. However, current models do not fully account for groundwater – surface water interactions that influence stream temperatures. These processes are governed by aquifer characteristics such as aquifer thickness, porosity, hydraulic conductivity, and bedrock type and depth. This study will utilize the Fernow Experimental Forest in WV to improve thermal stream model efficacy in small and intermediate watersheds by collecting new groundwater temperature measurements, assessing the influence of differing bedrock geology in the same watershed, and exploring the efficacy of these models in hydrologically connected, nested watersheds and in watersheds in which air and stream temperature records exist across multiple decades. This study will advance the knowledge of groundwater contributions to headwater watersheds and intermediate watersheds into which they discharge and to the vulnerability of these watersheds to climate change. The current models (sine regression) being applied to large, continental size watersheds recognize the importance of local hydrogeology and geology on groundwater behavior and the subsequent effects on surface stream temperature patterns. However, no study has yet to intensively characterize the surface hydrology, hydrogeology, and bedrock geology of small watersheds and the contribution of all these factors on stream temperature patterns. This study will fill that gap and highlight the importance of characterizing the subsurface when making predictions about the surface. This project is jointly funded by the Earth Sciences Postdoctoral Fellowship program, the Established Program to Stimulate Competitive Research (EPSCoR) and the Hydrologic Sciences program. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.