Surface Water Quality Monitoring and Sampling

What is Surface Water?

Surface water — lakes, rivers, streams, reservoirs, wetlands, estuaries — are all threatened daily from harmful algal blooms, anoxic conditions, sediment plumes, and much more. Now, more than ever, monitoring efforts are critical to protecting our water resources. While you're out on the front lines, know that you have our support. For over 70 years, YSI has partnered with water quality professionals to provide the tools necessary to make data-driven decisions in high-stakes environments.

Measurement Methods


Our multiparameter instruments allow for concurrent measurement of critical water quality parameters that are imperative to understanding, protecting, and improving aquatic habitats. These vital measurements include in-situ readings for dissolved oxygen, pH, turbidity, salinity, temperature, total algae content, and more. We offer instruments for both baseline sampling efforts, as well as continuous monitoring systems. These systems are capable of recording high temporal resolution data, which detects events (meteorological, pollution-related, or otherwise) that may impact water quality.

Spot Sampling & Continuous Monitoring

In-situ monitoring begins with handheld sensors. Today, handhelds remain a mainstay of water quality monitoring fieldwork, allowing people to gather lab-quality measurements in the field. They have made water quality testing more efficient and timelier, as they can capture measurements of parameters that may drift before they reach a laboratory. Led by YSI's Professional and ProDIGITAL Series handhelds, sampling instruments have become lighter, faster, and easier to use.  These industry-leading instruments open up opportunities for water quality measurements to a broader world of scientists and environmental managers.

Yet without monitoring water quality 24/7, 365 days a year, it is impossible to understand an aquatic environment. Sondes — French for "probe" — push in-situ water quality measurement to new heights, or at least to new depths. Protecting a suite of sensors in a sleek, ruggedized body, and channeling the data into onboard memory, sondes open the door to long term unattended monitoring — the constant monitoring that allows scientists to observe midnight activity and chart diurnal cycles. With the ability to monitor remote locations constantly, for long periods, without the need for an operator on-site, sondes are revolutionizing water quality monitoring.

Surface Water | Water Monitoring | Real Time Water Data

Water Quality Monitoring Equipment

Water quality instrumentation has evolved to produce higher accuracy data and repeatable measurements while requiring less maintenance. From photometers and colorimeters to electrochemical sensors to digital smart sensors and data sondes, there are many options available to those looking to spot sample and track long-term changes in water quality.

EXO Multiparameter Sondes

Water Monitoring

The EXO sonde platform is the pinnacle of multiparameter water quality monitoring instrumentation. Its titanium sealed, smart sensors with wet-mate connectors eliminate any risk of interference or data loss. Its integrated SmartQC ensures top performance for consistently reliable data, and the platform's industry-leading anti-fouling wiper enables extended deployments. With the broadest range of water quality parameters, EXO sondes will meet the need of any surface water application.

Water Monitoring

Monitoring Data Buoy Systems

Water Quality Monitoring Data

YSI Services has delivered and installed thousands of hydrometeorological data delivery solutions that utilize cutting edge telecommunication technology. Buoys can be easily customized to maximize instrumentation on a single monitoring platform. Add satellite, radio, or cellular telemetry to provide data to a custom visual display, making it easy for researchers and operators alike to receive critical data on a daily basis. We offer a variety of buoy platforms which can be tailored to fit your needs.

Water Monitoring Data Buoy

ProDIGITAL Handheld Meters

Water Quality Sampling

The ProDIGITAL family offers industry-leading technology to meet the demands of your water quality application. Customize your system by combining the handheld and probe options that work best for you. Digital smart sensors ensure you get the best data possible, and our powerful ProDSS, ProSwap, and ProSolo handhelds are loaded with advanced features to make analysis easy and intuitive. With superior functionality and maximum versatility, our top-of-the-line digital sampling systems can be customized to meet the demands of your application.

Water Quality Sampling Meter

Professional Series Handheld Meters

Water Monitoring Sampling System

The YSI Professional Series offers a variety of rugged and reliable handheld instruments that have become the standard in water quality sampling applications such as surface water, groundwater, coastal waters, and wastewater. Built around tried and true sensing technology, the full range of meters in the Professional Series can handle whatever nature throws their way. Choose from user-replaceable single, dual, or multiparameter cables with various length options.

Water Quality Monitoring

Auto Samplers

Water Sampler

Water samplers combine all the features needed to meet a wide variety of water sampling requirements, including those for stormwater, industrial discharge, water and wastewater treatment, waste collection systems, rivers, and streams.With multiple samplers to choose from and the ability to sample based on time, analog signal, digital pulse, and/or optional measurement from an SDI-12 device, a portable automatic sampler can be the final piece of your monitoring installation.

Water Sampling

Portable Colorimeters and Photometers

Water Quality Testing

These rugged, waterproof, single and multiparameter colorimeters are ideal for laboratory and field water quality testing. The instruments feature a large, backlit display, waterproof rating, data logging with the ability to export data to a computer using LSdata software, user-defined programs and a 2-year warranty. Economical photometers in small packages for any application. These portable photometers allow you to easily take readings directly in the field for 100+ parameters.

Water Quality Testing

Water Quality Parameters

Water Quality Parameters

Key water quality parameters include chemical, physical, and biological properties that are key to understanding and improving the quality of aquatic environments. Parameters frequently sampled or monitored for water quality include temperature, dissolved oxygen, depth, pH, conductivity, ORP, and turbidity. However, advanced water monitoring programs may also collect data on algae blooms, dissolved organic material, PAR, ISEs (ammonia, nitrate, chloride). They can even track water movement with sensors that detect rhodamine dyes.

Water Quality Monitoring

Surface Water Applications

Surface water monitoring is vital to understand how the quality of water is changing. As regulations push water quality measurement into the spotlight around the world, sampling and monitoring efforts provide baselines, reference numbers, quantitative goals, and compliance data. These data come from treatment plants to farm edges to midstream gauges. The examples below highlight a few applications where YSI products have helped a wide range of researchers, consultants, and engineers improve the quality of our world's most precious resource. For more information and success stories on additional water quality applications, please search the Application Note library.

Streams & Rivers

Monitoring Water Quality

Monitoring water quality parameters in streams and rivers ensures that the water traveling downstream is within compliance standards for drinking water and also healthy and sustainable for the ecosystem. By including a water quality monitoring system in this type of environment, sources of contamination or alteration – such as urban sewage, agricultural runoff, or industrial effluent – can be determined. With a combination of multiparameter instruments and automatic samplers, environmental managers can collect a wide swath of chemical and biological data. These data allow them to make inferences about the stream and riverine health, which could lead to effective decision-making about how to improve environmental conditions.

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Nutrients & HABs

Water Monitoring Nutrients HABs

Increases in the nutrient runoff to lakes, streams, and coastlines have resulted in massive economic impacts on these affected regions due to the accompanying algae blooms. Not all algae blooms are harmful, but they still impact many aspects of local economies, such as the tourism and recreational sectors. Direct contact--either physical or through the consumption of poisoned seafood--with toxic algae blooms, on the other hand, can cause serious illness. Using multiparameter instruments and automatic samplers can allow environmental managers to determine the likelihood of an algae bloom event.  Monitoring programs evaluate water quality trends of associated parameters, such as temperature and dissolved oxygen. Through the use of surrogate analysis, scientists can also model the likelihood of the algae containing harmful toxins like microcystin. These models compare algae pigments data like chlorophyll-a, phycocyanin, or phycoerythrin, to collected samples analyzed in the laboratory. Through the use of this instrumentation, early warning systems can be developed to better alert communities when bodies of water may be unsafe.

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Dredging Water Monitoring

There are two primary reasons for dredging operations to be conducted – removal of contaminated sediment and increasing water channel depth for shipping purposes. As sediment is transported downstream and into larger rivers, estuaries, and bays, large amounts of contaminants are often with them. Over time, these contaminants can begin to impact the environment, causing animal mortality or reproductive losses, and thus the sediment needs to be removed. Also, as globalization continues to drive new international commerce, shipping vessels have grown much larger in size to accommodate the increased volume of trade goods. Ports and harbors must be deeper to allow these larger vessels safe passage. With these two reasons in mind, water quality is also continually monitored to ensure environmental compliance as dredging takes place. The most common parameters measured during dredging are turbidity and dissolved oxygen due to the potential for significant adverse effects on the environment if these change from baseline conditions significantly.

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Limnology Monitor Lakes and Rivers

Lakes are complex ecosystems, and changes to the system can occur based on climate, seasonality, and inputs from the watershed. Many lakes are sources for drinking water, so by monitoring water quality in lakes, drinking water managers can make decisions on how to treat water in the lake or the treatment facility. Changes in temperature, pH, dissolved oxygen, and turbidity can have significant meaning in a reservoir when it comes to metals and algae. By monitoring these parameters, operators can make critical decisions that limit treatment costs. It is also essential to monitor lakes for recreational use as well, where accurate monitoring can help communicate with where it is safe to swim or engage in water-related community activities.

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Dissolved Oxygen at Energy Sites

Monitoring Dissolved Oxygen

Aquatic animals rely on aerated water to breathe, and unfortunately, dams can have dire unintentional consequences on habitats due to the removal of dissolved oxygen. Hydroelectric power plants are mandated to maintain certain levels of dissolved oxygen downstream of the dam. By monitoring this parameter throughout a channel, operators avoid disrupting the ecosystem and can take corrective actions if oxygen levels get too low. With the construction of new dams, it is common to monitor water quality conditions above and below the dam. These efforts provide a baseline understanding of ecosystem oxygen requirements that can then become thresholds for monitoring later on.

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