Using tracer-derived groundwater transit times to assess storage within a high-elevation watershed of the upper Colorado River Basin, USA

Journal Article · Thu Mar 15 04:00:00 EDT 2018 · Hydrogeology Journal

DOI:https://doi.org/10.1007/S10040-017-1655-4· OSTI ID:22780883

Kip Solomon, D. ^[1]; Heilweil, Victor M.; Miller, Matthew P. ^[2]

---

1. University of Utah, Department of Geology and Geophysics (United States)
2. US Geol Surv (United States)

Previous watershed assessments have relied on annual baseflow to evaluate the groundwater contribution to streams. To quantify the volume of groundwater in storage, additional information such as groundwater mean transit time (MTT) is needed. This study determined the groundwater MTT in the West Fork Duchesne watershed in Utah (USA) with lumped-parameter modeling of environmental tracers (SF{sub 6}, CFCs, and {sup 3}H/{sup 3}He) from 21 springs. Approximately 30% of the springs exhibited an exponential transit time distribution (TTD); the remaining ~70% were best characterized by a piston-flow TTD. The flow-weighted groundwater MTT for the West Fork watershed is about 40 years with approximately 20 years in the unsaturated zone. A cumulative distribution of these ages revealed that most of the groundwater is between 30 and 50 years old, suggesting that declining recharge associated with 5–10-year droughts is less likely to have a profound effect on this watershed compared with systems with shorter MTTs. The estimated annual baseflow of West Fork stream flow based on chemical hydrograph separation is ~1.7 × 10{sup 7} m{sup 3}/year, a proxy for groundwater discharge. Using both MTT and groundwater discharge, the volume of mobile groundwater stored in the watershed was calculated to be ~6.5 × 10{sup 8} m{sup 3}, or ~20 m thickness of active groundwater storage and recharge of ~0.09 m/year (assuming porosity = 15%). Future watershed-scale assessments should evaluate groundwater MTT, in addition to annual baseflow, to quantify groundwater storage and more accurately assess watershed susceptibility to drought, groundwater extraction, and land-use change.

• OSTI ID: 22780883
• Journal Information: Hydrogeology Journal, Journal Name: Hydrogeology Journal Journal Issue: 2 Vol. 26; ISSN 1431-2174
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CHLOROFLUOROCARBONS
COLORADO RIVER BASIN
COMPUTERIZED SIMULATION
DROUGHTS
FLOW MODELS
GROUND WATER
GROUNDWATER RECHARGE
HELIUM 3
LAND USE
POROSITY
STREAMS
SULFUR FLUORIDES
TIME DEPENDENCE
TRACER TECHNIQUES
TRITIUM
UTAH
WATER SPRINGS