Hydrological and geochemical data was collected from a small area within the 7.32-km$\sp2$ Cadwell Creek drainage basin in west-central Massachusetts for a period of one year. The hydrologic monitoring network included a tipping-bucket rain gauge, soil-moisture and soil-temperature probes, and continuous water-level recorders to measure changing groundwater levels and stream stage. The geochemical sampling network consisted of precipitation and throughfall collectors, soil water collectors, shallow and deep groundwater monitoring wells, and stream sampling locations. Water samples were collected on a weekly or bi-weekly basis for the entire study period. Both the hydrologic and geochemical information collected during the study period indicated that the majority of water reaching the stream, both during periods of high water level and storm flow and during baseflow periods in the summer months, was derived primarily from the top meter or two of the shallow water-table aquifer. Deeper groundwater exhibited a substantially different chemistry from that in the top 1-2 meters of the aquifer. The geochemical evidence clearly indicated that deep groundwater never entered the stream, even during baseflow periods. Instead, the stream in the vicinity of the study site became dry in the summer. Comparison of groundwater and stream chemistry during periods of high water level clearly indicated that the water in the stream was derived almost solely from the shallow groundwater, with little or no contribution from more dilute precipitation and soil water. Silica concentration, as well as alkalinity and pH values, proved to be an important indicator of the origin of water entering the stream. Specific factors affecting the degree to which acidic precipitation is neutralized before entering surface water within this watershed are primarily hydrologic in nature. The amount of time that precipitation water is in contact with the geologic materials prior to entering the stream appears to determine the degree to which it is neutralized. In this case, the depth to the top of the water table is a controlling factor. Silicate weathering dominated cation exchange as a neutralization mechanism in this watershed, at least in the vicinity of the instrumented site.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-8117 |
| Date | 01 January 1991 |
| Creators | Batchelder, Gail Louise |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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