HF010
Stream stage and water table elevation in hyporheic and ground water from McRae Ck well network, Andrews Experimental Forest, 1989-1993

CREATOR(S): Steven M. Wondzell

PRINCIPAL INVESTIGATOR(S): Steven M. Wondzell

ORIGINATOR(S): Steven M. Wondzell

DATA SET CONTACT PERSON: Donald L. Henshaw

ABSTRACTOR: Steven M. Wondzell

METADATA CREATION DATE:

15 Apr 2005

MOST RECENT METADATA REVIEW DATE:

4 Mar 2013

KEYWORDS:

Disturbance, Inorganic nutrients, hydrology, storms, disturbance, physical processes, hydrologic processes, streamflow, peak flows, low flows, modeling, inorganic nutrients, groundwater, hyporheic zone, forests, aquatic ecosystems, streams

PURPOSE:

To monitor changes in flows of stream water, hyporheic water and groundwater among seasons of the year and during storms in the fall, winter and spring. Data were used to parameterize a groundwater flow model (MODFLOW) which was then used to estimate fluxes of hyporheic water and groundwater through the study site. Water flux estimates were combined with water chemistry data (see CF004) to estimate nitrogen fluxes.

METHODS:

Experimental Design - HF010 :

Description: A network of wells was installed on a gravel bar and a portion of the adjacent floodplain of McRae Creek (see Figure) between 1989 and 1992. Water depths were measured in each well to monitor changes in the elevation of ground water and hyporheic water among seasons and within storms.

Field Methods - HF010:

Description:

Wells and well transects

Two types of wells were used in this study: observation wells to measure water table elevations and sample wells to collect interstitial water. Water depths were only measured from observation wells. Casings for observation wells were made from PVC pipe and screened by drilling 0.32 cm diameter holes into the bottom 50 cm of each PVC pipe, at an approximate density of 1 hole/cm².

All wells were driven by hand because the study site had no road access. Large cobbles and boulders throughout the study site hindered well placement so that the deepest wells penetrated only 2.5 m below the ground surface. Wherever possible, wells were placed in holes driven at least 50 cm below the surface of the water table at summer baseflow. Holes were back filled with the soil originally removed and, if necessary, additional fill was taken from nearby soil pits or recent root-throw pits. Following installation of the wells, back fill was washed and entrained sediments were removed from the well casing by repeated pumping.

A single transect of wells was established during late summer in 1989 as a pilot study. Additional transects of wells were installed during the summer of 1990 and an additional 18 wells were established on, and adjacent to, the gravel bar during 1991 and 1992.

Water depths and water table elevations:

Water depths measured from the well network were converted to elevation referenced to an arbitrary bench mark. All wells were surveyed and water table elevations were found by subtracting the depth to the free water (measured from the well head) from the surveyed elevation of the well head. Water depths were measured using a home-made depth sound consisting of a analog multi-meter and wire leads attached to a measuring tape. The multi-meter was set to record resistance. The tip of the wire leads were exposed and when dipped in water, the change in resistance would cause the multi-meter=s needle to jump. Measurement precision was excellent (" 1 mm). Overall, accuracy was somewhat less. Repeated surveys of well head heights had a precision of (" 1 cm). Further, the measuring tape with its attached wires would not hang perfectly straight nor were all wells exactly vertical. Expected accuracy of measurements is (" 2 cm).

SUPPLEMENTAL INFORMATION:

See WELLLIST.TXT for basic information describing each well and locations of each measurement point included in this data set.

SITE DESCRIPTION:

The McRae Creek study site was about 200 m long and 80 m wide and was located along the eastern bank of an unconstrained stream reach (see Figure). A complex of landforms is present within the study site, including a recently formed gravel bar, older floodplain surfaces, and terraces. Sediment of the gravel bar and stream channel is a poorly sorted mix of sand, gravel, cobbles, and boulders more than 1.5 m in depth. A layer of rounded, stream-worked cobbles and boulders, 10 to 50 cm in diameter, is present at 1 to 3 m depth within the floodplain. The sediment overlying this layer varies in texture from loam to fine sand. A small seep is present along the boundary between the terrace and floodplain, but is not gauged. There is no surface flow from this seep during late summer. Flows increase during the winter rainy season, and peak during storms.

TAXONOMIC SYSTEM:

None

GEOGRAPHIC EXTENT:

McRae Creek, H. J. Andrews Experimental Forest, Western Cascades, Oregon.

ELEVATION_MINIMUM (meters):

ELEVATION_MAXIMUM (meters):

MEASUREMENT FREQUENCY:

irregular

PROGRESS DESCRIPTION:

Complete

UPDATE FREQUENCY DESCRIPTION:

notPlanned

CURRENTNESS REFERENCE:

Ground condition