HYPORHEIC FLOW, RESIDENCE TIMES AND NITROGEN REACTIONS IN A RIFFLE-POOL SEQUENCE, TRUCKEE RIVER, NV.
type: CreativeWork
description: Excessive algal production and subsequent decomposition contributes to fine particulate organic matter that reduces riverbed porosity and permeability and promotes microbial activity that stimulates nitrogen transformations. In the hyporheic zone, physical and biogeochemical processes controlling nitrification and denitrification processes are directly linked. Thus, this dissertation investigates hyporheic flow, residence times, oxygen dynamics and nitrogen transformations of a riffle-pool sequence in the lower Truckee River. The overall objectives of this research are to examine the physical and chemical controlling variables of nitrogen cycling in the hyporheic zone. The research approach was to 1) monitor continuous stage, sediment temperature and pressure to parameterize a flow and solute transport model to examine rates, flow direction, and residence times, 2) monitor the spatial and temporal distribution of dissolved oxygen, inorganic nitrogen (nitrate and ammonium) concentrations, and 3) relate hyporheic flow and residence times to observed nitrogen concentrations. In this first of its kind application of heat as a tracer applied to a hyporheic system, a riffle-pool sequence was heavily instrumented with in-stream piezometers and bank monitoring wells to monitor thermal and physical gradients to parameterize a two-dimensional heat and solute transport model. The model was calibrated using continuous observations of temperature and pressure in a single and multi-objective calibration approach. Field data and model results indicate the presence of a discontinuous low-permeability deposit that limited the vertical penetration of seepage beneath the riffle, whereas deeper exchange existed where the low-permeability deposit was absent. Hyporheic flow paths above the low-permeability deposit have mean residence times of 10 - 28 days at shallow depths (<0.2 m). Through global parameter estimation methods, using observations of pressure and temperature, it was possib…
abstract: Excessive algal production and subsequent decomposition contributes to fine particulate organic matter that reduces riverbed porosity and permeability and promotes microbial activity that stimulates nitrogen transformations. In the hyporheic zone, physical and biogeochemical processes controlling nitrification and denitrification processes are directly linked. Thus, this dissertation investigates hyporheic flow, residence times, oxygen dynamics and nitrogen transformations of a riffle-pool sequence in the lower Truckee River. The overall objectives of this research are to examine the physical and chemical controlling variables of nitrogen cycling in the hyporheic zone. The research approach was to 1) monitor continuous stage, sediment temperature and pressure to parameterize a flow and solute transport model to examine rates, flow direction, and residence times, 2) monitor the spatial and temporal distribution of dissolved oxygen, inorganic nitrogen (nitrate and ammonium) concentrations, and 3) relate hyporheic flow and residence times to observed nitrogen concentrations. In this first of its kind application of heat as a tracer applied to a hyporheic system, a riffle-pool sequence was heavily instrumented with in-stream piezometers and bank monitoring wells to monitor thermal and physical gradients to parameterize a two-dimensional heat and solute transport model. The model was calibrated using continuous observations of temperature and pressure in a single and multi-objective calibration approach. Field data and model results indicate the presence of a discontinuous low-permeability deposit that limited the vertical penetration of seepage beneath the riffle, whereas deeper exchange existed where the low-permeability deposit was absent. Hyporheic flow paths above the low-permeability deposit have mean residence times of 10 - 28 days at shallow depths (<0.2 m). Through global parameter estimation methods, using observations of pressure and temperature, it was possib…
author: Naranjo, Ramon C.
keywords: groundwater-surface water interaction, heat transport, hyporheic zone, nitrogen cycling, streambed
date published: 2012
date modified: 2026-07-27T21:46:41Z
provider: University of Nevada - Reno
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Nevada - Reno

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11714/3738