Earth and Planetary Sciences ETDs

Publication Date

4-10-1997

Abstract

A hydrologic budget analysis for the Los Alamos Canyon watershed was prepared including annual budgets for the 1993, 1994, and 1995 water years and detailed budget calculations for the upper basin and middle/upper canyon areas covering nine separate stress periods from 7/10/94 to 11/2/95 corresponding to varying alluvial aquifer behaviors. Data sources included daily measurements of precipitation and snowpack depths, streamflow discharge, and latent heat energy flux from which evapotranspiration rates were determined. Average annual precipitation rates over the watershed varied from ~23 to ~31 inches during the analyzed periods. The annual evapotranspiration component was determined to represent between ~ 71 % and ~84% of the total budget. Annual infiltration rates were calculated as residuals to the basic hydrologic mass balance equation and ranged from ~4 to ~ 7 inches/year, representing between ~ 14% and ~26% of the total water budget on an annual basis.

A groundwater flow model of the alluvial system was constructed using Visual MODFLOW® which implements the U.S. Geological Survey's three-dimensional finite­difference groundwater flow code. Both steady-state and transient simulations were run. MODFLOW's drain package was used to simulate infiltration seepage from the system, while the hydrologic budget analysis results constrained the recharge and evapotrans­piration stresses. The steady-state model was calibrated to well data by varying the drain conductances. The ZONEBUDGET and MODPATH codes were also utilized, and results showed that infiltration seepage dominated the loss components of the modeled system's water budget, representing ~69% of the total losses, compared to ~28% for evapotrans­piration and ~3% for downgradient flow, which was characterized with an average advective velocity of 727 feet/year. Results also quantified enhanced infiltration seepage within the Guaje Mountain fault zone. An error analysis generally corroborated the model results, and a sensitivity analysis was conducted which showed that the model was most sensitive to errors in recharge and evapotranspiration.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Michael E. Campana

Second Committee Member

Illegible

Third Committee Member

Bruce M. Thomas

Fourth Committee Member

Illegible

Project Sponsors

The funding for this project was provided through Los Alamos National Laboratory's Environmental Restoration Project as part of the site characterization activities for Operable Unit 1098 and Los Alamos Canyon.

Language

English

Document Type

Thesis

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