Watershed Sciences Faculty Publications

Large Shift in Source of Fine Sediment in the Upper Mississippi River

Patrick Belmont et al. — Thu, 07 Feb 2013 12:36:11 PST

Although sediment is a natural constituent of rivers, excess loading to rivers and streams is a leading cause of impairment and biodiversity loss. Remedial actions require identification of the sources and mechanisms of sediment supply. This task is complicated by the scale and complexity of large watersheds as well as changes in climate and land use that alter the drivers of sediment supply. Previous studies in Lake Pepin, a natural lake on the Mississippi River, indicate that sediment supply to the lake has increased 10-fold over the past 150 years.Herein we combine geochemical fingerprinting and a suite of geomorphic change detection techniques with a sediment mass balance for a tributary watershed to demonstrate that, although the sediment loading remains very large, the dominant source of sediment has shifted from agricultural soil erosion to accelerated erosion of stream banks and bluffs, driven by increased river discharge. Such hydrologic amplification of natural erosion processes calls for a new approach to watershed sediment modeling that explicitly accounts for channel and floodplain dynamics that amplify or dampen landscape processes. Further, this finding illustrates a new challenge in remediating nonpoint sediment pollution and indicates that management efforts must expand from soil erosion to factors contributing to increased water runoff.

Revisiting scaling laws in river basins: New considerations across hillslope and fluvial regimes

Chandana Gangodagamage et al. — Thu, 07 Feb 2013 12:36:08 PST

Increasing availability of high‐resolution (1 m) topography data and enhanced computational processing power present new opportunities to study landscape organization at a detail not possible before. Here we propose the use of “directed distance from the divide” as the scale parameter (instead of Horton’s stream order or upstream contributing area) for performing detailed probabilistic analysis of landscapes over a broad range of scales. This scale parameter offers several advantages for applications in hydrology, geomorphology, and ecology in that it can be directly related to length‐scale dependent processes, it can be applied seamlessly across the hillslope and fluvial regimes, and it is a continuous parameter allowing accurate statistical characterization (higher‐order statistical moments) across scales. Application of this scaling formalism to three basins in California demonstrates the emergence of three distinct geomorphic regimes of divergent, highly convergent, and moderately convergent fluvial pathways, with notable differences in their scaling relationships and in the variability, or spatial heterogeneity, of topographic attributes in each regime. We show that topographic attributes, such as slopes and curvatures, conditional on directed distance from the divide exhibit less variability than those same attributes conditional on upstream contributing area, thus affording a sharper identification of regime transitions and increased accuracy in the scaling analysis.

Automatic geomorphic feature extraction from lidar in flat and engineered landscapes

Paola Passalacqua et al. — Thu, 07 Feb 2013 12:36:05 PST

High-resolution topographic data derived from light detection and ranging (lidar) technology enables detailed geomorphic observations to be made on spatially extensive areas in a way that was previously not possible. Availability of this data provides new opportunities to study the spatial organization of landscapes and channel network features, increase the accuracy of environmental transport models, and inform decisions for targeting conservation practices. However, with the opportunity of increased resolution topographic data come formidable challenges in terms of automatic geomorphic feature extraction, analysis, and interpretation. Low-relief landscapes are particularly challenging because topographic gradients are low, and in many places both the landscape and the channel network have been heavily modified by humans. This is especially true for agricultural landscapes, which dominate the midwestern United States. The goal of this work is to address several issues related to feature extraction in flat lands by using GeoNet, a recently developed method based on nonlinear multiscale filtering and geodesic optimization for automatic extraction of geomorphic features (channel heads and channel networks) from high-resolution topographic data. Here we test the ability of GeoNet to extract channel networks in flat and human-impacted landscapes using 3 m lidar data for the Le Sueur River Basin, a 2880 km2 subbasin of the Minnesota River Basin. We propose a curvature analysis to differentiate between channels and manmade structures that are not part of the river network, such as roads and bridges. We document that Laplacian curvature more effectively distinguishes channels in flat, human-impacted landscapes compared with geometric curvature. In addition, we develop a method for performing automated channel morphometric analysis including extraction of cross sections, detection of bank locations, and identification of geomorphic bankfull water surface elevation. Using the slope plotted along each channel-floodplain cross section, we demonstrate the ability to identify and measure the height of river banks and bluffs. Finally, we present an example that demonstrates how extracting such features automatically is important for modeling channel evolution, water and sediment transport, and channel-floodplain sediment exchange.

Closing the Gap Between Watershed Modeling, Sediment Budgeting, and Stream Restoration

Sean M.C. Smith et al. — Thu, 07 Feb 2013 12:36:03 PST

The connection between stream restoration and sediment budgeting runs both ways: stream restoration is proposed as a means to reduce sediment yields, but an accurate understanding of sediment supply is necessary to design an effective project. Recent advances in monitoring technology, geochemical techniques, high-resolution topography data, and numerical modeling provide new opportunities to estimate sediment erosion, transport, and deposition rates; upscale them in a geomorphically relevant fashion; and synthesize sediment dynamics at watershed scales. For practical application at large scale, watershed models used to predict yield often do not resolve lower-order channels, leaving an essential “blind spot” regarding sediment processes. We illustrate the challenges and emerging approaches for estimating sediment budgets using examples from two very different physiographic settings: the Mid-Atlantic Piedmont and the agricultural plains of southern Minnesota. We highlight common challenges and themes in defining an effective watershed sediment model. In both cases, reliable estimates of sediment yield depend essentially on the accurate identification of sediment sources and sinks and, hence, require careful delineation of landscape units and identification of dominant sediment sources and sinks. The primary elements needed to bridge the gap between sediment budgeting, watershed modeling, and stream restoration are (1) specificity regarding location, mechanism, and rates of erosion, (2) accurate accounting of sediment storage, (3) appropriate methods for upscaling local observations, (4) efficient means for incorporating multiple lines of evidence to constrain budget estimates, and (5) stream restoration methods that incorporate sediment supply in assessment and design procedures.

The Great Salt Lake’s Deep Brine Layer and Its Importance for Mercury Bioaccumulation in Brine Shrimp (Artemia franciscana)

Wayne A. Wurtsbaugh et al. — Mon, 07 Jan 2013 14:30:59 PST

Mercury in water bodies is receiving increased attention due to the toxicity of methylmercury (MeHg). Some authors have suggested that stratified lakes with anoxic hypolimnia experience higher rates of mercury methylation. It is believed that this biochemical pathway is promoted by high levels of H2S and organic matter in the deep layers that fuel sulfate‐reducing bacteria that produce methylmercury as a byproduct.

Eutrophication and Metal Concentrations in Three Bays of the Great Salt Lake (USA)

Wayne A. Wurtsbaugh et al. — Mon, 07 Jan 2013 14:30:56 PST

The Great Salt Lake, bordered by several major population centers in the State of Utah, has received heavy loading of various pollutants that until recently have received little attention. However, during the last decade management agencies and environmental groups have become concerned that these contaminants might limit the beneficial uses of the lake. Recent work by the Utah Department of Environmental Quality, The Utah Division of Forestry, Fire and State Lands, universities, and federal agencies have focused on how selenium, mercury, eutrophication and salinity may influence recreational use of the lake and the migratory bird populations that rely on the lake for feeding and nesting.

Pseudo-diel vertical migration in zooplankton: a whole-lake ¹⁵N tracer experiment

Xavier Armengol et al. — Mon, 07 Jan 2013 14:30:53 PST

Diel vertical migration (DVM) of zooplankton is commonly considered an adaptation for feeding in food-rich and warm surface waters at night and avoiding visual predators during the day. However, the critical assessment of migration patterns frequently suggests that: (i) zooplankton may leave deeper waters with rich, deep-chlorophyll layers and move into the epilimnion where food resources are lower and/or (ii) the night-time increase in epilimnetic plankton abundance is not matched by a density decrease in deeper strata. To study these discrepancies, we measured DVM of zooplankton in a 1.3-ha Spanish karst lake (Laguna del Tejo) where the phytoplankton in the deep chlorophyll layer had been labelled with the isotopic tracer 15N. There were only limited changes in the vertical distribution patterns of rotifers and copepods over the diel cycle, but night-time biomass (mg L−1) of the cladoceran, Diaphanosoma brachyurum in the water column of the oxic zone increased 168% in the central area of the lake but there was not a parallel reduction in their density in the metalimnion or hypolimnion. Additionally, the isotopic signatures of the zooplankton in the epilimnion stayed constant from day to night, suggesting that there was little vertical migration. The results suggest that horizontal movements rather than vertical migration explain the increasing abundance of zooplankton in the central epilimnion of Laguna del Tejo during the night and that low food resources in this layer provide no incentive for DVM.

Rationale for Control of Anthropogenic Nitrogen and Phosphorus in Inland Waters

William M. Lewis Jr. et al. — Mon, 07 Jan 2013 14:30:50 PST

Concentrations of phosphorus and nitrogen in surface waters are being regulated in the United States and European Union. Human activity has raised the concentrations of these nutrients, leading to eutrophication of inland waters, which causes nuisance growth of algae and other aquatic plants. Control of phosphorus often has had the highest priority because of its presumed leading role in limiting development of aquatic plant biomass. Experimental evidence shows, however, that nitrogen is equally likely to limit growth of algae and aquatic plants in inland waters, and that additions of both nutrients cause substantially more algal growth than either added alone. A dual control strategy for N and P will reduce transport of anthropogenic nitrogen through drainage networks to aquatic systems aquatic ecosystems that may be nitrogen limited. Control of total phosphorus in effluents is feasible and is increasingly being required by regulations. The control strategy for nitrogen in effluents is more difficult, but could be made more feasible by recognition that a substantial portion of dissolved organic nitrogen is not bioavailable; regulation should focus on bioavailableN(nitrate, ammonium, and some dissolved organic nitrogen) rather than total N. Regulation of both N and P also is essential for nonpoint sources.

Nitrogen Partitioning and Transport Through a Subalpine Lake Measured with an Isotope Tracer

David M. Epstein et al. — Fri, 30 Nov 2012 09:02:02 PST

We used a stable isotope tracer to measure nitrogen (N) assimilation and transfer through Bull Trout Lake, a 0.3-km2 mountain lake in Idaho, specifically to explore the relative importance of pelagic and benthic producers. was added into the inflow stream above the lake during spring runoff and the resulting mass of tracer was measured within the various ecosystem compartments, including the outflow stream. Although a portion of the moved through the lake quickly due to a low hydraulic residence time during the addition, the tracer was also assimilated rapidly by seston in the water column and at a slower rate by benthic primary producers. By the end of the 10-d injection, 10% of the tracer had left via outflow, 21% was within seston, and 17% was in epiphytes and macrophytes. However, 70 d after the termination of the injection, only ∼ 1% of the tracer remained within seston, whereas 10% was within the benthic primary production compartment as N was recycled within the benthic zone. Quantitative transfer of 15N to invertebrate and fish consumers was low, but turnover in these compartments was slow. A conservative water mass tracer (bromide) indicated that the turnover rate for lake water was 1.8% d−1, whereas 15N turnover for the whole lake was only 0.7% d−1, demonstrating how lakes exert drag on nutrients as they move through the watershed. Due to uptake and storage of nutrients, Bull Trout Lake strongly influenced the timing and magnitude of nutrient export from its watershed.

Nitrogen Flow Pathways Through an Alpine Lake

David E. Epstein et al. — Thu, 04 Oct 2012 11:20:16 PDT

Nitrogen Transport Through a Sub-Alpine Lake: Bull Trout Lake Whole Ecosystem ¹⁵N Tracer Study

David E. Epstein et al. — Thu, 04 Oct 2012 11:20:14 PDT

Nutrient Transport Through Lakes in a Sub-Alpine Watershed in the Sawtooth Mountains of Idaho

David E. Epstein — Thu, 04 Oct 2012 11:20:12 PDT

Spatial Analyses of Trophic Linkages between Basins in the Great Salt Lake

Wayne A. Wurtsbaugh et al. — Thu, 09 Aug 2012 09:34:01 PDT

Although the Great Salt Lake is frequently treated as if it were a single body of water, the natural bays and transportation causeways have divided it into a system of four bays. The bays, however, do not function independently because water, nutrients and other contaminants flow between them. The purpose of our study was to analyze the water quality in three of the bays (Farmington, Bear River and Gilbert), to determine fluxes of nutrients between them, and to determine how this was influencing brine shrimp populations in the lake. Discharge and nutrient concentrations were measured at constrictions separating the three bays from May through December of 2006. Phytoplankton and nutrients in the bays were sampled periodically to help understand factors controlling blooms of phytoplankton. Three synoptic analyses were done in May, June and December to look at water quality and plankton concentrations at 29 stations in the three bays. The synoptic work was coupled with an analysis of MODIS satellite imagery to determine spatial and temporal changes in the abundance of phytoplankton in the lake.

Analysis of Phytoplankton Nutrient Limitation in Farmington Bay and the Great Salt Lake

Wayne A. Wurtsbaugh et al. — Wed, 18 Jul 2012 10:48:59 PDT

The Great Salt Lake is bordered to the south and east by a growing metropolitan area that contributes high nutrients to Farmington Bay. This large bay is eutrophic, and there is concern that continued increases in effluents from the Salt Lake City area could extend to impact the much larger, and currently less productive, Gilbert Bay. This study focused on determining how nutrient supplies might limit, and therefore control, algal populations in Farmington Bay and Gilbert Bay at different salinities. We tested both short and long-term responses of algal growth using laboratory nutrient addition bioassays in the summer and fall of 2003. Because some phytoplankton can alleviate nitrogen deficiency by fixing atmospheric nitrogen, we also determined how nutrients and salinity influenced nitrogen fixation.

Brine Shrimp Ecology In The Great Salt Lake, Utah

Wayne A. Wurtsbaugh — Wed, 18 Jul 2012 10:48:56 PDT

Hypersaline lakes are noted for their simple communities which facilitate understanding ecological interactions (Williams et al. 1990; Wurtsbaugh 1992; Jellison and Melack 1988). Nevertheless, we still cannot easily predict how environmental changes will effect the population dynamics in these lakes, at least in part because even these simple ecosystems may be more complex than we .realize. Many hypersaline lakes are dominated by the brine shrimp Artemia spp. The production of brine shrimp is often very high because the terminal, saline lakes accumulate nutrients that make them rich, and because the short food chains in them (nutrients-->phytoplankton-->brine shrimp) minim ize the loss of materials and energy through trophic-transfer inefficiencies (Lindeman 1942). Brine shrimp are not, however, the end of the food chain. Waterfowl and shorebirds often depend heavily on the shrimp for food (Cooper et al. 1984; White et al. 1992). The shrimp and their cysts are also harvested commercially, primarily to support a world-wide shellfish and finfish aquaculture industry.

Comparative Analysis of Pollution in Farmington Bay and the Great Salt Lake, Utah

Wayne A. Wurtsbaugh et al. — Wed, 18 Jul 2012 10:48:52 PDT

Farmington Bay covers 94 mi2 (260 km2) in the SW comer of the Great Salt Lake, and is essentially a separate lake because it is enclosed by Antelope Island and a causeway leading to the island from the mainland. The bay has received wastes from the adjoining Salt Lake City metropolitan area for decades. Because of water quality concerns for Farmington 8ay, the Aquatic Ecology Laboratory class at Utah State University studied the bay and a nearby control site (Bridger Bay) in the Great Salt Lake during the fall of 2001. Field sampling and laboratory experiments, as well as other data sources, demonstrated the bay is severely eutrophic and is one of the most polluted water bodies in the state of Utah. A preliminary nutrient loading estimate for the bay indicates that total phosphorus coming into the system is a-times higher than necessary for the bay to be classed as eutrophic. Sewage treatment plants discharging directly to the bay contribute approximately 500/0 of the nutrients. Metrics of eutrophication (chlorophyll, Secchi depth and total phosphorus) all indicated that the bay was hypereutrophic and the combined Trophic State Index was 91, higher than any other lake or reservoir in the state. Oxygen was supersaturated in the surface waters of Farmington Bay during the day, but the bottom water was anoxic. During the night, nearly the entire water column became anoxic due to respiratory demand of the biota. The anoxic conditions allowed high concentrations 'Of foul-smelling hydrogen sulfide to be produced. Brine shrimp were not abundant in Farmington Bay and the community was dominated by rotifers. In contrast, water quality in Bridger 8ay located on the main lake, was good and brine shrimp were abundant there. Our results, although restricted in scope, corroborate existing monitoring data from this bay. Water quality characteristics in Farmington Bay do not meet those mandated for the protection of aquatic life. Odor problems from the bay likely impact more people than are affected by any other polluted water body in the state. The impact of eutrophication and anoxia on the biota in Farmington Bay may also be substantial, although inadequate data exists to determine these impacts. There are substantial technical challenges to be overcome if water quality in the bay is to be improved to meet its designated use. However, before these technical issues can be solved, the responsible agencies will need to address the problem, and begin studies that may eventually lead to a solution to this serious water quality issue.

Comparison of the Aquatic Ecology of Side-Canyons and the Main Channel of Lake Powell

Wayne A. Wurtsbaugh et al. — Wed, 18 Jul 2012 10:48:48 PDT

From 18-21 April 1996, students in a Utah State University class (Aquatic Ecology Laboratory; FW 560) measured limnological and fisheries characteristics in two side canyons (Halls Creek Bay and Moki Canyon) and the main channel of Lake Powell. Inclement weather precluded sampling of two other side canyons. Most of the sub-projects, directed by indiVIdual students, addressed the following two hypotheses: (1) productivity gradients existed from the inflows of the side canyons toward the main channel and; (2) productivity was higher in the side canyons than in the main channel of the lake. In most cases, parameters were measured at 3-5 stations in each side canyon. Near the inflows, Secchi depths were near 1.0 m in both side canyons, but increased rapidly and were greater than 10m in the main channel. Similarly, vertical light extinction coefficients ranged from 0.9 (Halls) and 1.6 (Moki) near the inflows, to 0.29 in the main channel. The estimated depth of the photic zone (1 % light) increased from 3 to 16 m along the gradients. Suspended inorganic sediments (SS) contributed significantly to the extinction of light: near the inflows SS ranged from 152 to 216 mg/L, whereas in the main canyon levels were near 70 mglL. Conductivity measurements indicated that side canyons were relatively well mixed: higher conductivities indicative of non-mixed conditions occurred only at depths> 40 m. Oxygen levels were above 75% of saturation at all depths in the side canyons. The lowest oxygen levels (66%) were found in the deep monomolimnion of the main channel. Measurements of total phosphorus suggested that levels were near 20 J.1g/L in the main channel, and increased to near 70 J.1g/L near the inflow of Moki Canyon. Phosphorus measurements in Halls Creek Bay were unsuccessful.

Comparison of the Aquatic Ecology of Side-Canyons and the Main Channel of Lake Powell 1997

Wayne A. Wurtsbaugh et al. — Wed, 18 Jul 2012 10:48:40 PDT

Physical characteristics of lakes are highly interrelated with biological characteristics. We measured and analyzed the physical characteristics of two side canyons in order to better understand differences in productivity between side canyons and the main channel and to provide general information on the characteristics of the lake.

Continuing Analysis of Phytoplankton Nutrient Limitation in Farmington Bay and the Great Salt Lake

Wayne A. Wurtsbaugh et al. — Wed, 18 Jul 2012 10:48:36 PDT

Farmington Bay is a nutrient-enriched, highly eutrophic embayment of the Great Salt Lake. The highly variable salinity of the bay influences what species of plankton can survive there. Previous analyses suggested that cyanobacteria (blue-green algae) may not be able to survive or fix atmospheric nitrogen at high salinities, thus maintaining the lake in a nitrogen-limited state. To determine the interacting influence of nutrients and salinity on the growth and nitrogen fixation of plankton we performed a 28-day bioassay with water from Farmington and Gilbert Bays in October 2004. We tested the response of the plankton to additions of nitrogen (N) and phosphorus (P) at salinities of 3%, 5%, 70/0, 9% or 11 %. Algal inocula from a variety of salinities were added to provide colonists for the cultures.

Continuing Studies of Water Quality in Farmington Bay and the Great Salt Lake, Utah

Amy Marcarelli et al. — Wed, 18 Jul 2012 10:48:33 PDT

For the past three years, an Aquatic Ecology Practicum class at Utah State University has conducted research examining the limnology of Farmington Bay. In 2000, our class discovered that Farmington Bay could be classified as hypereutrophic, and had significantly higher levels of chlorophyll and phytoplankton than the Great Salt Lake proper (Marcarelli et al. 2001). In 2001, individual student projects identified high phosphorus loading into Farmington Bay from surrounding sewage treatment plants, brine shrimp biomass five times lower than in the Great Salt Lake, and that the water in the bay lost all oxygen on a windy night in October (Wurtsbaugh et al. 2002). Additional sampling in 2002 indicated that brine flies were less abundant in Farmington Bay than in the less eutrophic Ogden Bay. These results prompted us to examine two major research themes in October, 2002: oxygen effects on chemical, physical and biological characteristics of Farmington Bay, and other factors that may control the abundance of organisms in Farmington Bay and the Great Salt Lake. The nine student reports produced this year spanned a broad array of topics and included most of the food web of the Great Salt Lake, with birds being the major exception.