Simulations of stream-subsurface water exchange (hyporheic exchange) using a three-dimensional steady state groundwater flow model and a particle tracking model in unconstrained and constrained reaches of small (2nd-order) and intermediate (5th-order) mountain streams were conducted to estimate the effects of geomorphic features on the extent, volume and residence time of...
Changes in the concentrations of dissolved ammonia (NH4+1), nitrate (NO3-1), organic nitrogen (DON) were monitored along ground water flow paths to determine the importance of the ground water system to the stream nitrogen budget. The study site was located on a wide floodplain along a fourth-order
stream in the Oregon...
Stream chemistry studies conducted in the forested Watershed 1 of the HJ Andrews Experimental Forest show a contribution of CO2 from the hyporheic zone. Hyporheic CO₂ concentrations, measured as pCO₂, have a seasonal trend as well as a responsiveness to storm events. Concentrations are highest at the end of the...
Freshwater systems are an important component of the global carbon cycle as they outgas disproportionately large quantities of carbon compared to the terrestrial landscape. Of particular importance are headwater streams, which represent roughly 90% of the channel network by length and have been conservatively estimated to outgas roughly 36% of...
Streams and rivers play a critical role in global carbon (C) cycling by processing, storing, and transporting C. Headwater streams which make up more than 95% of the length of streams and rivers worldwide have disproportionate influence on fluvial C dynamics. The hyporheic zone (HZ) of headwater streams is a...
Pacific salmon (Oncorhynchus spp.) face numerous challenges associated with climate change. Most research has emphasized the potential effects of elevated summer water temperatures; however, climatic changes are also projected to significantly alter incubation and rearing habitats during the late autumn, winter, and spring months ("the incubation period"). Along the southern...
:
_________________________________________________________________________________________________________
Steven M. Wondzell
Pacific salmon (Oncorhynchus spp.) face numerous challenges associated
Rangelands span over 50% of the globe and approximately 70% of the United States. Although livestock production is an important use of rangelands, the benefits of rangelands are highly diverse. Humans find intrinsic value in protecting these unique and variable landscapes for wildlife, vegetation, and recreation enthusiasts. Woodland plant encroachment...
Streams across the western United States are impaired from human alterations that have reduced freshwater habitat by simplifying channel complexity and disconnecting floodplains (Knox et al., 2022; Waples et al., 2008; Wohl, 2014). Climate change is likely to continue exacerbating these risks by warming summer surface stream temperatures (Crozier et...
The rapid pace of climate change is increasing tree mortality and highlighting the need to improve the mechanistic understanding of plant function under increased water stress. However, the processes that control soil moisture availability in steep mountainous terrain are poorly understood, as are the relative effects of atmospheric and soil...
This study investigated carbon dynamics in the hyporheic zone of a steep, forested catchment in the Cascade Mountains of western Oregon, USA. Water samples were collected monthly from a headwater stream and well network during baseflow conditions from July to December 2013 and again in March 2014. We also sampled...
Ecological resources available to freshwater fish shift spatially, temporally and across life stages. To better understand how spatial-temporal availability of resources influence fish, I examined the phenologies of hatching and emergence of Coho Salmon (Oncorhynchus kisutch) in streams with contrasting and strongly defined seasonal thermal variability. The study streams included...
The specific objectives of this dissertation are to determine subsurface flow
behaviors across different antecedent wetness conditions from a top-down perspective
and to mechanistically assess the hydrological controls on DOC and N transport at the
hillslope and catchment scale. The study area is a small catchment where hillslopes
issue directly...
We examined the spatial and temporal variability of stream carbon dioxide (CO₂) and the drivers of these variations in a headwater catchment. To examine temporal variation and drivers, we measured stream and hyporheic pCO₂ at high temporal resolution over 11 months in a 95.9-ha forested headwater catchment in the Western...
Hyporheic zones are important regions that reside below and along the sides of streams. Within this region, several ecosystem services are provided including stream temperature regulation, habitats for a large variety of species, pollutant removal, and nutrient cycling. Exchange between the hyporheic zone and stream occurs across multiple scales, but...
The feedbacks between hydrology and biogeochemical cycling of nitrogen (N) are of critical importance to global bioavailable N budgets. Human activities are dramatically increasing the amount of bioavailable N in the biosphere, which is causing increasingly frequent and severe impacts on ecosystems and human welfare. Streams are important features in...
The glaciated coastal mountain watersheds that drain into the Gulf of Alaska (GOA) provide a model laboratory to explore the challenges of hydrological modeling and study the impact of climate and glacier cover change on regional hydrology. The region is data-sparse and contains a complex assemblage of topography and land...
Low-tech habitat restoration techniques, including Stage 0 treatments, are increasingly applied but often lack robust evaluation of their effects. In 2018, one kilometer of the South Fork McKenzie (SFMK) River, OR was modified to the Stage 0 condition for the benefit of ESA-listed Chinook by raising the incised channel to...
Studies of the effects of forest harvest on streams and fish have a long history in the Pacific Northwest. Results of this work have prompted development of new forest harvest practices that are more protective of these resources, but the effectiveness of these new practices has not been fully evaluated....
Land use and climate change occur simultaneously around the globe. Fully understanding their separate and combined effects requires a mechanistic understanding at the local scale where their effects are ultimately realized. Here we applied an individual-based model of fish population dynamics to evaluate the role of local stream variability in...
Water transient storage zones are hotspots for metabolic activity in streams although the contribution of different types of transient storage zones to the whole-reach metabolic activity is difficult to quantify. In this study we present a method to measure the fraction of the transient storage that is metabolically active (MATS)...
Mountainous headwater streams make up ~80 % of stream length globally and are strongly connected with catchment hillslopes and riparian areas, which can influence water quantity, quality, and availability for downstream uses. Accordingly, effective management of headwater streams and riparian zones to maintain desired ecosystem services downstream is critical, particularly...
The primary goal of this research project is to quantitatively measure the temporal scales of hyporheic exchange along a stream network. Our goal is to examine how hyporheic exchange varies with increasing stream size. Many previous studies focus on single stream reaches or on several reaches of similar sized streams,...
Forest harvesting and climate change induced shifts in precipitation characteristics (i.e., intensity, type) may affect how water is partitioned on the landscape, with more water potentially being lost to evaporation or groundwater, and less water being partitioned into the stream. Long-term, paired watershed data allows us to assess these possible...
This research investigates the direct and downstream impacts of clearcut harvest units on stream temperature as a part of the Hinkle Creek Paired Watershed Study. The Hinkle Creek watershed is located in the foothills of the Cascade Mountains about 30 kilometers northeast of Roseburg, Oregon, is privately owned, and supports...
Restoration to achieve Stage 0 is a valley-scale, process-based (hydrologic, geologic and biological) approach that aims to reestablish stream depositional environments to maximize longitudinal, lateral, and vertical connectivity at base flows and facilitate development of dynamic, self-formed and self-sustaining wetland-stream complexes. The term Stage 0 originally described complex multi-channel conditions...
Surface water and groundwater interactions are a key component in the functioning of stream ecosystems. Exchange of water between the stream and the hyporheic zone creates habitat for aquatic organisms and serves as a control for stream biogeochemical, thermal, and flow processes. This study takes a multi-method field-based approach to...
Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream...
Timber harvesting practices can increase fine sediment inputs to streams due to increased hillslope soil erosion and mass wasting of roads, hillslopes, and stream channels. Excessive fine sediment depositions have been shown to impact aquatic ecosystems, fish habitat, and downstream community water supply. Despite these deleterious impacts, the influence of...
We present a systems modeling approach to the development of a place-based ecohydrological model. The conceptual model is calibrated to a variety of existing observations, taken in watershed 10 (WS10) at the HJ Andrews Experimental Forest (HJA) in Oregon, USA, a long term ecological research (LTER) site with a long...
Riparian forests provide a myriad of ecosystem functions for adjacent streams and rivers, and due to these linkages, changes in riparian forest conditions can have direct implications for stream ecosystems. Resource managers in the coast redwood forests (Sequoia sempervirens) of northern California (USA) are actively thinning second-growth stands to accelerate...
In- stream water temperature is one of the most important environmental
factors associated with the decline in salmonid populations and their habitats in the
Pacific Northwest. Most ecological restoration practices that attempt to reduce instream
temperatures center on replanting or reestablishing riparian vegetation and
increasing flows. However, in a large...
Conceptually, the dynamics of wood in streams can be viewed in terms of input and in-channel processes. Input processes are associated with both the riparian (tree fall, bank cutting, windthrow) and upslope forests (mass failures). In-channel processes include log breakage, movement, and decomposition. A mechanistic view of these processes is...
Aquatic ecological investigation is expanding to encompass considerations of
multiple scales across large landscapes. Much of the analysis included in this work
focuses specifically on coho salmon (Oncorhynchus kisutch) in multiple subbasins on
the Oregon coast. Coho salmon were chosen for an investigation of spatial scales,
network connections, and life...
The widespread fragmentation, channelization, and simplification of river ecosystems has had acute environmental impacts, including degradation of water quality and habitat and biodiversity loss (Vörösmarty et al., 2010). These concerns have incited an increased focus on reestablishing ecological and hydrogeomorphological functions and improving habitat that has been lost in riverine...
Wet meadow ecosystems are a useful natural laboratory in which to explore feedbacks between biogenic and geologic controls on valley bottom landforms. Characterized by flat valley floors flanked by higher-gradient hillslopes, these meadows are singular both in that they represent depositional features in what is primarily an erosional environment, and...
This report discusses major characteristics of western Oregon’s lowland rivers, streams, and estuaries that the IMST finds to be important to wild salmonids. IMST describes how landscape scale factors (landscape structure, landscape function, disturbance regimes, and landscape scale biological processes) historically supported salmonid populations in western Oregon lowlands. The report...
Oregon's estuaries are important ecosystems for scientific study. Consequently, knowledge of what research has been conducted helps us identify benchmarks and plan new projects. A comprehensive bibliography of published research, technical reports, local documents, and data sets is one means of recording this knowledge. For these reasons, the Guin Library...