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Surface Water: Our essential guide to surface water and the impact of algae

Tuesday, 11 July 2023

Table of contents

  1. How do you define surface water?
  2. What causes eutrophication?
  3. What are algae?
  4. What causes algae and how is it formed?
  5. Impact of algae on surface water?
  6. How to get rid of algae?

Our essential guide to algae and surface water surface water and the increasing environmental challenge of algae and algal blooms: major causes and how to prevent it building up in our drinking water ecosystems.

How do you define surface water?

Surface water can be defined, according to the National Geographic encyclopedic entry is: "Any body of water above ground, including streams, rivers, lakes, wetlands, reservoirs, and creeks. The ocean, despite being salt water, is also considered surface water."

“Research conducted by the USGS in 2015 revealed that 70 per cent of all water used in the United States came from surface water.”

A key part of the hydrologic cycle, precipitation and water runoff feed surface water bodies. Surface water can lose water through evaporation and seepage of water into the ground - what is known as groundwater. Although surface water and groundwater can also feed into one and other.

However, the amount of water now stored in half of the largest lakes and reservoirs around the world is declining as a result of climate change and human activity, according to new research in the American Association for the Advancement of Science. 

Surface water

Image credit: National Geographic

There are three types of surface water:

  • Perennial - Perennial, or permanent, surface water persists throughout the year and is replenished with groundwater when there is little precipitation.
  • Ephemeral - Ephemeral, or semi-permanent, surface water exists for only part of the year. Ephemeral surface water includes small creeks, lagoons, and water holes.
  • Man-made - Man-made surface water is found in artificial structures, such as dams and constructed wetlands.

Surface water versus groundwater

Surface water is our most easily accessible water, far more so than groundwater. As our main source of drinking water, it also plays a vital role in the irrigation. Research conducted by the USGS in 2015 revealed that 70 per cent of all water used in the United States came from surface water.

What causes eutrophication?


Image credit: Eniscuola

Nature defines eutrophication as being "characterized by excessive plant and algal growth due to the increased availability of one or more limiting growth factors needed for photosynthesis, such as sunlight, carbon dioxide, and nutrient fertilizers."

Eutrophication takes place naturally over centuries as lakes and rivers age they become filled with debris. However, increased agricultural and industrial human activity has accelerated this natural phenomenon through both point-source discharges and non-point loadings of limiting nutrients, such as nitrogen and phosphorus.

“Eutrophication affects 54 per cent of Asian lakes, 53 per cent of those in Europe, 48 per cent of those in North America.”

A survey of the State of the World’s Lakes carried out in 2008 carried out by the University of Alberta, found that eutrophication affects 54 per cent of Asian lakes, 53 per cent of those in Europe, 48 per cent of those in North America, 41 per cent of those in South America and 28 per cent of those in Africa.


Image credit: Eniscuola

Eutrophication is caused by three main factors:

  • Fertilisers - Agricultural practices and the use of fertilisers in the soil contribute to the accumulation of nutrients. When these nutrients reach high concentration levels and the ground is no longer able to assimilate them, they are carried by rain into rivers and groundwater that flow into our surface water ecosystems.
  • Discharge of wastewater - Around the world, and in commonly developing countries, wastewater is discharged directly into surface water bodies. This results in the release of a high quantity of nutrients which stimulates the growth of algae.
  • Reduction of self-purification capacity - Lakes and rivers over time become contaminated with foreign objects, such as organic material and human garbage. These foreign objects are able to absorb large amounts of nutrients and pollutants. The accumulation of these objects in the basin of the surface water increases the interactions between water and the foreign objects, the leads to the resuspension of nutrients present at the bottom of the surface water.

What nutrients are in water?

Water is comprised of hydrogen and oxygen, and naturally calorie-free. Surface water can sometimes contain traces of minerals like calcium, magnesium, sodium, zinc, and copper.

Nutrients are an important indicator of surface water quality because inorganic nitrogen and phosphorus control the growth of aquatic plants. Excessive growth of aquatic plants can cause dissolved oxygen concentrations in streams to decrease during the night to levels that may not sustain certain species of fish.

What does cyanobacteria mean?


Image credit: EPA

Cyanobacteria is a type of algae that lives in water whose microorganisms are capable of performing photosynthesis. They are commonly referred to as 'blue-green' algae.

Because they are bacteria, they are quite small and usually unicellular, though they often grow in colonies that are large enough for us to see.

The word 'cyanobacteria', according to the Collins English dictionary, means; "a group of photosynthetic bacteria (phylum Cyanobacteria) containing a blue photosynthetic pigment".

They have the distinction of being the oldest known fossils, as they are more than 3.5 billion years old.

Where are cyanobacteria found?

Cyanobacteria can be found naturally in all types of water, according to the CDC. The single-celled organisms live in fresh, brackish (combined fresh and saltwater), and marine water.

One of the most common types of algae, cyanobacteria do not require anything other than sunlight to grow, making most open surface water bodies perfect habitats for it to grow.

Further topics in the essential guide:

  • What are algae?
  • What causes algae and how is it formed?      
  • Impact of algae on surface water?
  • How to get rid of algae?

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