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Watersheds

There are nine gaged watersheds at the Hubbard Brook Experimental Forest, four of which have been treated experimentally. A tenth ungaged watershed was also treated. The table below includes summary data, and more detailed information on each watershed can be found below.


Cursor over number to the right for a 'zoom in' map, WS Area Slope* Aspect Elevation Gage Type Initial
or click for more information to below.   (ha) (°)   (m)   Year
1 11.8 18.6 S22°E 488-747 90° V-notch weir 1956
2 15.6 18.5 S31°E 503-716 120° V-notch weir 1957
3 42.4 12.1 S23°W 527-732 120° V-notch weir 1957
4 36.1 15.6 S40°E 442-747 120° V-notch weir 1960
5 21.9 15.4 S24°E 488-762 90° V-notch weir, 3' wide San Dimas flume 1962
6 13.2 15.8 S32°E 549-792 90° V-notch weir, 2' wide San Dimas flume 1963
7 77.4 12.4 N16°W 619-899 120° V-notch weir, 4' wide San Dimas flume 1965
8 59.4 14.0 N12°W 610-905 120° V-notch weir, 4' wide San Dimas flume 1968
9 68.4   NE 685-910 120° V-notch weir 1995
101 12.1   SE 470-595 None 1970

     * Slope measurements are the slope of a plane fitted to the circumference.

 
Watershed 1

Area:  11.8 ha
Slope:   18.6°
Aspect:   S22°E
Elevation:   488-747 m
Gage type:   V-notch weir
Initial year:   1956

Treatment: In October 1999 the Ca content of soil was increased through the application of wollastonite (CaSiO3).

Objective: To evaluate the role of Ca supply in regulating the structure and function of base-poor forest and aquatic ecosystems.
 
Watershed 2

Area:  15.6 ha
Slope:   18.5°
Aspect:   S31°E
Elevation:   503-716 m
Gage type:   V-notch weir
Initial year:   1957

Treatment:
  1. Devegetated for three years, 1965-1967.
  2. In December 1965, all the trees and shrubs on Watershed 2 were felled and left in place.
  3. During the growing seasons of 1966, 1967 and 1968 the watershed herbicides were applied to prevent vegetation regrowth.
Objective: To assess the ecosystem response to deforestation.

Resulting observations:
  1. Discharge of snowmelt was advanced by several days.
  2. Annual streamflow increased by 40, 28 and 26 percent during the 3 years of devegetation.
  3. Annual average weighted value of nitrate in streamwater increased from <1 mg/L in 1965-1966 to >50 mg/L two years later.

Continued research/treatment: Monitor changes in water yield and stream chemistry.

 
Watershed 3

Area:  42.4 ha
Slope:   12.1°
Aspect:   S23°W
Elevation:   527-732 m
Gage type:   V-notch weir
Initial year:   1957

Treatment: None

Comments: Watershed 3 is used as a hydrologic reference watershed.
 
Watershed 4

Area:  36.1 ha
Slope:   15.6°
Aspect:   S40°E
Elevation:   442-747 m
Gage type:   V-notch weir
Initial year:   1960

Treatment:
  1. Strip cut in three phases during the autumns of 1970, 1972 and 1974.
  2. Strips were roughly parallel to watershed contours and were progressive 25 meter wide swaths.
  3. All merchantable materials were removed.
Objective: To determine how progressive strip cutting affects nutrient and hydrological cycling and stand regeneration relative to clearcutting.

Resulting observations:
  1. Streamwater nutrient concentrations and water yield increased during and immediately after strip cutting, but not as much as following clearcutting of Watersheds 2 and 5.
  2. At year 10, the strip cut had a more desirable mix of commercial species than the block cut on Watershed 101, with higher densities of yellow birch and sugar maple and lower densities of pin cherry.
  3. In 1992, the vegetation on all strips was inventoried resulting in average biomass of 88 t/ha.

Continued research/treatment: Monitor changes in water yield, stream chemistry and vegetation.

 
Watershed 5

Area:  21.9 ha
Slope:   15.4°
Aspect:   S24°E
Elevation:   488-762 m
Gage type:   V-notch weir, San Dimas flume
Initial year:   1962

Treatment:
  1. A whole-tree harvest was conducted during the dormant season of 1983-1984 resulting in the removal of 180 t/ha of biomass.
  2. Prior to treatment, the watershed was surveyed into 360 25 x 25 meter plots to be used for research.
Objective: To assess the ecosystem response to whole-tree harvest.

Resulting observations:
  1. An increase in temperature (as much as 6°C) at the soil surface and in streams, unless streamside buffers of trees are left.
  2. An increase in moisture content of the soil.
  3. A maximum increase in streamflow of approximately 40 percent, and an increase in summer peak flows averaging 20 percent.
  4. An increase in nitrification.
  5. An increase of nutrients, especially nitrate, in soil solution subject to leaching loss or uptake by plants and microorganisms.
  6. No appreciable increase in erosion and sedimentation.
  7. Rapid decomposition and fragmentation of slash (75 to 80 percent breakdown in the first 14 years).
  8. Rapid growth of pin cherry and raspberry from seed which had remained viable in the soil for decades; these pioneer plants conserve nutrients that otherwise might be leached from the site.

Continued research/treatment: Monitor changes in water yield and stream chemistry.

 
Watershed 6

Area:  13.2 ha
Slope:   15.8°
Aspect:   S32°E
Elevation:   549-792 m
Gage type:   V-notch weir, San Dimas flume
Initial year:   1963

Treatment: None

Comments: Watershed 6 is used as a biogeochemical reference watershed.
 
Watershed 7

Area:  77.38 ha
Slope:   12.4°
Aspect:   N16°W
Elevation:   619-899 m
Gage type:   V-notch weir, San Dimas flume
Initial year:   1965

Treatment: None

Comments: None
 
Watershed 8

Area:  59.4 ha
Slope:   14.0°
Aspect:   N12°W
Elevation:   610-905 m
Gage type:   V-notch weir, San Dimas flume
Initial year:   1968

Treatment: None

Comments: None
 
Watershed 9

Area:  68.4 ha
Slope:   
Aspect:   NE
Elevation:   685-910 m
Gage type:   V-notch weir
Initial year:   1995

Treatment: None

Comments: None
 
Watershed 101

Area:  12.1 ha
Slope:   
Aspect:   SE
Elevation:   470-595 m
Gage type:   None
Initial year:   1970

Treatment:
  1. Commercially logged as a stem-only, block clearcut in November 1970.
  2. Branches and tops were left on site.
Objective: To study the effect of block clearcutting on watershed hydrology and nutrient flux and cycling.


Resulting observations:
  1. Simulated streamflow increased 36 percent the first year after cutting and declined steadily until it returned to precutting levels by year six.
  2. Streamwater ion concentrations increased from 295 ueq/L to 593 ueq/L two years after the harvest before returning to precutting levels by year three.

Continued research/treatment: Monitor changes in water yield and stream chemistry.

Comments: Watershed 101 has no streamgage, so streamflow was estimated using the hydrologic model Brook2.

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