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ASAE Technical Paper

Impact of a Constructed Low Water Stream Crossing, an Innovative BMP, on Microbial Water Quality of a Rangeland Pasture Stream

Chris G. Henry , Extension Engineer II

University of Nebraska – Lincoln, Biological Systems Engineering , 217 LWC, Lincoln, NE 68583-0726 , USA

Jeanette A. Thurston-Enriquez , Microbiologist

USDA-ARS , 138 Keim Hall, UNL East Campus, Lincoln, NE 68583-0934 , USA

This is not a peer-reviewed article.

Paper No: 032313
An ASAE Meeting Presentation

Written for presentation at the

2003 ASAE Annual International Meeting
Sponsored by ASAE
Riviera Hotel and Convention Center
Las Vegas, Nevada, USA
27- 30 July 2003

Abstract. The impact that livestock in pastures have on microbial water quality is poorly understood. A low water stream crossing (LWSC) was designed and constructed in the middle of a stream pasture segment to evaluate it’s effectiveness as a potential BMP and as an alternative to excluding livestock from streams with permanent fencing. The construction and application of the crossing is discussed. The stream segment was investigated for the presence of indicator microorganisms and protozoan parasites commonly associated with livestock. Stream samples and flow data were collected approximately twice per month during a period of 6 months. Water samples were assayed for total coliforms, Escherichia coli, Enterococcus, Giardia cysts, and Cryptosporidium oocysts. Concentrations of indicator organisms appear to exceed new recommended EPA guidelines for recreational contact for E. coli and Enterococcus. The presence of cattle in the studied pasture was the likely cause of increased concentrations of indicator microorganisms downstream of the cattle crossing.

Keywords. Low Water Stream Crossing, Pasture, Livestock, Cattle, Enterococcus, Escherichia coli , Total Coliforms, Giardia , Cryptosporidium.


Introduction

EPA estimates that more than 20,000 water bodies in the US are polluted, totaling more than 300,000 river and shoreline miles. In EPA region seven alone, which include the states of Nebraska, Kansas, and Missouri, 1556 impaired waters do not meet water quality standards. Of the impaired waters assessed, 81% are identified as streams, creeks, or rivers. Fecal bacteria, indicators of fecal contamination by warm-blooded animals, were the cause of 726 impairments (EPA, 1998).

Since human pathogens are excreted in the feces of humans and animals, identification of fecal bacteria may indicate their presence in water bodies. Serving as indicators of fecal pollution, fecal bacterial contamination in streams nearby dairy farms and cattle pastures (Gary et al., 1983; Niemi and Niemi, 1991) surface runoff grazed pastures, (Doran and Linn, 1979; Jawson et al., 1982) springs and wells within the hydrological catchments of pastures (Howell et al., 1995), and subsurface runoff from manure applied fields (Culley and Phillips, 1982) demonstrate the ability of manure to serve as a vector for the transmission of fecally-derived bacteria.

Fecal contamination is also introduced by human sources such as municipal wastewater discharges and urban runoff. Nonpoint sources of fecal pollution include direct deposition from wildlife and livestock and runoff events that draw fecal contaminants from urban and agricultural land. Rain or other runoff events that flush fecally-contaminated sites, such as urban areas, manure-applied fields, animal pens and other manure management sites, can actively transport pathogens to surface waters that are critical to a variety of human uses. Fecally polluted surface water used for recreation, drinking water sources, and for irrigation of crops that are minimally processed before consumption can significantly increase the risk of illness by waterborne pathogens.

Waterborne Protozoan Pathogens

Giardia and Cryptosporidium are not only important causes of diarrhea in humans, but also infect farm animals (swine, cattle, sheep). For both protozoa, the stage excreted into the environment is present in high numbers in the feces, infectious upon release, and is extremely resistant to environmental conditions. Both protozoa cause self-limiting diarrheal illness, but cryptosporidiosis can be fatal in immunocompromised patients. Previous studies have reported high concentrations of protozoa at different locations within cattle operations that can contaminate nearby water supplies via runoff events. Ong et al. (1996) found significantly higher oocysts and cysts downstream from a cattle ranch compared to upstream samples, indicating that cattle located within watersheds can be sources of Giardia cysts and Cryptosporidium oocysts.

Low Water Stream Crossings for Cattle (LWSC)

Livestock access to streams, specifically, cattle access to streams in pastures has become of concern in the development of Total Maximum Daily Loads (TMDLs). There is very little information available to planners on the contribution of nitrogen, ammonia, phosphorus, and human health-related microorganisms to stream segments from rangeland cattle. A common modeling solution in the development of TMDLs is to exclude livestock from streams in order to reduce nutrient loads. Although this approach seems simplistic, it is problematic for owners and managers of rangeland livestock.

Many producers are now choosing to supply water to their livestock from man-made drinking water sources supplied by groundwater, surface water or rural water supplies. In addition to providing a higher quality source of water for livestock, these approaches have the added benefit of minimizing the amount of time livestock spend near surface water sources. These practices along with rangeland management techniques such as rotational grazing (cross fencing) have increased the production capacity of pastures.

LWSCs (Figure 1) are permanent crossing locations in streams or other conduits of surface water that a) provide access across the stream; b) minimize erosive effects of unprotected stream banks; and c) is comparable in cost to entire stream exclusion (fencing). LWSCs have been utilized for a wide range of crossing applications including tanks, farm machinery and livestock. LWSCs can be made from a variety of materials, including concrete, rock and riprap, and bricks. They are generally exempt from section 404, Army Corp of Engineer Permit requirements, since they are considered an unregulated access road. As with any construction project, regulatory requirements should be verified with all state and local authorities before construction.

032313BR_files/image1.jpg

Figure 1. A concrete LWSC for cattle.

Design and Application of LWSCs for Livestock

One of the biggest challenges of a LWSC in a pasture is determining the proper location for its installation. In our experience, several things must be considered:

The approaches of a LWSC should not exceed 5:1 slopes, although some conservation practice standards allow up to 4:1. Care should be taken to ensure that the approach and slope of the LWSC is not too steep, especially concrete structures, as cattle may not have adequate traction to negotiate the crossing. The surface of the crossing should be made to minimize slippage and abrasion to animal hooves. For concrete construction, surfaces should be roughened. For aggregate construction, the LWSC should be surfaced with limestone screenings or similar material to provide a stable and uniform surface for livestock. During construction of a LWSC, the stream should be dammed and the stream flow should be discharged below the construction site. The stream must be returned to its original elevations. Crossings should be placed a minimum of 0.2 feet below the natural elevation of the stream channel. LWSC’s should not obstruct stream flow.

A hoof contact zone of at least 2 inches should be placed on aggregate crossings. They can be made from sand, limestone screenings, ground limestone, rock screenings, or other similar material (USDA, 1986a). The Wisconsin Conservation Practice Standard (USDA, 1986a) suggests that crossing widths for cattle be 4-10 feet in width. The authors recommend that crossings are at least 10 feet in width since it has been observed that 2-3 animals may attempt to use the crossing at the same time. Immediately after construction, temporary fencing may be required to protect vegetation and to encourage livestock use of the crossing.

Recommended surface material thicknesses are:

Soft Foundations

Recommendations for firm foundations are included in the most NRCS conservation practice standards (USDA-NRCS Wisconsin 1989a, USDA-NRCS Wisconsin1989b, USDA-NRCS Wisconsin 2002). If a geotextile fabric is used, rock thickness can be reduced substantially. A non-woven fabric is recommended by the authors. Figure 2 illustrates a generic plan used for two concrete LWSC’s constructed in Nebraska. Construction costs for these LWSCs in Nebraska averaged about $5,000 for materials and labor. The Nebraska Environmental Trust provided cost share for these structures.

032313BR_files/image2.gif

Figure 2. Generic plan for LWSC

Evaluation of LWSC by Stream Sampling

The studied pasture is located in south central Nebraska. The pasture maintains a good stand of native grass vegetation. A perennial stream is located within the pasture. The study site is located in an area of agricultural production that includes irrigated cropland and rangeland pastures. Background concentrations of microorganisms most likely originate from these sources and wildlife.

Selection of sample locations

Sampling locations within the study pasture are shown in Figure 3. Samples were taken at the inlet, immediately downstream of the LWSC, and at the exit of the studied pasture. The distance between the inlet and the crossing is 689 meters and the distance along the stream from the crossing to the exit is 509 meters. The direction of stream flow is south to north, or from the bottom to the top of the figure.

032313BR_files/image3.jpg

Figure 3. Study site and sample locations

Stream Flow Measurement

The accepted practice of measuring stream flow is to integrate the stream cross section, by breaking the stream section into equal segments, flow is taken from each segment and the segment widths and depths are multiplied by the flow velocity (Rickly Hydrologic Company; Bureau of Reclamation, 1997). Flow velocity was determined with a USGS style pygmy meter. Current meter measurements for stream flows are typically done by breaking a stream cross-section into a series of partial sections. The measurements are the summation of the products of the partial areas of the stream cross-sections and their respective average velocities. It is assumed that the velocity at each location represents the average velocity of the partial rectangular section. These partial flow sections are then added up to represent the total flow of the stream cross-section. In the stream studied, only one flow measurement, or one rectangular partial section, could be obtained. To better estimate the stream flow, another approach was used to estimate the stream cross sectional area.

Sampling stream flow in pastures can be challenging if they are shallow and have low flow velocities. The stream segment investigated was a shallow, low flow stream that is typical of Nebraska streams. The traditional method of stream flow measurement yielded only one partial section, and would under-estimate actual stream flow. To overcome this, stream channel sample locations were surveyed with a total survey station, marked, and the stream velocity was determined. A relationship based on the stream depth was derived from this survey and used to estimate the cross-sectional area of the stream. The depth and stream velocity for every sampling event was measured with the pygmy meter. Most velocities recorded approached the lowest threshold readings of the pygmy meter. Permanent samplers were not used since their destruction by livestock or tampering by passer-by’s was possible. The pygmy meter is highly accurate between velocities of 0.1 and 20 feet per second (Rickly Hydrologic Company).

Stream Water Collection and Storage

Stream samples were obtained approximately every two weeks from June 7 through September 5. Grab samples were taken for analysis of microbial indicators, protozoan parasites and physical/chemical parameters. Water temperature was determined on-site, however pH and turbidity was assessed within 4 hr of collection. Water samples were filled to the top of sterile polypropylene 1 l bottles (bacterial and physical/chemical parameter analyses) and 10 l carboys (protozoan parasite analyses). Water samples were stored on ice during transport and at 4°C in the laboratory. Bacterial and protozoan parasite analyses were completed within 6 and 96 hr of collection, respectively.

Laboratory Methods

Total coliforms and Escherichia coli , and enterococccus were analyzed using IDEXX Corporation’s Colilert and Enterolert methods, respectively. Undiluted or diluted (1:10 or 1:100) water samples were mixed with the IDEXX reagent and placed in Quantitray/2000 and incubated according to the manufacturer’s instructions (Coilert product insert; IDEXX Laboratories, Westbrook, ME). Following incubation, the most probable number (MPN) of indicator bacteria per 100 ml was determined according to manufacturer’s instructions. Concentration of Giardia cysts and Cryptosporidium oocysts in up to 10 L stream water was determined using US EPA Method 1623 (EPA, 1999).

Results

Stream water samples were collected from June through September 2002. A total of 42 samples were collected from the inflow of the pasture, immediately downstream of the cattle crossing (middle of pasture), and at the outflow of the pasture. Stream water samples were collected during two periods, 24 samples when cow/calf pairs were grazing within the pasture and 18 when they were absent. Geometric averages and ranges of indicator bacteria concentrations (MPN/100 ml) for each sampling period are listed in Table 1. Stream water concentrations of indicator bacteria were highest for total coliforms, followed by enterococcus and E. coli . Significantly higher concentrations of E. coli (P < 0.01) and enterococcus (P < 0.01) were observed for samples collected when cattle were present compared to when they were absent from the studied pasture. For total coliforms, concentrations between the two periods were not significantly different (P > 0.05). A significant (P ? 0.01) trend in indicator bacteria concentrations during dates when cattle were present was observed to be: middle of pasture > outlet of pasture > inflow to pasture.

Stream flow data was collected for only 5 stream samples for times when cattle were present and 6 samples when cattle were absent from the pasture. Flow-weighted indicator bacteria concentrations (MPN/s) during these periods are listed in Table 2. No statistically significant relationships were present between indicator flow-weighted concentrations and locations within the pasture during times when cattle were present (P>0.05). Due to limited data, no statistical comparisons could be carried out for flow-weighted indicator concentrations between periods of cattle presence and absence in the study pasture. Table 3 lists percent indicator concentration increases, MPN/100 ml and MPN/s, observed from periods of cattle presence and absence from the pasture. Large increases in E. coli were observed at the crossing sample location compared to the inlet.

Temperature, turbidity, and pH ranged from 15 to 29 oC, 4.6 to 944 nephelometric units, and 7.6 to 8.2, respectively. Correlation analysis revealed significant (P<0.05), positively correlated, relationships between turbidity and total coliform and E. coli concentrations. While not as statistically significant (P = 0.07), enterococcus was also positively correlated with turbidity. Stream water turbidity, during times when cattle were in the pasture, were significantly (P<0.05) different between sampling sites where, middle of pasture > outlet of pasture > inlet to pasture. Stream water temperatures were positively correlated (P<0.0001) with concentrations of E. coli and enterococcus. No significant relationships were observed for indicator concentrations and pH (P>0.05).

Thirty-three percent of stream water samples tested positive for Giardia cysts and Cryptosporidium oocysts. Ranges of protozoa in stream water samples varied from <1.0 to 10 Giardia cysts/10 L and <1.0 to 40 Cryptosporidium oocysts/10 L during cattle absence and<1.0 to 30 Cryptosporidium oocysts and Giardia cysts/10 L during cattle presence. Table 4 lists the ranges of concentrations of Giardia cysts and Cryptosporidium oocysts for samples collected during periods of cattle presence and absence.

Current velocities for the period of study averaged 0.29 ft/s, with a maximum velocity of 0.8 ft/s and a minimum of 0.074 ft/s. The average flow was 3.35 l/s (0.12 cfs) and the maximum flow observed was 30 l/s (1.05 cfs) while the minimum flow recorded was 0.29 l/s (0.01cfs) during the study period.

Table 1. Geometric means and ranges of indicator bacteria concentrations in stream samples for each sampling site.

Microbe

(MPN/100 ml)

Pasture Inlet

Middle of Pasture

Pasture Outlet

Cattle

Cattle Absent

Cattle

Cattle Absent

Cattle

Cattle Absent

E. coli

Geomean:

Range:

2.4 x 102

5.8 x 102

3.3 x 103

4.2 x 102

1.1 x 103

8.3 x 102

63 –

1.2 x 103

3.1 x 102 –

1.7 x 103

1.2 x 103 –

3.5 x 104

56.0 –

1.3 x 103

3.0 x 102 –

5.0 x 103

3.0 x 102 –

2.5 x 104

Enterococcus

Geomean:

Range:

1.3 x 103

1.2 x 103

3.5 x 103

3.5 x 103

3.9 x 103

3.1 x 103

6.4 x 102 - 5.4 x 103

1.2 x 102 – 2.7 x 103

1.2 x 103 - 1.9 x 103

2.2 x 103 -1.6 x 104

9.9 x 102 -1.0 x 104

2.0 x 102 - 2.0 x 104

Total coliforms

Geomean:

Range:

2.0 x 104

5.2 x 104

7.6 x 104

5.3 x 104

6.5 x 104

4.1 x 104

1.5 x 104 - 4.4 x 104

1.7 x 104 -1.5x104

3.4 x 104 -2.7 x 105

9.8 x 103 -1.9 x 105

4.1 x 104 -1.2 x 105

2.2 x 104 -1.1 x 105

Table 2. Geometric averages and ranges for flow-weighted bacterial indicator concentrations (MPN/s) during times when cattle were present and absent from the studied pasture.

Microbe

(MPN/s)

Pasture Inlet

Middle of Pasture

Pasture Outlet

Cattle

No Cattle

Cattle

No Cattle

Cattle

No Cattle

E. coli

Geomean:

Range:

1.3 x 104

7.3 x 104

6.5 x 104

7.7 x 103

6.4 x 103

1.3 x 104+

2.2 x 103 - 6.2 x 104

3.1 x 104 - 2.5 x 105

1.5 x 104 -2.9 x 105

9.9 x 103 -1.8 x 104

9.7 x 102 -2.4 x 104

NA++

Enterococcus

Geomean:

Range:

3.6 x 104

7.2 x 104

6.6 x 104

3.8 x 104

1.4 x 104

1. 6 x 104*

7.9 x 103 -1.3 x 105

1.8 x 104 – 4.0 x 105

3.1 x 104 -1.6 x 105

1.6 x 104 –7.0 x 104

3.2 x 103-1.1 x 105

NA++

Total coliforms

Geomean:

Range:

9.4x 105

4.4 x 106

1.6 x 106

1.3 x 106

3.5 x 105

2.8 x 105*

1.8 x 105 -2.7 x 106

1.7 x 106 -1.6 x 107

6.8 x 105-4.5 x 106

5.0 x 105 -2.8 x 106

1.7 x 105 –2.0 x 106

NA++

+ Only one data point.

++ Not applicable.

Table 3. Percent increases of indicator bacterial concentrations from sampling sites during the absence compared to the presence of cattle in the inlet versus the middle and outlet of the pasture.

Microbe

Middle of Pasture

Pasture Outlet

E. coli

% increase MPN/100ml

% increase MPN/s

695%

734%

30%

NA+

Enterococcus

% increase MPN/100ml

% increase MPN/s

0%

74%

27%

NA

Total coliforms

% increase MPN/100ml

% increase MPN/s

43%

25%

58%

NA

+Not applicable due to only one data point collected.

Table 4. Ranges of Giardia cysts and Cryptosporidium oocysts for stream water samples collected during the presence and absence of cattle in the studied pasture.

Protozoan Parasite

(per 10 L)

Pasture Inlet

Middle of Pasture

Pasture Outlet

Giardia cysts

Cattle Present

% of samples containing cysts

Cattle Absent

% of samples containing cysts

<1 - 1

38%

ND+

0%

<1 - 20

25%

ND

0%

<1 - 30

38%

<1 - 10

50%

Cryptosporidium oocysts

Cattle Present

% of samples containing cysts

Cattle Absent

% of samples containing cysts

<1 - 2

25%

ND

0%

<1 - 30

25%

ND

0%

<1 - 2

13%

<1 - 40

33%

+None detected.

Discussion

A significant deterioration in microbial water quality, as determined by E. coli and enterococcus concentrations, was observed when cattle were present in the studied pasture. Numbers of total coliforms, however, did not significantly increase with the introduction of cattle in the studied pasture. This may not be surprising since members of the total coliform group may multiply in the environment (Gerba, 2000) and there are many environmental sources of these bacteria. These, and other reasons have caused the EPA to recommend the use of E. coli and enterococci as indicators of microbial water quality, replacing the total coliform group of bacteria. Within the pasture and during times of cattle presence, highest concentrations of all indicator bacteria were observed downstream of the crossing whereas lowest concentrations occurred at the inlet to the pasture. Not only did the cattle impact the stream water quality by increasing indicator concentrations, but these concentrations far exceeded EPA recreational water recommendations (EPA 1986).

Guidance on water quality criteria for bacteria is given in the May 2002 EPA Draft (EPA, 2002) that, if approved, will replace the 1986 EPA recommendations. In the Draft, EPA recommends using either E. coli or enterococci as indicators of fecally contaminated fresh recreational water. These indicators may be included in National Pollutant Discharge Elimination System permits and for development of TMDLs. Recommended limits of indicator bacteria concentrations differ depending on the recreational use and regulation authority’s decision on acceptable illness rates for the surface water in question. For primary contact recreational water, waters where contact and immersion are likely, EPA recommends that water quality criteria for these indicator bacteria be based on a given illness rate. Based on epidemiological data, acceptable illness rates have been established for fresh waters that are known or expected to be in contact with people. These illness rates equate to the maximum geometric mean ( ? 5 samples over a 30-day period) density of E. coli and enterococci that are the allowable per 100 ml fresh water. For popular beaches, a single sample maximum allowable geometric mean density is 126 and 33 per 100 ml E. coli and enterococci, respectively. Recommended levels of E. coli and enterococci for fresh waters that have the potential for human recreational activities, termed secondary contact recreation sources, are five times the concentrations of primary contact recreation recommendations (639 E. coli/100 ml and 165 enterococci/100 ml). Secondary recreational waters include those where minimal direct water contact occurs, such as wading, canoeing, motor boating and fishing. In comparison to the current study, E. coli concentrations exceeded EPA recommendations for secondary contact recreation in 63% and 44% of samples collected when cattle were present and absent, respectively. For enterococcus, 100% and 89% of samples exceeded EPA recommendations for samples collected when cattle were present and absent from the pasture. Contributions from upstream sources and wildlife sources within the pasture may have impacted these indicator concentrations causing them to exceed the recommended standards.

Although E. coli and enterococcus concentrations exceeded recommended standards when cattle were not present in the pasture, the magnitude of their concentration was significantly higher when cattle were grazing in the pasture . E. coli concentrations, for example, increased by almost 700% from the inflow to the sampling site located in middle of the pasture. These results suggest that E. coli are more efficient indicators of cattle presence compared to the other indicator bacteria assayed since the magnitude of enterococcus and total coliforms was not as large between the inflow and other sampled sites. Moreover, increased concentrations of enterococcus and E. coli at the crossing, compared to the inflow and outflow, suggest that cattle may have been using the crossing. Further studies will be conducted this summer (2003) to determine the activity of the cattle in relation to the crossing.

Percent increases in all indicator bacteria between the inflow and the outflow of the pasture during cattle grazing were not nearly as high as those observed between the inflow and the middle of the pasture. This decrease suggests that natural attenuation of the study microorganisms occurs as the stream water flows from downstream of the crossing to the pasture outlet. This relationship may further suggest the use of the crossing by cattle and that the crossing is the bacterial source. Factors such as natural die-off, predation, sunlight, adsorption to particulate matter and sedimentation may be involved in the reduction of indicator bacteria. With the low flow and high turbidity that was observed during the course of study, it would not be surprising to find that the microorganisms assessed in this study may be removed through attachment to particulate matter and sedimentation. Thus, it follows that streambed sediments may serve as a store for these microorganisms. Determination of whether or not streambed sediments are a reservoir of indicator and pathogenic manure-borne pathogens will be assessed in further studies with this pasture stream in the summer and fall of 2003.

Rarely is flow data included in microbial assessments of surface water quality. Flow-weighted concentrations provide information regarding the impact that a surface water segment and its associated land-use have on the total microbial load affecting surface water downstream. In the current study, limited information on flow was obtained and no statistically relevant relationships were observed for all parameters analyzed. Assessments of flow-weighted microbial concentrations will continue over the summer and fall of 2003.

Seasonal variation was observed with indicator bacteria concentrations. Increasing stream water temperatures over the sampling period coincided with increasing indicator bacterial concentrations, a commonly reported trend in the literature (Hunter et al., 1999; Jawson et al., 1982). Turbidity, like stream water temperature, was also positively correlated to indicator bacterial concentrations. Turbidity, therefore, may serve as an on-site water quality indicator since it can be measured in the field. It may be useful in identifying sampling sites that are suspected to exceed microbial water quality standards.

Concentrations of Giardia cysts and Cryptosporidium oocysts ranged from 25-38% when cattle were grazing to 0-50% when cattle were absent from the pasture. Concentrations were relatively low for the majority of samples; however, these protozoa can cause infection at fairly low concentrations. While the methods used to determine whether these protozoa were viable or infectious to humans was not possible by the standard method used, the presence of cattle during the period of study did not greatly impact the concentration of protozoa within the stream segment.

Conclusions

A LWSC was installed in a small pasture in 2001. The goal of the project was to establish if cattle were using the LWSC and not crossing the stream at other points along the stream. Eyewitness accounts support the conclusion that cattle are using the crossing. The low flow conditions, a result of the drought experienced in 2002, may have been the cause of the high microbial concentrations observed. Evidence that cattle were spending time near the crossing was observed. A significant trend in indicator bacteria concentrations and turbidity during dates when cattle were present was observed to be: middle of pasture > outlet of pasture > inflow to pasture.

Obtaining accurate flow data for small streams in pastures can be a major challenge. Stream flow was not obtainable for many of the samples and therefore, no statistical relationships could be found. However, several statistical relationships were found from concentration data (grab samples). A significant deterioration in microbial water quality, as determined by E. coli and enterococcus concentrations, was observed when cattle were present in the studied pasture. E. coli concentrations exceeded EPA recommendations for secondary contact recreation in 63% and 44% of samples collected when cattle were present and absent, respectively. For enterococcus, 100% and 89% of samples exceeded EPA recommendations for samples collected when cattle were present and absent from the pasture. Contributions from upstream sources and wildlife sources within the pasture must have impacted these indicator concentrations causing them to exceed the recommended standards. Different methods other than simple concentration (grab samples) may be needed to quantify the microbial water quality of these types of streams.

Further Studies

Sampling of the pasture will continue through 2003. Additional microbial parameters will include assay of stream water for bacterial pathogens such as E. coli O157:H7 and Salmonella . An effort to determine whether or not stream bed sediments serve as a store of this study’s indicator and pathogenic bacteria and protozoan parasites will also be carried out.

Acknowledgements

We are grateful to the Nebraska Environmental Trust for providing funding for this project and to the participating producer and the Little Blue Natural Resource District for their participation and assistance.

References

Bureau of Reclamation. 1997. Water Measurement Manual. Third Edition. United States Government Printing Office. Denver, CO.

Culley, J. L., and P. A. Phillips. 1982. Bacteriological quality of surface and subsurface runoff from manured sandy clay loam soil. J. Environ. Qual. 11: 155-158.

Doran, J. W., and D. M. Linn. 1979. Bacteriological quality of runoff water from pastureland. Appl. Environ. Microbiol. 37: 985-991.

EPA. 1998. Total Maximum Daily Loads Section 303(d) List Fact Sheet for EPA Region 7. http://oaspub.epa.gov/waters/region_rept.control?p_region=7

EPA. 1986. Ambient water quality criteria for Bacteria. EPA 440/5-84-002. EPA Office of Water, Washington D.C.

EPA. 1999. Method 1623: Cryptosporidium and Giardia in water by filtration/IMS/FA. Method EPA-821-R-99-006. EPA Office of Water, Washington D. C.

EPA. 2002. Implementation guidance for Ambient Water Quality Criteria for Bacteria. EPA-823-B-02-003. EPA Office of Water, Washington, D. C.

Gary, H. L., S. E. Johnson, and S. L. Ponce. 1983. Cattle grazing impact on surface water quality in a Colorado front range stream. J. Soil Wat. Conserv. 124-128.

Gerba, C. P. 2000. Indicator microorganisms, p. 491-503. In: R. M. Maier, I. L. Pepper, and C. P. Gerba (ed.), Environmental Microbiology. Academic Press, San Diego.

Hunter, Colin, Joy Perkins, Jamie Tranter, and John Gunn. 1999. Agricultural land-use effects on the indicator bacterial quality of an upland stream in the Derbyshire peak district in the U.K. Wat. Res. 33: 3577-3586.

Howell, J. M., M. S. Coyne, and P. Cornelius. 1995. Fecal bacteria in agricultural waters of the bluegrass region of Kentucky. J. Environ. Qual. 24: 411-419.

Jawson, M.D., L. F. Elliott, K. E. Saxton, and D. H. Fortier. 1982. The effect of cattle grazing on indicator bacteria in runoff from a pacific northwest watershed. J. Environ. Qual. 4: 621-627.

Niemi, R. M. and J. S. Niemi. 1991. Bacterial pollution of waters in pristine and agricultural lands. J. Environ. Qual. 20: 620-627.

Ong, C.. W. Moorehead, A. Ross, and J. Isaac-Renton. 1996. Studies of Giardia spp. and Cryptosporidium spp. in two adjacent watersheds. Appl. Environ. Microbiol. 62: 2798-2805.

Rickly Hydrologic Company. No Date. Discharge Measurements at Gaging Stations. Rickley Hydrologic Company. Columbus, Ohio.

USDA-NRCS, Wisconsin, 1989a. Access Road (ft). Conservation Practice 560. Section 4 of Field Office Technical Guide.

USDA-NRCS, Wisconsin 2002. Access Road (ft). Conservation Practice 560. Section 4 of Field Office Technical Guide.

USDA-NRCS, Wisconsin. 1989b. Rock Channel Crossings. Engineering Field Manual Notice 210-WI, Wisconsin.

Appendix or Nomenclature

BMP = best management practice

E. coli = Escherichia coli

LWSC = low water stream crossing

MPN = most probable number

o.c.e.w . = on center each way

TMDLs = total maximum daily loads


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