Heating of shallow groundwater flow by conduction from a paved surface: Requirements for coldwater stream protection

Temperatures of shallow groundwater depend on ground surface temperatures and water recharge temperatures. Important heat transfer processes that contribute to groundwater temperatures are conduction from the soil surface into the ground(water), infiltration of warm surface water, and advection by the horizontal flow in the aquifer. Shallow groundwater temperatures respond to ground surface temperatures and infiltration regimes. Both of these are modified by urban development and climate change. In this paper we explore concepts and relationships by which shallow groundwater temperature change can be analyzed or predicted. We estimate the projected seasonal temperature change in an aquifer of given depth, thickness and flow velocity (permeability) and below a vegetated (grassy) surface when a paved surface (parking lot) of given size is added on the ground surface. The analysis is in 2-D, and groundwater temperatures are simulated as a function of horizontal and vertical distance in the aquifer, and as a function of time of the year. Results are explained and presented in a form useful for practical applications, and examples are presented.