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Ipswich-Parker Suburban WATershed CHannel |
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Definition - The volume of water flowing through a point in the stream per second. Also called discharge. One cubic meter per second (m3/s) = 1000 liters per second (l/s) = 35.31 cubic feet per second (ft3/s) = 264.2 gallons per second
Water Quality Standard - No general standard - is site dependent
Issues - Water flowing in streams has run off of land either over impermeable surfaces, through soils or from groundwater. Following a rain event, there is often a quick increase in flow due to rainwater reaching the stream, followed by a relatively long decline back to baseflow. The rapid increase in flow can result from rainwater quickly running off of impermeable surfaces or through soils. Alternatively, the rapid increase could be due to rainwater pushing out water that had been stored in wetlands or groundwater. Baseflow is the amount of water that would drain absent any rain inputs, and is usually from groundwater.
What to look for in the data - When looking at flow data, think about how quickly flow rises and how long it takes to drop back down. A sharp peak in flow is often an indicator of a large amount of roads, because rainwater is quickly transferred to the stream. A broad peak is an indicator of a lot of wetlands, which capture water and then slowly release it back to the stream. How do the discharge peaks differ in the developed and forested watershed?
Definition - Temperature of the water!
Water Quality Standard - Values above the standard (29.4 C or 85 F maximum temperature) indicate poor water quality
Issues - Water temperature in streams varies over the course of the day much in the way that air temperature varies. The maximum daily temperature is usually several hours after noon, and the minimum is around day break. Over seasons, water temperature also varies the way air temperature does. In streams, other factors that affect water temperature at a particular site is the level of shading upstream of the site.
What to look for in the data - Notice the daily cycle of temperature change, and also notice how it changes over the course of several days. Is the temperature trending upward or downward?
Definition - Oxygen dissolved in water required by aquatic life for metabolism (i.e. breathing)
Issues - If the amount of DO falls below the standard, some life forms such as certain insects and fish cannot survive. Dissolved oxygen enters into water from the atmosphere by diffusion, and from algae and aquatic plants when they photosynthesize. Dissolved oxygen is removed from the water when organisms metabolize or breathe. Because photosynthesis occurs during the day when there is light, DO often increases in the day. At night, DO drops as organism metabolize. DO can be low in streams if metabolism (breathing) is greater than DO inputs or if water flowing in from upstream is already low. Low DO often occurs when organic matter or nutrient inputs are high, and light inputs are low.
What to look for in the data - Notice the daily cycle of dissolved oxygen change, particularly in the larger streams. These cycles correspond with the changes in light determine oxygen production via photosynthesis. Look for places and times where dissolved oxygen falls below 5 mg/l, the freshwater DO standards. When DO falls below these levels, certain fish and insects cannot survive.
Definition - A measure of the amount of acidity in the stream. A low pH indicates more acidity.
Water Quality Standard - Values outside the standard (pH 6.5 - 8.3) indicate poor water quality
Issues - Acid rain is an important issue in the northeastern U.S. Rainfall is naturally acidic, but fossil fuel combustion in the mid west has made rain in the northeast even more acid. When rain hits the earth and enters the soil, the acidity is often reduced by other elements in the soil. Water running off in streams is therefore often neutralized to a level acceptable for most aquatic life. It is only once the neutralizing elements in soils are depleted, or if rain does not pass through the soil at all, that stream acidity increases (causing a lower pH).
What to look for in the data - The low end of the pH standard is 6.5. Look for when and where pH falls below that level. Look especially for how pH responds following a rain event when water flow spike upward due to rainwater inputs. What are the differences between developed and forested watersheds?
Definition - The amount of ionic material dissolved in the water. Ionic materials are things like salts. Seawater has a high and freshwater a low conductivity.
Water Quality Standard - No single water quality standard determined. In general, a higher conductivity indicates that more material is dissolved material, which may contain more contaminants.
Issues - Conductivity in water is influenced by the conductivity of rainwater, by road salt application, fertilizer application, and evaporation. Rainwater has variable conductivity depending on whether the rain clouds formed over the ocean (which tends to have higher conductivity due to ocean salts) or land. Because the Parker and Ipswich River watersheds are influenced by the same weather patterns, differences in conductivity among different sub watersheds are likely due to interactions with soils as well as human activity. In winters, areas that apply road salt will have higher conductivities. Conductivity can be used as an indicator human activity.
What to look for in the data - Compare the conductivity in the stream at the various sites. Notice how conductivity changes during spikes in discharge following rain events. The conductivity change following storm events are due to differing proportions of groundwater and rainwater reaching the stream after a rain event. How do the forested (Cart Cr.) and developed (Saw Mill Br.) subwatersheds respond to rain events?