Site

• Will your proposed site provide adequate water level to keep your instrument submerged?
• Can you locate your instrument near an existing structure, like a pier, or do you need to deploy in open water?
• If you are deploying in open water, do you need a pontoon or buoy platform? If using a pontoon or buoy platform, do you need a single-point or multi-point mooring system?
• Do you need to measure at a fixed location, or do you need data from multiple depths?
• How many sampling points are required in the water column?
• For stream deployments, will your site be buried in sediment during storm events?
• For flow measurements, does your site offer a straight channel?
• Is there enough sun exposure to keep your battery sufficiently charged, if using a solar panel?
• Is your proposed site prone to vandalism? If so, how will you protect your instrument to prevent vandalism?
• Is your site protected from debris that may float downstream?
• If you are planning to use telemetry, do you have adequate communications (e.g., cellular) coverage at your location?

• Ensure there is a fixed structure where an instrument can be deployed. Typically this is a secure PVC pipe with flow holes and treated with antifouling paint. Fixed pipes monitor at a fixed elevation regardless of water level. Site access or permits may be required by the locality to install the system, and the installation should comply with all laws and regulations.
• If no structure is available, then consider a monitoring buoy to hold the instrument. Monitoring buoys can sample a fixed distance from the water surface because they float; however an appropriate mooring design should take into account the field conditions like waves, currents, and water depth.
• Most continuous monitoring sondes want to have a minimum of 4inches of water if the meter is deployed horizontally, or 12 inches of water if deployed vertically. Ideally the sensors will remain off the ground to minimize interferences from the bed or flow events. Sometimes during storm events sediment can bury a monitoring sonde, so the mounting structure should be positioned accordingly and rigid enough to survive these events. Additionally if debris is common in the monitoring location a deployment structure should be designed to mitigate impact.
  
  
• If using a fixed site, it should have a southern exposure (in the northern hemisphere) to maximize solar exposure. Tree canopy and bridge overhangs will adversely impact charging for solar-powered systems.
• If using telemetry, then verify cellular coverage or if using spread-spectrum radios, like 2.4G hz or 900 Mhz, then verify line of site from the remote station back to the base station antenna.
• Flow rates, depth of water, temperature, salinity, nutrients, and solar exposure can greatly impact biofouling at a continuous water monitoring site. Generally a site with some constant flow rate at a greater depth will experience less biofouling.

• Flow conditions should be constant over the physical area occupied by the velocity profiling beams. Typically a straight section of channel is desired -- in curves, there can be flow variations. Also, without a sufficient water depth the instrument cannot measure correctly, so be sure to select a site that consistently has water.
• Doppler velocimeters should be installed as far as possible from control structures, at least 12 stream/canal widths from a control structure.
  
  
• The instrument's measurement axis should be aligned with flow. Large tilt angles (>3-5°) can cause stage and velocity errors.
• SonTek/YSI Argonaut-SL and SW meters should be installed with a bubble level; the SL ("side looking") parallel to flow and the SW perpendicular to flow ("bottom looking").
• It is important to consider the trajectory of velocity profiling beams. Remove or avoid obstructions so that you can obtain a full range of data.

Accessibility and site stability are important factors. The site needs to be accessible for routine maintenance and periodic stream gauging. The trade-off to accessibility is protected the site against vandalism. Rugged enclosures and locked deployment tubes help prevent unwanted access.

The site needs to be stable so that measurements can be taken consistently in the same place. It is important to avoid sites that have turbulence, vegetation, uneven cross-sections (rapid changes in depth), as well as sites with high levels of erosion and sedimentation. Site maintenance is the single most costly factor when dealing with environmental instrumentation, therefore a stable site not only provides quality data, but can also reduce operation costs.

If you need assistance with evaluating, surveying, and selecting your monitoring site, contact AMJ Environmental, YSI's field services team.

info@amjenviro.com
877-392-9950 or 727-565-2201