Turbidity
Turbidity
Turbidity Graph
This is a graph of turbidity at the sampling sites in the Nequasset watershed. As water flow has increased with additional rainfall in September, turbidity significantly drops in the stagnant tributaries while turbidity increases in the main stream. Due to the iron oxide precipitation, the water body becomes cloudier in Delano Road Tributary and Wright Lane sites where the water body is stagnant, possibly due to a low base-flow conditions in the fall, leading to a higher level of turbidity. Rainfall helps reduce the amount of turbidity in these sites because rain flushes iron oxide.Higher flow can carry more sediment in suspension which increases turbidity in the main stream.
The sources of turbidity can either be physical (e.g., fine sediment particles), biological (e.g., algal blooms), or chemical (e.g., precipitation of ion oxide). Phosphorus and nitrogen are one of the major sources to enrich nutrients in the water, which ultimately increases algal blooms, making the water body more turbid. Flushing time of the water body also influences turbidity. If the water is stagnant, sediments sink and settle in the bottom, making the water less turbid. However, at the same time, if the water body acquires something such as iron oxide precipitation, it would stay in the water for a longer time because it would not leave the water body rapidly, leading to a higher level of turbidity. If the water moves rapidly (perhaps due to a rainfall), it picks up the sediments and makes the water more turbid, but at the same time it can also decrease turbidity because the water flow increases. Moreover, the amount of water affects turbidity. Less water in a lake can favor eutrophication that leads to a higher turbidity level.
Construction Sites
These pictures are taken near Delano Road tributary. Construction sites can increase the runoff of sediments which include phosphorus and nitrogen into the water body which might increase its turbidity. With a new house construction, loss of vegetation occurs, leading to a higher level of runoff because trees which would have otherwise been there to consume nutrients cannot reduce runoff. Since clear-cut forest area increases turbidity, silt fence is built which is designed to prevent most of the runoff, protecting the quality of the water.
Turbid Water vs. More Clear Water
Wright Lane Tributary water shows its characteristic of a higher level of turbidity compared to other streams. Moderately higher level of elevation in this site can cause a faster flow in this tributary, increasing turbidity because sediments cannot settle in the bottom. Also, all the runoffs are going directly in to the water because of the effect of steeper slopes. The lack of wetlands could also be the reason for the higher level of turbidity because sediments do not have the chance to settle in the bottom in wetlands.
Meadow Road Tributary water shows its low level of turbidity. This might be due to the wetlands in relative to flat area that slow the water flow and settle down sediments. The lack of mineral sediments due to the dominance of wetlands could also be the reason for the low level of turbidity.
