The Effect Of Non-Point Source Pollution In Halls Mill Creek

Jennifer J. Robinson, Department of Earth Sciences, University of South Alabama, Mobile, AL, 36688. E- MAIL:


            Non-point pollution is a major contributor to the reduction of the quality of our waters. A main source of pollution is runoff of sediments near or at construction sites. Most contractors have been informed on how to use Best Management Practices (BMPs), but many sites continue to become problems due to the lack of their consideration. In return our waters have become dumping grounds. I tested water parameters in Halls Mill Creek, starting at the headwaters. The tests include temperature, (both air and water), pH, dissolved oxygen, turbidity, hardness, and alkalinity. Three site areas were tested twice a week and twice each day for four weeks in the months of March and April. The test results showed a problem at Site 1. This problem did seem to dissipate farther down stream. There could be many reasons for the poor test results, including construction.

            Keyword: non-point pollution, runoff, water parameters   





Halls Mill Creek (HMC) is just one of many streams in the Dog River Watershed. The head of the creek is located in the western part of the county and then flows in an easterly direction. HMC is one of the cleaner streams of this area, but it does have a problem. The creek is being overloaded with non-point source pollution. Non-point source pollution (NPS) is described as what runoff collects and brings as it makes its way to a body of water or as what it can leave in the ground water. The EPA states “non-point pollution is the Nation’s leading source of water quality problems” (Opportunities for Public 2003). The EPA also says  the most common NPA pollutants are sediment and nutrients” (Nonpoint Source Pollution 2003). According to the EPA “ the most recent National Water Quality Inventory reports that runoff from urban areas is the leading source of impairments to surveyed estuaries and the third largest source of water quality impairments to surveyed lakes” (Managing Urban Runoff 2003). 

 “Erosion material added to the waters of any stream has two major contacts with living organisms in that stream, first through the aqueous medium because of the physical and chemical changes which eroded sediment produces in the waters itself, and second, through alterations in bottom conditions resulting form subsequent settling out of all or part of the sediment load” (Ellis 1936). This is a reason why all of us should be a little more in tune to what is taking place in our waters.

            The water parameters that were used helped to identify possible problems. “Natural factors that fundamentally influence aquatic ecosystems include streamflow, light, heat, sediment, nutrients, and dissolved gases” (Poole et al. 2004). The water and air temperature, measured in centigrade, show the “affects of physical and chemical properties of water that greatly influence aquatic organisms by affecting their feeding, reproduction, and metabolic rates”(Alabama 2002). The pH measures “how acidic or basic the water is ”(Alabama 2002). The dissolved oxygen (DO) measures the amount of oxygen in the water. DO “decreases with increasing temperatures and decreases with increasing depth”(Alabama 2002). The Hardness of the water, which is measured in parts per million (ppm), “measures the amount of calcium and magnesium salts in the water ”(Alabama 2002). The alkalinity also measured in ppm can be used to find out “the pH buffering capacity of water”(Alabama 2002). The turbidity measured in JTU (Jackson Turbidity Units) gives an idea of how much sediment is in the water including silt, sand, and clay. 


Research Question

My hypothesis is:

•Ho:  Non-point source pollution is not causing a major disturbance on Halls Mill Creek 

Ha:  Non-point source pollution is causing a major disturbance on Halls Mill Creek


The answer to the hypothesis will be resolved in the results of the testing.



 Study Site


            Has runoff caused a problem in Halls Mill Creek?  I had three sites along Halls Mill Creek where I did water quality testing (Figure 1). I chose these sites because of construction that was being done on a dam above HMC 2. I thought that it was possible that there would be some damage to the water. This project did answer some questions, but there are still many more problems that need to be identified. The sites were located from the headwaters of Halls Mill Creek, Mobile, Al (HMC1 N30º38.339’ W088º14.353’), (HMC2 N30º37.298’ W088º13.989’),




I gathered water samples and tested for water parameters at all three sites along Halls Mill Creek. At this time I also collected water samples in plastic bottles that were tested for turbidity once I returned to the University of South Alabama. I tested the water beginning the third week of March and ending the second week of April, and I tested in the mornings and in the afternoons on Mondays and Fridays. The tests were made within an hour of the first sample taken on each testing day, to have accurate data.

 My first site (HMC1) was located at the head of Halls Mill Creek. I was hoping to get the best water samples from there, so I could use these results as a base for the other two sites. However due to the insufficient amount of rainfall, my results were inconclusive. Although the results were not what I had hoped for, something else did come up. HMC 1 has a problem within it. The results for HMC 1 were usually significantly off from the other sites. This will be discussed in a later section. The next site, HMC 2, is found farther down the road from HMC 1 and the dam that was under construction (Fig. 1) (Figure 2). “Although construction sites may occupy a relatively small percentage of the land area, erosion rates for construction sites can be extremely high, so the total nonpoint pollution yield is large” (Carpenter et al. 1998). HMC 3 was the third site that was located close to the mouth of Halls Mill Creek.

I sampled twice a week, two times a day for four weeks. I used a water sample kit to test the water. The items in the kit included a thermometer and chemicals and equipment for testing dissolved oxygen (DO), pH, alkalinity, and hardness. Pictures were taken to document the changes that were made to the dam. This gave a good example of poor BMPs and carelessness.

            Before I collected my water samples, I put out the thermometer to test the air temperature. I then proceeded to gather water samples for testing and used a dipper for this collection. The dipper was used so that there was enough water for all samples. If I had taken each water sample separately there was a chance of my test results being off. There could always be a possibility that something could have seeped into the creek while the other tests were being completed. The water temperature was tested in the dipper as well. The DO test was collected in two separate containers at the same time. This is also the same time that water was collected to be tested for turbidity. After all the water samples had been collected, I used chemicals to test for DO, pH, hardness, and alkalinity. The DO was the first to be tested since it did not have a long holding time.       

Once I returned to the University of South Alabama, the testing for turbidity was preformed on a turbidity meter. As each sample was tested, I wrote the values down. After each site was tested five times I added the values together to get the average. The averages from the turbidity were added to a chart that contained all other values from the water parameters.





            The first site (HMC 1) had an unusually low DO compared to the other sites (Figure 3). The turbidity is also higher at this site than HMC 2 and HMC 3 (Figure 4). There was also an abundance of sediment piled up at this location. I believe that this was due to a subdivision that was built on the opposite side of the road a few years ago. The damage has already been done to the water even though the construction for this subdivision is finished.  Now, the water quality and aquatic life will continue to deteriorate.

            HMC 2, which is farther down stream, is filtered, because it has a wetland to flow through. The area is filled with vegetation that continues to catch sediments and any debris that floats by. The dam is located above HMC 2 and this is why the sediments are being filtered out. Once this area is damaged, what will be left to help our waters become clean again?

            The third site, which was a couple of miles from the other two, also had evidence that it had been filtered. This would indicate that the water has been cleaned as it moves along vegetation along side the creek and is tumbled about. As we continue to clear out areas down to the water, more sediment will begin to run off into the water.


        Halls Mill Creek is just one stream in the county, but making a difference in one can help out more than realized. The dam that is under construction may eventually become a larger problem due to sediment runoff. This is only one example of neglect that could have been prevented. I hope that the dam, overtime, will not cause a problem like that of HMC 1. I do believe that this research did prove that runoff has caused major problems to Halls Mill Creek. There may be even some damage that we cannot see with the naked eye, but it’s there. “A U.S. Geological Survey study found that streams in areas with significant agricultural or urban development almost always contain complex mixtures of nutrients and pesticides” (Contamination 1999).

There could be several reasons for the poor test results. One reason for high turbidity could be due to the fact of sediment build up or there could have been an algal bloom during the time the testing took place. When the water becomes overloaded with nutrients problems as “toxic algal blooms, loss of oxygen, fish kills, loss of biodiversity, loss of aquatic plant beds and coral reefs, and other problems” can occur (Carpenter et al. 1998).

It could also be a possibility that pesticides from yards are running into the water, causing water quality and aquatic problems. “In addition to accidental contamination many pesticides are deliberately applied directly to fresh waters for suppression of aquatic animals or plants” (Cope 1966).

 Further research needs to be done to find out exactly what is causing a problem at HMC 1. Today we continue to see a decline in our waters and also aquatic life. “Sediment, nutrients, pathogenic organisms, and toxins still find their way into the nation’s water, where they degrade the ecosystem, pose health hazards, and impair the full use of water” (Liban 1998). If people would become more involved, then we may find ourselves with fewer problems. They would be able to see for themselves how much damage is being done. We will always have those who think that the water can take care of itself. It needs our help, we have destroyed too much. Doing this research will help the Dog River Clearwater Revival to see how much impact one small area is causing. They will then be able to look for areas such as this one and take action. 




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