OVERVIEW

This quarterly report discusses tasks undertaken and progress made on the USU REMAP project during the period April 1 to June 30, 1999. The primary task on the project during this period was the collection of field data to be used in developing the monitoring protocol. Within this report, we discuss this field data collection effort, and illustrate some of the procedures with photographs. Additionally, we present some preliminary thoughts on development of the protocol. Statistical analysis of data collected at field sites has not been undertaken at this time. Therefore, the ideas presented herein should be regarded as preliminary and based solely upon field observations.

We have organized this report into the following subsections:

Overview of field data collection

Characterizing rangeland watershed upland areas

Revision of stream/riparian area protocol

The utility of integrating GIS, GPS, and imagery

OVERVIEW OF FIELD DATA COLLECTION

This season’s field effort began on May 10^th with a team of seven (Figure 1) undertaking data collection. We started the data collection program in southern Utah, where most of the wintertime accumulation of snowpack had already melted. During the months of May and June, we completed nearly all of the upland data collection (soils, vegetation, and hydrologic data) for the four watersheds located in the Beaver River and Otter Creek basins (Figure 2). Fieldwork procedures are briefly presented in the following section. Stream and riparian area conditions were preliminarily assessed. However, the protocol for these areas is undergoing revision (see below), and we expect to return to collect these data later in the year. During the quarter beginning July 1^st, we expect to begin field data collection in the northern Utah watersheds.

CHARACTERIZING RANGELAND WATERSHED UPLAND AREAS

Upland areas or hillslopes may comprise 95 percent of the area of a watershed and are the primary source areas for water and sediment in rangeland watersheds. During this quarter, we have been collecting three types of field data at upland sampling points¾ vegetation, soils, and hydrologic. For each watershed, data are collected at 45 to 60 upland sample points. Selection of these sample points was through procedures discussed in the first quarter report. To ensure consistent and complete data collection, field data collection forms were created and bound into a notebook for each watershed. The accompanying figures illustrate the methods used for collecting these data. The project report will contain details of the procedures used for data collection. Data types being collected include:

Vegetation. Vegetation cover type frequency is collected using the "point intercept on a transect method." A total of 100 points along the tape are sampled using a l-foot spacing along an English unit tape (Figure 3). A thin, pointed, copper rod is extended downward at each 1 foot marker along the upslope side of the tape until it hits: vegetation (by species), litter (fallen vegetation), rock (greater than 1.27 centimeter or ½ inch), pebble (less than 1.27 cm or ½ inch), or bare soil (Figure 4). Hits are recorded on a cover data form (Figure 5). Percentage of cover at a height of 4 feet (1.2 meters) or taller is also determined along the tape, as are data for calculating an index of above ground biomass.

Soils. Soil samples are taken and several soil tests are made at 10, 20, and 30 meters locations along the tape. Soil strength characteristics are measured in the field using a pocket penatrometer and shear vane. Bulk density samples are obtained by driving a aluminum cylinder of known volume into the ground to collect a soil sample (Figure 6). Bulk density samples are collected for 0-5 cm and 5-10 cm at each of the three locations along the tape. Data are recorded on a soils data form (Figure 7). Wet bulk density is determined by a field measurement, and dry bulk density is calculated after oven-drying the samples.

Hydrologic. At the 10-, 20-, and 30-meter locations along the tape, the rate of water infiltration into the ground is being measured. Infiltration rate is measured using a 7.62 cm (3 inch) single ring infiltrometer cut from a piece of PVC pipe. The infiltrometer is driven into the ground to a depth of 5 cm. The amount of water required to refill the infiltrometer is recorded every one or five minutes on a special data form (Figure 8). The small size allows refilling of the infiltrometer with a graduated cylinder (Figure 9). Antecedent moisture conditions are derived from the difference between wet and dry bulk densities for the soil bulk density sample collected at the site.

REVISION OF STREAM/RIPARIAN AREA PROTOCOL

Our initial fieldwork in southern Utah suggested that streams and riparian areas of small, rangeland watersheds will likely need assessment and monitoring procedures substantially different from those currently employed in other landscape types. Methods proposed in the project proposal, which were based upon standard procedures used by government agencies (eg., Harrelson et. al, 1994; USDA Forest Service, 1992), appear to be of questionable utility in the watersheds we are evaluating. Some of the issues raising doubts about the applicability of these standard methods to rangeland watershed monitoring include:

The streams of rangeland watersheds are likely to be ephemeral. Thus, methods such as the ‘greenline’ method (USDA Forest Service, 1992) which require measurement along the stream-edge water line are not applicable.

Ephemeral streams of small rangeland watersheds may have channel beds that are completely sediment covered to completely vegetation covered. Existing methods do not account for this vegetation component, which may be significant from a sediment filtering perspective.

Ephemeral streams of small rangeland watersheds are typically small, usually less than a meter in width. Methods developed for larger streams, such as pacing methods used in sediment sampling (Rosgen, 1996), may not be applicable.

The flow paths of small rangeland watersheds may not contain a central stream. Herein, we utilize the term ‘flow paths’ to delineate those linear areas along the drainage network where concentrated water, solute, and sediment flow occur. Instead of channelized flow, groundwater flow or a diffuse overland may occur along these flow paths.

The flow paths of these watersheds may not have associated riparian areas due to low moisture levels. However, they may show differences in plant species composition or cover frequency when compared with adjacent upland areas, and at some point downstream, may have riparian plant indicators.

The watersheds delineated for this investigation are no larger than second-order. Second-order watersheds are defined herein using Strahler’s (1957) modification of Horton’s (1945) stream ordering system. In this system, a stream with no tributaries is considered first order. A second-order stream begins at the confluence of two first order streams and ends at the confluence with another second or higher order stream. The order a stream segment is given is highly dependent upon the method used to delineate the stream channel network. A stream network and its stream ordering may be identified using topographic maps, digital elevation models, aerial photography, or field mapping. Field mapping provides the most accurate depiction of a complete channel network, although data collection expense usually limits use of this method (Gandolfi and Bischetti, 1997). Aerial photography may provide results nearly as good as field mapping. Stream networks are frequently defined using the "blue lines" on U.S. Geological Survey topographic maps due to the availability of such maps. Unfortunately, topographic map blue lines are cartographic generalizations that portray the stream network using the cartographer’s subjective judgement (Leopold, 1994, page 227). Also, because of the large scales of these maps, blue line streams may underestimate "true" field derived stream order by several or more orders (Leopold et. al., 1964, p. 388). From a management perspective, however, topographic map blue line streams provide a readily accessible reference of the stream network of higher order streams.

The selection of our research watersheds was described in this project’s first quarter report. With one exception, all are second order based upon blue line streams on USGS 1:24,000 scale topographic maps. However, two characteristics are noteworthy for the watersheds being investigated:

The USGS blue line networks underestimate the actual flow path networks of these watersheds when compared with air photo analysis and field observations. This result is not unexpected, as the discussion of the previous paragraph would indicate.

The flow paths of these watersheds, including those identified by blue lines on USGS topographic maps, may not be stream channels with definable beds and banks.

Figure 10a illustrates the delineation of the second-order Otter Creek Watershed No. 1 on a USGS 1:24,000 scale topographic map. The three first order streams of this watershed are identified by the labels a, b, and c in this figure. Air photo analysis, field investigation, and geographic information system (GIS) analysis indicate a much greater flow path network. Figure 10b, for example, illustrates a GIS-derived flow network using a constant support area as the basis for defining stream heads. This flow network was derived using a 10-meter digital elevation model and setting the threshold contributing support area to 0.053 hectares. This support area was chosen based upon the support area at the head of the ‘a’ tributary¾ the smallest support area of the three blue line tributaries. The drainage network shown in Figure 10b compares favorably with that derived from the field investigation. Using this drainage network yields a third-order watershed with 10 first-order tributaries. As would be expected, using only the USGS blue line network for locating monitoring points could dramatically limit potential stream/riparian sampling locations within a watershed. Thus, a method or methods for identifying the ‘actual’ drainage network should be incorporated into the monitoring protocol.

Conversely, even those streams identified by blue lines on USGS topographic maps do not appear to be what most people would consider as streams. Figure 11 presents views of the three blue line streams for the Otter Creek Watershed No. 1. Each of the three photographs in Figure 11 was taken looking downstream at the location where the topographic map (Figure 10a) identifies each respective stream head. Heavy vegetation and small, indistinct channels are characteristic of the streams and flow paths of this watershed and the others being investigated in southern Utah.

Monitoring Protocol Modifications

Our observations during this quarter’s fieldwork suggest that alternative approaches to monitoring the flow paths of small rangeland watersheds must be developed. Two possible approaches are currently being evaluated:

Vegetation frequency monitoring. Because many of the flow pathways of these small watersheds have some degree of vegetation cover, monitoring the frequency of cover type similar to that being done for upland areas may prove worthwhile. Changes in hydrologic conditions of a watershed could potentially be assessed through changes in species frequency or the frequency of plant versus non-plant (bare sediment or litter) cover in the flow path. This approach would likely be similar to an upland transect, with the tape being strung down the valley center (Figure 12).

Sediment size monitoring. Cross-stream pacing and pebble counts are frequently conducted to characterize stream sediment size (Rosgen 1996). The typical pebble count method does not appear to be usable for sediment characterization for these watersheds for two reasons. First, the channels are usually less than one meter (one pace) wide. Second, up to 100 percent of the sediment may fall into the sand-size or smaller category identified in the field while conducting a pebble count. We will therefore be evaluating the potential for collecting sediment along the channel for size analysis by laboratory methods.

THE UTILITY OF INTEGRATING GIS, GPS, AND IMAGERY

Much of the protocol development is utilizing GIS for data management and data analysis (see the quarter 2 report). To enable GIS usage, all data collection locations are being assigned a Universal Transverse Mercator (UTM) metric coordinate (northing and easting) to identify their positions on the earth’s surface. Data collection points are randomly selected using grid points from a digital elevation model (DEM) of a watershed. Sample points are located in the field using GIS printed air photo images displaying sample point locations. Additionally, a table of sample point UTM coordinates and a global positional system (GPS) unit are used to locate the geographic coordinate (Figure 13).

Because we will be attempting to integrate the field data with GIS layer information, accurate location of field sample points is necessary. A combination of relatively inexpensive GPS units and high resolution air photos (or USGS digital orthophotoquads) appears to be allowing us very accurate location of data collection points. Relocation of these points in the future should be relatively straightforward. Figure 14 illustrates a sample point from Otter Creek Watershed No. 1.

REFERENCES

Gandolfi, C., and G. B. Bischetti, 1997.  Influence of drainage network identification methods on geomorphological properties and hydrological response.  Hydrological Processes 11:353-375.

Harrelson, C. C., C. L. Rawlins, and J. P. Potyondy, 1994. Stream channel reference sites: An illustrated guide to field technique, USDA Forest Service GTR RM-245, Fort Collins, 61 pp.

Horton, R. E., 1945.  Erosional development of streams and their drainage basins: hydrophysical approach to quantitative geomorphology.  Geol. Soc. Amer. Bull. 56: 275-370.

Leoplod, L. B., M. G. Wolman, and J. P. Miller.,  1964.  Fluvial processes in geomorphology.  W. H. Freeman and Company, San Francisco, 522 p.

Leopold, L. B.,  1994.  A view of the river.  Harvard University Press, Cambridge, Mass., 298 p.

Rosgen, D. A., 1996.  Applied river morphology.  Wildland Hydrology, Pagosa Springs, Colorado.

Strahler, A. N., 1957.  Quantitative analysis of watershed geomorphology.  Amer. Geophysical Union Trans. 38: 913-920.

USDA Forest Service, 1992.  Integrated riparian evaluation guide.  USDA Forest Service, Intermountain Region, Ogden, Utah.  60 p.