Notes from Dave Gochis’ visit to the site (April 2008)

Site Description:

Coordinates: 39.1008° N, 105.1002° W

Elevation range: ~7700’-8000’ (2340-2430m)

Physiographic characterization: Rocky Mountain Front Range and Rocky Mountain pediment.

• Terrain along west side of highway 67 is generally rolling and characteristic of pediment.
• Terrain slope of sites are dominantly west to east and secondarily south to north.
• Ponderosa parkland with canopy of varying density. Proposed tower site #2 appeared to have a denser canopy than #1. Neither canopy can be characterized as ‘closed’.
• Mixed age classes of tree ranging mostly from ~30-90 years old. Little evidence of trees older than about 100yrs and site literature indicates virtually no ‘old-growth’ remains. Many new seedlings and sprouts emerging (particularly following wet winter/spring of 2007).
• Surface cover is grasses, sage, crocus, forbs and exposed cryptogrammic soils.
• Patchy evidence of gopher and burrowing animals.
• Fairly consistent (1-2 cm) duff/litter layer
• Little to no direct evidence of any overland flow or channelized flow on region surrounding towers. However, significant evidence of flow and erosion on nearby burn sites approx. 1-3 km north of tower sites.
• Tower sites are approx. 1-1.5 mi. east of edge of Hayman burn and approx. 1 km to Trout creek riparian corridor
• Prescribed groundfire burn was executed approx. 100-200m north of proposed tower sites during Sept. of 2007. Notable removal of undercanopy cover, grasses and fire scaring to lower canopy
• Site manager indicates that there is a very significant amount of lightning activity during summer storms which highlights need for robust instrument grounding.
• Site is actively allocated for seasonal grazing activity. The name of the allotment encompassing the proposed tower sites is ‘Painted Rocks”. Current permit allocates gazing (?? head) for approximately 37 days from July 27-Sept. 1. Permittee, Jerry Johnston, needs to be informed and incorporated in site development progress.

Site Fauna:

• Observed fresh deer, elk, cougar tracks (2-4 days old)
• Observed droppings from deer, elk, rabbit, and other misc. rodents
• No active of recent livestock evidence despite presence of grazing allotment.
• Site manager indicates that rodents will vigorously chew on any exposed ground wiring.

Hydrologic characteristics:

• Regional W-E terrain slope is approx: 5-6% across site (based on site topo maps). Regional S-N slope across site is ~ 1% or less.
• W-E terrain gradient in cross-cut by several ‘swales’ of varying relief. Local slopes across swales may reach > 10% but only over a few meters.
• Deeper swales show some plant evidence of moisture collection such as presence of aspens, alders, sedges. Swales appears to be ephemeral features in space that develop and dissipate downslope
• No visual evidence of recent overland flow or channelized flow on the site.
• Vegetation and terrain appeared to be fairly consistent across tower site area.
• A few large sedimentary rock outcrops. Highly stratified red, pink, orange and white sandstones.
• Largest changes in vegtation appeared to occur at riparian corridor interface on the east and at the edge of Hayman burn on the west.
• Component of local groundwater flux across site and into Trout Creek river flow is unknown. Much larger component of GW flow expected from steep eastern drainages into Trout Creek.
• Site manager indicates that snow cover across site rarely, if ever persists throughout the entire winter.
• Soils:
  • Soil exhibited surprising uniformity across 7 boreholes that were drilled along the main axis of terrain slope from W to E between proposed tower sites. Only distinct heterogeneity between sites was the presence of a hardpan layer in some, though not all, holes nearer the Tower 2 site ranging in depth from 20-40 cm. Composition of hardpan layer is unclear since there was no significant evidence in change of soil type or color. Likely induced by local change in chemical bonding in these layers perhaps from evaporites.
  • Besides hardpan layers, no impermeable strata where encountered throughout drill bit depth to approx. 1.5 m.
  • Soil profile is broadly characterized as follows: (see handwritten notes for individual borehole characterization)
    • 0.5-2cm duff/litter layer composed of dead grasses, pine needles, decaying wood, forbs and cryptogrammic biota
    • 10-20cm loamy-organic layer that is brown in color, has relatively high root density from grasses and trees and occasional gravel
    • 20cm-1.5m bright red sand layer with varying amounts of pebbles, gravel and cobbles. This layer appeared highly uniform (i.e. unstratified) across all boreholes
    • Max rooting depth of observed boreholes was approx. 0.5-0.7 m
    • Soils appeared uniformly moist throughout profile at all sites

   

  Synopsis:

  Site characteristics suggest a local hydrologic regime that is largely infiltration dominated. Since the total soil depth and depth to saturated zone (if present) is unknown it is difficult to speculate on how significant saturated subsurface flow is as a plant moisture supply or to streamflow into Trout Creek. Neglecting a significant saturated hydrologic component, suggests a system that is largerly ‘pulse’ driven by periodic hydrologic forcing such as ephemeral snow melt throughout the winter season and warm season rainfall, most of which should infiltrate locally. This behavior may imply that plant activity may also be ephemeral throughout much of the year as moisture becomes available.

  Remaining site characterization needs:

  • Improved survey of upland and ‘upwind’ conditions surrounding proposed tower sites
  • Some more constrained estimates of depth to bedrock in the area (perhaps using ground-penetrating radar)
  • Infiltration tests across surface cover types w/ comparison to observed local rainfall intensities
  • Improved mapping of saturated depth from Trout Creek across site.
  • Improved understanding of site history. Site literature suggests that timber, grazing and cultivated agriculture were very active throughout site history beginning in the mid- to late-1800’s. Mixed stand age with max. ages of 80-100years supports this though fire disturbance has also played a major role across the site. In order to generalize findings from Manitou to other Ponderosa Pine parkland systems under similar climate regimes, these features need to be better understood.

   

  Expected ‘hydrologic’ research themes:

  If this ‘vertically-dominated’ characterization holds true research emphasis would be on characterizing various partitions in the 1-d moisture budget including:

  • Open area precipitation
  • Canopy interception as functions of precipitation type and precipitation intensity
  • Spatially distributed soil moisture measurements across site throughout root zone to depths of approx. 2m.
  • Estimates of surface ET from open patches in order to decompose total ET flux from sparse canopy as observed by tower measurements
  • Additional/ancillary data should be collected on carbon exchange, nitrogen deposition and uptake.