Hållbar utveckling som begrepp används frekvent i dagens samhälle och är också det övergripande målet för svensk nationell strategi. Syftet med den här uppsatsen är att undersöka i vilken utsträckning hållbar utveckling och/eller ekologisk modernisering beskriver miljöpolicyn hos de två största politiska partierna i Sverige. Dessa två partier, Socialdemokraterna och Moderaterna, tillhör varsitt partipolitiskt block med olika ideologier. Resultaten i uppsatsen visar att det finns väsentliga skillnader mellan de båda partiernas miljöpolicys som är grundade i olika politiska ideologier. Socialdemokraterna har sina rötter i frågor som demokrati, social rättvisa och välfärdsfrågor, och deras miljöpolicy överensstämmer till stor del med hållbar utveckling. Moderaterna utgår från liberalkonservativa idéer med utgångspunkt i individualism och marknadsbaserade ekonomier och deras miljöpolicy harmoniserar överlag med ekologisk modernisering. Att dessa skillnader existerar kan uppfattas som något överraskande eftersom båda partierna stödjer den nationella strategin för hållbar utveckling tillsammans med att senaste ordförandeskapet för kommissionen för hållbar utveckling innehades av Moderaternas partiledare. / Sustainable development as a concept is frequently utilized nowadays in our society and is additionally used as a comprehensive goal of Swedish national strategy. The purpose of this essay is approach this issue and to examine whether sustainable development and/or ecological modernization best describes the environmental policy of the two major political parties in Sweden. Socialdemokraterna and Moderaterna belong to opposite ideological parties, one on the left wing and the other one on the right wing. The result of this essay concludes that there are essential differences between the environmental policies of the two parties that are related to the underlying political ideology. Socialdemokraterna, on the one hand, has its root in democracy, social justice and welfare issues and the environmental policy mostly agrees with sustainable development. Moderaterna, on the other hand, takes its starting point in liberal-conservative thoughts with individualism and market-based economies and their environmental policy is in almost every aspect in accordance with ecological modernization. Yet, the differences in environmental policies are to some extent unexpected since both parties support the national strategy of sustainable development. Besides, the latest chairman of the Commission on Sustainable Development was the party leader of Moderaterna.

Ekosystembaserad förvaltning bygger på en helhetlig syn på ekosystemen och dess förhållande till mänsklig aktivitet. Förvaltningsplanen för Barents hav utanför Norge är ett de längst framskridna försöken till implementering av denna förvaltningsmodell. Lång väg återstår dock för att uppnå de målsättningar som satts och särskilt gäller detta miljömålet för biologisk mångfald. Trots att fiskeri utpekats som den största påverkningsfaktorn på biologisk mångfald har det varit lite fokus på fiskeriernas negativa konsekvenser i arbetet med förvaltningsplanen. Den här uppsatsen försöker ge en bild av hur personer som jobbar inom förvaltningen ser på värdet med förvaltningsplanen, hur de uppfattar dess brister, och just varför de tror att fiskeriet negativa konsekvenser fått liten uppmärksamhet. Helhetlighet och tvärsektoriellt samarbete kunde konkluderas som de främsta värdena med förvaltningsplanen. Organisationsproblem, konservatism och maktkamper ansågs dock skapa problem för implementering och samarbete över sektorerna, bland annat genom genom dålig kommunikation mellan utredningsgrupper och den implementerande organisationen. Konservatism och maktkamp uttrycktes i form av en ovillighet från andra att samarbeta över sektorerna, att bryta det sektoriella tankesättet, och en vilja att värna om sin maktsfär.  Strukturella problem lyftes även fram som en av de bakomliggande anledninganar till att fiskeriernas negativa effekter inte fått mer fokus. Starkt kulturellt fäste, fokus på petroleumsverksamhet och dålig kunskapsförmedling var andra faktorer som togs upp. / Ecosystem based management is a management approach that seeks to integrate ecological, social and economic goals. The Norwegian management plan for the Barents Sea is one of the most advanced attempts to ecosystem based management. There is, however, still a long way to go to achieve the goals that have been set. This is especially true for the environmental objective of biodiversity. Even though fishing activity has been pointed out as one of the main reasons for biodiversity loss, little attention has been drawn to this fact. This paper therefore tries to give the answer to the questions of how people working within the management perceive the plan; the core values of it, its flaws, and why they beleave that the negative consequenses of fisheries have been out of focus.   The holistic viewpoint and the cooperation between the various sectors were the most emphazised values of the management plan. Organizational problems, conservatism, and power struggles were regarded as the main problems in trying to reach these goals. Lack of communication between  implementing bodies and investigating bodies was one example of this. Conservatism and power struggles were described as unwillingnes among individuals to adopt to the new intersectoral structures, and a wish to safeguard ones own power. The reason why the negative consequenses of fisheries have been out of focus, was also blamed on structural problems to a large extent. Other contributing factors were also the strong cultural role fisheries play in the norweigan society, the political focus on petroleum activity, and an insufficient spread of knowledge.

Karlstads kommun har satt upp mål i transportstrategin som syftar till att öka antal cykelresor i Karlstad. Vid användning avger cykeln varken växthusgaser eller föroreningar. Vardagsbeslut att ta cykeln exempelvis till arbetet leder till att koldioxidutsläpp kan reduceras. Cykling kan därmed bidra till att uppfylla viktiga miljömål. Cykling främjar hälsa. Världshälsoorganisationen WHOs rekommenderade dagsbehov av 30 min fysisk aktivitet kan med fördel utföras på cykel. Cykeltrafikens omfattning påverkas av fysiska förutsättningar, psykologiska faktorer samt politikens utformning.   Syftet med undersökningen är att ta reda på vilka faktorer som påverkar cykeltrafiken i Karlstad. Hur påverkar dom faktorerna Karlstadsbornas val och motivation att cykla och vilka av dessa faktorer går att påverka? För att få ett underlag till analys utfördes en enkätundersökning bland 50 invånare i Karlstad. Av de svar som gavs på enkätens öppna och stängda frågor framkom att det som påverkar Karlstadsinvånarnas val att cykla väl samstämde med tidigare teorier och forskning.   Det främsta motivet till att invånarna i Karlstad cyklar framkom vara motion. Den främsta orsaken till att välja ett annat transportmedel är långa transportsträckor. Undersökningen pekar på att de åtgärder som förknippas med förbättrande av cykeltrafikens infrastruktur är mest efterfrågade. Genom att underlätta för Karlstadsborna att ta sig fram på cykel kan cykeltrafiken ökas. / Karlstad municipality has in their transport strategy set targets which aims to increase the number of bicycle trip within the city. When used the bicycle emits either greenhouse gases or pollutants. Everyday decisions to take the bike to work for example can lead to reduction of carbon dioxide emissions, cycling can thus contribute to the meeting of important environmental objectives. Cycling promotes health. The World Health Organization’s (WHO) recommended daily ration of 30 minutes of physical activity can readily be performed on a bicycle. Bicycle traffic volumes are affected by physical conditions, psychological factors and political policies.   The purpose of this investigation is to determine which factors affect bicycle traffic in Karlstad. How do these factors influence Karlstad inhabitants choice and motivation to ride their bicycles, and which of these factors can be influenced? To obtain a basis for analysis a survey among 50 inhabitants of Karlstad was conducted. From the responses given to the open and closed questions, it appeared that what influences the inhabitants of Karlstad´s choice to cycle were in tune with previous theories and research.   The primary motive of the inhabitants of Karlstad for cycling appeared to be exercise. The main reason for choosing a different mean of transportation is long distances. This survey suggests that the measures associated with enhancement of bicycle transport infrastructure are most in demand. By making it easier for Karlstad locals to get around by bike, bicycle traffic can be increased.

<p>Groundwater has an important role in forging the composition of surface water, supplying nutrients crucial for the development of balanced ecosystems and potentially introducing contaminants into otherwise pristine surface water. Due to water-rock interactions radium (Ra) in groundwater is typically much more abundant than in surface water. In saline environments Ra is soluble and is considered a conservative tracer (apart for radioactive decay) for Ra-rich groundwater seepage. Hence in coastal environments, where mostly fresh groundwater seep into saline surface water, Ra has been the prominent tracer for tracking and modeling groundwater seepage over more than three decades. However, due to its reactivity and non-conservative behavior, Ra is rarely used for tracing groundwater seepage into fresh or hypersaline surface water; in freshwater, Ra is lost mostly through adsorption onto sediments and suspended particles; in hypersaline environments Ra can be removed through co-precipitation, most notably with sulfate salts. </p><p>This work examines the use of Ra as a tracer for groundwater seepage into freshwater lakes and rivers and into hypersaline lakes. The study examines groundwater-surface water interactions in four different environments and salinity ranges that include (1) saline groundwater discharge into a fresh water lake (the Sea of Galilee, Israel); (2) modification of pore water transitioning from saline to freshwater along their flow through sediments (pore water in sediments underlying the Sea of Galilee, Israel); (3) fresh groundwater discharge into hypersaline lakes (Sand Hills, Nebraska); and (4) fresh groundwater discharge into a fresh water river (Neuse River, North Carolina). In addition to measurement of the four Ra isotopes (<super>226</super>Ra, <super>228</super>Ra, <super>223</super>Ra, <super>224</super>Ra), this study integrates geochemical (major and trace elements) with additional isotopic tools (strontium and boron isotopes) to better understand the geochemistry associated with the seepage process. To better understand the critical role of salinity on Ra adsorption, this study includes a series of adsorption experiments. The results of these experiments show that Ra loss through adsorption decreases with increasing salinity, and diminishes in salinity as low as ~5% of the salinity of seawater. </p><p>Integration of the geochemical data with mass-balance models corrected for adsorption allows estimating groundwater seepage into the Sea of Galilee (Israel) and the Neuse River (North Carolina). A study of the pore water underlying the Sea of Galilee shows significant modifications to the geochemistry and Ra activity of the saline pore water percolating through the sediments underlying the lake. In high salinity environments such as the saline lakes of the Nebraska Sand Hills, Ra is shown to be removed through co-precipitation with sulfate minerals, its integration into barite (BaSO₄) is shown to be limited by the ratio of Ra:Ba in the precipitating barite. </p><p>Overall, this work demonstrates that Ra is a sensitive tracer for quantifying groundwater discharge even in low-saline environments. Yet the high reactivity of Ra (adsorption, co-precipitation, production of the short-lived isotopes) requires a deep understanding of the geochemical processes that shape and control Ra abundances in water resources.</p> / Dissertation

<p>Mitochondria are the primary energy producers of the cell and play key roles in cellular signaling, apoptosis and reactive oxygen species (ROS) production. Mitochondria are the only organelles that contain their own genome which encodes for a small subset of electron transport chain (ETC) proteins as well as the necessary tRNAs and ribosomal subunits to translate these proteins. Over 300 pathogenic mitochondrial DNA (mtDNA) mutations have been shown to cause a number of mitochondrial diseases emphasizing the importance of mtDNA maintenance and integrity to human health. Additionally, mitochondrial dysfunction and mtDNA instability are linked to many wide-spread diseases associated with aging including cancer and neurodegeneration. Mitochondria lack the ability to repair certain helix-distorting lesions that are induced at high levels in mtDNA by important environmental genotoxins including polycyclic aromatic hydrocarbons, ultraviolet C radiation (UVC) and mycotoxins. These lesions are irreparable and persistent in the short term, but their long-term fate is unknown. Degradation of mitochondria and mtDNA is carried out by autophagy. Autophagy is protective against cell stress and apoptosis resulting from exposure to mitochondrial toxicants suggesting that it plays an important role in removal of unstable mitochondria that can serve as a source of ROS or initiate apoptotic cell death. Furthermore, dysfunctional mitochondria can be specifically targeted for degradation by the more specific process of mitophagy influenced in part by the processes of mitochondrial dynamics (i.e., fusion and fission). </p><p>The goals of this dissertation were to investigate the long-term fate of helix-distorting mtDNA damage and determine the significance of autophagy and mitochondrial dynamics in removal of and recovery from persistent mtDNA damage. Removal of irreparable mtDNA damage and the necessity of autophagy, mitophagy, fusion and fission genes in removal of this damage were examined using genetic approaches in adult <italic>Caenorhabditis elegans</italic>. In order to investigate the significance of autophagy, fusion and fission genes in recovery from mtDNA damage-induced mitochondrial dysfunction <italic>in vivo</italic>, an experimental method was developed to specifically induce persistent mtDNA damage and mitochondrial dysfunction without persistent nDNA damage in developing <italic>C. elegans</italic>. Additionally, the effect of persistent helix-distorting DNA damage on mitochondrial morphology, mitochondrial function and autophagy was investigated in <italic>C. elegans</italic> and in mammalian cell culture. The rate and specificity of mitochondrial degradation was further examined in cell culture using live-cell fluorescence microscopy and transmission electron microscopy. </p><p>Removal of UVC-induced mtDNA damage was detectable by 72 hours in <italic>C. elegans</italic> and mammalian cell culture, and required mitochondrial fusion, fission and autophagy, providing genetic evidence for a novel mtDNA damage removal pathway. UVC exposure induced autophagy with no detectable effect on mitochondrial morphology in both systems; mitochondrial function was inhibited in the <italic>C. elegans</italic> system but not in the cell culture system in which the degree of mtDNA damage induced was less. Furthermore, mutations in genes involved in these processes as well as pharmacological inhibition of autophagy exacerbated mtDNA damage-mediated larval arrest, illustrating the <italic>in vivo</italic> relevance of removal of persistent mtDNA damage. Mutations in genes in these pathways exist in the human population, demonstrating the potential for important gene-environment interactions affecting mitochondrial health after genotoxin exposure.</p> / Dissertation

<p>Organophosphorus pesticides (OPs) are neuroactive compounds that can affect the development of the nervous system and behavior. Using zebrafish, we compared the effectiveness of three different OPs, chlorpyrifos (CPF), diazinon (DZN) and parathion (PA) on survival, AChE inhibition and larval motility. We conclude that at equimolar concentrations CPF is the most effective OP of the three tested. 300nM CPF inhibited AChE when measured at 5 days post fertilization (dpf) by 80%, which correlated to a 35% decrease in larval motility when measured at 6 dpf. </p><p>We isolated the cDNA of <italic>zfkcc2</italic>, which encodes for an important cation-chloride cotransporter responsible for establishing a chloride gradient that allows for the neurotransmitter GABA to become inhibitory for a subset of neurons. By isolating the cDNA of <italic>zfkcc2</italic>, we were able to characterize its expression pattern up to 4 dpf. Using qRT-PCR, we showed that the expression of <italic>zfkcc2</italic> rises from 2 to 96 hours post fertilization (hpf). The expression of <italic>zfkcc2</italic> is found at 1 dpf in the forebrain, midbrain and hindbrain in a distinct pattern. By 3 dpf, zfkcc2 expression is found throughout most of the developing zebrafish brain. We were then able to characterize the expression pattern of zfnkcc1, which encodes for a cation-chloride cotransporter that works opposite to <italic>zfkcc2</italic> and establishes a chloride gradient allowing GABA to be excitatory during development. Expression of <italic>zfnkcc1</italic> is found at 1 dpf throughout most of the developing zebrafish head including in some non-neural tissue, but appears concentrated to the otic vesicle at 3 dpf. Using double in situ hybridization, we investigated the nature of the developmental switch from zfnkcc1 to zfkcc2 by looking at regions where there was an interaction between both genes' expression patterns in the developing zebrafish nervous system. </p><p>We preliminarily examined how affecting nicotinic signaling with exposures to nicotinic agonists/antagonists can affect the expression of <italic>zfnkcc2</italic> and <italic>zfkcc2</italic>. While there were no apparent changes in the expression pattern from any of the exposures at 2 dpf, we found that by 3 dpf nicotine and CPF exposures resulted in an incomplete expression pattern for <italic>zfkcc2</italic> that seemed to be delayed. However, the expression of <italic>zfnkcc1</italic> at the otic vesicle was unaffected by exposure. </p><p>Our results suggest that disrupting nicotinic signaling during development can affect the expression of an important cation-chloride cotransporter, <italic>zfkcc2</italic>, that plays a major role in establishing the necessary chloride gradient for the proper functioning of GABA during development. Future studies should focus on investigating the nature of the developmental switch between <italic>zfnkcc1</italic> and <italic>zfkcc2</italic> to see if the possibility of their regulation being coupled is a target for exposures.</p> / Dissertation

<p>Seasonally dry ecosystems cover large areas over the world, have high potential for carbon sequestration, and harbor high levels of biodiversity. They are characterized by high rainfall variability at timescales ranging from the daily to the seasonal to the interannual, and water availability and timing play key roles in primary productivity, biogeochemical cycles, phenology of growth and reproduction, and agricultural production. In addition, a growing demand for food and other natural resources in these regions renders seasonally dry ecosystems increasingly vulnerable to human interventions. Compounded with changes in rainfall regimes due to climate change, there is a need to better understand the role of climate variabilities in these regions to pave the way for better management of existing infrastructure and investment into future adaptations. </p><p>In this dissertation, the ecohydrological responses of seasonally dry ecosystem to climate variabilities are investigated under a comprehensive framework. This is achieved by first developing diagnostic tools to quantify the degree of rainfall seasonality across different types of seasonal climates, including tropical dry, Mediterranean, and monsoon climates. This global measure of seasonality borrows from information theory and captures the essential contributions from both the magnitude and concentration of the rainy season. By decomposing the rainfall signal from seasonality hotspots, increase in the interannual variability of rainfall seasonality is found, accompanied by concurrent changes in the magnitude, timing, and durations of seasonal rainfall, suggesting that increase in the uncertainty of seasonal rainfall may well extend into the next century. Next, changes in the hydrological partitioning, and the temporal responses of vegetation resulting from these climate variabilities, are analyzed using a set of stochastic models that accounts for the unpredictability rainfall as well as its seasonal trajectories. Soil water storage is found to play a pivotal role in regulating seasonal soil water hysteresis, and the balance between seasonal soil water availability and growth duration is found to induce maximum plant growth for a given amount of annual rainfall. Finally, these methods are applied in the context of biodiversity and the interplay of irrigation and soil salinity, which are prevailing management issues in seasonally dry ecosystems.</p> / Dissertation

<p>Polybrominated diphenyl ethers (PBDEs) are a class of flame retardant chemicals that were added to furniture foam, electronics, plastics, and some textiles to reduce their flammability. While PBDEs have been phased out from use in current products, huge reservoirs of products containing PBDEs still exist. It is likely exposure to PBDEs will continue as older products are discarded and recycled. PBDEs are ubiquitous contaminants in indoor and outdoor environments due to their widespread use in many products and their ability to migrate out of treated materials.</p><p> Major health effect concerns from PBDE exposure identified in laboratory studies include neurotoxicity, reproductive/developmental toxicity, and thyroid disruption. Importantly, mammals metabolize PBDEs into the hydroxylated polybrominated diphenyl ethers (OH-BDEs), which are structurally similar to endogenous thyroid hormones. Thyroid hormones are essential for metabolic processes, growth, and development, particularly brain development. Multiple studies have demonstrated enhanced potency of OH-BDEs relative to the parent PBDE chemicals, particularly for neurodevelopmental processes. Additionally, in fish species, thyroid hormones are essential for transitioning between larval, juvenile, and adult life stages. Therefore, studying the effects of both PBDEs and OH-BDEs during sensitive developmental life stages (i.e. larval and juvenile development) is warranted. The hypothesis of this thesis research is that PBDE metabolites interfere with thyroid hormone signaling (through interacting with thyroid receptor and deiodinase enzymes) which may result in decreased growth, morphological deficits, and altered neurodevelopment. The objectives of this research project were to evaluate the toxicity of PBDE metabolites and mixtures of PBDEs/OH-BDEs on larval and juvenile zebrafish development, examining both potential modes of action as well as functional consequences of exposure in developing animals. </p><p>In the first aim of this thesis research, structural relationships were examined between eleven different halogenated phenolic compounds (OH-BDEs, OH-PCBs, halogenated phenols, and TBBPA) to test developmental toxicity in zebrafish from 0-6 days post fertilization (dpf). In addition, follow up studies were performed with the most toxic compound, 6-hydroxy- 2,2’,4,4’-tetrabromodiphenyl ether (6-OH-BDE-47), to examine effects on TH-mediated morphological development and to better understand its mechanism of action in zebrafish. Thyroid disrupting agents including propylthiouracil, iopanoic acid, and native thyroid hormones were also used as positive controls for morphologic studies. Exposures to 6-OH-BDE-47 (10 nM to 100 nM) during development resulted in severe delays, similar to exposures from the T3 and thyroid disrupting agents. Lower jaw deformities and craniofacial cartilage malformations were also observed following exposure to 6-OH-BDE-47 at doses greater than 50 nM. Of interest, these developmental delays were rescued by overexpression of TRβ mRNA during the exposure period. These data indicate that OH-BDEs can adversely affect early life development of zebrafish and suggest they may be impacting thyroid hormone regulation in vivo through downregulation of the thyroid hormone receptor. </p><p>In the second aim of this dissertation research, neurobehavioral performance was monitored in larval and juvenile fish following a developmental exposure to 6-OH-BDE-47. 6-OH-BDE-47 has been identified as a neurotoxicant in previous cell based assays, and was identified as overtly toxic to zebrafish larvae in Aim 1 of this research. Developmental exposures (0-6 dpf) to 6-OH-BDE-47 resulted in decreased larval swimming activity at 6 dpf, with persisting impacts on behavior at 45 dpf. Young adult fish, when tested at 45 dpf, exhibited increased fear/anxiety response in the novel tank diving task and hyperactivity in a test of sensorimotor habituation. These data indicate that exposures to PBDE flame retardants and their metabolites during critical developmental windows can alter long term cognitive responses more than a month after the exposure has ceased.</p><p>Finally, for the third aim of this dissertation research, zebrafish undergoing larval-juvenile metamorphosis were exposed to a mixture of PBDEs (30-600 µg/L DE-71) and OH-BDEs (1-300 nM) from 9-23 dpf. Metamorphosis is a unique developmental period in fishes which is partially mediated by thyroid hormones. Juvenile animals, like larval animals, represent a sensitive and unique subpopulation of animals. At the end of the exposure period (23 dpf), a subset of fish were reared in clean water until 45 dpf for neurobehavioral testing. Fish samples were collected at 3 time points throughout the experiments, Days 12, 23, and 45. Tissue accumulation of test chemicals was monitored, and juvenile fish treated with the High Mixture were found to accumulate over 100 µg/g ww ∑PentaBDEs. The highest mixture treatment was found to be acutely toxic to zebrafish juveniles, resulting in >85% mortality within 14 days of exposure. Fish treated with 30 nM 6-OH-BDE-47 or the lower mixture exhibited reduced morphology scores relating to fin, pigmentation, and swim bladder maturation. In addition, reduced skeletal ossification and caudal area was observed at earlier time points with treatment to 6-OH-BDE-47. These alterations were accompanied by increases in chondrogenic gene expression, declines in osteogenic gene expression, and increases in thyroid receptor expression. Approximately 3.5 weeks after the exposure period, juvenile fish were tested on neurobehavioral tasks of novel tank exploration and sensorimotor habituation, however, no significant treatment related effects on task performance were observed. Collectively, these data suggested that the larval/juvenile development stage is a sensitive developmental window which can be adversely impacted by PBDE/OH-BDE exposure.</p> / Dissertation

<p>By concentrating materials and increasing the speed with which rainfall is conveyed off of the landscape, nearly all forms of land use change lead to predictable shifts in the hydrologic, thermal, and chemical regimes of receiving waters that can lead to the local extirpation of sensitive aquatic biota. In Central Appalachian river networks, alkaline mine drainage (AlkMD) derived from mountaintop removal mining for coal (MTM) noticeably simplifies macroinvertebrate communities. In this dissertation, I have used this distinct chemical regime shift as a platform to move beyond current understanding of chemical pollution in river networks. In Chapter Two, I applied a new model, the Hierarchical Diversity Decision Framework (HiDDeF) to a macroinvertebrate dataset along a gradient of AlkMD. By using this new modeling tool, I showed that current AlkMD water quality standards allow one-quarter of regional macroinvertebrates to decline to half of their maximum abundances. In Chapter Three, I conducted a field study in the Mud River, WV to understand how AlkMD influences patterns in aquatic insect production. This work revealed roughly 3-fold declines in annual production of sensitive taxa throughout the year in reaches affected by AlkMD. These declines were more severe during summer base flow when pollutant concentrations were higher, thereby preventing sensitive organisms from completing their life cycles. Finally, in Chapter Four I described the idea of chemical fragmentation in river networks by performing a geospatial analysis of chemical pollution in Central Appalachia. In this work I showed that the ~30% of headwaters that remain after MTM intensification over the last four decades support ~10% of macroinvertebrates not found in mined reaches. Collectively my work moves beyond the simple tools used to understand the static, local consequences of chemical pollution in freshwater ecosystems.</p> / Dissertation

Canal maintenance, involving mechanical removal of sediments and algal growth from canal basins, is necessary for sustaining the viability of the irrigation water delivery system in the Imperial Valley of California. Maintenance activities, however, disturb canal sediments laden with bacteria and can negatively impact water quality downstream. Our work quantified fecal indicator bacteria (Escherichia coli) and pathogens (Salmonella) in canal water prior to, during, and post-maintenance events. The goal of this study was to construct a post-maintenance time matrix that will allow growers downstream to estimate when canal water once again meets water quality guidelines. In addition, we assessed the water quality impacts of lining canals with concrete, which is a costly endeavor in the short term, but may be beneficial in the long term as lined canals do not require routine dredging to maintain canal integrity. During eight maintenance events from March 2013 through August 2014, 22% of 396 water samples collected exceeded the irrigation water quality guidelines (<126 MPN E. coli 100 mL-1) during canal maintenance. During summer months (July and August 2013-2014), E. coli concentrations in water samples commonly reached maximum values (>2419.6 MPN E. coli 100 mL-1), and these samples were more readily collected from unlined canal sampling sites. During winter and spring months, 80.8% of E. coli exceedances for unlined canals met guideline standards in less than 22 hours, while 19.2% of exceedances took longer (up to 48 hours) to return to acceptable levels; in lined sites, 63.6% and 36.4% met guidelines in less than 22 hours and 48 hours, respectively. Summer months showed a different trend: in unlined canal sites, 56.3% of E. coli exceedances met standards within 22 hours and 43.7% within 48 hours; in lined sites, 100% of water samples met standards in less than 22 hours. Unlined sites averaged higher temperatures overall compared to lined sites, and canal water in July (2013) was extremely warm (averaging 32.8°C) and reached human body temperature (37°C) at several unlined sites, a temperature at which enteric bacteria are known to thrive. Culturable Salmonella were detected in water samples collected in summer, with 22.2% of Salmonella-positive samples within 1°C of human body temperature. E. coli concentrations were significantly correlated with temperature and pH in unlined canals only. Unlined canals showed 15.2% of water samples were Salmonella-positive during summer maintenance whereas 1.7% of lined canals were positive. Salmonella significantly correlated with pH in lined canals. Fecal indicators (E. coli) did not predict pathogen (Salmonella) presence. Molecular methods (qPCR) suggested far higher levels of Salmonella when compared to cultural methods, with molecular markers for Salmonella exceeding culturing by more than 600%. The results of this work suggest that growers should exercise caution when irrigating after canal maintenance events, and to be completely certain of acceptable irrigation water quality, should wait for 48 hours following the onset of maintenance (typically 24 hours following the re-introduction of water to the channels) prior to irrigating crops. Further, irrigation district guidelines may consider: 1) disposing of the“first flush”of canal water following maintenance into nearby open areas, rather than sending poor-quality water into the irrigation canal system; 2) collect sediments and algae deposited on canal banks and transport to a secondary location to prevent precipitation runoff and re-introduction of bacteria-laden sediments to canals, and 3) consider the long-term costs and benefits of canal lining.