Browsing by Subject "Water Resources Science"

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An Assessment of land use impacts on channel morphology in a Western Minnesota watershed.
(2009-12) Christner Jr., William Thomas
This research is a comprehensive investigation encompassing land use changes in an agricultural watershed and corresponding changes to the rainfall-runoff relationship and stream channel morphology. The Lac qui Parle (LqP) watershed is one of eleven major watersheds within the Minnesota River Basin (MRB). Agriculture is the dominant land use within the MRB occurring on more than 90-percent of the landscape. This research investigates the spatial and temporal changes in channel morphology and land use between 1965/66 and 2002/03. Historical data were obtained from the US Army Corps of Engineers for the South Fork Lac qui Parle (SF LqP) River. Sixty-five cross-section sites were re-surveyed and evaluated. Current channel morphology was assessed through a second year of data collection. Additional data were collected and analyzed for crop history, riparian vegetation, agricultural drainage, annual discharge, annual peak discharge, and monthly and annual precipitation. Results indicate crop diversity within the SF LqP River has diminished and is currently dominated by corn and soybean. Surface and subsurface drainage of agricultural lands was documented on 37-percent of the sub-watershed area evaluated. Analysis of the discharge and precipitation records indicates an increase in the Q/P ratio and average annual runoff volume post-1960. The analysis indicates land use changes within the SF LqP watershed have impacted the channel morphology of the SF LqP River post-1965/66. Significant changes in channel cross-sectional area were noted in the Middle and Upper watersheds. Results corresponds to a channel enlargement ratio (CER) of 1.02 - 1.30. Changes in cultivation practices and drainage activities correspond with higher CER of 2.32 - 2.6. Similar increases were noted for peak discharge (1.30 - 1.35). CERs match values developed for storm sewered streets in urbanized areas. All changes were significant at the 95-% confidence level. A separate investigation evaluated the use of natural channel design for agricultural ditches. Results indicate natural channel design provides more efficient sediment transport, increased channel diversity/complexity, and may reduce channel maintenance costs.
Characterizing groundwater flow in the Twin Cities metropolitan area, Minnesota a chemical and hydrostratigraphic approach.
(2012-06) Tipping, Robert G.
Historic chemical and isotopic data for groundwater within the 11 county Twin Cities Metropolitan Area, extended (TCMAx) were used to distinguish three regional groundwater types based on similar chemical and isotopic composition: 1.) recent waters, characterized by detectable tritium, elevated chloride and/or the presence of anthropogenic compounds; 2.) waters with elevated strontium to calcium plus magnesium ratios; and 3.) naturally elevated chloride-distinct from recent waters based on carbon-14 dating and low chloride to bromide ratios where sufficient data exists. The three-dimensional distribution of these hydrochemical facies were compared to permeability of unconsolidated sediments, the distribution of macropores within sedimentary (Paleozoic) bedrock, and the regional distribution of vertical hydraulic head gradient. Results of this investigation demonstrate that groundwaters within the TCMAx can be broadly categorized by chemical composition, and that their distribution is controlled both by regional differences in subsurface permeability and natural hydraulic head gradients, and by regional changes in hydraulic gradient due to high-capacity pumping. Chloride content and chloride to bromide ratios, in particular, can be used to identify the presence of recently recharged groundwater in bedrock aquifers and further characterize the movement of these recent waters through bedrock macropores. Urban groundwater systems present unique challenges for resource management and scientific investigations due in large part to the transient nature of hydraulic head gradients and changing landuse. For urban planners charged with groundwater resource management, results in this thesis demonstrate the utility of having groundwater hydrochemical types fully integrated with a hydrogeologic framework model in a three-dimensional geographic information system (GIS) environment, where age and chemical quality of groundwaters can be compared with other, more familiar factors, such as locations and pumping levels of high capacity wells. For groundwater modelers of urban aquifers, these same results can guide conceptual models of recharge to bedrock aquifers and constrain model calibration to produce flux estimates in agreement with flowpaths indicated by the distribution of recent waters.
Determining the impacts of damming, water-level fluctuations, climate, and landscape changes in Voyageurs National Park and vicinity.
(2010-06) Bleser, Claire Serieyssol
In the past century, the border lakes in and near Voyageurs National Park have been subject to anthropogenic and natural stressors. These stressors include logging, damming, hydromanagement, human population growth, and climate change, which can be broadly categorized into three groups: land use, hydromanagement, and climate. In order to determine how these stressors have impacted the lakes, we developed a before-after control-impact paleolimnological study. Lakes included in the study were the dammed lakes of Namakan, Rainy, and Kabetogama, which are all in the Voyageurs National Park region, and undammed Lac La Croix, which is upgradient in protected wilderness lands. One sediment core was retrieved from each lake and analyzed for 210Pb inventory, loss-on-ignition, and diatoms. Multiple statistical analyses (species richness and turnover, cluster analysis, multivariate ordination, diatom-inferred water quality, and variance partitioning) were used to provide a more comprehensive picture of how these lakes were affected uniquely and interactively by the different stressors. Among the various stressors, land use generally explained the greatest amount of variance in diatom communities. Nevertheless, it is important to note that the interactive effects among land use, climate, and hydromanagement were also highly significant. Although hydromanagement is a primary source of concern in this region, multiple stressors and their interactions were identified as drivers of change in the diatom community and therefore must be considered in the management of the border lakes. The International Joint Commission who has been managing this system since 1940 has been mostly re-active in its decision making. However, in the late 1990s enough awareness was raised in regards to the deterioration of biological communities that they choose to modify the water-level rules in the border lakes. This step created a new decision-making process in this region; a move from being re-active to been pro-active. As part of this new rule change, the IJC required local agencies to evaluate the change in the rule curve. The ruling board located in the Rainy-Namakan System also has taken part in the new International Watershed Initiative which approaches the management of watersheds in an ecosystem approach. This step is extremely important as it promotes interactions between all stakeholders and therefore is able to fully integrate concerns in decision-making. Nevertheless, there are still concerns for the management of the resources in a sustainable way. Repeatedly, agencies in the region have raised concerns in the lack of funding from the IJC to maintain monitoring station. These stations are extremely important when making sustainable decisions especially during a time of unprecedented climate change. Thus, it is important that the IJC not only pro-active in its decision-making but also consider long-term sustainability.
Development and evaluation of methodologies for the classification of ecological communities.
(2008-12) Wan, Haibo
I developed and evaluated methodologies for studying ecological communities. The first component of my work, Chapter 2, develops a scientific framework, referred to as the nutshell philosophy, for classifying aquatic habitats in the St. Croix National Scenic Riverway. The "nutshell" is a compact philosophy for practitioners, including two parts: (1) a classification framework using a small set of environmental predictor variables; and (2) test of the classification using biological data. My classification resulted in two units: segments and reaches. Segments have a dimension of 15+ km and are delineated by major tributary outlets and channel slopes. Reaches are nested within the segments, with a dimension of 2+ km and are delineated by changes in stream substrate. A data set of mussel communities was clustered to test the classification. The clusters were consistent with the segments. The "nutshell" philosophy was validated in this case. The second component of my work, Chapter 3, introduces a method investigating stream substrate with underwater videos. With it a desired large area can be covered, and the resulting videos can be archived and used for quantitative analysis. The third component of my dissertation, Chapters 4 and 5, relate to clustering methods. Chapter 4 investigates impacts of selected cluster number on the accuracy of clustering algorithms. I clustered data sets of known structure with three different methods, varying the cluster number; clustering accuracy was evaluated using the Rand statistic. The Elbow phenomenon was typically found for the response of the Rand statistic with the cluster number. I described the Rand curves with an analytical relationship and proposed a threshold slope of 0.001 to locate the optimal cluster number. Chapter 5 evaluates performance of an emerging clustering method, Self-Organizing Map (SOM), with the more traditional methods of K-mean and Unweighted-Pair-Group-Method-using-Arithmetic-Averages (UPGMA). The SOM method was similar to the K-means in performance, and it was the best clustering method overall because of its additional and exceptional visualization feature. Although the UPGMA method also has visualization feature and worked well with data of low complexity, its performance decreases substantially with data of medium or high complexity.
Development, validation, and application of molecular microbial source tracking methods to be used in the assessment of environmental waterways.
(2009-11) Sawdey, Richard Charles
The fecal loading of aquatic environments by various animal hosts is of concern for public and environmental health. The microbiological contamination of waterways is amongst the most commonly listed water quality impairment in the U. S. The federal Clean Water Act (CWA) requires individual states to provide the U. S. Environmental Protection Agency (USEPA) with an aggregate quality assessment of its waterways every biennium, in effort to identify waters that do not meet state and federal quality standards. Once waterways are deemed impaired, states must conduct a Total Maximum Daily Load (TMDL) assessment in order to mitigate the impairment and restore the water body to acceptable quality. Successful bacterial TMDL implementation strategies require the use of microbial source tracking (MST) technologies that accurately and efficiently characterize the host-specific source of bacterial loading of waterways, and the relative quantities of each bacterium. Here I report that suppression subtraction hybridization (SSH) was found useful to identify gene markers specific to E. coli derived from swine fecal sources. The ability of this marker gene set to identify 62.3% of E. coli isolated from swine hosts suggests it may be useful in determining their fecal contribution to impaired waterways. I also investigated the influence of cattle grazing operations on the microbiological impairment of a small stream system in Southeastern Minnesota. Impairment by fecal indicator bacteria (FIB) was assessed by using plate count analyses and a quantitative PCR (q-PCR) was developed to estimate the presence of a bovinespecific Bacteroides marker gene in the waterway. The q-PCR data were compared to E.coli plate count data, revealing a lack of correlation between the two methods. Several physical and environmental factors likely influenced the level of E. coli found in the stream, confirming the hypothesis that other information will be needed to supplement current efforts to monitor fecal indicator bacteria in order to determine accurate sourcespecific fecal impacts. Lastly, spatial and temporal variation in the population structure of a fecal pathogen (Salmonella) in association with an alternate host and habitats, including the green alga Cladophora found in stream and lake water, aquatic plants, beach sand, and sediments, was evaluated by use of horizontal fluorophore-enhanced rep-PCR (HFERP) DNA fingerprinting. It was revealed that Salmonella populations associated with Cladophora varied both spatially and temporally, suggesting potentially different input sources of Salmonella over space and time. In addition, differing environmental stressors may play a role in selecting particular Salmonella genotypes that are best suited for growth in these environments The use of rapid molecular-based assays to determine the presence and source-specific loading of fecal indicator bacteria and pathogens has the potential to improve the accuracy and efficacy of TMDL studies, and to expedite implementation strategies to remediate impaired waterways.
A dual dye approach to measuring sunlight in lotic systems.
(2012-08) Welsh, Elizabeth J.
Light is an energy source that affects the metabolism of an aquatic system by providing energy for photosynthesis, the thermal structure by the transfer of light to heat energy, and the chemical make-up by providing energy for both indirect and direct photochemical reactions. This thesis considers the use of two dyes (rhodamine WT and fluorescein) as a way to measure the amount of light affecting lotic systems. These dyes are common tracers usually used in aquatic systems to measure water flow and mixing. Rhodamine WT exhibits photo-stability; while fluorescein exhibits photo-lability. Combining these two could potentially provide a Lagrangian measure of sunlight exposure in a lotic system; a previously unattainable view of the light field in such systems. In this thesis, several lab experiments were performed to test the effects of temperature and pH on the fluorescence of the dyes and to test the effects of pH and wavelength of light on the photoresponse of the dyes upon irradiation. A correction factor for temperature was found in lab experiments that matched previously published results. When pH remained within the normal range of North Shore streams (6.99-7.54), rhodamine WT exhibited photo-stability while fluorescein exhibited photo-lability; however, changes in response were seen as a function of pH and there are indications that rhodamine WT may be photo-labile at high pH. Irradiation of the dyes showed that wavelengths at and/or above 420 nm degrade the fluorescein. The dual-dye approach was tested in Amity Creek, a designated trout stream located on the north shore of Lake Superior. During deployment along a given reach, the dyes showed robust applicability on base flow, high irradiance days but no appreciable photoresponse on high flow days. During base flow deployments, the fluorescein to rhodamine WT ratio decreased linearly over time (with an R2 ranging from 0.971-0.998). Overall, in-stream Lagrangian deployments showed similar degradation rates to those seen in batch samples of stream water placed on the stream bed in a fixed position in sunlight for the same period of time. This concurs with visual observations that there is no significant canopy cover down this stream reach. Although the dual-dye methodology was successful in acting as an in situ light monitor and is applicable to streams if temperature is recorded and pH is within a certain operating range, more work needs to be done to demonstrate if the use of fluorescein and rhodamine WT is a practical alternative to current methods of light measurement.
Effects of perennial and annual vegetation on a soil water balance and groundwater recharge.
(2010-06) Trost, Jared Jeffrey
The movement of land applied fertilizers, pesticides, and other agricultural chemicals from land surface to groundwater is a major environmental concern, especially in regions of coarse textured soils with shallow unconfined aquifers. A replicated field experiment was conducted on the Anoka Sand Plain, Minnesota, to examine the effects of perennial and annual vegetative cover on the movement of water through the unsaturated zone to groundwater. A Darcian analysis of soil water flow, water table hydrograph analysis, and chemical analysis of a bromide tracer in pore water in the unsaturated and saturated zones were utilized to estimate recharge rates and amounts to a shallow unconfined aquifer beneath four land cover types: corn (Zea mays), well-established prairie, newly-established hay, and bare ground. Soil water storage and precipitation were measured directly. Evapotranspiration estimates were determined by difference in the other water balance terms. Prairie soils to 125 cm were maximally drier than corn by mid-July each season due to greater early season ET demands by prairie than corn, with the maximum difference in soil water storage being 6.3 cm. Hay, prairie, corn, and bare ground recharge estimates from 6/3/2008 through 12/31/2009 were 31.6 +/- 4.5 cm, 37.9 +/- 3.3 cm, 40.2 +/- 3.4 cm, and 43.7 +/- 6.8 cm representing 28 %, 33%, 35%, and 39% of precipitation, respectively. Piston flow model estimates of residence time in the upper 225 cm of the soil profile were 312, 410, 352, and 318 days for hay, prairie, corn, and bare ground respectively. Bromide mass loss as determined for soil pore water 160 cm below land surface in one continuously monitored plot of each treatment resulted in 0.7%, 34%, 34%, and 100% of applied bromide leaching in prairie, hay, corn, and bare ground plots respectively. Peak bromide concentrations in prairie soil water were marginally significantly lower than all other treatments. Bromide was detected in the groundwater of all five replicate plots for hay, bare ground, and corn treatments, but only detected in two of five prairie replicate plots. Results indicate that on coarse soils, well established annually harvested perennial prairies have the potential for reducing inputs of land applied chemicals to groundwater relative to corn through slight reductions in recharge and reductions in solute transport.
Evaluation of lake-wide, early-season herbicide treatments for controlling invasive curlyleaf pondweed (Potamogeton crispus) in Minnesota Lakes.
(2010-05) Johnson, James Aaron
Submersed aquatic plants play an important role in freshwater systems, affecting nutrient dynamics, trophic interactions, biological assemblages, and fish productivity. However, waters infested with non-native invasive aquatic plants often experience severe impairment of ecological and recreational quality due to excessive plant growth. Curlyleaf pondweed (Potamogeton crispus L.), one such exotic submersed aquatic plant, has become a widespread nuisance in temperate regions of North America. Curlyleaf’s early-season growth, propensity to form dense surface mats, and ability to out-compete native aquatic plants allow it to degrade the ecological and recreational quality of lakes. Consequently, there has been a great deal of interest in adopting lake-wide management strategies that can reduce the negative impacts of curlyleaf and provide some degree of long-term control. We collaborated with the Minnesota Department of Natural Resources in 2006, 2007, and 2008 to evaluate lake-wide, early-season herbicide treatments for curlyleaf management. Six curlyleaf-infested lakes were treated with herbicide (endothall or fluridone) for at least three consecutive years. Three additional lakes with established curlyleaf infestations were selected to serve as untreated reference lakes during the same period. For all study lakes, we annually assessed the frequency and biomass of curlyleaf in May and June, documented the production of new curlyleaf turions (reproductive buds) on standing plants, and tracked changes in the abundance and viability of turions in lake sediments. Previous studies have shown that biomass is a key metric for evaluating aquatic plant management projects. We used a boat-based rake method for collecting biomass samples rather than the standard diver (SCUBA) quadrat method because it allowed us to collect a greater number of samples in each lake and provided a higher degree of safety than the diver quadrat method. However, this boat-based rake method had not been thoroughly evaluated to determine whether it produced biomass estimates that were comparable to the diver quadrat method. Consequently, we conducted a separate study to compare the vertical rake sampling method to the diver quadrat method. Results of this study showed that biomass estimates from rake samples were comparable to diver quadrat samples for most individual plant taxa. However, the rake method produced substantially higher estimates than the quadrat method when sampling in dense stands of aquatic plants, particularly in areas dominated by coontail (Ceratophyllum demersum L.). Although rake estimates of plant biomass were significantly less precise than quadrat estimates, we determined that the rake method allowed us to collect a sufficiently greater number of samples to offset the method’s lower precision. Consequently, we concluded that the biomass data we collected were precise enough to make meaningful relative comparisons in our study lakes. After three to four consecutive years of herbicide treatment, curlyleaf frequency, biomass, turion production, and sediment turion abundance were all reduced and were all significantly lower in treated lakes than in untreated reference lakes. However, viable turions remained in lake sediments after three consecutive years of treatment. These results suggest that serial lake-wide, early-season herbicide treatments can effectively decrease the negative impacts of curlyleaf infestation and reduce the abundance of curlyleaf turions in lake sediments, but ongoing management will likely be required to maintain long-term control of curlyleaf in infested lakes.
Evaluation of Minnesota’s subsurface sewage treatment system professional experience program.
(2011-06) Haig, Nicholas John
Minnesota rules for Subsurface Sewage Treatment System (hereinafter, SSTS) professionals require field experience with a certified professional before obtaining a full certification. A workgroup was commissioned by the Minnesota SSTS advisory committee to investigate the extent to which the SSTS experience and mentoring requirements under Minnesota Rules Chapters 7083.1500 and 7083.2000 adequately meet the needs of the SSTS industry in Minnesota. Triangulated results from three focus groups indicate that SSTS professionals value experiential learning, but share concerns about the manner in which aspiring practitioners are prepared. Focus group results informed the development of a survey instrument and were confirmed by a random sample of 1100 SSTS professionals with various levels of certification. The response rate was sufficient to carry out statistical analysis. Data about the knowledge, attitudes and practices of SSTS professionals were analyzed to prepare recommendations about the mentoring program. The study found that the current program was not implemented equitably across the industry and lacks clear guidance for both mentors and apprentices. SSTS professionals value a combination of classroom and experiential learning. Emphasizing mentoring relationships beyond the context of current requirements and introducing additional quality assurance measures may be the most practical ways to address programmatic shortcomings and improve the public health and environmental benefits that result from consistent, high-quality SSTS design, installation, and inspection practices.
An Evaluation of the Importance of Mysis relicta to the Lake Superior Fish Community
(2010-05) Isaac, Edmund Jacob
Mysis relicta is a major prey item for many fish species in Lake Superior, However, its importance to an entire fish community as a whole has not been quantified. We describe seasonal prey selection of the major fish species collected across 18 sites in Lake Superior, and again at five locations in western Lake Superior in 2006 using a selection index (Chesson's Alpha). We also used bioenergetics models to estimate the consumption of prey items by the fish community at the same locations. Additionally, we modeled the production of Mysis, to evaluate this prey resource in terms of demand and supply. We found that rainbow smelt, kiyi, and bloater selected for Mysis over other prey items during all seasons, while lake whitefish only selected for Mysis in the spring and summer. Cisco selected for large zooplankton, while all three sculpin species exhibited neutral selection of prey items. Burbot and siscowet selected for deepwater sculpin and Mysis during all seasons, with juveniles showing a stronger selection for Mysis than did adults. Mysis was the most consumed prey item lakewide, with higher annual consumption offshore than nearshore. Predation on Mysis was mainly from rainbow smelt, bloater, and lake whitefish nearshore, and deepwater sculpin and kiyi offshore. Our estimates of Mysis production (supply) were higher than the consumptive demand by the fish community at nearly all locations, with this balance indicating stability in the food web. Mysis relicta was found to be a sought after prey item by many fish species, and is directly responsible in supporting the fish communities both nearshore and offshore. Thus, Mysis plays a pivotal role in the structure and function of the Lake Superior fish community.
Habitat selection and ecological stoichiometry: the role of seston C:P in Daphnia daytime spatial location.
(2009-01) Forman, Mary Rebecca
Diel vertical migration (DVM) of zooplankton has intrigued ecologists for over 100 years. Traditional DVM theory holds that Daphnia migrate into the hypolimnion during the daytime to escape predation pressure from visually-hunting predators, while nighttime ascent into the epilimnion facilitates feeding and growth. It has been demonstrated that Daphnia behavior may be altered by algal quantity, predator cues, and temperature or light levels. However, little was known about how algal quality (in terms of nutrient content) affects Daphnia vertical position. This dissertation examines the effects of algal quality on the daytime habitat selection of Daphnia through laboratory experiments and analysis of field data. Laboratory studies examined the movements of Daphnia in a thermally-stratified water column. When algal quality was high (C:P ~ 150) throughout the water column, mature Daphnia were found in the epilimnion during the daytime, despite the presence of a predator cue. However, when algal quality was low (C:P ~1500) throughout the water column, mature Daphnia tended to spend the daytime in the hypolimnion. These habitat preferences were not detected when the experiment was repeated using young juveniles (age 0-5 days), though at age 6 days, juveniles’ behavior appeared to begin to shift toward that of adults. As expected, body mass, fecundity, and net reproductive rate were found to be positively correlated with increased environmental temperature, and fecundity and net reproductive rate were positively correlated with increased food quality. A field study of 34 lakes revealed that habitat selection was not only food-quality dependent, but also species-specific. D. retrocurva and D. mendotae exhibited a preference for the upper lake layer when food quality was good throughout the water column, but not when food quality was poor in the upper layer. D. pulicaria did not exhibit any layer preference in either lake environment. The results from this research provide insight into Daphnia’s ability to balance the multiple factors associated with a heterogeneous vertical gradient in order to realize maximum productivity, and thus maximum fitness, in the presence of visually-hunting predators. The results further indicate that food quality is an important factor in determining habitat selection, productivity, and ultimately fitness.
How do the availability of fish and rice affect occupation and food security in the Lower Mekong Basin?
(2011-09) Bouapao, Lilao
This study aims to contribute to our understanding of how rice and fish availability affect occupation and food security of people in the Lower Mekong Basin (LMB), including Cambodia, Lao PDR, Thailand, and Vietnam. The study focuses on subsistence and commercial fishers and farmers. The data obtained for my research are from the first basin-wide survey conducted across the four countries using a common methodology and timing in 2009. Results of the study show that the extent of dependence of people on rice and fish availability for occupation, income, and food and their resilient capacities varies greatly between strata and across study sites. If both fish and rice decline at a common rate applicable to the whole LMB, cash income of at least one of four strata in each site will easily fall below the poverty line of $1.00 per capita per day. Seen from the perspective of food, all strata of all sites will be significantly affected if the availability of rice and fish decline. Altogether, fish and rice account for more than 81% of the total daily calorie intake. With uneven distribution of population by countries and varied social-ecological zones and livelihood activities, impacts of changes in the rice and fish availability will not distribute evenly. If changes occur throughout the Mekong, the number of people impacted will be highest in Vietnam, followed by Cambodia and Lao PDR. Thailand will be affected the least. Please see separate PDF files for the questionnaire in five languages.
Identifying critical portions of the landscape for water quality protection using GIS terrain analysis.
(2009-11) Galzki, Jacob Craig
Terrain attributes can be calculated using readily available digital elevation models (DEMs) and Geographic Information System (GIS) software. This study investigates the effectiveness of using terrain attributes to identify different critical source areas of contaminants on the landscape. A full suite of terrain attributes were calculated using 3 and 30-meter resolution DEMs for areas within the Le Sueur River Watershed in south central Minnesota, a watershed known to contribute disproportionate amounts of sediments and nutrients to the Minnesota River. Terrain attributes employed throughout this study included slope (S), flow accumulation (FA), compound topographic index (CTI), and stream power index (SPI). Thresholds applied to these attributes combined with ancillary GIS data, such as SSURGO soil data, resulted in spatial data layers identifying critical areas on the landscape. These critical areas accumulate flow along with associated contaminants and are hydrologically connected to nearby surface waters. Field visits aided in determining attribute thresholds and data layer combinations. Low resolution DEMs were useful for delineating critical portions of the landscape that were controlled by broad landscape patterns, such as artificially drained upland depressions. High resolution DEMs were useful for delineating critical areas at the sub-field scale, such as ephemeral gullies. Terrain analysis using a combination of low and high resolution DEMs can rapidly identify critical landscape areas at various spatial scales for water resource protection, and best management practices (BMPs) can be applied to these critical areas to mitigate their detrimental effects on surface water quality.
Impact of large-scale irrigation on a closed basin wetland: Water flow alterations and participatory irrigation management effects on the Sultan Marshes ecosystem in Turkey
(2008-07) Celik, Filiz Dadaser
This dissertation analyzes alterations in a closed-basin wetland system resulting from the construction of a large-scale irrigation project in its catchment. The study was conducted at the Sultan Marshes ecosystem (Develi Basin, Turkey), which has been severely degraded within the last 20 years due to diversion of its major water sources for agricultural irrigation. Spatial changes in the Sultan Marshes from 1980 to 2003 were analyzed using satellite remote sensing. Changes in the areal coverages of lakes, marshes, agricultural, and steppe areas determined by unsupervised classification of four Landsat images showed that both lakes and marshes became smaller after construction of the irrigation project. Steppe areas expanded onto wetlands. Significant portion of northern (Kepir) marshes were converted to agriculture. Hydrologic changes in the Sultan Marshes were analyzed statistically and used to develop a dynamic hydrologic model of the system. Water levels dropped more than one meter in the lakes and marshes from 1993 to 2003, and decreases were observed in ground-water levels and spring flows, although precipitation and evaporation rates remained mostly stable. Simulations with the hydrologic model showed that even if surface water continues to be used for irrigation, reductions in appropriations from ground water and springs would restore and protect water levels in the marshes. Agricultural and environmental changes in the Develi Basin were analyzed after the irrigation management was transferred from state to "irrigation associations" in 1994. The analyses showed that irrigated areas and water use in the Develi Basin showed significant fluctuations. The area allocated to production of high water-consuming plants increased. Water fee collection rates were lower than 100%. Although soil and water quality in the Develi Basin did not change significantly, ground-water levels, flow rates from springs and water levels in the Sultan Marshes all dropped. Four recommendations were developed that would help to resolve the conflict between agricultural and wetland water requirements: (1) a basin-wide approach water planning, (2) more realistic water pricing, (3) demand-based irrigation scheduling, and (4) rehabilitation of the irrigation system. Economic costs and benefits associated with water diversions from agriculture to the wetlands were estimated, and the optimum or economically-efficient amount of water diversion was determined. When only direct-use values of the wetland (reed cutting, animal grazing and ecotourism) were included, the annual optimum amount of water diversion to the wetlands was found to be 5.2 million m 3 yr -1 (165 L s -1 ) compared to about 62 million m 3 yr -1 (1,957 L s -1 ) used in irrigation. Diversion of 5.2 million m 3 yr -1 water would be sufficient to restore the conditions in the marshes. The analysis showed that economically-efficient restoration of water levels in the Sultan Marshes is feasible with moderate amounts of water diversion.
Instream wood transport, and effects of forest harvest on geomorphology and fish, in northern Minnesota streams.
(2009-06) Merten, Eric Christopher
Trees provide critical functions to the ecology of streams. Trees affect hydrology, mitigate sediment inputs, and buffer water temperatures by providing shade. Watersheds with a higher proportion of mature forest tend to have less variable hydrographs, and older trees provide larger pieces of wood to streams. Instream wood itself affects nearly every process in stream ecology. Despite their ecological importance, trees and instream wood have been greatly modified by humans. The studies described in this dissertation advance current knowledge as follows: We demonstrate that headwater streams in northern forests can require ten years to recover from a large input of fine sediment, depending on the occurrence of stormflows. Our analyses suggest that, at the basin scale, warmer air temperatures in summer are more important to the abundances of some headwater fish species than instream habitat or spring precipitation. The analyses also lend support to previous findings that riparian forest harvest can cause local stream warming. Wood transport in streams is a dynamic process. Forty-one percent of over 800 wood pieces were mobilized (at least 10m) during a study period by a single high flow event. Thirty-two percent of the mobilized pieces became entrapped again before leaving their study reach. Mobilization of wood in streams is a complex function of both mechanical and hydraulic factors. Eleven potential predictor variables were studied, and seven were identified as significant to wood mobilization using multiple logistic regression. The seven predictors were burial, effective depth, length ratio, bracing, rootwad presence, downstream force ratio, and draft ratio. Entrapment of wood in streams is related primarily to the length ratio and weight of the wood pieces. The mechanisms for entrapment are not always clear; wood pieces may simply be entrapped wherever they are located when high water recedes. Together, this dissertation suggests that forest harvest should avoid excess sediment inputs (due to persistence) and stream warming (due to effects on fish). It also develops models that can be used for more informed management of instream wood. Stream managers and restorers can apply the results presented to reverse the impacts of historic logging and wood removal on streams.
Spatial and temporal variability in zooplankton-fish interactions in freshwater communities.
(2011-06) Holbrook, Beth Victoria
Abiotic and biotic factors interact at multiple scales to create heterogeneity in the distribution of zooplankton and zooplanktivorous fish in the pelagic area of freshwater lakes. In this dissertation, I explored the predator-prey relationship between these trophic levels in four studies conducted at a variety of spatial and temporal scales. The objective was to identify the processes that may structure spatial heterogeneity in these populations. At the smallest scales in the laboratory, I simulated light and temperature conditions similar to those found in an oligotrophic lake and observed interactions between age-0 lake trout (Salvelinus namaycush) and mysids (Mysis diluviana), and determined that the intake rate of age-0 lake trout (mg min-1) could be modeled as a function of mysid biomass (mg m-2). I then applied this model to field data collected at intermediate scales at a spawning shoal in Lake Superior and determined that age-0 lake trout distributed in a spatially predictable pattern based on maximizing their growth rate potential. I also explored the more general relationship between pelagic zooplankton biomass and fish density at intermediate spatial scales in three north temperate lakes. In all six depth strata that I analyzed, there was consistent and significant autocorrelation in the distribution of zooplankton biomass, but spatial structure in the distribution of fish density was weaker and more variable. I also detected a significant bottom-up influence of zooplankton biomass on the spatial structure of fish density in three of the six depth strata that I analyzed, but I did not detect any top-down influences of fish density on the spatial structure of zooplankton biomass. Finally, I explored the influence of surface temperature and mesoscale eddies on the distribution of epilimnetic zooplankton biomass and fish density at large scales in Lake Superior. Circulation patterns associated with prevailing wind conditions could explain some of the spatial patterns in zooplankton biomass, but epilimnetic fish distributions showed no pattern during both years of the study.
Spatial and temporal variability of preferential flow in a subsurface- drained landscape in North-Central Iowa.
(2012-03) Smith, Erik Allen
Preferential flow can have a direct impact on agricultural chemical transport, especially where preferential flow allows a significant fraction of the total rainfall to quickly move to underlying subsurface drains. The spatial and temporal variability of preferential flow was studied from 2006-2008 in a 38.8 hectare row-cropped (corn, soybeans) agricultural field with two topographically-located subsurface drains (north-central Iowa). Continuous measurements of water levels, soil moisture, stream and drain discharge, stream and drain specific conductance (SC) and precipitation were obtained. Persistent, but variable preferential flow was found to exist at the study site throughout the growing season. Four independent mathematical approaches were used to explore the spatial and temporal variability of preferential flow. A specific conductance end-member mixing analysis (EMMA) was performed based on the temporally varying SC in the subsurface drain water for two separate events, with 54 events classified solely on decreases in SC without accounting for drain flow (full calculations in supplementary file: SCanalysis.xlsm) . These 54 events were utilized to calculate the mean onset time of preferential flow and the mean time to maximum preferential flow. The maximum water velocity was calculated based on the initial rise of the observed water level relative to rainfall (full calculations in supplementary file: MaxTransportVelocity.xlsx). The highest maximum water velocity values occurred in the early spring and mid-to-late summer (i.e., higher number of preferential flow pathways), and the slowest maximum water velocity in the fall and early summer (i.e., lower number of preferential flow pathways). Spatial and temporal variability of preferential flow was best assessed with maximum water velocity. A simple unsaturated zone, one-dimensional, dual domain model (source-responsive) was conducted based on the timing and magnitude of the change in ground water levels relative to precipitation events (full calculations in supplementary file: S-Rmodel.xlsm). The source-responsive model described the size of the preferential flow space necessary to accommodate preferential flow. Finally, a simple theoretical model of soil infiltration and flow to subsurface drains (DRAIN-Pro), based on the Green-Ampt and Hooghoudt equations, accounted for preferential flow by estimating the effective vertical and horizontal hydraulic conductivities.
Stream Metabolism Along an Urban to Rural Gradient in Lake Superior Tributary Streams
(2011-01) Erickson, Jeremy Michael
The North Shore streams of Lake Superior are known for their clear cool waters that flow through expanses of undeveloped land. However, many North Shore watersheds are experiencing rapid urbanization, resulting in increased impervious surface cover (ISC). Previous research on the impact of ecological disturbances on stream health have seldom focused on ecosystem processes such as stream metabolism. This study assesses the effect of increasing urbanization on whole stream community respiration (CR) and gross primary production (GPP) rates during summer and autumn base flow periods for nine low productivity, heterotrophic streams spanning a watershed ISC gradient. Land cover was measured as a percentage of the whole watershed and by distance-weighting to evaluate the possible influence of spatial position of land cover on stream function. Stream metabolism rates were determined using high frequency diel dissolved oxygen changes at a single station coupled with propane evasion to estimate stream reaeration rates. GPP estimates ranged from 0.02 to 2.02 g O2 m-2d-1 and CR from 0.17 to 6.09 g O2 m-2d-1. During summer base flows there were strong correlations between urban development measures and both stream metabolism and nutrients. However, the associations between land use and stream metabolism were not observed during the autumn base flow period. Our data suggest the variability in stream flow and leaf off along with stream temperature changes appear to be the dominant factors influencing the relationship between land use and stream metabolism in these Lake Superior tributary streams. Distance-weighting did not improve the predictive power on stream metabolism and water chemistry variables.
Targeting Audiences for Improved Lawn Management: Can Grouping Households Assist with Nonpoint Water Pollution Reduction
(2011-01) Wein, Sarah Nicole Panzer
In urban ecosystems, households are important decision-making units that are resource consumers and contributors to urban water pollution. At the landscape level, individual household choices regarding lawn management vary greatly, contributing to the detriment or protection of water resources. To better target household behavior change, we need to understand the social influences that determine how and why households manage their lawns differently, and what characteristics of the household could be driving these differences. We suggest that a better understanding of households could inform targeted policies and programs for effective change strategies. By spatially examining income, house age and proximity to a lake, we analyzed whether household groupings reflect households that think and act in similar ways with respect to lawn management. We obtained data for this research through a 2008 mail survey completed by the Twin Cities Household Ecosystem Project in Ramsey and Anoka Counties, Minnesota. Responses to questions pertaining to fertilization, leaf and lawn clipping management, vegetation choice, and lawn management attitudes were analyzed. When households were grouped spatially across the landscape with respect to proximity to a lake, few significant differences were found between household groups within 200 meters vs. farther than 200 meters. While income did influence particular lawn management attitudes and behaviors, it did not group spatially at a county scale, or at the finer scale of Saint Paul, the major city in our study area. House age showed significant relationships with almost every attitude and behavior examined, and was the only factor to demonstrate important spatial grouping. The correlation of house age with lawn attitudes/behaviors, however, is partially an artifact of housing density and number of trees on a household’s property. This study demonstrates that it may be possible to target households based on particular factors in order to tailor educational programming and policy to influence lawn management behavior, reduce pollutants leaving household lawns, and therefore improve water quality.
Validation of the MBT-CBT paleotemperature proxy:Effects of environmental and seasonal variability in soils and lacustrine sediments.
(2010-11) Bernhardt, Beth A.
Branched glycerol dialkyl glycerol tetraethers (GDGTs) are bacterial derived membrane lipids found ubiquitously in soils and lacustrine sediments (Weijers et al. 2006b, Blaga et al. 2009). The degree of methylation and cyclization of these lipids have been shown to be dependent on the temperature and pH of the growth environment (Weijers et al. 2007a). These relationships are the basis of the MBT-CBT proxy, which has been used to reconstruct paleotemperature from marine and lacustrine sediment archives (Weijers et al. 2007b, Blaga et al. 2010). Here, we aim to test the validity of the MBT proxy in terrestrial soils and lake sediments to determine whether branched GDGT distributions do refl ect annual mean air temperature (MAT) of the watershed, as suggested by studies, and how other environmental factors, such as seasonality of growth and sub-environments within a watershed, might infl uence the preserved MBT-CBT temperature signal. GDGT-derived annual MAT was compared with instrumental temperature measurements at three sites in the continental United States. Watershed soils were collected monthly for one year under three different types of vegetative cover in Minnesota and Ohio. In Florida, soils were collected twice from an open fi eld environment. Sediment cores were collected from corresponding lakes in each of the three states. We observed no signifi cant differences in soil proxy-derived annual MAT or soil GDGT concentration with seasonal changes in temperature at any of the three sites. Concentrations of GDGTs in the soil were found to have a slight positive correlation with organic carbon content. The effects of vegetative cover on proxy estimates of annual MAT were minimal. Only under deciduous vegetation in Minnesota and Ohio, did proxy-derived annual MAT differ signifi cantly from instrumental measurements. Soil GDGT concentration was unaffected by vegetation type in Minnesota, and in Ohio, pine soils had consistently higher concentrations, usually by an order of magnitude, than other vegetation types. The CBT proxy was found to be an accurate estimate of soil pH in some sub-environments, but in Minnesota and Ohio deciduous soils and Ohio open fi eld soils, CBT-pH differed signifi cantly from measured values. In the sediments of all three lakes studied, the MBT-CBT proxy provided a good estimate of measured annual MAT within the error of the proxy. Proxy-derived temperatures from the surface sediments of all lakes studied were cooler than corresponding instrumental measurements. These cooler surface temperatures could be attributed to in-situ production of branched GDGTs, but surface sediment MBT-MAT only differs signifi cantly from instrumental measurements in Bath Pond, Ohio.

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