Date of Award:

1975

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Watershed Sciences

Advisor/Chair:

Gerald F. Gifford

Abstract

During 1973 and 1974 a water quality study was conducted in San Juan County, southeastern Utah. In 1973, baseline water quality data was collected from study locations which had been chained to remove pinyon-juniper vegetation six years earlier. The area had been chained under two different techniques: (1) doubled chained, with debris-left-in-place and (2) chained, with debris windrowed. An "undisturbed, natural" woodland was left between these two treatments in order to serve as a control area.

In the fall of 1973 and spring of 1974 secondary treatments of burning and grazing were superimposed upon the debris-in-place and windrowed sites, respectively.

All water collected and analyzed for the several water quality parameters was generated through use of a small plot Rocky Mountain infiltrometer which creates a simulated rainstorm. Resultant runoff was collected and analyzed for each of the parameters in question.

No significant changes were noted from these point source measurements in terms of fecal and total coliform production (fecal pollution bacterial indicators). The point source approach was a technique for sampling a much larger land area through many small plots (0.23 m2). There is an element of risk involved whenever the data generated from such a small area is projected to the larger land area. Based on this small plot data it appears, however, that this level of livestock grazing (2 hectares/AUM) does not constitute a public health hazard in terms of fecal pollution indicators when grazed on similar semi-arid watershed areas.

Some significant changes were noted following burning, however. Significant increases in potassium and phosphorus were noted. Apparently the fire "released" these nutrients which were tied up in the debris scattered across the site. Potassium registered an increase of about 4 ppm (400 percent) while phosphorus showed an increase of about 0.2 ppm (400 percent). No significant treatment changes were detected for sodium, calcium, or nitrate-nitrogen, however.

Sediment production was also measured under the various treatment conditions. High natural variability is present among these sites, and no significant treatment effect was defected following our prescribed burning or grazing treatments.

Infiltration rates were also monitored. No significant treatment differences were noted among the initial treatment means during 1973. Apparently any differences in infiltration rates due to chaining technique had been overcome by the passage of six years since the initial chaining had been completed.

During 1974, however, secondary treatment was in effect. Infiltration rates on the grazed and burned watersheds were significantly depressed during certain time intervals in comparison to the "undisturbed, natural" woodland location. Apparently this level of secondary treatment could have an effect on the hydrology of the area, at least in terms of infiltration rates.

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