NUTRIENT BALANCES FOR THE EVALUATION OF NUTRIENT SOURCES IN WATER QUALITY MANAGEMENT1

ABSTRACT. This paper describes the methodology for a nutrient balance to evaluate the sources and distribution of nutrients in a small river basin. Loadings for total nitrogen and phosphorus are calculated from measured nutrient concentration and river discharge data. Using a special retrieval program and a data storage and processing system, loadings are accumulated over a given time period to allow for time of passage through the basin and seasonal changes in nutrient distribution. Nutrient balances are made with the accumulated loadings to obtain the relative contribution of each nutrient source and the retention of nutrients within the basin through sedimentation and aquatic growth. The methodology has been used to study nutrients in the Qu'Appelle River Basin, Saskatchewan, Canada.     

Establishing a Context for River Rehabilitation, North Fork Gunnison River, Colorado

Initial river rehabilitation efforts along the North Fork Gunnison River in Colorado focused on the use of in-stream structures and channel stabilization to create a single-thread channel with pools along a braided river. These efforts were based on the assumption that the river’s braided planform results primarily from land use during the past century. In order to establish a context for further rehabilitation, we evaluated the possibility that the river might be braided as a result of processes independent of land use. We estimated volume, grain-size distribution, and lithology of sediment sources along the river corridor and evaluated the planform stability of the river during the past century using historical sources, aerial photographs covering 1939–1997, and comparison of bankfull discharge and gradient in the study area to values published for braided and meandering rivers. Our results indicate that the North Fork Gunnison River has been primarily braided in its lower reaches during the past few hundred years, although the channel planform tends toward a single-thread channel during decades of lower precipitation and discharge. Although land use is not the primary cause of braiding along the North Fork Gunnison River, it has decreased channel stability, and rehabilitation efforts should be designed to reduce these effects. Our results illustrate the importance of planning river rehabilitation measures within a historical context that accounts for both catchment-scale and reach-scale controls on channel processes and planform.     

复合酶生物促进剂在底泥生物修复中的应用

通过测定河道底泥中微生物的生化呼吸线来表征复合酶生物促进剂对河道自净过程的影响。研究结果表明复合酶生物促进剂对微生物具有激活作用,使微生物的累积耗氧量明显增加,有效地提升了水体的自净能力。复合酶生物促进剂能够有效地修复受萘污染的底泥,修复后底泥中多环芳烃萘的释放量和有机质的含量均明显低于对照样,并可显著降低底泥对上覆水...     

水体底泥对污染物的吸附-解吸机理的研究

水体底泥污染已经成为世界范围内的一个重要的环境问题,其污染物主要通过大气沉降、废水排放、雨水淋溶冲刷等进入水体,最后沉积到底泥中并逐渐富集,使底泥受到严重污染。吸附-解吸是底泥污染的重要过程,为了控制水体底泥污染,对底泥对各种污染物的吸附-解吸机理及其影响因素的研究显得极其重要。本文总结了底泥中氮、磷和重金属等的吸附-解吸的影响因素及机理,对今后水体底泥污染方面的研究具有重要意义。     

MONITORING SUSPENDED PARTICULATE MATTER IN PUERTO RICO: FIELD MEASUREMENTS AND REMOTE SENSING1

ABSTRACT: The spatial distribution of suspended particulatematter (SPM) was estimated in Mayagüez Bay on the west coast of Puerto Rico by using traditional ship board measurements and remotely sensed data acquired over four days during January 1990. This effort was part of a joint project between NASA and the University of Puerto Rico to develop techniques to monitor the water quality of a Caribbean coastal zone. This paper presents the methods and algorithms developed to map and analyze short term changes in the source and spatial distribution of SPM in Mayagüez Bay by using remotely sensed data acquired by the Calibrated Airborne Multispectral Scanner (CAMS). A PC-based data acquisition system was developed to record continuous ship measurements of select in- water variables. Spectral reflectances derived from CAMS red and near-IR data were corrected for atmospheric effects and then used to generate maps of SPM. These maps displayed SPM plumes associated with the mouths of the bay's three river systems. Significant day-to-day differences in the spatial characteristics were observed, suggesting that changes in river discharge occurred. However, an analysis of estimated river discharge, sediment yield, local wind field, and thermal river plume indicates that observed sediment plumes result primarily from wind-driven resuspension events.     

Sedimentary Causes and Management of Two Principal Environmental Problems in the Lower Yellow River

Flood and water shortage are two of the leading environmental problems around the world, and among the causes of the problems is sedimentation. The Yellow River brought disastrous floods in its lower reaches in Chinese history. Today, although floods caused by the river are still a formidable hazard hanging over China, it cannot provide the lower reaches with enough usable water. The ineradicable flood hazard and newly emerged water shortage problems of the river are proved to be closely associated with its immense sediment load. The over loaded flow of the river can quickly fill the reservoirs and unceasingly raise the riverbed, attenuating the capacity of reservoirs to suppress floods and provide more water for dry seasons and of river channels to convey floods. Also, the high sediment content pollutes the water and reduces the volume of usable water. In virtue of the intimate linkage between these problems and the formidable sediment load in the river, the solution to these problems should be based on sedimentation management. After reviewing the defects and merits of management measures implemented and proposed, a management scenario composed of multiple measures are recommended. Beside of persistent soil conservation to reduce the huge sediment load, more reservoirs to check sediment and regulate river flows, approaches to alleviating riverbed accretion, interbasin water transfer to mitigate water deficiency, and so on, an emphasis should be laid on use of muddy flows in order to scatter the sediment in a vast area, which was a natural process but has been interrupted by construction of embankments.     

DISCHARGE AND SUSPENDED SEDIMENT PATTERNS OF AN INTERMITTENT COLD DESERT STREAM1

Sage Creek in south‐central Wyoming is listed as impaired by the U.S. Environmental Protection Agency (USEPA) due to its sediment contribution to the North Platte River. Despite the magnitude of sediment impacts on streams, little research has been conducted to characterize patterns of sediment transport or to model suspended sediment concentration in many arid western U.S. streams. This study examined the relationship between stream discharge and suspended sediment concentration near the Sage Creek and North Platte River confluence from 1998 through 2003. The objectives were to determine patterns of stream discharge and suspended sediment concentration, produce a sediment prediction model, and compare sediment concentrations for the six‐year period. Stream discharge and suspended sediment transport responded rapidly to convective storms and spring runoff events. During the study period, events exceeding 0.23 m³/s accounted for 92 percent of the sediment load, which is believed to originate from erodible headwater uplands. Further analysis of these data indicates that time series modeling is superior to simple linear regression in predicting sediment concentration. Significant increases in suspended sediment concentration occurred in all years except 2003. This analysis suggests that a six‐year monitoring record was insufficient to factor out impacts from climate, geology, and historical sediment storage.     

Disturbance regimes,resilience, and recovery of animal communities and habitats in lotic ecosystems

Disturbance regime is a critical organizing feature of stream communities and ecosystems. The position of a given reach in the river basin and the sediment type within that reach are two key determinants of the frequency and intensity of flow-induced disturbances. We distinguish between predictable and unpredictable events and suggest that predictable discharge events are not disturbances. We relate the dynamics of recovery from disturbance (i.e., resilience) to disturbance regime (i.e., the disturbance history of the site). The most frequently and predictably disturbed sites can be expected to demonstrate the highest resilience. Spatial scale is an important dimension of community structure, dynamics, and recovery from disturbance. We compare the effects on small patches (⩽1 m²) to the effects of large reaches at the river basin level. At small scales, sediment movements and scour are major factors affecting the distribution of populations of aquatic insects or algae. At larger scales, we must deal with channel formation, bank erosion, and interactions with the riparian zone that will affect all taxa and processes. Our understanding of stream ecosystem recovery rests on our grasp of the historical, spatial, and temporal background of contemporary disturbance events.     

Freshwater Mussel Population Status and Habitat Quality in the Clinch River,Virginia and Tennessee,USA: A Featured Collection

The Clinch River of southwestern Virginia and northeastern Tennessee is arguably the most important river for freshwater mussel conservation in the United States. This featured collection presents investigations of mussel population status and habitat quality in the Clinch River. Analyses of historic water‐ and sediment‐quality data suggest that water column ammonia and water column and sediment metals, including Cu and Zn, may have contributed historically to declining densities and extirpations of mussels in the river's Virginia sections. These studies also reveal increasing temporal trends for dissolved solids concentrations throughout much of the river's extent. Current mussel abundance patterns do not correspond spatially with physical habitat quality, but they do correspond with specific conductance, dissolved major ions, and water column metals, suggesting these and/or associated constituents as factors contributing to mussel declines. Mussels are sensitive to metals. Native mussels and hatchery‐raised mussels held in cages in situ accumulated metals in their body tissues in river sections where mussels are declining. Organic compound and bed‐sediment contaminant analyses did not reveal spatial correspondences with mussel status metrics, although potentially toxic levels were found. Collectively, these studies identify major ions and metals as water‐ and sediment‐quality concerns for mussel conservation in the Clinch River.     

COMPUTATION OF STAGE-DISCHARGE RELATIONSHIPS AFFECTED BY UNSTEADY FLOW1

ABSTRACT: The dynamic relationship between stage and discharge which is unique to a particular flood for a selected station along the river can be determined via a mathematical model based on the complete one-dimensional equations of unsteady flow, i.e., the equations for the conservation of mass and momentum of the flood wave, and the Manning equation which accounts for energy losses. By assuming the bulk of the flood wave moves as a kinematic wave, the need for spatial resolution of the flood can be eliminated, and only the time variation of either the discharge or stage at the selected station is necessary for the computation of the other. The mathematical model can be used in river forecasting to convert the forecast discharge hydrograph into a stage hydrograph which properly reflects the unique dynamic stage-discharge relationship produced by the variable energy slope of the flood discharge. The model can be used also in stream gaging to convert a recorded stage hydrograph into a discharge hydrograph which properly accounts for the effects of unsteady flow. The model is applied to several observed floods at selected stations along the Lower Mississippi, Red, and Atchafalaya Rivers. The root mean square errors between observed and computed discharges are in the range of 3 to 7 percent, values well within the accuracy of the observations. A simple, easily-applied graphical procedure is also provided for estimating the magnitude of the effect of the unsteady flow on stage-discharge ratings. As a general rule, the dynamic effect may be significant if the channel bottom slope is less than 0.001 ft/ft (about 5 ft/mi) when the rate of change of stage is greater than about 0.10 ft/hr.     

高氟温泉水中氟在周边水环境中的分布特征与评价

针对温泉水中高氟现象,本实验利用离子选择性电极法,分析测定高氟温泉水周边河水中氟含量及河水底泥中氟含量。通过对高氟温泉水分布特征的研究可初步得知,温泉中高氟在周边水环境中分布因其氟含量大、不易被重视,对环境的影响相对较大。     

A comparison of sediment deposition in two adjacent floodplains of the River Adour in southwest France

Two floodplains within the catchment of the River Adour (SW France) have been examined in order to analyse spatio-temporal variations in discharge and suspended matter flux. Both floodplain zones were found to be excellent sites for the interception of suspended sediment. The narrow riparian vegetative strips (RVS) within each zone were found to retain 92-98% of the sediment trapped within the floodplain during each of three separate flood events. The precise level of sediment deposited within the floodplain was found to be dependent on micro-topographical features and the nature of the vegetation: the wooded areas within the RVS being particularly effective at trapping sediment. Mean masses of sediment collected in the flood plains ranged from 75kgm(-2) in the RVS to 0.02kgm(-2) in the areas of the floodplain inundated by back-up flows. Using data on discharge and sediment fluxes within the catchment gathered over a period of 25 years it is possible to discern how hydroclimatic fluctuations have affected the watershed with periods of sediment retention within the floodplain zones alternating with periods of sediment export. Anthropogenic activity, involving river management, including the cutting of meanders, the construction of dykes for flood prevention and the use of water for agricultural purposes, has also had a major impact during this period, particularly in the downstream areas of the catchment.     

From agricultural intensification to conservation: sediment transport in the Raccoon River, Iowa, 1916-2009

Fluvial sediment is a ubiquitous pollutant that negatively affects surface water quality and municipal water supply treatment. As part of its routine water supply monitoring, the Des Moines Water Works (DMWW) has been measuring turbidity daily in the Raccoon River since 1916. For this study, we calibrated daily turbidity readings to modern total suspended solid (TSS) concentrations to develop an estimation of daily sediment concentrations in the river from 1916 to 2009. Our objectives were to evaluate long-term TSS patterns and trends, and relate these to changes in climate, land use, and agricultural practices that occurred during the 93-yr monitoring period. Results showed that while TSS concentrations and estimated sediment loads varied greatly from year to year, TSS concentrations were much greater in the early 20th century despite drier conditions and less discharge, and declined throughout the century. Against a backdrop of increasing discharge in the Raccoon River and widespread agricultural adaptations by farmers, sediment loads increased and peaked in the early 1970s, and then have slowly declined or remained steady throughout the 1980s to present. With annual sediment load concentrated during extreme events in the spring and early summer, continued sediment reductions in the Raccoon River watershed should be focused on conservation practices to reduce rainfall impacts and sediment mobilization. Overall, results from this study suggest that efforts to reduce sediment load from the watershed appear to be working.     

AN ANALYTICAL FRAMEWORK FOR EVALUATING CHANNEL MAINTENANCE FLOWS IN COLORADO1

ABSTRACT: An accounting procedure is developed which determines a flow regime that is capable of transporting an amount of bedload sediment necessary to ensure channel stability downstream. The method allows for sediment buildup in the channel within geomorphic threshold limits during low flow periods. During periods of high runoff, enough water is bypassed to transport the stored sediment. The procedure utilizes only those flows of sufficient magnitude to maintain channel stability over the long run (25–50+ years). An example is presented which determines the volume of water and frequency of release for channel maintenance purposes downstream from a hypothetical water diversion project. Of some 1,200,000 acre feet generated during a 59-year period, 86,500 acre feet was required for channel maintenance flows. Bypass flows were not required each year, but only during those years when average daily flow reached bankfull or greater. Such releases were made on 202 of the 411 days when average flows either equalled or exceeded bankfull discharge.     

NUTRIENT LOADING ASSESSMENT IN THE ILLINOIS RIVER USING A SYNTHETIC APPROACH1

ABSTRACT: A synthetic relationship is developed between nutrient concentrations and discharge rates at two river gauging sites in the Illinois River Basin. Analysis is performed on data collected by the U.S. Geological Survey (USGS) on nutrients in 1990 through 1997 and 1999 and on discharge rates in 1988 through 1997 and 1999. The Illinois River Basin is in western Arkansas and northeastern Oklahoma and is designated as an Oklahoma Scenic River. Consistently high nutrient concentrations in the river and receiving water bodies conflict with recreational water use, leading to intense stakeholder debate on how best to manage water quality. Results show that the majority of annual phosphorus (P) loading is transported by direct runoff, with high concentrations transported by high discharge rates and low concentrations by low discharge rates. A synthetic relationship is derived and used to generate daily phosphorus concentrations, laying the foundation for analysis of annual loading and evaluation of alternative management practices. Total nitrogen (N) concentration does not have as clear a relationship with discharge. Using a simple regression relationship, annual P loadings are estimated as having a root mean squared error (RMSE) of 39.8 t/yr and 31.9 t/yr and mean absolute percentage errors of 19 percent and 28 percent at Watts and Tahlequah, respectively. P is the limiting nutrient over the full range of discharges. Given that the majority of P is derived from Arkansas, management practices that control P would have the most benefit if applied on the Arkansas side of the border.     

Footstep-induced sediment displacement in the Grand Canyon

The Glen Canyon Dam has severely altered the riparian zone of the Colorado River in the Grand Canyon. One result of the controlled river discharge is more efficient prediction of water stages at the major rapids, leading to higher visitor use. Increased visitation results in heavy foot traffic, trampling along the river banks, erosion of the campsite soils, and the destruction of vegetation. Erosion occurs when the surfaces are roughened, exposing them to wind transport and runoff. In addition, each footstep physically displaces sand downhill.The results of a field experiment designed to measure the amount of sand displaced by footsteps show that each year trampling alone displaces 230 m³ of sand downslope and into the river. With the controlled river flow, no natural processes exist to replace the lost sediment.     

Using Fly Ash as a Marker to Quantify Culturally‐Accelerated Sediment Accumulation in Playa Wetlands

Wetlands in the Rainwater Basin in Nebraska are vulnerable to sediment accumulation from the surrounding watershed. Sediment accumulation has a negative impact on wetland quality by decreasing the depth and volume of water stored, and the plant community species composition and density growing in the wetland. The objective of this study was to determine the amount of sediment that has accumulated in five selected wetlands in the Rainwater Basin in Nebraska. Soil cores were taken at five or six locations along transects across each wetland. This study used the fly ash, which is generated by coal‐burning locomotives that were present generally in the late 1800s and early 1900s, as a marker to quantify the sediment deposition rates. The cores were divided into 5 cm sections and the soils were analyzed using a fly ash extraction and identification technique. Results indicate that the average depth of sediment ranged from 23.00 to 38.00 cm. The annual average depth of sediment accumulation ranged from 0.18 cm/yr to 0.29 cm/yr. The annual sediment accumulation rate from both wind erosion and water erosion in these five sampling wetlands was between 1.946 and 3.225 kg/m²/yr. The results of this research can be used to develop restoration plans for wetlands. The fly ash testing technology can also be applied to other areas with the railroads across the United States.     

Comparison of Unsteady and Quasi‐Unsteady Flow Models in Simulating Sediment Transport in an Ephemeral Arizona Stream1

Hummel, Ryan, Jennifer G. Duan, and Shiyan Zhang, 2012. Comparison of Unsteady and Quasi‐Unsteady Flow Models in Simulating Sediment Transport in an Ephemeral Arizona Stream. Journal of the American Water Resources Association (JAWRA) 48(5): 987‐998. DOI: 10.1111/j.1752‐1688.2012.00663.x Abstract: Hydrodynamic and sediment transport models are useful engineering tools for predicting unsteady flood flow and sediment transport. Many models such as HEC‐RAS, HEC‐6, and IALLUVIAL apply quasi‐unsteady flow model, whereas others apply the unsteady flow model. It remains unknown if a quasi‐unsteady flow model is sufficiently accurate for simulating sediment transport in rapidly varied unsteady flood events, especially in ephemeral rivers in arid and semiarid regions. This study compared the quasi‐unsteady HEC‐RAS 4.1 model with one‐dimensional (1D) Finite Volume Method (FVM) based model in simulating flood flow and sediment transport in the Pantano Wash, a dryland river in the state of Arizona. The objective is to determine which sediment transport method is appropriate in predicting bed elevation changes in an ephemeral stream, Pantano Wash, and if an unsteady model is more accurate than a quasi‐unsteady flow model in predicting sediment transport. Results showed that the quasi‐unsteady HEC‐RAS model and the 1D FVM yielded similar results of bed degradation and aggradation for this dryland stream, although the FVM model predicted better flood hydrographs. Among the seven sediment transport formulas embedded in HEC‐RAS, Yang’s and Engelund‐Hansen’s equations gave the best matches with the field measurements for this particular case study.     

去学水电站生态流量泄放措施优化研究

水电站的建设会造成坝址下游河段减水,对水环境和水生生物造成不利影响,因此电站生态流量的确定和泄放措施的可行性对于维护河流生态环境至关重要。以硕曲河去学水电站为例,基于可行性研究阶段提出的生态流量泄放措施方案,采用数学模型和理论分析方法,从生态流量取水水温、泄洪洞事故条件下生态流量保证率以及水资源的合理高效利用等方面进一步对生态流量泄放方案进行了优化比选。提出的优化方案提高了生态流量取水口的布置高程,在泄洪洞之外单独布置生态泄放系统,并增设生态流量发电机组等。对比分析表明,该优化方案在改善生态流量的下泄水温、提高生态流量泄放保证率、合理高效利用水能资源等方面具有较大优势。本研究为水电工程中生态流量泄放措施保障等方面提供了科学依据和技术参考。     

Temporal and spatial distributions of sediment total organic carbon in an estuary river

Understanding temporal and spatial distributions of naturally occurring total organic carbon (TOC) in sediments is critical because TOC is an important feature of surface water quality. This study investigated temporal and spatial distributions of sediment TOC and its relationships to sediment contaminants in the Cedar and Ortega Rivers, Florida, USA, using three-dimensional kriging analysis and field measurement. Analysis of field data showed that large temporal changes in sediment TOC concentrations occurred in the rivers, which reflected changes in the characteristics and magnitude of inputs into the rivers during approximately the last 100 yr. The average concentration of TOC in sediments from the Cedar and Ortega Rivers was 12.7% with a maximum of 22.6% and a minimum of 2.3%. In general, more TOC accumulated at the upper 1.0 m of the sediment in the southern part of the Ortega River although the TOC sedimentation varied with locations and depths. In contrast, high concentrations of sediment contaminants, that is, total polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), were found in sediments from the Cedar River. There was no correlation between TOC and PAHs or PCBs in these river sediments. This finding is in contradiction to some other studies which reported that the sorption of hydrocarbons is highly related to the organic matter content of sediments. This discrepancy occurred because of the differences in TOC and hydrocarbon source input locations. It was found that more TOC loaded into the southern part of the Ortega River, while almost all of the hydrocarbons entered into the Cedar River. This study suggested that the locations of their input sources as well as the land use patterns should also be considered when relating hydrocarbons to sediment TOC.