Water Quality Data Collection
Often when we are setting up to go map an area people will pass buy and ask about the different sensors being used. When we bring up the fact that we are collecting water quality measurements in concert with each geolocated 360-degree panoramic image the next question is always, what are you measuring in the water? So here is an answer as it relates to the nearshore mapping we are doing in Puget Sound.
Puget Sound Water Quality
Puget Sound is a fjord with a diverse bottom bathymetry. It also has a diverse nearshore, encompassing urbanized, sub-urban and more natural shorelines. This diversity is the result of the size of the waterway, making up nearly 1300 miles of shoreline. Because of its shape and size many areas create bottlenecks to seawater exchange from tidal influences. This can result in long long times for seawater to remain in certain areas exacerbating any negative impacts to water quality by people. Marne life in the Sound has evolved to be very specific with regards to habitat and water conditions. Degradation of these water quality parameters therefore can have lasting impacts.
- One of the major concerns right now is acidification. pH of the water can decrease as a result of large amounts of carbon dioxide in the water. These levels have been decreasing because of climate change, destroying the calcium shells of baby oysters, clams and other shellfish, making it hard for them to reproduce.
- An equally problematic human induced water quality problem in Puget Sound is wastewater contamination from sewer overflows and leaky septic systems. The extra nutrient inputs from this contamination can cause harmful algal blooms which make shellfish poisonous. These blooms can also create eutrophication depleting certain areas of oxygenated water, creating “dead zones” where nothing can live. These zones have been seen at certain times of year in Hood Canal where tidal seawater exchange is slow.
- Toxic heavy metals are another source of severe impacts to water quality. These metals were, and still are introduced in urban industrial settings. Some of these areas have become SuperFund sites where hundreds of millions of dollars are spent to eliminate legacy pollution impacts.
Water Quality Fundamentals
When measuring water quality scientists test three major categories: physical parameters like temperature, pH, and dissolved oxygen, biological parameters like bacteria levels and chemical levels like PCB’s. We focus on the following physical parameters: Temperature, pH, Dissolved Oxygen, and Salinity. Below is a table describing the specifications of the measurements collected by the instrument we use.
Hana Water Quality Measurement Specifications
|pH range||0.00 to 14.00 pH|
|pH accuracy||+ or – 0.02 pH|
|pH/mV input range||+ or – 600.00mV|
|pH/mV input accuracy||+ or – 0.5mV|
|ORP range||+ or – 2,000.0mV|
|ORP accuracy||+ or – 1.0mV|
|Dissolved oxygen range||0.0 to 500.0% / 0.00 to 50.00mg/L|
|Dissolved oxygen accuracy||0.0 to 300.0%, + or – 1.5% of reading or + or – 1.0% (whichever is greater)300.0 to 500.0%, + or – 3% of reading0.00 to 30.00mg/L, + or – 1.5% of reading or 0.10mg/L (whichever is greater)30.00mg/L to 50.00mg/L, + or – 3% of reading|
|Conductivity range||0 to 200.0mS/cm (absolute EC up to 400mS/cm)|
|Conductivity accuracy||+ or – 1% of reading or + or – μ/cm, whichever is greater|
|Resistivity range||0 to 999,999Ωcm; 0 to 1,000.0kΩcm; 0 to 1.0000MΩcm|
|Resistivity resolution||Dependent on resistivity reading|
|TDS range||0 to 40,000mg/L or ppm (maximum value depends on TDS factor)|
|TDS accuracy||+ or – 1% or + or – mg/L (ppm), whichever is greater|
|Salinity range||0.00 to 70.00 PSU (Extended Practical Salinity Scale)|
|Salinity accuracy||+ or – 2% of reading or 0.01 PSU, whichever is greater|
|Temperature range||-5.00 to 55 degrees C/23 to 131 degrees F/268.15 to 328.15 degrees K|
|Battery type||(4) 1.5V alkaline C cells, or (4) 1.2V rechargeable C cells|
|Weight||Meter 750g/26.5oz.; Probe 750g/26.5oz.|
|Dimensions||221 x 115 x 55mm/8.7 x 4.5 x 2.2 inches (H x W x D)|
We take surface level measurements which means they are taken at a meter or less depth. Most of the time surveying the nearshore we are in water that is shallow. Before each survey we calibrate the instrument to make sure the measurements are accurate. These measurements provide a good baseline of conditions and provide information that can be used to find areas that one would want to explore in more detail and with greater scientific rigor.
Understanding Nearshore Matters
Water quality is directly related to the land water interface and improving Puget Sound water quality will require having the best possible understanding of what those nearshore conditions are like. This understanding is at the heart of our mission.