Slightly thermal springs and non-thermal springs at Mount Shasta, California: Chemistry and recharge elevations

Abstract

Temperature measurements, isotopic contents, and dissolved constituents are presented for springs at Mount Shasta to understand slightly thermal springs in the Shasta Valley based on the characteristics of non-thermal springs. Non-thermal springs on Mount Shasta are generally cooler than mean annual air temperatures for their elevation. The specific conductance of non-thermal springs increases linearly with discharge temperature. Springs at higher and intermediate elevations on Mount Shasta have fairly limited circulation paths, whereas low-elevation springs have longer paths because of their higher-elevation recharge. Springs in the Shasta Valley are warmer than air temperatures for their elevation and contain significant amounts of chloride and sulfate, constituents often associated with volcanic hydrothermal systems. Data for the Shasta Valley springs generally define mixing trends for dissolved constituents and temperature. The isotopic composition of the Shasta Valley springs indicates that water fell as precipitation at a higher elevation than any of the non-thermal springs. It is possible that the Shasta Valley springs include a component of the outflow from a proposed 210 ‡C hydrothermal system that boils to supply steam for the summit acid-sulfate spring. In order to categorize springs such as those in the Shasta Valley, we introduce the term slightly thermal springs for springs that do not meet the numerical criterion of 10 ‡C above air temperature for thermal springs but have temperatures greater than non-thermal springs in the area and usually also have dissolved constituents normally found in thermal waters. ß

Global Isotope Hydrogeology―Review

“…The isotope composition of groundwater sampled from a spring or well located at a relatively low elevation (elevation z s ) is represented by (see well in lowland in conceptual diagram). If the well extracts groundwater recharged at higher elevations (e.g., elevation z i , where z s < z i ), and the isotope composition of higher elevation recharge ( ) differs from that of local precipitation in the lowlands (δ P(annual) ), it may be possible to estimate the elevation at which the sample of groundwater recharged (e.g., right panel; e.g., see δ 18 O‐elevation figures by Mazor et al, ; Nathenson et al, ; Caranto, ; Jefferson et al, , ; Günay, ; Paternoster et al, ; González‐Fernández et al, ; Jeelani et al, ; N'da et al, ; Oumarou Danni et al, ; Peters et al, ).…”

Seasonal macrophyte growth constrains extent, but improves quality, of cold‐water habitat in a spring‐fed river

“…However, due to upstream water storage and flow regulation (see Null, Deas, & Lund, for a description of surface water infrastructure in the Shasta River basin), streamflow in the Shasta River below Dwinnell Dam and Lake Shastina is derived predominantly from discrete springs discharging cool (11–13°C) and nutrient‐rich groundwater (Dahlgren et al, ; Lusardi et al, ; Nichols et al, ; NRC, ). The limited annual precipitation (24–46 cm year −1 ; NCRWQCB, ) in the Shasta River basin infiltrates Quaternary basalts and basaltic andesites of the High Cascades bounding the Shasta River to the north and east (Blodgett, Poeschel, & Thornton, ; Nathenson, Thompson, & White, ), ultimately discharging downslope at numerous springs along the eastern edge of the Shasta Valley. Principal among these are a group of springs located at the headwaters of the tributary Big Springs Creek (Figure ).…”

Isotopic characterization of three groundwater recharge sources and inferences for selected aquifers in the upper Klamath Basin of Oregon and California, USA

“…2a). The isotopic signature of springs around Mount Shasta, from Nathenson et al (2003), is similar to that of the Cascade Range springs and Medicine Lake Volcano snow and springs with a d 18 O range of À15.4& to À11.1&. Because water from Medicine Lake volcano and water from the main axis of the Cascade Range are isotopically indistinguishable in the available data, they are considered a single source for this study and are referred to as the Cascade Range source.…”