Spring temperatures in the Sagehen Basin, Sierra Nevada, CA: implications for heat flow and groundwater circulation

Abstract

Heat flow in the Sierra Nevada, CA, is low despite its young geologic age. We investigate the possibility that advective heat transport by groundwater flow leads to an underestimate of heat flow in the Sierras based purely on borehole measurements. Using temperature and discharge measurements at springs in Sagehen Basin, we find that groundwater removes the equivalent of approximately 20-40 mW m )2 of geothermal heat from the basin. This is comparable with other heat flow measurements in the region and indicates that, in this basin, at least, groundwater does transport a significant amount of geothermal heat within the basin. Additionally, we use estimates of the mean residence time of water discharged at the springs along with hourly temperature records in springs to provide constraints on groundwater flow depths within the basin. An analytical model based on these constraints indicates that the heat removed by groundwater may represent 20% to >90% of the total heat flow in the basin. Without better constraints on the regional hydrogeology and the depth of circulation, we cannot determine whether the heat discharged at the springs represents a change in the mode of heat transfer, i.e. from conduction to advection at shallow depths (<100 m) or whether this is a component of heat transfer that should be added to measured conductive values. If the latter is true, and Sagehen Basin is representative of the Sierras, basal heat flow in the Sierra Nevada may be higher than previously thought.

The pulse of a montane ecosystem: coupling between daily cycles in solar flux, snowmelt, transpiration, groundwater, and streamflow at Sagehen Creek and Independence Creek, Sierra Nevada, USA

“…4). This temporal pattern has also been observed in previous studies of evapotranspirationinduced daily cycles in streamflow and groundwater levels during dry periods (e.g., Kozeny, 1935;Troxell, 1936;Dunford and Fletcher, 1947;Hiekel, 1964;Klinker and Hansen, 1964;Burt, 1979;Kobayashi et al, 1990;Lundquist and Cayan, 2002;Butler et al, 2007;Wondzell et al, 2007;Gribovszki et al, 2008Gribovszki et al, , 2010 and has been attributed to daytime riparian evapotranspiration in response to strong solar fluxes and low relative humidity (Fig. 4).…”

“…Lithology is dominated by Tertiary volcanic rocks, primarily Miocene-Pliocene andesitic flows (and, on the north side of the lower Sagehen basin, Pliocene basalt flows), overlying several hundred meters of Tertiary volcaniclastic deposits which in turn overlie Cretaceous granodiorites of the Sierra Nevada batholith (Hudson, 1951;Sylvester and Raines, 2017). This >400 m layer of volcanic rocks hosts a substantial groundwater aquifer, with geothermal data suggesting groundwater circulation to depths exceeding 100 m (Brumm et al, 2009). Mean groundwater ages in springs feeding Sagehen Creek have been estimated at approximately 28 years during baseflow conditions and 15 years during snowmelt (Rademacher et al, 2005), varying from year to year in response to changes in annual snowmelt volumes and thus recharge rates (Manning et al, 2012).…”

Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

“…A linear increase in temperature with depth does not mean that the observed temperature is unaffected by fluid flow. Advection in permeable layers, deeper than depths at which temperature is measured, can increase [ Ziagos and Blackwell , 1986] or decrease [ Brumm et al , 2009] the apparent heat flow while still maintaining a constant temperature gradient near the surface where temperature is measured. At Site U1397, there are very coarse, thick (up to ten meters) turbidite units below the depths at which temperature could be measured.…”

Modeling thermal convection in supradetachment basins: example from western Norway

“…; Brumm et al . ). Compaction‐driven flow operates with a limited amount of fluids initially trapped within the sediments.…”