Background & Rationale

In 1999, Belsky et al.(1) completed a comprehensive review of the impacts of livestock grazing on streams and riparian ecosystems on arid rangelands in the western United States. Detrimental impacts were found in 80% of streams and riparian ecosystems and affected a range of stream characteristics including: water quality and seasonal quantity, stream channel morphology, riparian zone soils, instream and streambank vegetation, and aquatic and riparian wildlife.

In the past ten years, streambank fencing has been recommended by environmental protection agencies and implemented by land managers as a beneficial management practice (BMP) to minimize pollution of streams and rivers from livestock grazing on pastures and rangeland.  However, studies on the effect of exclusion fencing on various riparian health parameters have yielded conflicting results(2).  Many authors have reported improvements in riparian health parameters following exclusion fencing(3).  Others have documented no recovery of certain riparian health parameters such as stream morphology following livestock exclusion(4).

 

Figure 3.  Stream and riparian habitat impacts from cattle use of a watercourse and riparian pasture

Figure 4. Adjacent land uses in addition to cattle ranching with potential to impact stream water quality.

Research Objectives

As water quality assessment is a common tool used to monitor aquatic health and environmental risk in streams, rivers and lakes, this research project aims to examine how water quality alters with the application of a riparian fencing BMP that excludes cattle stream access. 

Cattle grazing adjacent to streams can contribute contaminants (sediment, nutrients like nitrogen and phosphorus, and pathogens) directly to the stream by fecal deposition and indirectly by cattle traffic within the stream and on streambanks.  Removal of cattle disturbance should therefore result in improvements in water quality parameters:
* reduction in bank disturbance and erosion=> decreased Total Suspended Solids, turbidity
* increase in riparian plant growth and shading of channel=> decrease in water temperature, increase in dissolved oxygen
* removal of direct faecal deposition => decrease in E.coli, decrease in nitrogen and phosphorus species, decrease in algal growth.
 

Expected Results

Possible results include, for each year from 2004 to 2007:
- finding no significant difference (a=0.05) in annual mean E.coli concentrations between background water quality levels and levels after treatment with an 800 m long fenced riparian pasture, or
- finding a significant difference in annual mean E.coli concentrations between background water quality and water quality after fencing treatment. 

If a significant difference is found, the difference may be positive (the fencing treatment improves water quality by reducing E.coli concentration) or negative (the fencing treatment reduces water quality by increasing E.coli concentration).  If no significant difference is found in annual means, then it is possible that there may be a difference in direction of the effect from week to week - this interaction would confound the experimental examination of the treatment effect.

Practical implications of this work include the demonstration of water quality benefits resulting from BMP implementation that can support ranchers’ selection of BMPs and that can be used in benefit:cost analyses by land managers funding BMP projects.
 

Cited references:

(1)  Belsky, A.J., A. Matzke, and S. Uselman. 1999. Survey of livestock influences on stream and riparian ecosystems in the western United States. J. Soil and Water Conserv. 54:419-431.
(2)   Sarr, D.A. 2002. Riparian livestock exclosure research in the western United States: a critique and some recommendations. Environ. Mge. 30:516-526;   Agouridis, C.T., S.R. Workman, R.C. Warner, and G.D. Jennings. 2005. Livestock grazing management impacts on stream water quality: a review. J. Am. Water Resour. Assoc. 41:591-606.
(3)   Kauffman , J.B., W.C. Krueger, and M. Varva. 1983. Impacts of cattle on streambanks in Northeastern Oregon. J. Range Manage. 36:683-685;   Platts, W.S. and R.L. Nelson. 1985. Stream habitat and fisheries response to livestock grazing and instream improvement structures, Big Creek, Utah. J. Soil and Water Conserv. 40:374-379;   Trimble, S.W., and Mendel, A.C. 1995. The cow as geomorphic agent-a critical review. Geomorphology 13:233-253;   Magilligan, F.J. and P.F. McDowell. 1997. Stream channel adjustments following elimination of cattle grazing. J. Amer. Water Resour. Assoc. 33:867-878;   Dobkin, D.S., A.C. Rich, and W.H. Pyle. 1998. Habitat and avifaunal recovery from livestock grazing in a riparian meadow system of the Northwestern Great Basin. Conserv. Biol. 12:209-221; Scrimgeour, G.J. and S. Kendall. 2003. Effects of livestock grazing on benthic invertebrates from a native grassland ecosystem. Freshwater Biol. 48:347-362.
(4)   Kondolf, G.M. 1993. Lag in stream channel adjustment to livestock exclosure, White Mountains, California. Restor. Ecol. 1:226-230; Allen-Diaz, B., R.D. Jackson, and J. Fehmi. 1998. Detecting channel morphology change in California’s hardwood rangeland spring ecosystems. J. Range Manage. 51:514-518;   George, M.R., R.E. Larsen, N.K. McDougald, K.W. Tate, J.D. Gerlach, Jr. and K.O.Fulgham. 2002. Influence of grazing on channel morphology of intermittent streams. J.Range Manage. 55:551-557.