Classification of Ephemeral,Intermittent, and Perennial Stream Reaches Using a TOPMODEL‐Based Approach

Whether a waterway is temporary or permanent influences regulatory protection guidelines, however, classification can be subjective due to a combination of factors, including time of year, antecedent moisture conditions, and previous experience of the field investigator. Our objective was to develop a standardized protocol using publically available spatial information to classify ephemeral, intermittent, and perennial streams. Our hypothesis was that field observations of flow along the stream channel could be compared to results from a hydrologic model, providing an objective method of how these stream reaches can be identified. Flow‐state sensors were placed at ephemeral, intermittent, and perennial stream reaches from May to December 2011 in the Appalachian coal basin of eastern Kentucky. This observed flow record was then used to calibrate the simulated saturation deficit in each channel reach based on the topographic wetness index used by TOPMODEL. Saturation deficit values were categorized as flow or no‐flow days, and the simulated record of streamflow was compared to the observed record. The hydrologic model was more accurate for simulating flow during the spring and fall seasons. However, the model effectively identified stream reaches as intermittent and perennial in each of the two basins.     

DISSOLVED OXYGEN MODEL OF A SHORT DETENTION TIME RESERVOIR WITH ANAEROBIC HYPOLIMNION1

ABSTRACT: A vertical dissolved oxygen model was calibrated and verified using independent field data sets from 1972 and 1973 in Lake Lyndon B. Johnson (LBJ), a short detention time reservoir with anaerobic hypolimnion. Ammonia, carbonaceous BOD, conductivity, and temperature were also simulated as state variables. The conductivity results provided a check on the mass balance and the method of entering the inflows to the reservoir model. Emphasis was placed on calculating the sinks of dissolved oxygen in the hypolimnion which could be useful in management decisions.     

THE DETERMINATION OF PRIMARY PRODUCTION IN A STREAM USING AN EXACT SOLUTION TO THE OXYGEN BALANCE EQUATION1

ABSTRACT. A promising technique for recognition of early stages of cultural eutrophication relies on determining production and respiration in streams. The most successful and most widely used method of estimating production of a segment of a stream is the upstream-downstream, diurnal curve method introduced by Odum [1956]. This technique is equivalent to obtaining an approximate solution to the oxygen balance equation. We report here an exact solution of the balance equation as a method for calculating primary production. Data presented by Owens [1966] are analyzed; effects of depth and oxygen saturation are studied. A major advantage of the method described here is that continuous temporal variation of net production may be rigorously handled. The method is shown to be well suited to our ultimate goal of studying energy budgets of streams, and thereby the eutrophication process.     

LAKE QUALITY DISCRIMINANT ANALYSIS1

ABSTRACT: Despite the fact that lake phosphorus loading criteria have proven to be valuable tools in lake management, they are generally subjective in nature or incomplete in form. In order to address these shortcomings, the oxic-anoxic transition point was selected as an objective quality criterion and discriminant analysis was used to construct a lake classification function. This function is dependent upon lake phosphorus loading, mean depth, and overflow rate. The value of the function may be expressed as a probability of classification (as either oxic or anoxic). When used in prediction, inclusion of the input error permits the estimation of the change in classification probability as input uncertainty is reduced. Further, the form of the discriminant function suggests that the annual volumetric loading is a more informative term for the expression of phosphorus loading than is the annual areal loading.     

Comparative performance study of different configurations of organic Rankine cycle using low-grade waste heat for power generation

This paper aims at analyzing the feasibility of a waste heat recovery power generation plant based on parametric optimization and performance analysis using different organic Rankine cycle configurations and heat source temperature conditions with working fluid R-12, R-123, R-134a, and R-717. A parametric optimization of turbine inlet temperature(TIT) was performed to obtain the irreversibility rate, system efficiency, availability ratio, turbine work output, system mass flow rate, second-law efficiency, and turbine outlet quality, along the saturated vapor line and also on superheating at an inlet pressure of 2.50 MP in basic as well as regenerative organic Rankine cycle. The calculated results reveal that selection of a basic organic Rankine cycle using R-123 as working fluid gives the maximum system efficiency, turbine work output, second-law efficiency, availability ratio with minimum system irreversibility rate and system mass flow rate up to a TIT of 150°C and appears to be a choice system for generation of power by utilizing the flue gas waste heat of thermal power plants and above 150°C the regenerative superheat organic Rankine cycle configuration using R 123 as working fluid gives the same results.     

LOW-HEAD HYDROPOWER IMPACTS ON STREAM DISSOLVED OXYGEN1

ABSTRACT: A method to evaluate the effect of hydropower development on downstream dissolved oxygen (DO) is presented for a low head dam. Water, previously aerated during release over spillways and under gates, is diverted through the hydropower facility without further aeration. The oxygen transfer that occurs as a result of air entrainment at the various release points of a dam is measured. Oxygen transfer efficiencies are calculated and incorporated into an oxygen transfer model to predict average release DO concentrations. This model is used to systematically determine the effect of hydropower operation on downstream DO. Operational alternatives are investigated and a simple operational guide is developed to mitigate the effects of hydropower operation. Combinations of reduced generation and optimal releases from the dam allow the hydropower facility to operate within DO standards.     

High Sediment Oxygen Demand Within an Instream Swamp in Southern Georgia: Implications for Low Dissolved Oxygen Levels in Coastal Blackwater Streams1

Todd, M. Jason, George Vellidis, R. Richard Lowrance, and Catherine M. Pringle, 2009. High Sediment Oxygen Demand Within an Instream Swamp in Southern Georgia: Implications for Low Dissolved Oxygen Levels in Coastal Blackwater Streams. Journal of the American Water Resources Association (JAWRA) 45(6):1493‐1507. Abstract: Sediment oxygen demand (SOD) is considered a critical and dominant sink for dissolved oxygen (DO) in many river systems including blackwater streams and is often poorly investigated or roughly estimated in oxygen budgets. The purposes of this study are to (1) characterize and document the magnitude and variability of SOD in representative instream swamps found on the Georgia Coastal Plain; (2) predict SOD from more readily measured parameters such as soil, sediment, and litter organic carbon; and (3) obtain an accurate representation of SOD values within this understudied habitat to help improve water quality models and the continued development of DO as an appropriate water quality standard. Results show SOD rates ranging from 0.491 to 14.189 g O₂/m²/day, up to 18 times higher than values reported for southeastern sandy‐bottomed streams and suggest that instream swamps are repositories of large amounts of organic matter and are thus areas of intense oxygen demand and a major factor in determining the oxygen balance of the watershed as a whole. These areas of intense oxygen demand in relatively unimpacted areas indicate that low DO concentrations may be a natural phenomenon. SOD rates were significantly correlated (alpha = 0.05) with a number of sediment parameters, with organic carbon and total organic carbon being the best predictors of SOD rate. When developing water quality models, managers should pay closer attention to the influence of SOD as it plays a critical role in determining DO levels within instream swamps and the river system.     

上海市2003年生态足迹计算与分析

本文应用Wackernagel等提出的生态足迹概念和方法对上海区2003年的生态足迹和承载力进行计算和分析。结果表明,2003年上海市人均生态足迹为3．36hm^2,人均生态承载力为0．46hm^2。在此基础上提出了减缓上海市生态赤字的一系列措施,最后对模型的完善作出了展望。     

Factors Affecting Sediment Oxygen Demand Dynamics in Blackwater Streams of Georgia’s Coastal Plain1

Abstract: Sediment oxygen demand (SOD) is believed to be an important process affecting dissolved oxygen (DO) concentrations in blackwater streams of the southeastern coastal plain. Because very few data on SOD are available, it is common for modelers to take SOD values from the literature for use with DO models. In this study, SOD was measured in seven blackwater streams of the Suwannee River Basin within the Georgia coastal plain for between August 2004 and April 2005. SOD was measured using four in situ chambers and was found to vary on average between 0.1 and 2.3 g O₂/m/day across the seven study sites throughout the study period. SOD was found to vary significantly between the watersheds within the Suwannee River Basin. However, land use was not found to be the driving force behind SOD values. Statistical analyses did find significant interaction between land use and watersheds suggesting that an intrinsically different factor in each of the watersheds may be affecting SOD and the low DO concentrations. Further research is needed to identify the factors driving SOD dynamics in the blackwater streams of Georgia’s coastal plain. Results from this study will be used by the Georgia Department of Natural Resources – Environmental Protection Division as model input data for the development and evaluation of DO total maximum daily loads in the Georgia coastal plain.     

Nutrient Response Modeling in Falls of the Neuse Reservoir

In order to study system responses of Falls of the Neuse Reservoir (Falls Lake) to varied nutrient loadings, a coupled three-dimensional hydrodynamic and eutrophication model was applied. The model was calibrated using 2005 and 2006 intensive survey data, and validated using 2007 survey data. Compared with historical hydrological records, 2005 and 2007 were considered as dry years and 2006 was recognized as a normal year. Relatively higher nutrient fluxes from the sediment were specified for dry year model simulations. The differences were probably due to longer residence time and hence higher nutrient retention rate during dry years in Falls Lake. During the normal year of 2006, approximately 70% of total nitrogen (TN) and 80% of total phosphorus (TP) were delivered from the tributaries; about 20% (TN and TP) were from the sediment bottom. During the dry years of 2005 and 2007, the amount of TN released from sediment was equivalent to that introduced from the tributaries, indicating the critical role of nutrient recycling within the system in dry years. The model results also suggest that both nitrogen and phosphorus are limiting phytoplankton growth in Falls Lake. In the upper part of the lake where high turbidity was observed, nitrogen limitation appeared to dominate. Scenario model runs also suggest that great nutrient loading reductions are needed for Falls Lake to meet the water quality standard.     

EFFECTS OF VARIABLE DISCHARGE SCHEMES ON DISSOLVED OXYGEN AT A HYDROELECTRIC STATION1

ABSTRACT: The effects of variable discharges during the summer on the dissolved oxygen (DO) content and water temperature upstream and downstream of the Conowingo Hydroelectric Power Station were investigated. The DO dynamics are controlled primarily by meteorological factors that are independent of the mode of hydrostation operation. DO stratification occurred during the summer in Conowingo Pond, but thermal stratification was not observed. The magnitude and duration of off-peak discharges including a run-of-the-river operation did not affect DO stratification in Conowingo Pond; little vertical mixing occurred. However, strong winds and/or high river flows temporarily destroyed DO stratification. The run-of-the-river operation or off-peak continuous discharge schemes did not provide better DO conditions downstream of the hydrostation than the peaking operation with intermittent off-peak releases. A statistical model predicted that a DO of 5 ppm occurs 0.6 miles downstream of the powerhouse when the natural river flow is consistently greater than 15,000 cfs and water temperature is less than 80°F. A mean daily DO of at least 4 ppm was predicted to occur over 80 percent of the time during the 92-day summer period. Farther downstream (1.3 miles from the powerhouse) a mean daily DO of at least 4 ppm was predicted to occur 90 percent of the time in summer.     

THE LIMNOLOGY OF LAKE WABUKAYNE,A STORM-WATER IMPOUNDMENT1

ABSTRACT The limnology of a 1.9-ha storm-water detention pond is described. The eutrophic nature of this impoundment is attributed to the nutrients in runoff from the surrounding residential area. During the summer, photosynthetic activity of the phytoplankton caused surface waters to become super-saturated with oxygen, while decomposing organic material greatly reduced dissolved oxygen concentrations in the deeper water. Sediment derived from construction activity within the drainage basin caused the impoundment to be turbid. The use of road deicing salts within the drainage basin produced high chloride concentrations and a temporary meromixis during the winter and early spring. The benthic fauna consisted primarily of oligochaetes, chironomids, and chaoborids. High densities of oligochaetes were present in the settling basin. Chaoborid larvae were abundant in the deep basin where low oxygen concentrations reduced the numbers of other benthic macroinvertebrates.     

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.     

Exploratory Analysis of the Winter Chemistry of Five Lakes on the North Slope of Alaska1

Abstract: Lakes are important water resources on the North Slope of Alaska. Freshwater is required for oilfield production as well as exploration, which occurs largely on ice roads and pads. Since most North Slope lakes are shallow, the quantity and quality of the water under ice at the end of winter are important environmental management issues. Currently, water‐use permits are a function of the presence of overwintering fish populations, and their sensitivity to low oxygen concentrations. Sampling of five North Slope lakes during the winter of 2004‐2005 shed some light on the winter chemistry of four lakes that were used as water supplies and one undisturbed lake. Field analysis was conducted for oxygen, conductivity, pH, and temperature throughout the lake depth, as well as ice thickness and water depth. Water samples were retrieved from the lakes and analyzed for Na, Ca, K, Mg, Fe, dissolved‐organic carbon, and alkalinity in the laboratory. Lake properties, rather than pumping, were the best predictors of oxygen depletion, with the highest dissolved‐oxygen levels maintained in the lake with the lowest concentration of constituents. Volume weighted mean dissolved‐oxygen concentrations ranged from 4 to 94% of saturation in March. Dissolved oxygen and specific conductance data suggested that the lakes began to refresh in May.     

生态足迹在城市可持续性定量测度中的应用——以济南市2003年为例

根据生态足迹模型,对济南市2003年的生态足迹、生态承载力和生态赤字进行了实证计算和分析.结果表明:济南处于不可持续发展中.造成生态赤字大的原因是能源结构、对自然资源开发过度和人口密度大.因此,提高土地生产力、严格控制人口数量、建立资源节约型生产和消费体系势在必行.     

地方“资源诅咒”与“生态赤字”的经济学分析——以“榆林市”等资源型城市为例

我国陕西省榆林市、甘肃省白银市、辽宁省抚顺市及四川省古蔺县等地区,依托丰富的铜、煤炭、天然气等矿产资源带动了当地经济的快速发展。然而,对资源的过度依赖和开发,使地方经济无可回避地面临"资源诅咒"和"生态赤字"问题。本文在界定"资源诅咒"和"生态赤字"概念,及其产生的经济学根源的基础上,对"榆林市"、"白银市"等典型资源型城市的"生态赤字"现状予以分析,提出基于"3E系统模型"视角下,解决资源型城市"资源诅咒"和"生态赤字"问题,实现地方经济可持续发展的路径选择。     

A System Dynamics Model for Conjunctive Management of Water Resources in the Snake River Basin

The Pacific Northwest is expected to witness changes in temperature and precipitation due to climate change. In this study, we enhance the Snake River Planning Model (SRPM) by modeling the feedback loop between incidental recharge and surface water supply resulting from surface water and groundwater extraction for irrigation and provide a case study involving climate change impacts and management scenarios. The new System Dynamics‐Snake River Planning Model (SD‐SRPM) is calibrated to flow at Box Canyon Springs located along a major outlet of the East Snake Plain Aquifer. A calibration of the model to flow at Box Canyon Springs, based on historic diversions (1950‐1995) resulted in an r² value of 0.74 and a validation (1996‐2005) r² value of 0.60. After adding irrigation entities to the model an r² value of 0.91, 0.88, and 0.87 were maintained for modeled vs. observed (1991‐2005) end‐of‐month reservoir content in Jackson Lake, Palisades, and American Falls, the three largest irrigation reservoirs in the system. The scenarios that compared the impacts of climate change were based on ensemble mean precipitation change scenarios and estimated changes to crop evapotranspiration (ET). Increased ET, despite increased precipitation, generally increased surface water shortages and discharge of springs. This study highlights the need to develop and implement models that integrate the human‐natural system to understand the impacts of climate change.     

Heterogeneity of Hydrologic Response in Urban Watersheds1

Meierdiercks, Katherine L., James A. Smith, Mary Lynn Baeck, and Andrew J. Miller, 2010. Heterogeneity of Hydrologic Response in Urban Watersheds. Journal of the American Water Resources Association (JAWRA) 46(6):1221–1237. DOI: 10.1111/j.1752-1688.2010.00487.x Abstract: The changing patterns of streamflow associated with urbanization are examined through analyses of discharge and rainfall records for the study watersheds of the Baltimore Ecosystem Study (BES). Analyses utilize a decade (1999-2008) of observations from a dense U.S. Geological Survey stream gaging network and Hydro-NEXRAD radar rainfall fields. The principal study watershed of the BES is Gwynns Falls (171 km²). Focus is given to two Gwynns Falls basins with contrasting patterns and histories of development, Dead Run and Upper Gwynns Falls. The sharp contrasts in streamflow properties between the basins reflect the differences in urban development prior to implementation of stormwater management regulations (much of Dead Run) and development for which stormwater management is an integral part of the hydrologic system (Upper Gwynns Falls). The mean annual runoff in Dead Run (558 mm) is 35% larger than that of Upper Gwynns Falls; larger contrasts in runoff properties typify the “warm season” and are linked to storm event hydrologic response. Spatial heterogeneities in storm event response are reflected in seasonal and diurnal properties of streamflow. Analyses of storm event response are presented for June 2006, during which monthly rainfall over the BES region ranged from less than 150 to more than 500 mm. Baisman Run, the BES forest reference watershed, and Moores Run, a highly urbanized watershed in Baltimore City, provide “end-member” representations of urban impacts on streamflow.     

EFFECT OF FLOW VELOCITY ON SEDIMENT OXYGEN DEMAND: COMPARISON OF THEORY AND EXPERIMENTS1

ABSTRACT: Theoretical equations that establish the relationship between sediment oxygen demand (SOD) in a lake and the flow velocity and dissolved oxygen concentration in the bulk water already exist. These theoretical equations for oxygen consumption in the sediment express biological consumption with Michaelis-Menten kinetics, and chemical consumption by a first order reaction. Data from laboratory experiments that were conducted to validate the theoretical equations also exist. These experiments were performed in a laboratory channel with well defined flow characteristics for three types of sediments. Herein, the theoretical equations are used to model the experimental data for the three types of sediments. The values used for the parameters in the theoretical equations are determined by iteration until a best fit is obtained for the relationship of SOD to flow velocity from both the theoretical model and experimental data. The goodness of fit is measured by the standard error of prediction and the regression coefficient.     

Recycling Irrigation Reservoir Stratification and Implications for Crop Health and Production

Recycling irrigation reservoirs (RIRs) are an emerging aquatic ecosystem and water resource of global significance. This study investigated the vertical distribution of water temperature, dissolved oxygen (DO), and pH in eight RIRs at two nurseries each in Virginia and Maryland from 2011 to 2014. Monomictic thermal stratification was observed from April to October in all RIRs, despite their shallow depths (0.75‐3.89 m). The strongest stratification had a top‐bottom temperature difference of 21.53°C. The top‐bottom temperature difference was positively correlated with water column depth, air temperature, and daily light integral (p < 0.05). Wind speed did not impact the thermal stratification, likely due to their relatively small surface areas. Thermal stratification affected the vertical distribution of DO and pH. The top‐bottom differences in DO and pH were greater during stratification periods than nonstratification periods. Water pH in all RIRs was higher at the top than at the bottom with the greatest difference of 4.16 units. Discovery and characterization of thermal stratification in RIRs helps understand water quality dynamics in this novel ecosystem and promote safe and productive water reuse for irrigation. Specifically, water withdrawal depths should be adjusted according to variations in temperature, DO, and pH during the stratification and nonstratification periods to mitigate pathogen risk and improve water treatment efficacy and crop production.