Hydrologic response, episodic streamwater chemistry, and the sources of streamflow and solutes in a small forested watershed in central Pennsylvania

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5477941

Potter, III, F I

The purpose of this study was to identify and quantify the processes that contribute to episodic stream acidification during rainfall events. The hydrologic response to 12 storms and the chemistry of streamwater during three of these events were used to identify/quantify source area contributions of water and solutes during the growing season. This research was conducted on a headwater stream in central Pennsylvania that has documented episodic pH depressions as large as 2.37 pH units. A perched water table overlying a shallow soil fragipan produced a saturated soil zone on the study site. The depth to the saturated soil zone was observed to decrease rapidly in response to storm inputs. The greatest decrease was 57 cm, which occurred in a 30-min period prior to peak streamflow. Stream channel expansion during storm events increased inputs of direct channel precipitation. The percent of stormflow from direct channel interception increased during the event, up to the time of peakflow. The chemistry of waters sampled in the study area changed significantly during stormflow in response to rainfall that was acidic (pH 3.9-4.2) and contained relatively high concentrations of nitrate and sulfate. Concentrations of potassium and nitrate increased in concentration, while chloride, sodium, and pH decreased. Sulfate exhibited a variable response. Stormflow was separated into atmospheric water, saturated soilwater, and groundwater components employing a chemical mass balance model. Groundwater was found to be the largest contributor to total stormflow (42.6% to 53.6%). Soilwater contributed 27.8% to 40.3% of total stormflow and atmospheric water contributions ranged from 4.6% to 29.6%. The percentage of stormflow from atmospheric sources was greatest during the rising limb of the hydrograph.

• Research Organization: Pennsylvania State Univ., Middletown, PA (United States)
• OSTI ID: 5477941
• Country of Publication: United States
• Language: English

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