Using Heat as a Tracer to Characterize Streambed Water Fluxes of the Brenta River (Italy)

This work deals with the characterization of the spatial and temporal variability of water exchange fluxes from/to the Brenta river streambed (Veneto, Italy), critically important to regional water resources management. The aquifer system is structurally quite complex. It evolves from a large undifferentiated aquifer near adjacent mountain ranges to a wellstructured multi-layer system made up of six well-defined confined aquifers which constitute the noteworthy subsurface reservoirs of the area. Both the undifferentiated and the multiaquifer systems are heavily exploited for urban, industrial and agricultural uses. A three-dimensional groundwater flow model of the multi-aquifer system of the Central Veneto has been set up within a 3,300-km(2) area. The model integrates a large amount of available geological, geophysical, climatic and hydrologic data, has been specifically developed to analyze the behavior of such large, complex and well-monitored sedimentary system and to aid sustainable large-scale water resources management. A hydrothermal model of the river and of the underlying aquifer was implemented to improve the estimation, obtained for the 3D flow model, of the water exchange between the Brenta river and its underlying aquifer systems. The contribution of streambed exchanges is quantified by comparing simulations of water flow and heat transport to observed temperature and levels in river and in groundwater

Temporal Response of Hydraulic Head, Temperature, and Chloride Concentrations to Sea-Level Changes, Floridan Aquifer System, USA

Three-dimensional density-dependent flow and transport modeling of the Floridan aquifer system, USA shows that current chloride concentrations are not in equilibrium with current sea level and, second, that the geometric configuration of the aquifer has a significant effect on system responses. The modeling shows that hydraulic head equilibrates first, followed by temperatures, and then by chloride concentrations. The model was constructed using a modified version of SUTRA capable of simulating multi-species heat and solute transport, and was compared to pre-development conditions using hydraulic heads, chloride concentrations, and temperatures from 315 observation wells. Three hypothetical, sinusoidal sea-level changes occurring over 100,000 years were used to evaluate how the simulated aquifer responds to sea-level changes. Model results show that hydraulic head responses lag behind sea-level changes only where the Miocene Hawthorn confining unit is thick and represents a significant restriction to flow. Temperatures equilibrate quickly except where the Hawthorn confining unit is thick and the duration of the sea-level event is long (exceeding 30,000 years). Response times for chloride concentrations to equilibrate are shortest near the coastline and where the aquifer is unconfined; in contrast, chloride concentrations do not change significantly over the 100,000-year simulation period where the Hawthorn confining unit is thick