Protocols & Data

STREAM FLOW PROJECT: PROTOCOLS AND DATA

This project is assessing the hydrologic impact created by installing a series of small in-stream structures on flow regimes and ground water levels in two West Virginia headwater watersheds. Structures designed to enhance bank and alluvial storage of water, for the purpose of increasing stream flow during base flow, are installed on first and second order streams.

Data collected for this project include flow, groundwater "level", stream height, precipitation, and water temperature. Changes in the system will be detected based on comparisons between sites, in particular, between control and experimental sites, and between upstream and downstream locations within the experimental study areas.

The schematic drawing at right shows the standard layout of the most important elements of this project: the streams, groundwater stations (piezometers), flow stations and structures. Click on any of these to learn more.

The Streams. We are conducting a pilot study in which structures designed to enhance bank and alluvial storage of water, for the purpose of increasing stream flow during base flow, are installed on first and second order streams. Three watersheds were selected for study. One stream remains unaltered to serve as a control. One stream has two segments receiving treatments, a meadow with a broad floodplain, and an upland forest. The second experimental site is an upland meadow that is enrolled in USDA-CREP. The following table provides a brief description of each of the four study sites, including a list of data points.

Site Data
Site	Stream Length (ft)	# Flow / Precip. Sites	# Regular Groundwater Sites	# Piezometer Nests	# Structure Grids	# Structures
SRE Forest	850	2 / 1	10	0	0	7 pending
SRE Meadow	2100	2 / 2	22	6	2	15
Description. The SRE Forest site is totally forested, with a small amount of pasture at the headwaters of the drainage. The lower end is roughly 2000' upstream of SRE Meadow. The stream has a slope of 2.7%. The Meadow site is in a broad floodplain with extensive wetlands. The stream has a slope of 1.7%. An important "feature" of this meadow is abundant multiflora rose that often slump into the stream channel.
Control	1940	2 / 2	8	3	0	none
Description. The control site has only a small, forested section and is mostly grassy. It winds through a narrow valley, and passes back and forth across a road. The stream has a slope of 3.2%. There is a pond near the headwaters of this stream - a pond that has had a tendency over the years to blowout and create some scouring downstream flows.
CBE Site	1000	3/2	11	3	2	7-8 pending
Description. This site is an upland meadow, and is enrolled in the USDA Conservation Reserve and Enhancement Program (CREP). The stream has a slope of 2.4% and a narrow area with alluvial deposits. This site has a sizeable side stream that delivers significant flow to the system roughly 400 feet above the bottom of the study reach. Flows are taken there as well as at the top and bottom of the main stream.

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Flow. Stream flow is the product of the speed of the water and the cross section of water at a stream site. When you multiply the speed (for example: in feet per second) by the wetted area (for example: in square feet), the result is a volume of water moving past a site over some period of time - such as cubic feet per second. We're interested in flow for this project because an increase in flow between experimental and control sites will tell us if we are having the effect we are trying to achieve. Flows are taken at the top and bottom of each study area.

The very small, meandering streams selected for this project provide particular challenges for accurate measurement of stream flow across all ranges of flow, and a mixture of methods suitable for different conditions have been utilized. Flow measurement equipment includes a Global Flow Probe Model FP101 and the "Insta-Weir." The portable Insta-Weir was developed for this project because of our need to measure flow at very low levels, where stream depth or flow rate precludes use of the Flow Probe and really any other device we have seen. The Insta-Weir works by backing up the stream and constraining the outflow through a V or box -shaped weir; outflow is collected in a waterproof bucket or bag for direct volumetric measurement. It captures most of the flow of the stream (if the bottom is firm and does not have deep cobble or gravel or undercut banks), and the volume of water is measured in a calibrated Tidy Cat^TM bucket at the outlet. Looks silly as can be, but it works in many locations. Many thanks to Meredith Pavlick for all her efforts testing various iterations of this device, and to Bob Markley and Pat Bowen for helping to develop the concept.

Highly significant statistical relationships between control and experimental sites, and between upstream and downstream locations within the experimental study areas during the pre-installation phase of this project, are essential in understanding changes in flow that occur due to structure installation. Fortunately, very strong correlations were found between the four flow stations in the Experimental Site 1, with r-values ranging from 0.940 to 0.997. These sites were all also significantly correlated with the two flow stations in the control area, with r-values ranging from 0.88 to 0.98, and also very strongly correlated with the upper two flow stations at experimental site 2, with r-values ranging from 0.935 to 0.994.

The flow correlation results, and the results of regression analysis, indicate that a strong predictive relationship exists between flows in upstream and downstream sites, as well as control and experimental sites. Graphs of this data (such as the one below at right) show a tight cluster of data points along the regression line, particularly at lower flows; this is very good, because lower flows are where we expect to see the largest change. Very preliminary data indicate that both the slope and the y-intercept are higher in post structure data than in pre-structure data, which tells us that the flow at the downstream site was higher than at the upstream site after structures were installed than before. As noted, this is very preliminary - but encouraging - data. Ultimately, we expect the y-intercept to increase more, and the slope actually to decrease due to a greater effect at low than high flows.

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Global Flow Probe in use.	The fabulous Insta-Weir - measuring flow where all other flow equipment fails.	This graph compares flow at an upstream site (SRE3) with a downstream site (SRE1).

Groundwater. Why are we interested in groundwater? Because the ground is our project's reservoir. Rather than creating dams to create large surface reservoirs, we are using the spaces between soil and rocks in the ground to store our water. We do this by installing small structures in the stream channel that raise the water level just a bit, to increase contact with the soil and allow water to flow into the floodplain. Later, when the streams drop, the stored water can flow back into the stream channel and keep the stream flowing. The structures are intended to mimic the hydrological effect of small beaver dams . . . and beavers provide the appropriate ecological context for this project.

Alluvial groundwater is being measured using a network of piezometers. Piezometers are like groundwater measuring wells, except they only have a hole(s) at the bottom instead of up and down the sides. They can provide information about the direction of water movement in the ground, instead of only elevation. Our piezometers were constructed from 1¼ inch PVC pipe, with nylon mesh placed on the bottom end of the pipe and secured in place using a 1¼ inch PVC cap which is perforated with six 1/4 inch holes. Spring steel measuring tapes were cut to length and inserted in the piezometers, and a water-soluble ink daubed on the tapes serves as a crest height recorder between sampling trips.

Piezometers were installed according to two protocols.

The first is a longitudinal network of piezometers spaced every 100 ft along the length of the stream segment, 10 ft from the edge of the stream (if possible), with the bottom of the piezometer level with the stream's thalweg (lowest point in the channel). Piezometer nests were installed every 400-ft of stream length (where possible). In nests, each piezometer is a different depth in the ground, and the relative water elevation in the three piezometers tells us if the water in the ground is rising, falling, or neither

The second piezometer protocol is called a Structure Grid, which consists of a grid of three rows of three piezometers (if possible) used to measure changes in groundwater levels across a width of floodplain area caused by the installation of a structure. One row is centered on a structure, one is upstream, and one is downstream.

Although there are useful correlations between a number of the sites, the piezometer data is far less predictable than the flow data discussed previously, at least when viewed in mass. There are four major patterns. Piezometers that:

usually have water, with little difference between daily and maximum levels, and a relatively small range of water levels;
usually have water, with little difference between daily and maximum levels, and a relatively large range of water levels;
are often dry, with large difference between daily and maximum levels, and a relatively large range of water levels; and
are in a condition of dynamic change that has nothing whatsoever to do with the installation of structures (may include the defining characteristics of 1-3 above).

The differences in 1-3 appear to relate to the speed of the hydraulic connection to the stream, and piezometers in close proximity to one another may behave very differently (see graphs below). A mosaic of statistical and visual methods will be used to assess the piezometer data.

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Piezometer installation - Greg and Bob digging holes with a gas-powered auger.	Christian removes measuring tape from piezometer at nest.	Reading the tape. Water soluble ink tells us how high the water is . . . and how high it has been.

The piezometer graphs below illustrate piezometer patterns No. 1 & 3. Piezometer data is far less predictable than the flow measurements discussed previously. The two graphs below illustrate this point in a number of ways. These SRE Meadow piezometers are located only ten feet apart, both ten feet from the edge of the stream, and the depth of the piezometers in the ground differs by only 0.04 ft. And yet, the patterns of current and maximum water elevations, and the relationships between maximum and current, are quite different. Water levels in SB190 (top graph) range narrowly through less than 0.5 feet, and the current and maximum levels are usually very close. Water levels in SB200 (bottom graph) range over nearly one foot, and the current and maximum levels are often quite different.

There is no missing data in these graphs; when no bar appears on the graph it means there was no water in the piezometer. The piezometer at SB200 was dry on 10 of the 25 visits shown here, while SB190 was dry only four times (during a very dry period in August). We think the differences are caused by a difference in the speed of the hydraulic connection to the stream. The piezometers with water levels that rise and fall quickly along with stream levels probably have a nearly open channel, underground connection to the stream. Those that rise and fall more slowly are probably buffered from rapid changes in stream height by well consolidated alluvial soils. That these two conditions can, and do, occur in such close proximity was quite a surprise.

By the way, a "dry pipe" is not "no data", it is the rather oxymoronic unquantifiable data. The information that you don't get from a "dry hole" is very different from a below-detection-limit result in a chemical analysis. In the latter case, you always have a known, absolute lower limit -zero, while a dry piezometer only tells you that the water level is somewhere below the bottom of the pipe. This creates some interesting challenges in data analysis.

The piezometer graphs below illustrate piezometer pattern No. 4 - a condition of dynamic change that has nothing whatsoever to do with the installation of structures (well, until the end). The following two graphs provide a wonderful, and our most extreme, example of this. This site has a multiflora rose dam in the stream, immediately upstream of the piezometer nest at SREM 1600; this natural dam is probably the source of what we see here. The top graph shows daily and maximum water levels in the SB (stream bottom elevation) piezometer, and the trend of increasing water level over time is unmistakable. We are fortunate that this is one of the piezometer nest sites, and Graph B provides a closer look at what is happening here. The relatively high water in the low piezometer for sampling period from 2-11 clearly indicates a rising water level in the ground during this time. After this, groundwater "direction" appears to vacillate between steady, rising, and falling, and appeared to have stabilized roughly between elevation 1889.60 and 1989.80 . . . until sampling period 28-30, which occurred after a pair of structures were installed at this site to preserve the elevated groundwater impact of the multiflora dam that was rapidly disintegrating. You can see these 2 structures in the structure slide show.

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Structures are installed longitudinally in series in the experimental streams to create a progression of small pools, rather than single isolated structures. We expect that alluvial water storage caused by upstream pools will extend periods of stream flow further downstream and create a multiplier effect, like batteries wired in series.

Structures were modeled after a variant of the cross vane that we observed during a visit to a stream restoration project in Big Bear, PA. Log structures at this site had been installed on a sizeable, high-gradient stream by two men in one day, using no heavy equipment, and have successfully withstood a number of major floods. Biological studies at this site found that neither their stone nor log cross vanes created an impediment to movement of stream life. Structures are built to or below bankfull elevation at the edges and lower in the center of the stream to provide a spillway. The cross vane’s inverted-V design directs the force of the water away from the banks and toward the center of the channel, reducing bank erosion and enhancing long-term stability. They can be built symmetrically to center the flow, or asymmetrically to direct the flow of water through a bend in the stream. Click here to see all the structures that have been installed so far.

While construction methods at each site vary somewhat, in general the method is as follows: 1) The primary members of the cross vane are driven or cut into the stream banks at the appropriate angle and elevation. 2) The upstream edges of the logs are trimmed and fitted to each other, and then either wired, through-bolted, or nailed together. 3) At the point where the cross vane members enter the bank, model 68-DB-1 duckbill earth anchors (1,100 lbs. holding capacity) are driven into the bank at a right angle to the member, with the cable fastened to the member using a cable clamp. 4) Galvanized wire mesh and erosion cloth are stapled to the upstream edge of the exposed portions of each member, and run 1'-2’ upstream of the structure. The erosion cloth is included to reduce seepage through the structure, and is held below the line of sight for aesthetic reasons. 5) A layer of leaves or hay is placed on top of the erosion cloth and then rocks of cobble and larger size are placed on the full length of the wire mesh upstream to the height of the top of the members.

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