Factors affecting water quality

Learning Intention

Investigate the factors that contribute to poor water quality

Inquiry Questions

What is the relationship between water delivery, sedimentation and nutrient levels on the quality of water and particularly Blue-green algae in Lake Albert

What is Blue-Green Algae

Blue-green algae is not actually an algae. It is bacteria-like and belongs to the Cyanobacteria family.

Blue-green algae is a naturally occuring lifeform found in naturally in Lakes, rivers and waterways.

When Blue-green algae grows uncontrollably it forms blooms that release toxins and negatively effect freshwater ecosystem functioning.

Requirements of Blue-Green Algae

Blue-green algae is similar to most algae. It needs:

· Sunlight

· Nutrients

· Carbon dioxide

· Oxygen

· Water

for photosynthesis and growth to occur.

Blue-Green Algae thrives when

Blue green algae can grow very quickly when conditions are favourable including:

· Abundant sunlight

· Little to no water flow

· Abundant levels of Phosphorous and Nitrogen ( present in the form of Ammonia)

· Warming of water in the top layer ( Stratification)

In Lake Albert all these conditions readily occur during the warmer summer months and this is when Blue-green algae blooms occur.

Important Nutrients

Nitrogen ( Ammonia test) is a naturally occurring nutrient that can slowly be broken down by sunlight.

Phosphorous is stored in sediments and does not break down and can be released by bacteria.

Nitrogen ( Ammonia test) and phosphorous can be introduced into a freshwater body by a number of ways including:

· Fertilisers ( Agricultural and garden)

· Household detergents

· Sewage runoff

· Stormwater

· Surface runoff and sedimentation

Sedimentation

Crooked creek and Stringybark Creeks have been slowly and continuously depositing sediment ( Sand and silt) for the life of Lake Albert.

Over 6000 cubic metres of sediment was entering the lake each year from Stringybark and Crooked Creeks. Estimates projected that the lake would eventually fill with sediment. Originally the lake was a swamp until the creeks were diverted into it turning it into a lake. Crooked Creek was originally diverted into the lake in 1902. Stringybark Creek was diverted into the lake in 1977.

Sedimentation is the process of depositing of soil materials over time.

Sedimentation is the main storage bank of Phosphorous in Lake Albert.

The continual deposition of sediment over time leads to the formations of Deltas as seen at Crooked Creek and Stringybark Creek.

The combination of shallow water and high mechanical wave action ( wind and boats) stirs up the sediment continually releasing stored nutrients.

The cross section to the left shows the deposition of sediment over time. The grey layer shows the oldest layer with the yellow layer the youngest. All these layers together show the process of sedimentation.

The sediment layers will contain the nutrients like Phosphorous that will contribute to the chemistry of the lake.

Problems caused by Blue-Green Algae

Blue-Green Algae can produce harmful toxins that can be harmful and potential fatal to humans and animals consuming the polluted water.

Algae blooms will leave the water unusable for drinking, agriculture, irrigation and recreational use.

For Geographers this can be analysed through economic, cultural and environmental impacts.

Managing Blue-Green Algae

A range of strategies can be used to manage Blue-Green Algae and blooms. These include:

1. Minimising nutrients entering the system from Agriculture

2. Minimising nutrients entering the system from Urban runoff ( Stormwater and sewage)

3. Increasing vegetation to remove nutrients

4. Regenerative agriculture and soil conservation practices

5. Closing waterways when Blue-green algae blooms

6. Emerging technologies including ultrasonic treatment

7. Reducing the impacts of stratification and mechanical action of sediments

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