The water cycle is the process by which water flows and is regenerated in nature, covering evaporation, condensation, precipitation, groundwater recharge, and flow to the oceans. The water cycle is important, especially in terms of water quality monitoring.

What is the water cycle?

The water cycle, also known as the water cycle process or the water cycle cycle, is a natural process of continuous circulation and redistribution of water on Earth. This process moves water from different stores and states of the Earth, including atmospheric water vapor, surface water and groundwater, glaciers, snow and ice.

  • Evaporation: Solar energy turns the Earth’s bodies of water, such as water in oceans, lakes, rivers, and soil, into water vapor, which is the beginning of the water cycle.
  • Condensation: Water vapor cools in the atmosphere and condenses into small water droplets or ice crystals, forming clouds.
  • Precipitation: When the water droplets in a cloud grow large enough, they fall as precipitation, e.g., rain, snow, or hail.
  • Surface Runoff: Precipitation flows into rivers, lakes, and oceans to form surface runoff. These bodies of water can continue to evaporate, enter the atmosphere, and fall again.
  • Infiltration and Groundwater: A portion of precipitation infiltrates into the soil and percolates into the ground as groundwater. This water can be pumped by groundwater pumps or enter streams through natural infiltration.
Water cycle in natural processes
Water cycle in natural processes

Why is the water cycle important?

The water cycle is important because it maintains the Earth’s water supply, supports the functioning of ecosystems, preserves climate balance, and provides human societies with the freshwater resources they need to live. This continuous cycle allows for the reallocation of the Earth’s water resources to meet ecosystem, urban, industrial and agricultural water needs, maintaining the sustainability and viability of the planet.

Water Quality In The Water Cycle

WaterA major component of the water cycle that can exist in different states, including liquid, gas, and solid.
Dissolved GasesAtmospheric gases can be dissolved in water, such as oxygen and carbon dioxide.
Dissolved solidsCan dissolve a variety of solids, including salts, minerals, and organic matter.
MicroorganismsWater contains a variety of microorganisms, including bacteria, algae, and zooplankton, which play an important role in the water cycle and can also be used as indicators of water quality.
ChemicalsIn some applications, chemicals such as disinfectants, anti-scaling agents, corrosion inhibitors, etc. are added to the water to achieve specific water quality control.
Table of water quality in the water cycle

How do you treat water quality?

Treating water in the water cycle typically involves a range of processes and methods to improve water quality, remove contaminants, provide safe drinking water, or utilize water for industrial and agricultural purposes.

  1. Filtration: The use of different types of filtration systems (e.g. sand filters, activated carbon filters, membrane filters, etc.) to remove suspended solids, particulate matter, microorganisms, and organic matter.
  2. Disinfection: Application of disinfection methods (e.g. chlorine disinfection, ultraviolet disinfection, ozone disinfection, etc.) to kill or remove pathogens, bacteria, viruses, and other microorganisms from water.
  3. Sedimentation: The use of settling tanks or precipitators to separate suspended solids and particles from water to form a sediment, which is then separated from the clear water.
  4. Softening: Softening water by removing calcium and magnesium ions from hard water, usually using ion exchange resins or other softening agents.
  5. Reverse osmosis: Removal of dissolved solids, salts, and ions from water through a reverse osmosis membrane system to produce high-purity water.
  6. Desalination: the use of desalination methods (such as electro deionization, distillation, etc.) to remove the salt in the water, usually applied to desalination and high-purity water production.
  7. Biological treatment: the use of biological reactors or wetland systems to degrade organic substances and pollutants, usually applied to wastewater treatment.
  8. Deep treatment: Advanced treatment methods for specific pollutants (e.g., heavy metals, organic compounds), including chemical precipitation, oxidation, and other specialized techniques.

How do you monitor water quality in the water cycle?

Sensors and Instruments: A variety of water quality sensors and instruments are used to measure key parameters in water such as pH meters, dissolved oxygen, turbidity, conductivity, temperature, and chlorine concentration.

  1. PH meter: Used to measure the pH of the water, a key indicator of acidity and alkalinity. pH meters can provide real-time pH values. The Apure A20 Water pH ORP Controller is a new type of controller. It is highly intelligent and flexible. It can measure pH/ORP value and temperature simultaneously.
  1. Dissolved oxygen meter: Used to measure the concentration of dissolved oxygen in the water, a key indicator of oxygen content in the water, which is critical to the biological ecosystems in the water body.
  2. Conductivity meter: Used to measure the conductivity of water, which reflects the concentration of ions in the water and is usually related to the concentration of dissolved substances.
  3. Turbidiy meter: Used to measure the turbidity of water, which is the degree of cloudiness of water due to suspended particles, microorganisms and dissolved substances.
  4. Ammonia sensor: Used to measure the concentration of ammonia in water, which is an important parameter indicative of eutrophication of a body of water.
  5. Chlorine Meter: Used to measure the concentration of residual chlorine in the water, which is a chemical used to kill pathogens during the disinfection process.
  6. Nitrate Tester: Used to measure the concentration of nitrate in water, a common pollutant in water bodies.

Online Water Quality Monitoring System: An online water quality monitoring system installed in a water treatment plant, industrial process, or pipeline that continuously monitors water quality and triggers alarms or control operations.

Meteorological stations: Monitor environmental, meteorological factors such as precipitation, temperature, and flow to understand the effects of meteorological conditions on water bodies.


As technology continues to evolve, water quality monitoring will become more efficient and accurate, enabling precise measurements of the quality of water bodies in the water cycle, as well as ensuring the sustainable use of water resources.

Apure Brands is a company committed to innovation and quality, specializing in advanced water treatment solutions. As one of the industry leaders, we have extensive experience and expertise in water treatment and continue to push the boundaries of technology and process innovation to meet the ever-changing needs of our customers. We offer high-quality pressure measurements, temperature measurements, and ozone generators. We are committed to helping you achieve accurate and reliable water quality monitoring, so please feel free to contact us.