基于ISM和ANP的水库水华发生影响因素分析

为提高水库水华发生预警能力,从水华形成机理着手,引入营养盐条件、水动力条件、光热条件和浮游植物生长状况,建立水库水华发生影响因素模型。首先,基于文献研究,建立水库水华发生影响因素体系,共包含10个指标;其次,利用解释结构模型(ISM)建立水库水华发生影响因素递阶结构模型;最后采用网络层次分析法(ANP)构建权重模型,并借助Super Decision(SD)软件求解。结果表明:叶绿素a浓度、悬浮物浓度、磷浓度、氮浓度、铁等微量盐浓度、水流流速、温度和溶解氧为表层直接影响因素,光照和风速为深层根本影响因素;重要度排序为:叶绿素a浓度、悬浮物浓度、磷浓度、水流流速、氮浓度和溶解氧。     

Three-dimensional numerical simulation of water quality and sediment-associated processes with application to a Mississippi Delta lake

A three-dimensional water quality model was developed for simulating temporal and spatial variations of phytoplankton, nutrients, and dissolved oxygen in freshwater bodies. Effects of suspended and bed sediment on the water quality processes were simulated. A formula was generated from field measurements to calculate the light attenuation coefficient by considering the effects of suspended sediment and chlorophyll. The processes of adsorption–desorption of nutrients by sediment were described using the Langmuir Equation. The release rates of nutrients from the bed were calculated based on the concentration gradient across the water–sediment interface and other variables including pH, temperature and dissolved oxygen concentration.The model was calibrated and validated by applying it to simulate the concentrations of chlorophyll and nutrients in a natural oxbow lake in Mississippi Delta. The simulated time series of phytoplankton (as chlorophyll) and nutrient concentrations were generally in agreement with field observations. Sensitivity analyses were conducted to demonstrate the impacts of varying suspended sediment concentration on lake chlorophyll levels.     

ASSESSMENT OF NUTRIENT EFFECTS AND NUTRIENT LIMITATION IN LAKE OKEECHOBEE1

ABSTRACT: Lake Okeechobee, the third largest lake in the United States, is a shallow, mixing basin with annual total phosphorus concentrations ranging from 50–100 μg P/L. Data, mainly from unpublished agency reports, are analyzed to determine if nutrients limit phytoplankton, to describe spatial and temporal variability in trophic state parameters, and to evaluate conclusions obtained from empirical trophic state models. Algal bioassay experiments that have been used to assess nutrient limitation have produced equivocal results. However, seasonal minima in orthophosphorus and inorganic nitrogen indicate that both nutrients may be limiting seasonally. Strong, but reverse north-south gradients and large seasonal changes in phosphorus and nitrogen concentrations, show that empirical models based on annual phosphorus loadings or concentrations are not adequate to predict chlorophyll concentrations or other trophic state variables. Spatially-segmented, multi-class phytoplankton-nutrient models of seasonal phytoplankton responses that are coupled with hydrodynamic models may provide predictability in assessing effects of changing nutrient loads on phytoplankton composition and standing crop. Successful modeling efforts of responses to nutrients also must deal with resuspended and benthic algae, periphyton, and emergent and submergent aquatic plants that must play important trophic roles in some of the lake basin.     

A Method and Rationale for Deriving Nutrient Criteria for Small Rivers and Streams in Ohio

A mechanistic understanding of the effects of nutrient enrichment in lotic systems has been advanced over the last two decades such that identification of management thresholds for the prevention of eutrophication is now possible. This study describes relationships among primary nutrients (phosphorus and nitrogen), benthic chlorophyll a concentrations, daily dissolved oxygen (DO) concentrations, and the condition of macroinvertebrate and fish communities in small rivers and streams in Ohio, USA. Clear associations between nutrients, secondary response indicators (i.e., benthic chlorophyll and DO), and biological condition were found, and change points between the various indicators were identified for use in water quality criteria for nutrients in small rivers and streams (<1300 km²). A change point in benthic chlorophyll a density was detected at an inorganic nitrogen concentration of 0.435 mg/l (±0.599 SD), and a total phosphorus (TP) concentration of 0.038 mg/l (±0.085 SD). Daily variation in DO concentration was significantly related to benthic chlorophyll concentration and canopy cover, and a change point in 24-h DO concentration range was detected at a benthic chlorophyll level of 182 mg/m². The condition of macroinvertebrate communities was related to benthic chlorophyll concentration and both minimum and 24-h range of DO concentration. The condition of fish communities was best explained by habitat quality. The thresholds found in relationships between the stressor and the response variables, when interpreted in light of the uncertainty surrounding individual change points, may now serve as a framework for nutrient criteria in water quality standards.     

Nutrient Uptake in a Large Urban River1

Abstract: Small streams have been shown to be efficient in retaining nutrients and regulating downstream nutrient fluxes, but less is known about nutrient retention in larger rivers. We quantified nutrient uptake length and uptake velocity in a regulated urban river to determine the river’s ability to retain nutrients associated with wastewater treatment plant (WWTP) effluent. We measured net uptake of soluble reactive phosphorus (SRP), dissolved organic phosphorus, ammonium (NH₄), nitrate, and dissolved organic nitrogen in the Chattahoochee River, Atlanta, GA by following the downstream decline of nutrients and fluoride from WWTP effluent on 10 dates under low flow conditions. Uptake of all nutrients was sporadic. On many dates, there was no evidence of measurable nutrient uptake lengths within the reach; indeed, on several dates release of inorganic N and P within the sample reach led to increased nutrient export downstream. When uptake occurred, SRP uptake length was negatively correlated with total suspended solids and temperature. Uptake velocities of SRP and NH₄ in the Chattahoochee River were lower than velocities in less‐modified systems, but they were similar to those measured in other WWTP impacted systems. Lower uptake velocities indicate a diminished capacity for nutrient uptake.     

PHYTOPLANKTON PRODUCTIVITY AND BIOMASS IN THE CHARLOTTE HARBOR ESTUARINE SYSTEM,FLORIDA1

ABSTRACT: Phytoplankton carbon-14 productivity at a depth of 50 percent of surface light and chlorophyll-α concentrations were measured every other month from November 1985 through September 1986 at 12 stations in the Charlotte Harbor estuarine system. Maximum productivity and chlorophyll-α concentrations occurred during summer or early autumn near the mouths of tidal rivers. Most of the variability in light-normalized productivity and chlorophyll-α could be attributed to two factors derived from Principal Component Analysis of ambient water-quality characteristics. One factor related to seasonal variability and the other to spatial variability. The seasonal factor incorporated the interaction of temperature and nutrients. The spatial factor incorporated the interaction of salinity, nutrients, and water color that resulted from the mixing of freshwater inflow and seawater. Although freshwater inflow increased the availability of nutrients in low salinity (less than 10‰) waters, the highly colored freshwater restricted light penetration and phytoplankton productivity. Maximum productivity and biomass occurred where color associated with the freshwater inflow had been diluted by seawater so that light and nutrients were both available. Concentrations of inorganic nitrogen were often at or below detection limit throughout most of the high salinity (greater than 20‰) waters of the estuary and was probably the most critical nutrient in limiting phytoplankton productivity.     

富营养化发生机理及水华暴发研究进展

概述了目前富营养发生的机理和水华暴发机制的最新研究方向。从营养物质的循环、水体热分层、水化学平衡方面论述和总结了富营养发生机理的研究现状;从氮磷比、其它营养元素限制、沉积物营养物质的循环等方面对水华暴发机制作用的研究进行了展望。本文对富营养化发生机理及水华暴发研究领域现状和未来的研究方向有一定的借鉴作用。     

Performance of an overland flow system for advanced treatment of wastewater plant effluent

Overland flow (OF) systems were evaluated and compared for advanced treatment of municipal and industrial effluents, including nutrients and nondegradable chemical oxygen demand (COD) removal. Three pilot plants were constructed at the Shahin Shahr Wastewater Treatment Plant (WWTP), Isfahan, Iran. Each pilot was assigned a specific wastewater and all were simultaneously operated for 8 months. Treatment of primary effluent, activated sludge secondary effluent, and lagoon effluent of textile wastewater was investigated at application rates (ARs) of 0.15, 0.25, and 0.35m(3)m(-1)h(-1). During 5 months of stable operation after a 3-month acclimation period, mean removals of total 5-day biochemical oxygen demand (TBOD(5)), total COD (TCOD), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP) and turbidity were 74.5%, 54.8%, 66.2%, 39.4%, 35.8%, and 67.7% for primary effluent; 52.9%, 52.9%, 66.5%, 44.4%, 39.8%, and 50.1% for activated sludge effluent; 65.7%, 58.7%, 70.3%, 41.7%, 41.3%, and 54.9% for textile wastewater lagoon effluent, respectively. The model of Smith and Schroeder, 1985. Field studies of the overland flow process for the treatment of raw and primary treated municipal wastewater. Journal of Water Pollution Control Federation 57, 785-794] was satisfactory for TBOD(5). For all treatment parameters a standard first-order removal model was inadequate to represent the data but a modified first-order model provided a satisfactory fit to the data. Based on the results of this study, it can be concluded that an OF system as advanced treatment had the ability to meet effluent discharge permit limits and was an economical replacement for stabilization ponds and mechanical treatment options.     

Dry Weather Water Quality Loadings in Arid,Urban Watersheds of the Los Angeles Basin,California, USA1

Abstract: Dry weather runoff in arid, urban watersheds may consist entirely of treated wastewater effluent and/or urban nonpoint source runoff, which can be a source of bacteria, nutrients, and metals to receiving waters. Most studies of urban runoff focus on stormwater, and few have evaluated the relative contribution and sources of dry weather pollutant loading for a range of constituents across multiple watersheds. This study assessed dry weather loading of nutrients, metals, and bacteria in six urban watersheds in the Los Angeles region of southern California to estimate relative sources of each constituent class and the proportion of total annual load that can be attributed to dry weather discharge. In each watershed, flow and water quality were sampled from storm drain and treated wastewater inputs, as well as from in‐stream locations during at least two time periods. Data were used to calculate mean concentrations and loads for various sources. Dry weather loads were compared with modeled wet weather loads under a range of annual rainfall volumes to estimate the relative contribution of dry weather load. Mean storm drain flows were comparable between all watersheds, and in all cases, approximately 20% of the flowing storm drains accounted for 80% of the daily volume. Wastewater reclamation plants (WRP) were the main source of nutrients, storm drains accounted for almost all the bacteria, and metals sources varied by constituent. In‐stream concentrations reflected major sources, for example nutrient concentrations were highest downstream of WRP discharges, while in‐stream metals concentrations were highest downstream of the storm drains with high metals loads. Comparison of wet vs. dry weather loading indicates that dry weather loading can be a significant source of metals, ranging from less than 20% during wet years to greater than 50% during dry years.     

Using a Multi-Component Indicator Toward Reducing Phytoplankton Bloom Occurrences in the Swan River Estuary

The Swan River estuary is an icon of the city of Perth, Western Australia, running through the city centre and dividing the northern from the southern part of the city. However, frequent phytoplankton blooms have been observed in the estuary as a result of eutrophication. The Index of Sustainable Functionality (ISF), a composite index able to indicate for sustainable health of the estuary, was applied, taking into account the hydrology and highly seasonal nature of the estuary to inform the management of the estuary, towards the aim of reducing bloom occurrences. The study period was from the beginning of intensive monitoring in 1995 to mid-2009. The results emphasize the importance of physical controls on the ecology of the estuary. No significant trend in the estuary's low functionality was found, indicating that despite extensive restoration efforts, the frequency of algal bloom occurrences has remained relatively stationary and other mitigating factors have maintained an annual average ISF value at around 70 % functionality. We identified that the low flow season consistently performs the worst, with (high) temperature found as the most dominant variable for phytoplankton growth and bloom. Thus in managing the estuary, vigilance is required during periods of high temperature and low flow. Focusing on the risk of phytoplankton bloom, a nutrient reduction program that is in place is a long term solution due to high concentrations in the estuary. Other management measures need to be considered and adopted to effectively reduce the occurrences of future phytoplankton blooms.     

Landfill Bioreactor Cells as Ecofilters for Extraction of Bio-energy and Nutrients from Solid Wastes

This paper describes a modified, ecologically based waste treatment technique, where municipal solid waste is anaerobically treated in landfill reactorcells in a way that both bio-energy and nutrients can be recovered. The controlled landfill reactorcell ('bioreactor-cell') serves as an anaerobic filter, where energy is extracted as biogas while nutrients are recovered through the leachates. The leachates can be used as fertilizer in e.g. energy forests within the controlled landfill area, and thus nutrients can be brought back into an ecocycle. At the same time anaerobic conditions result in an effective immobilization of heavy metals and other pollutants, e.g. through complexation to organic matter or as insoluble metal sulphides, which are immobilized in the fermentation residue. The long-lived organic fraction, remaining after the fermentation process has declined, containing a high content of lignine, serves as a water-holding matrix. Thus it helps to enforce a sustainable high moisture level, resulting in sustainable anaerobic conditions with heavy metals retained on a long-term basis. Also non-degradable products, like plastics, help to shield off oxygen and maintain reliable anaerobic conditions. Landfilling of organic matter under anaerobic conditions is a measure to counteract increasing concentrations of CO₂ in the atmosphere, resulting from human activities. A small fraction of the organic matter is long-term accumulated in the landfill, and the processes can be compared to those of natural wetlands.     

Biological nutrient removal from pre-treated landfill leachate in a sequencing batch reactor

Biological treatment of landfill leachate usually results in low nutrient removals because of high chemical oxygen demand (COD), high ammonium-N content and the presence of toxic compounds such as heavy metals. Landfill leachate with high COD content was pre-treated by coagulation-flocculation with lime followed by air stripping of ammonia at pH=12. Nutrient removal from pre-treated leachate was carried out using a lab-scale sequencing batch reactor (SBR). Three different operations consisting of different numbers of steps were tested and their performances were compared. These operations were the three-step anaerobic (An)/anoxic (Ax)/oxic (Ox); the four-step (An/Ox/Ax/Ox), and the five-step (An/Ax/Ox/Ax/Ox) operations with total residence time of seven hours each. Experiments were carried out using three consecutive operations with a total cycle time of 21 h at a constant sludge age of 10 days. The lowest effluent nutrient levels were realized by using the five-step operation which resulted in effluent COD, NH4-N and PO4-P contents of 1,400, 107 and 65 mg l(-1), respectively, at the end of 21 h. Addition of domestic wastewater (1/1, v/v) and powdered activated carbon (PAC, 1 g l(-1)) to the pre-treated leachate improved nutrient removals in the five-step SBR operation, resulting in 75% COD, 44% NH4-N and 44% PO4-P removals after 21 hours of operation.     

Environmental Control and Limnological Impacts of a Large Recurrent Spring Bloom in Lake Washington,USA

A series of statistical analyses were used to identify temporal and spatial patterns in the phytoplankton and nutrient dynamics of Lake Washington, an mesotrophic lake in Washington State (USA). These analyses were based on fortnightly or monthly samples of water temperature, Secchi transparency, ammonium (NH₄), nitrate (NO₃), inorganic phosphorus (IP), total nitrogen (TN), total phosphorus (TP), dissolved oxygen (DO), pH and chlorophyll a (chl a) collected during 1995–2000 from 12 stations. Lake Washington has a very consistent and pronounced annual spring diatom bloom which occurs from March to May. During this bloom, epilimnetic chl a concentrations peak on average at 10 μg/L, which is 3 times higher than chl a concentrations typically seen during summer stratified conditions. The spring bloom on average comprised 62% diatoms, 21% chlorophytes and 8% cyanobacteria. During summer stratification, diatoms comprised 26% of the phytoplankton community, chlorophytes 37% and cyanobacteria 25%. Cryptophytes comprised approximately 8% of the community throughout the year. Overall, 6 phytoplankton genera (i.e., Aulacoseira, Fragilaria, Cryptomonas, Asterionella, Stephanodiscus, and Ankistrodesmus) cumulatively accounted for over 50% of the community. These analyses also suggest that the phytoplankton community strongly influences the seasonality of NO₃, IP, DO, pH and water clarity. According to a MANOVA, seasonal fluctuations explained 40% of the total variability for the major parameters, spatial heterogeneity explained 10% of variability, and the seasonal-spatial interaction explained 10% of variability. Distinctive patterns were identified between offshore and inshore sampling stations. The results of our analyses also suggest that spatial variability was substantial, but much smaller than temporal variability.     

The performance of constructed wetlands treating primary, secondary and dairy soiled water in Ireland (a review)

In Ireland, no database detailing the design, influent loading rates or performance of constructed wetlands (CWs) exists. On account of this, they are designed without any protocol based on empirical data. The aim of this paper was to provide the first published data on the performance of free-water surface flow (FWSF) CWs treating primary and secondary-treated municipal wastewater, and agricultural dairy soiled water (DSW) in Ireland. In total, the performance of thirty-four FWSF CWs, comprising fourteen CWs treating primary-treated municipal wastewater, thirteen CWs treating secondary-treated municipal wastewater, and seven CWs treating DSW, were examined. In most CWs, good organic, suspended solids (SS) and nutrient removal was measured. At an average organic loading rate (OLR) of 10 and 9 g biochemical oxygen demand (BOD) m(-2) d(-1), CWs treating primary and secondary wastewater removed 95 and 84% of influent BOD. Constructed wetlands treating DSW had an average BOD removal of 98%. At average SS loading rates of 6 and 14 g m(-2) d(-1), CWs treating primary and secondary wastewater had a 96 and an 82% reduction, and produced a final effluent with a concentration of 14 and 13 mg L(-1). Constructed wetlands treating DSW produced a final effluent of 34 mg L(-1) (94% reduction). Similar to other studies, all CWs examined had variable performance in ammonium-N (NH(4)(+)-N) removal, with average removals varying between 37% (for CWs treating secondary wastewater) and 88% (for CWs treating DSW). Variable ortho-phosphorus (PO(4)(3-)-P) removal was attributable to different durations of operation, media types and loading rates.     

WATER QUALITY STRATIFICATION IN SHALLOW WASTEWATER STABILIZATION PONDS1

ABSTRACT: The physical limnology of three modern wastewater stabilization ponds serving a small community in Minnesota was investigated over a 1-year period (July 1989 - October 1990). Water temperatures and associated meteorological parameters were recorded continuously; underwater light, dissolved oxygen, pH, and Secchi depth were measured intermittently (about weekly). Measurements of nutrients and planktonic species were made by other investigators. Water quality stratification dynamics were studied by analyzing variations of water temperature, dissolved oxygen, and pH distributions with time and over depth. Intermittent stratification and mixing of the shallow waste stabilization ponds (1–2 m deep) were documented and related to weather. The strong response of the ponds to seasonal and daily weather variations was observed. Three types of pond stratification conditions have been identified: (1) completely mixed during consecutive day and night, (2) stratified during the day and well-mixed during the night, and (3) continuously stratified during day and night. A diurnal cycle of stratification dynamics was first noticed in late April and persisted through summer and into fall. Differences in light attenuation and hence temperature stratification and DO distribution between pond 1 (primary), pond 2 (second primary) and pond 3 (secondary) in the wastewater treatment system were documented and related to different waste loading conditions. Temperature stratification affects chemical, microbial, and planktonic processes in the ponds. Results presented in this paper can be used to provide guidance for water quality sampling in monitoring of pond performance. Information on true mixing conditions is also needed to gain better understanding of important factors affecting pond operation, and for process simulations and reactor modeling of waste stabilization ponds.     

Valuing algal bloom in the Black Sea Coast of Bulgaria: A choice experiments approach

Increased interest in water quality in coastal and marine areas stemming from the Water Framework Directive and the Marine Strategy Framework Directive has led to important questions in relation to policies that address nutrient loadings. This paper presents the results from a choice experiment study to assess the recreational damage associated with algal blooms caused by nutrients flows into Varna Bay, Bulgaria. Varna Bay is an important beach destination on the Black Sea coast of Bulgaria. Algal bloom events have been experienced frequently in the area. A choice experiment questionnaire was developed and applied in the Varna Bay area to assess the extent to which the quantity of algal blooms and the duration of the bloom affect recreational activities. The amount of bloom was found to be important, as respondents were on average willing to pay a one off tax of 18.97 Leva (€9.73) for a program that provides beaches free from algal blooms.     

Model‐Based Nitrogen and Phosphorus (Nutrient) Criteria for Large Temperate Rivers: 2. Criteria Derivation

Nitrogen and phosphorus criteria were developed for 233 km of the Yellowstone River, one of the first cases where a mechanistic model has been used to derive large river numeric nutrient criteria. A water quality model and a companion model which simulates lateral algal biomass across transects were used to simulate effects of increasing nutrients on five variables (dissolved oxygen, total organic carbon, total dissolved gas, pH, and benthic algal biomass in depths ≤1 m). Incremental increases in nutrients were evaluated relative to their impact on predefined thresholds for each variable; the first variable to exceed a threshold set the nutrient criteria. Simulations were made at a low flow, the 14Q5 (lowest average 14 consecutive day flow, July‐September, recurring one in five years), which was derived using benthic algae growth curves and EPA guidance on excursion frequency. An extant climate dataset with an annual recurrence was used, and tributary water quality and flows were coincident with the river's 10 lowest flow years. The river had different sensitivities to nutrients longitudinally, pH being the most sensitive variable in the upstream reach and algal biomass in the lower. Model‐based criteria for the Yellowstone River are as follows: between the Bighorn and Powder river confluences, 55 μg TP/l and 655 μg TN/l; from the Powder River confluence to Montana state line, 95 μg TP/l and 815 μg TN/l. Pros and cons of using steady‐state models to derive river nutrient criteria are discussed.     

NUTRIENT DISTRIBUTION AND VARIABILITY IN THE CHARLOTTE HARBOR ESTUARINE SYSTEM,FLORIDA1

ABSTRACT: The sources and distribution of nutrients in the Charlotte Harbor estuarine system were evaluated using nutrient dilution curve models. Except for ammonia, nutrient concentrations were highest and most variable in the rivers, and generally decreased with increasing salinity. Observed and theoretical dilution curves for phosphorus were generally in close agreement, which suggests conservative behavior. Phosphorus concentrations sagged below a straight line because phosphorus-rich water from the upper Peace River basin was diluted by tributaries in the lower basin. The concentrations of dissolved silica appeared to be conservative on some occasions. On other occasions, dissolved silica appeared to be removed at low salimties or released at higher salinities. Concentrations of ammonia were highly variable along the salinity gradient, presumably because of variations in ammonia regeneration and uptake. Concentrations of nitrite plus nitrate were well below conservative dilution curves, probably due to phy-toplankton uptake. At salinities greater than 20%, nitrite plus nitrate concentrations were usually at or below the detection limit and may limit phytoplankton productivity. Projected increased nitrogen loadings from urban development in the basin would favor undesirable increases in phytoplankton and benthic algal growth in waters where sufficient light is available.     

Contribution of Wastewater Treatment Plant Effluents to Nutrient Dynamics in Aquatic Systems: A Review

Excessive nutrient loading (considering nitrogen and phosphorus) is a major ongoing threat to water quality and here we review the impact of nutrient discharges from wastewater treatment plants (WWTPs) to United States (U.S.) freshwater systems. While urban and agricultural land uses are significant nonpoint nutrient contributors, effluent from point sources such as WWTPs can overwhelm receiving waters, effectively dominating hydrological characteristics and regulating instream nutrient processes. Population growth, increased wastewater volumes, and sustainability of critical water resources have all been key factors influencing the extent of wastewater treatment. Reducing nutrient concentrations in wastewater is an important aspect of water quality management because excessive nutrient concentrations often prevent water bodies from meeting designated uses. WWTPs employ numerous physical, chemical, and biological methods to improve effluent water quality but nutrient removal requires advanced treatment and infrastructure that may be economically prohibitive. Therefore, effluent nutrient concentrations vary depending on the particular processes used to treat influent wastewater. Increasingly stringent regulations regarding nutrient concentrations in discharged effluent, along with greater freshwater demand in populous areas, have led to the development of extensive water recycling programs within many U.S. regions. Reuse programs provide an opportunity to reduce or eliminate direct nutrient discharges to receiving waters while allowing for the beneficial use of reclaimed water. However, nutrients in reclaimed water can still be a concern for reuse applications, such as agricultural and landscape irrigation.     

Spatiotemporal Associations of Reservoir Nutrient Characteristics and the Invasive,Harmful Alga Prymnesium parvum in West Texas

Golden alga (Prymnesium parvum) is a harmful alga that has caused ecological and economic harm in freshwater and marine systems worldwide. In inland systems of North America, toxic blooms have nearly eliminated fish populations in some systems. Modifying nutrient profiles through alterations to land or water use may be a viable alternative for golden alga control in reservoirs. The main objective of this study was to improve our understanding of the nutrient dynamics that influence golden alga bloom formation and toxicity in west Texas reservoirs. We examined eight sites in the Upper Colorado River basin, Texas: three impacted reservoirs that have experienced repeated golden alga blooms; two reference reservoirs where golden alga is present but nontoxic; and three confluence sites downstream of the impacted and reference sites. Total, inorganic, and organic nitrogen and phosphorus and their ratios were quantified monthly along with golden alga abundance and ichthyotoxicity between December 2010 and July 2011. Blooms persisted for several months at the impacted sites, which were characterized by high organic nitrogen and low inorganic nitrogen. At impacted sites, abundance was positively associated with inorganic phosphorus and bloom termination coincided with increases in inorganic nitrogen and decreases in inorganic phosphorus in late spring. Management of both inorganic and organic forms of nutrients may create conditions in reservoirs unfavorable to golden alga.