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Open Access Thesis

Keywords

Water-supply--Iowa--Gilbertville Region; Water quality--Iowa--Gilbertville Region; Agricultural pollution--Iowa--Gilbertville Region; Agricultural pollution; Water quality; Water-supply; Academic theses;

Abstract

The transport of nutrients and contaminants from farm fields to the aquifer surrounding Gilbertville, Iowa, was monitored over a six-month period. The Gilbertville city water supply is obtained from the Silurian-Devonian aquifer, which has been determined to be highly susceptible to contamination because of the hydraulic characteristics of the aquifer and the overlying materials that allow contaminants to move to the aquifer fairly quickly. Monthly water samples were collected from April through September of 2004 from 26 private wells and 8 surface water sites within the source water protection area of the town's three wells. Each sample was tested for dissolved oxygen (DO), temperature, conductivity, total dissolved solids (TDS), pH, nitrate (NO3-), sulfate (SO4=), chloride (Cl-), sodium (Na+), potassium (K+), calcium (Ca++), and magnesium (Mg++). In April, 64% of the wells had their lowest nitrate level for the six-month period or a level below detection; only 12% of the wells exceeded 45 ppm in April. Nitrate levels increased in May and June with 23% of the wells exceeding 45 ppm. The highest concentration of nitrates in a private well, 86.0 ppm, also occurred during June. A slight decrease in nitrate levels occurred in July. Overall, the highest nitrate levels occurred in August with 28% of the wells exceeding 45 ppm. Throughout the six-month period, 16% to 20% of the wells sampled had no nitrates detected. By way of comparison, nitrates exceeded 45 ppm in the Cedar River during the months of June and July at an average of 56.4 and 45.5 ppm, respectively. The lowest nitrate level in the Cedar River, an average of 17.1 ppm, occurred during September. Total dissolved solids in the wells ranged from 289 ppm to 663 ppm, while pH fell between 6.30 and 8.00 during the study. All other parameters fell within the normal range for natural waters. This study indicates that the ground water in the Gilbertville area is significantly impacted by agricultural practices.

Year of Submission

2005

Degree Name

Master of Science

Department

Department of Earth Science

First Advisor

Mohammad Z. Iqbal

Second Advisor

James C. Walters

Third Advisor

Maureen E. Clayton

Comments

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Date Original

2005

Object Description

1 PDF file (141 leaves)

Language

en

File Format

application/pdf

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