1. Investigating the Effect of Row-Crop Runoff
on Water Quality in the
Big Walnut Creek Watershed
Peter Steiner, Sarah White, Nick Meszaros, and Amelia Wilson-Wright
Faculty advisor: Jeanette Pope
8. Local agricultural runoff contributes
toward a national problem
Concerns from Agricultural Runoff
Nitrogen and Phosphorus
Eutrophication is the driving force
behind the Gulf hypoxia crisis
Schematic diagram developed by Tulane University and available at
http://images.universityherald.com/data/images/full/5788/hypoxia.png?w=60
0
9. What is a Watershed?
A watershed is the area of land that drains to
a particular point along a stream
Subwatershed
Catchment
Sarah : This slide was to open the presentation and to give a brief definition of what agricultural runoff actually is, and how we need to focus on using the land in a way that has minimal environmental repercussions. There are over 330 million acres of land use that is dedicated to agriculture in the U. S. alone – and with this large portion of land dedicated to agricultural use, we must make an effort as a society to monitor the land, and the water that is running off of the land. The river (as pictured) has a slight discoloration, due to the numerous chemicals, pesticides, fertilizers, and pollutants running off the land due to surface flow (usually rain, or even snow).
Sarah: This slide was a representation of how pollutants can enter into large bodies of water, such as streams, rivers, lakes, and eventually, oceans. I mentioned point source pollution to begin – highlighting how, although it is a problem that industries can dump their waste directly into the river, the amount of waste as well as the concentration of pollutants, the Clean Water Act can legally monitor point source pollution. Therefore, an industry or large treatment plant may be held accountable for the pollutants it is discharging directly into the river. I then shifted the focus to nonpoint source runoff, in which pollutants can be deposited into the water by means of discharge from rainwater into the river. Any pollutants that remain: oil from cars, acid or salts from city streets, animal waste, and the most important to our research: row-crop runoff. Chemicals that are sprayed on row-crop agriculture runoff into the river, causing large amounts of nutrients entering the water. The reason we are investigating this type of nonpoint pollution is because it is not monitored under law by the Clean Water Act. Row-crop agriculture is also the main type of farmland surrounding the Big Walnut Creek Watershed.
Sarah: This picture represents the amount and frequency at which row-crop agriculture is sprayed with pesticides and fertilizers. A perfect representation of nonpoint source pollution, we do not know where these chemicals will go after the plants absorb what they can, but we can guess that the only place for these chemicals to go is into a water source, either through surface runoff or groundwater flow.
Sarah: This picture shows the consequence of nonpoint pollution. This is a picture of a large algae bloom, also known as eutrophication. Eutrophication occurs when there is a influx of nutrients entering a system. The nutrients we are focusing on the most are nitrogen and phosphorus. These nutrients are a catalyst for a large algae bloom, which is where we can see the discoloration and green, murky water.
Sarah: This is a diagram that shows how agricultural runoff, starting from the spraying of chemicals, leading to the occurrence of eutrophication, can lead to the death of fish and other organisms within the water.
Sarah: This diagram represents the process of eutrophication. I simplify it down by explaining how the nutrients enter the water through discharge, the algae blooms, and as they die and as bacteria consume the algae, the water is depleted of oxygen. This is known as hypoxia, which is also known more famously as Gulf Hypoxia, a giant dead zone in the Gulf of Mexico. This oxygen depleted water is deadly to the organisms living in the water, and generates large fish kill zones. I transition into the next slide by explaining how local practices and mispractices contribute to a significant national problem. I highlight the importance of best management practices within the Big Walnut Creek Watershed .
A watershed is an area of land where all of the water flows to one point referred to as the base level.
Watersheds are further divided up into subwatersheds, with the same idea in mind. That all water flows to a base level within a subwatershed.
Subwatersheds are then further divided up into Catchments with the same idea applying within as well.
Our research will be focusing on row crop runoff on the Catchment level. This provides us a higher resolution picture than assessing runoff on a subwatershed scale.
We will be sampling in Big Walnut Creek Watershed. It is located in Hendricks, Boone, and Putnam counties and covers approximately 425 square miles.
Greencastle is the largest Urban area in the subwatershed.
Land usage is mostly forest in the southwestern part of BWCW.
Land usage is mostly agricultural production in the northeastern part of BWCW.
We will be measuring water quality in subwatersheds 1-4 located at the northeastern most part of BWCW. The potential for agricultural runoff is greatest here due over 75% of the land being used for agriculture, and a lack of forests. Subwatersheds 1-4 are also located at the headwaters of the entire watershed so what pollution enters here could potentially impact the water quality throughout the entire watershed, including Greencastle.
Forested areas act as riparian buffers around streams, i.e. they can absorb excessive nutrients introduced to runoff from fertilizers and or pesticides and prevent the stream or creek from being contaminated to some extent.
Agricultural ditches (as pictured on the right) and streams that lack riparian buffers have little to no protection from excessive nutrients and chemicals entering into the stream from agricultural runoff. Pollution potential is highest at these sites.
A map zoomed in on a single subwatershed. The red dots signify sampling locations. This is illustrative of how we spread out our sampling locations to get meaningful data: we want both upstream and downstream along individual waterways where possible, and a representation of different tributaries. Sampling near a confluence on the tributary streams and then further downstream can be useful in showing how the areas drained by the tributaries impact the downstream chemical composition of the watershed.
Photographic depiction of the two ways in which water was extracted from the site to obtain samples. Hand samples were taken by wading into the water source and collecting directly, and less accessible locations were dealt with using the PVC “bridge sampler” to remove a portion that could be used. Triple wash protocol was implemented to maintain the most accurate representations of the local water possible, and pH and temperature measurements were taken in the field. All further work was performed in the laboratory.
The Ion Chromatograph is the instrument that was used to provide out more in-depth analysis of water from each site, by showing the concentrations of the different chemical species. Pictured in the slide, it works by running the sample through the analytical column, which is filled with charged beads. These beads preferentially attract species based on their charge/size ratio, which is diagnostic for each ionic species. This preferential degree of attraction based on the charge/size ratio causes separation of the chemical species as they travel through the analytical column, with each one having a diagnostic “retention time” that transpires before it reaches the other end. Upon exiting the column, it is registered by a conductivity meter, and spikes in conductivity represent each species. The time of the spike tells us which species it is (due to the diagnostic retention time) and the area under the peak represents the concentration once calibrated to a standard.
The data can reveal trends that are either temporal or spatial in nature. A temporal trend would be one in which a pattern is seen over time at any one site, such as the decrease in sulfate over the course of the summer. A spatial trend would be one in which a pattern is seen from location to location based on their relative positions at any one time, such as the sharp increase in nitrate between the two furthest upstream sites in subwatershed four.
