Date of Award
4-20-2017
Document Type
Dissertation
Degree Name
Environmental Sciences, Ph.D.
First Advisor
Jennifer Bouldin
Committee Members
Hubert Stroud; Jonathan Merten; Travis Marsico; Virginie Rolland
Call Number
LD251.A566d 2017 K55
Abstract
As the world population grows and agricultural production expands, increased stress is placed on many waterways. Water quality is often degraded and can serve as a source for areas of downstream environmental impacts. Of particular concern is the Gulf of Mexico hypoxic zone, a result of agricultural inputs from the Mississippi River Basin. One watershed identified as a potential source for this hypoxic zone is the Cache River Watershed in northeastern Arkansas. This watershed has approximately 67% of its land in row-crop production. Waterways within this watershed have poor water quality because of excessive turbidity, nutrients, pathogens and metals. In this study, 23 (19 headwater sub-watersheds, four main channel) sites were sampled monthly within the Cache River Watershed from August 2013 to July 2016. Contaminant concentrations including nutrients, sediment and lead (Pb) were assessed spatially and in terms of land alteration to identify source areas and to determine locations in which Best Management Practices (BMPs) could be effectively implemented. Land alteration had a significant relationship with overall contaminant concentrations with most- or moderately-altered sites having significantly greater sediment and nutrient loads than least-altered sites. Pb in all forms was ubiquitous throughout the Cache River Watershed, though detection frequencies and mean concentrations were generally greater in most-altered sites than in least- altered sites. Pb detections/concentrations were positively correlated with discharge but not with precipitation, suggesting that other components of discharge, such as irrigation runoff could be contributing to Pb contamination within this watershed. Although several sites did have excessive levels of dissolved Pb, accompanying toxicity tests indicated that measured environmental concentrations were much lower than those required to produce acute or chronic toxicity within aquatic organisms, though behavior could potentially be affected. This study shows the value in performing greater spatial sampling at the cost of temporal sampling, particularly when identifying areas for BMP implementation within a watershed. Although water quality issues were detected, concentrations of all contaminants decreased along a downstream gradient of the Cache River, likely due to the unaltered state of the Lower Cache River, which is unchannelized and has relatively large amounts of natural wetlands and riparian buffers.
Rights Management
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Kilmer, Mary Katherine, "Water Quality of The Cache River Watershed, Arkansas: Contributions of Agricultural Activity in Sub-Watersheds to Nutrient, Sediment and Lead (Pb) Contamination and Potential Toxicity Implications to Aquatic Organisms" (2017). Student Theses and Dissertations. 557.
https://arch.astate.edu/all-etd/557
