Runoff Sources Research Articles

QUANTIFICATION OF <I>ESCHERICHIA COLI</I> AND ENTEROCOCCI LEVELS IN WET WEATHER AND DRY WEATHER FLOWS

Forty percent of rivers, 45% of lakes and 50% of estuaries assessed by the National Water Quality Inventory (2000) were not clean enough to support designate d fishing and swimming uses. Pathogens were found to be one of the leading causes of impairments in these waters. Urban runoff is recognized as a leading source of organisms potentially indicating the presence of pathogens. Urban runoff can be defined as any discharge from a separate storm drainage system. Urban runoff traditionally had been defined to in clude precipitation and wash off from lawns and other landscaped areas, buildings, roadways and parking lots. However, other flows may enter the storm drainage system from such sources a s infiltrating groundwater, leaking domestic water supplies and sewage, washwaters, and other inappropriate entries to the storm drainage system. This research was conducted to quantify th e levels of indicator bacteria, and their sources, in urban areas. The main objective of t his research was to identify possible sources of E. coli and enterococci bacteria in dry and wet-weather flows in storm drainage systems. An urban area consists of many different kinds of land uses such as residential, institutional, commercial, industrial open spaces, etc. Each type of la nd use consists of various types of source areas, such as roofs, parking lots, landscaped areas, play grounds, driveways, undeveloped areas, sidewalks. Four representative source area types were sa mpled during this research; including rooftops, parking lots, open spaces, and streets. Two paralle l sites were sampled for each source area type; one affected by birds and other animals, and an other set with less influence from birds and other animals. A section of Cribbs Mill Creek in Tusc aloosa, Alabama, was also selected for dry weather sampling at outfalls. The section of the cr eek was selected such that the drainage areas contributing to outfalls had either commercial or residential land uses. Potential inappropriate discharge water samples were also obtained, including influent samples from the Tuscaloosa sewage treatment plant, local springs, irrigati on runoff water, domestic water taps, car wash, and laundry water. Overall, total coliforms, E. coli and enterococci bacterial analyses were conducted on 202 wet weather and 278 dry weather flow water samples. All samples were analyzed using IDEXX Quantitray enumeration procedures. E. coli and enterococci levels larger than 2,400 and 24,000 MPN/100 mL, r espectively, were observed in wet weather samples collected from various source areas which could not possibly be contaminated with sanitary sewage. The levels of ind icator bacteria present in the urban runoff source area samples exceeded the EPA 1986 single sa mple maximum value water quality criteria in 31% of the samples for E. coli and in 74% of the samples for enterococci. The geometric mean criteria were exceeded in 100% of the source area samples. Since both the indicator organisms studied ( E. coli. and enterococci) only originate in intestines of warm

RUNOFF CHARACTERISTICS IN A SMALL CATCHMENT OF TARUMAE VOLCANIC AREA

Few studies have addressed the runoff mechanism in volcanic basins, because the flood discharge in such basins tends to be small. However, after volcanic eruptions it is important to review therunoff characteristics of the basin, because eruptions can profoundly alter the runoff mechanism. This study analyzes the runoff mechanism during rainfall in an experimental basin at Volcano Tarumae, according to field survey results. We reached these conclusions: 1) The runoff in the upper part of a basin is composed of runoff from areas adjacent to the river channel and large-scale groundwater runoff (mainly spring water at the riverhead). 2) Changes in rainfall have little influence on the runoff source area. 3) The discharge of spring water depends on average rainfall intensity and ground moisture in thebasin.

Varying depositional environments of gypsum successions in the Upper Miocene Eskisehir-Sivrihisar lacustrine basin, NW Turkiye

The basement rocks of Eskisehir-Sivrihisar basin are made of Upper Paleozoic metamorphic rocks and Upper Cretaceous ophiolite complex. These rocks are overlain by Middle Miocene sedimentary rocks the base. Upper Miocene-Pliocene stratigraphic succession consists of basal conglomerates, sandstones, claystones, limestones, dolomites and tuffs are thinly interbedded with cyclic evaporites. The main clay mineral assemblage consists of smectite, illite and sepiolite that are enriched in different percentage in different horizons. The Upper Miocene-Pliocene stratigraphic succession consists of alterations of gypsum, clayey carbonates and unconsolidated very soft dolomite beds, which are conformably underlain by sepiolite-bearing clayey carbonates and disconformably overlain by alluvium and conglomerate series of Pleistocene age. The Upper Miocene unit includes three different facies, based on sedimentary properties of gypsum from the base to the top; (I) laminated gypsum beds are thinly interbedded with dolomites and green clays; (2) gypsum rosettes within thin reddish and greenish clays and carbonates; and (3) scattered gypsum mainly within carbonates. Gypsums had been deposited in somewhat different depositional conditions in the same basin where multi-periodic evaporative episodes, ranging from saline to schizohaline environments, had been involved. During these episodes, under high Eh-pH intervals and high salinity conditions, three different types of gypsum formations had been developed in a meromictic-type lake under the influence of varying paleoclimatologic conditions and pore water chemistry of brines. All these gypsum morphologies respectively reflect the different conditions of environments of deposition in a Miocene playa lake basin: (1) subaqueous environments in playa lakes with short evaporation episodes; (2) marginal swamps with cyclic fluctuation of lake level; and (3) extended closed-lake with evaporatic lake water. These different gypsum morphologies are associated with distinctive sedimentary subfacies, which are also primarily related to cyclic climatic changes, alternating semi-arid and evaporite conditions, fluctuation of lake water level and sulphate input in the chemistry of lake water from runoff and hydrothermal source adjacent to basin.

Application of enterococci antibiotic resistance patterns for contamination source identification at Huntington Beach, California

Huntington Beach, California, one of the most popular surfing spots in the world, is plagued by sporadic, elevated levels of fecal bacteria. To assist with pollution source identification, we analyzed antibiotic resistance patterns (ARPs) of enterococci from four known sources (bird feces, urban runoff, coastal marsh sediment and sewage effluent from local sanitation district) and one unknown source (seawater) using seven antibiotics at four concentrations each. Of 2491 enteroccoci tested, all were resistant to at least one antibiotic at some level. Discriminant analysis indicated that the average correct classification rates for bird feces and urban runoff sources were above 80%. Sewage effluent contained mixed fecal sources. Sixty-four percent of the sewage isolates classified with the sewage category, while the other 35% of isolates were assigned evenly across the other three categories. When enterococci isolated from the seawater were classified using the known ARP database, it was evident that bird feces were the source of surf zone contamination on some days while the coastal salt marsh and sewage plume may have impacted the surf zone water quality to various degrees during other times.

Towards integrating tracer studies in conceptual rainfall‐runoff models: recent insights from a sub‐arctic catchment in the Cairngorm Mountains, Scotland

AbstractHydrochemical tracers (alkalinity and silica) were used in an end‐member mixing analysis (EMMA) of runoff sources in the 10 km2 Allt a' Mharcaidh catchment. A three‐component mixing model was used to separate the hydrograph and estimate, to a first approximation, the range of likely contributions of overland flow, shallow subsurface storm flow, and groundwater to the annual hydrograph. A conceptual, catchment‐scale rainfall‐runoff model (DIY) was also used to separate the annual hydrograph in an equivalent set of flow paths. The two approaches produced independent representations of catchment hydrology that exhibited reasonable agreement. This showed the dominance of overland flow in generating storm runoff and the important role of groundwater inputs throughout the hydrological year. Moreover, DIY was successfully adapted to simulate stream chemistry (alkalinity) at daily time steps. Sensitivity analysis showed that whilst a distinct groundwater source at the catchment scale could be identified, there was considerable uncertainty in differentiating between overland flow and subsurface storm flow in both the EMMA and DIY applications. Nevertheless, the study indicated that the complementary use of tracer analysis in EMMA can increase the confidence in conceptual model structure. However, conclusions are restricted to the specific spatial and temporal scales examined. Copyright © 2003 John Wiley & Sons, Ltd.

The transition of nutrient concentration and the runoff source of nutrient on the upper Tone river basin.

The transition of nutrient concentration and the runoff source of nutrient on the upper Tone river basin.

Polyacrylamide preparations for protection of water quality threatened by agricultural runoff contaminants

Waste streams associated with a variety of agricultural runoff sources are major contributors of nutrients, pesticides and enteric microorganisms to surface and ground waters. Water soluble anionic polyacrylamide (PAM) was found to be a highly effective erosion-preventing and infiltration-enhancing polymer, when applied at rates of 1–10 g m−3 in furrow irrigation water. Water flowing from PAM treated irrigation furrows show large reductions in sediment, nutrients and pesticides. Recently PAM and PAM+CaO and PAM+Al(SO4)3 mixtures have been shown to filter bacteria, fungi and nutrients from animal wastewater. Low concentrations of PAM [175–350 g PAM ha−1 as PAM or as PAM+CaO and PAM+Al(SO4) mixture] applied to the soil surface, resulted in dramatic decreases (10 fold) of total, coliform and fecal streptococci bacteria in cattle, fish and swine wastewater leachate and surface runoff. PAM treatment also filtered significant amounts of NH4, PO4 and total P in cattle and swine wastewater. This points to the potential of developing PAM as a water quality protection measure in combination with large-scale animal feeding operations. Potential benefits of PAM treatment of animal facility waste streams include: (1) low cost, (2) easy and quick application, (3) suitability for use with other pollution reduction techniques. Research on the efficacy of PAM for removal of protozoan parasites and viruses and more thorough assessment of PAM degradation in different soils is still needed to completely evaluate PAM treatment as an effective waste water treatment. We will present analysis and feasibility of using PAM, PAM+Al(SO4)3, and PAM+CaO application for specific applications. Our results demonstrate their potential efficacy in reducing sediment, nutrients and microorganisms from animal production facility effluents.

Trace metal pollution in Umtata River

Dissolved trace metals, i.e Fe, Mn, Al, Cu, Zn, Pb and Cd were determined in the Umtata River. High levels of Al, Cd, Pb, Zn and Cu were observed, which may affect the “health” of the aquatic ecosystem. The high levels of Al, Cd and Pb may also affect the health of the rural community that uses the river water directly for domestic use without treatment. Generally the sources of the metals in the river appear to be diffuse, which include rural, urban and agricultural runoff sources in the catchment, although there may be contributions from natural and point sources. WaterSA Vol.28(2) 2002:183-190

Dynamics of stormflow generation—A hillslope‐scale field study in east‐central Pennsylvania, USA

AbstractA 40 m × 20 m mowed, grass hillslope adjacent to a headwater stream within a 26‐ha watershed in east‐central Pennsylvania, USA, was instrumented to identify and map the extent and dynamics of surface saturation (areas with the water table at the surface) and surface runoff source areas. Rainfall, stream flow and surface runoff from the hillslope were recorded at 5‐min intervals from 11 August to 22 November 1998, and 13 April to 12 November 1999. The dynamics of the water table (0 to 45 cm depth from the soil surface) and the occurrence of surface runoff source areas across the hillslope were recorded using specially designed subsurface saturation and surface runoff sensors, respectively. Detailed data analyses for two rainfall events that occurred in August (57·7 mm in 150 min) and September (83·6 mm in 1265 min) 1999, illustrated the spatial and temporal dynamics of surface saturation and surface runoff source areas. Temporal data analyses showed the necessity to measure the hillslope dynamics at time intervals comparable to that of rainfall measurements. Both infiltration excess surface runoff (runoff caused when rainfall intensity exceeds soil infiltration capacity) and saturation excess surface runoff (runoff caused when soil moisture storage capacity is exceeded) source areas were recorded during these rainfall events. The August rainfall event was primarily an infiltration excess surface runoff event, whereas the September rainfall event produced both infiltration excess and saturation excess surface runoff. Occurrence and disappearance of infiltration excess surface runoff source areas during the rainfall events appeared scattered across the hillslope. Analysis of surface saturation and surface runoff data showed that not all surface saturation areas produced surface runoff that reached the stream. Emergence of subsurface flow to the surface during the post‐rainfall periods appeared to be a major flow process dominating the hillslope after the August rainfall event. Copyright © 2002 John Wiley & Sons, Ltd.

Phosphate run-off in the Nevezis River (Lithuania).

The long-term (40 yr) observation results of phosphates-phosphorus concentration and its runoff in the Lithuanian fourth largest river Nevezis are analysed. Amounts and peculiarities of background runoff, agricultural runoff, and point source pollution from towns were studied for various periods. It has been determined that phosphates enter into the river Nevezis mainly from towns (76.5%), from agriculture only up to 16%, and the background runoff for 7.5%. Considerable agricultural influence was observed in 1979-1991, when the phosphate runoff increased to 22 kg P km(-2) a(-1) and formed in 1984 33% of the entire runoff. A relation of the phosphates runoff from agriculture, for the entire study period, was obtained with the number of animals in the river's basin. Since 1990, when the number of animals started to decrease, the runoff of phosphates decreased too. Now the phosphates runoff from agriculture formed only 2% of the entire runoff. Water in the river Nevezis is heavily polluted with phosphate, according to the EU general classification of the water quality of rivers, although the Lithuanian pollution norms for effluents discharging to surface water are not exceeded. Norms for effluents discharging in the rivers from point-sources pollution should be made stricter and the highest permitted ratio between the phosphorus load in the river and its water discharge should be established.

Systematic variation of soil infiltration rates within and between the components of the vegetation mosaic in an Australian desert landscape

AbstractVegetation mosaics have commonly been thought to include two principal zones with distinctly different hydrology: relatively bare and impermeable runoff source zones (intergroves) and more strongly absorbing vegetated runon zones (groves). However, the data required to verify the internal uniformity of hydrologic response within these components of mosaic landscapes have been lacking, as have data on the nature (abrupt or gradational) of the boundaries between them. This study examines the degree of internal uniformity of key soil properties in the intergroves and groves of an Australian vegetation mosaic.Infiltration rates, soil water content, shear strength, bulk density and texture were determined at intervals of 1·5–2·5 m across several grove–intergrove cycles of an Australian banded shrubland. Results demonstrate that order‐of‐magnitude variability in soil infiltration rates can occur across intergroves, with lesser variation in groves. Patterns of infiltration are systematically related to slope position. Rates are relatively high in the uppermost parts of the intergrove, and fall to low values only in the lowermost intergrove where soils are mechanically strong. Infiltration rates increase rapidly from the lowermost intergrove to reach maxima within the upper to middle grove, from where rates once again decline toward the next intergrove. However, there is only a gradational change in infiltration rates across the pioneer zone–grove boundary, which is the sharpest of the mosaic boundaries when identified using plant cover data.Hydrologic models built on the presumption that mapped plant cover units are equally distinct hydrologically may need to be refined to incorporate the presence of systematic internal variability of infiltration rates and gradational change in soil hydraulic properties. Copyright © 2002 John Wiley & Sons, Ltd.

The use of macrophyte-based systems for phosphorus removal: an overview of 25 years of research and operational results in Florida

Phosphorus (P) removal from wastewaters and surface runoff using macrophyte-based systems (MBS) has been a topic of great interest in Florida for over 25 years. During this period, P removal by both treatment wetlands and floating aquatic macrophyte systems has been evaluated from both a research and operational standpoint. Several factors have contributed to the increased focus on the use of MBS for P removal. First, there exist no conventional technologies that can cost-effectively achieve the low outflow P concentrations required to protect the integrity of Florida's relatively pristine surface waters. Second, because MBSs typically provide some water storage, they can accommodate the wide ranges of flows typical for runoff sources such as agricultural drainage waters. Finally, many regions in Florida have sufficient area for deployment of the relatively land-intensive MBS technologies. The first P removal work in Florida was initiated in the mid-1970s, and involved pilot-scale research on domestic wastewater treatment by natural wetlands. Parallel studies were performed with managed (periodically harvested) floating plant systems (i.e., Eichhornia crassipes) for tertiary treatment. Since that time, the range of operational systems that have been deployed include emergent macrophyte-based and forested wetlands, managed floating plant systems, and submerged macrophyte-based systems. Waters treated by MBS include domestic effluents, agricultural runoff and eutrophic lake waters. Phosphorus removal targets for MBS in Florida have been as low as 10 microg/L. In this paper, we summarize research and operational results for MBS in Florida over the past 25 years.

Application of GIS in Analysing Spatial Patterns of Multiple Runoff Events

Rainfall, topography and soil characteristics are considered to control spatial redistribution of phosphorus in catchments. To advance this research, a hydrology model is needed to describe spatial variation of soil moisture dynamics and runoff source areas in multiple runoff events. This study examined whether the spatially distributed, topographically based rainfall-runoff model, TOPMODEL provides superior performance for rainfall/runoff events in maritime climate and pastoral hill lands like New Zealand. Unlike previous efforts, we evaluate the hydrological model to identify runoff source areas for each individual runoff event. Geographical information system was used to analyse the model sensitivity on pattern dynamics of runoff, water tables and soil moistures of three major runoff events (low, medium and high). The model was tested for two catchments at Waipawa in Palmerston north, New Zealand. The study confirmed that TOPMODEL give high quality results (R2 of 84%) when validated against flow observations. Visual analysis on GIS systems showed that the predicted dynamics of variable source area and the component hydrological processes is realistic in the study area of pastoral farmlands. The TOPMODEL can be used to reflect both long-term evolutionary soil moisture content patterns and the short term forcing of flow dynamics during storm events in typical New Zealand mountainous and high rainfall volume (1200mm/year) regions.

Urban drainage redefined: from stormwater removal to integrated management

Even though urban drainage has been practised for more than 5000 years, many challenges arising from growing demands on drainage still remain with respect to runoff quantity and quality; landscape aesthetics, ecology and beneficial uses; and operation of existing urban wastewater systems. Further advances can be achieved by adopting an integrated approach, optimal operation of the existing infrastructure, advanced pollution and runoff source controls, improved resilience of receiving waters, and adaptive water management. The specific research needs include new technologies and strategies for stormwater management, advanced treatment of urban wet-weather effluents, and tools for analysis and operation of drainage systems. High diversity of demands on, and region/site specific conditions of, urban drainage shapes the role of urban drainage experts--as mediators among the many stakeholders and fields involved.

Investigating mechanisms of stormflow generation by natural tracers and hydrometric data: a small catchment study in the Black Forest, Germany

AbstractThe importance and interaction of various hydrological pathways and identification of runoff source areas involved in solute transport are still under considerable debate in catchment hydrology. To reveal stormflow generating areas and flow paths, hydrometric behaviour of throughfall, soil water from various depths, runoff, and respective concentrations of the environmental tracers 18O, Si, K, SO4 and dissolved organic carbon were monitored for a 14‐week period in a steep headwater catchment in the Black Forest Mountains, Germany.Two stormflow hydrographs were selected and, based on 18O and Si, chemically separated into three flow components. Their sources were defined using mixing diagrams. Additional information about stormflow generating mechanisms was derived from recession analyses of the basin's complete 5‐year hydrograph record. By providing insight into storage properties and residence times of outflowing reservoirs of the basin, recession analysis proved to be a valuable tool in runoff model conceptualization. Its results agreed well with hydrometric and hydrochemical data. Supported by evaluation of 30 hillslope soil profiles a coherent concept of stormflow generation could be derived: whereas in many steeply sloped basins in the temperate region soil water from hillslopes appears to have an immediate effect on the shape of the stormflow hydrograph, its role at this basin is basically restricted to the recharge of the groundwater reservoir in the near‐channel area. Storm hydrograph peaks appear to be derived from a small direct runoff component supplemented by a fast delivery of baseflow from the groundwater reservoir in the valley bottom. Copyright © 2001 John Wiley & Sons, Ltd.

Vibrio cholerae in recreational beach waters and tributaries of Southern California

Vibrio cholerae is the causative agent of the severe dehydrating diarrheal disease cholera. This bacterium has been detected in many estuaries around the world and the United States. In this study we examine the abundance and distribution of V cholerae in recreational beach waters and tributaries of Southern California. Water samples were taken from 11 beach locations adjacent to freshwater runoff sources between February 8th and March Ist, 1999. Water samples were also taken from rivers, creeks and coastal wetlands along the Southern California coast between May 19th and June 28th, 1999. In addition to the detection of V cholerae, environmental parameters including temperature, salinity, coliphage counts, viable heterotrophic plate counts and total bacterial direct counts were also determined to understand the relationships between the presence of V. cholerae and environmental conditions. A direct colony hybridization method using an oligonucleotide probe specific for the 16S-23S intergenic spacer region of V. cholerae,detected V. cholerae in 3 of the 11 beach samples with the highest concentration (60.9 per liter) at the mouth of Malibu Lagoon. V. cholerae and coliphage were not correlated for beach samples, indicating that the presence of V cholerae is independent of sewage pollution. V cholerae were detected in all samples taken from rivers, creeks and wetlands of coastal Southern California where salinities were between l to 34 parts per thousand (ppt), but was not found at a freshwater sampling site in upper San Juan Creek. The highest density of V cholerae was found in San Diego Creek with a concentration of 4.25 x 105 CFU/L. The geographical distribution of V. cholerae was inversely correlated with salinity. High concentrations of V cholerae were more frequently detected in waters with lower (but above 0) salinity. The results of this study provide insight into the ecology of this aquatic species and are potentially important to the understanding of the epidemiology of cholera on a global scale.

The contribution of old and new water to a storm hydrograph determined by tracer addition to a whole catchment

Two tracer experiments have been carried out at an enclosed catchment in southern Norway. The catchment was brought to steady state with respect to rainfall and runoff prior to the tracer addition. A known concentration of lithium bromide was then added to the rainfall for the duration of each event. The tight control on tracer concentration and rainfall amount enabled assessment of the contribution of old and new water to runoff, the dominant flow pathways and soil water residence times during a storm event. A significant volume of ‘old’ water contributes to runoff despite the hydrologically responsive nature of the catchment and several hours of tracer injected rainfall are required before ‘new’ water becomes the dominant runoff source. After 34 h of tracer injection, ‘new’ water apparently contributes c. 83% to instantaneous flow and c. 55% of the total tracer input to the catchment has been lost in runoff. Recovery of the tracer from soil water indicates that the organic soil surface layer is the dominant flow pathway for rainwater through the catchment and that a significant pathway also exists at the soil–bedrock interface. New water is retained in deep pockets of soil for several days. Assessment of the conservative behaviour of the tracer suggests that 10–14% of the input Br− is retained in the soil and the tracer is not conservative. Laboratory experiments indicate that sorption of Br− to organic soil is the likely mechanism of retention. This process is probably concentration dependent and will have occurred predominantly during the initial period of tracer application. Copyright © 2000 John Wiley & Sons, Ltd.

A conceptual framework for runoff generation in a permafrost environment

Hillslope runoff processes were studied in the tundra region of the Canadian western arctic in order to provide a physically-based, conceptual framework for runoff generation for basins in this environment. It was found that subsurface flow is the dominant mechanism of runoff to the stream channel, that this flow is conveyed predominantly through the peat of the inter-hummock channels, and that subsurface flow through the highly conductive upper peat layer and soil pipes can be as rapid as surface flow. Stream discharge was computed from computations of hillslope runoff and meltwater input from the snowpack in the stream channel. The similarity between the computed and measured stream discharge suggests that the approach used to compute discharge would be useful as a conceptual basis for a distributed hydrological model for this environment. Hydrological interaction among the basin subsystems was found to play an important role in runoff generation. For example, when the water table was in the highly conductive upper peat layer, and discharge from inter-hummock channels was relatively large (∽0·1–1·0 m3 d−1), the near-stream area, a zone of relatively thick peat, offered little attenuation to water draining toward the stream channel, and the source area for stream flow was relatively large. The duration of this high flow regime varied among hillsides due to variations in the width of the near-stream area, the gradient, length and inclination of hillslopes, and the water equivalent and melt rate of the snowpack. When the water table subsided into the lower peat layer, and discharge from inter-hummock channels decreased (<0·1 m3 d−1), the runoff source area was relatively small. Under this condition, if drainage into the near-stream area increased, the lateral expansion of the runoff source area would be delayed due to the relatively large storage capacity near the stream. Copyright © 1999 John Wiley & Sons, Ltd.

The influence of a heavily polluted urban river on the adjacent aquifer systems

Ankara Creek is often subjected to overflowing of sewage caused by rainfall or direct discharge of raw sewage. Alluvial aquifers adjacent to Ankara Creek and its tributaries have considerable groundwater potential. The present status of groundwater quality is far from drinking water standards. Groundwater contamination in Ankara is suspected to be caused by Ankara Creek which is heavily polluted by raw sewage discharge, surface runoff and other common sources. In order to investigate the influence of heavily polluted Ankara Creek on the groundwater contamination in the adjacent alluvial aquifers, five sampling stations on Ankara Creek and 25 water wells were monitored during 1996. At five different sampling periods, water samples were collected from both surface water and groundwater. Chemical analyses of basic ions, pollution parameters and heavy metals in natural waters were carried out. The organic pollution prevails in Ankara Creek whereas total dissolved solids (TDS) and heavy metal concentrations are considerably low. Starting from the idea that Ankara Creek somewhat influences the groundwater quality and the contaminants in groundwater should attenuate with respect to distance, a series of water wells in a certain area, each having different distance from the creek, were examined using four pollution parameters. It is concluded that Ankara Creek barely influences the aquifer systems in connection. This is attributed to two reasons: rapid attenuation of contaminants due to dilution in groundwater and a blanket of very fine sized materials covering the bottom of Ankara Creek.

SEDIMENT AND NITROGEN TRANSPORT IN GRASS FILTER STRIPS1

ABSTRACT: An 18‐month field experiment was conducted to evaluate the effectiveness of grass filter strips in removing sediment and various nitrogen species from runoff. Runoff was collected from six 3.7 m wide experimental plots with 24.7 m long runoff source areas. Two plots had 8.5 m filters, two plots had 4.3 m filters, and two plots had no filters. Runoff was analyzed for total suspended solids (TSS), total Kjeldahl nitrogen (TKN),. filtered TKN (FTKN), NH4+‐N, and NO3‐N. The Mann‐Kendall nonparametric test for trend (changes in filter effectiveness over time) indicated that there were no trends in the yields and concentrations of TSS, NO3‐‐N, NH4‐N, TKN, and FTKN for the 8.5 m filter over time. For the shorter 4.3 m filters, there were significant upward trends in TKN yield and downward trends in TSS, NH4‐N, and FTKN concentrations, indicating that trapping efficiency may have started changing with time. The Kruskal‐Wallis test indicated that the 8.5 m filters reduced median yields and concentrations of TSS and all N species, but the 4.3 m filters only reduced the median yields and concentrations of TSS, NH4+‐N, TKN, and the median concentration of FTKN. The 8.5 and 4.3 m filters reduced contaminate yields and concentrations from 42 to 90 percent and from 20 to 83 percent, respectively.