Water Quality and Lake Winnipeg Watershed Management Assignment 3

Water Quality and Lake Winnipeg Watershed Management

Eutrophication is the process by which nutrients in natural waters increase, causing an overgrowth of algae. Lake Winnipeg is one lake that has been adversely affected by eutrophication. Using Lake Winnipeg as a case study, this text demonstrates the causes of eutrophication, the effects of the same on aquatic life, and ways of minimizing its overall effects.

What are the key differences in the physical, chemical and biological features observed in a comparison of oligoptrophic with eutrophic water bodies? Which condition is more desirable based on the concept of sustainability? Why?

Eutrophication is the process by which nutrients in natural waters increase, causing a subsequent increase in the growth of algae and higher plants. A water body starts from a natural state (the oligoptrophic stage) through a mesotrophic state, and finally reaches the eutrophic state with the further addition of nutrients. In the eutrophic state, the water quality is low and nutrient build-up is evident in both sediments and water. Euphoric water bodies are characterized by among other things, i) low dissolved oxygen concentrations in deeper waters, ii) high nutrient concentration levels, iii) decreasing light penetration, iv) high phosphorus concentrations, and iv) an algae population that is predominantly cyanobacteria. A comparison of the biological, chemical and physical features of eutrophic and oligoptrophic waters is presented in the table below.

Features

Oligoptrophic

Eutrophic

Physical/Chemical Features

Depth

Deep

Shallow

Sediment levels

Low

High

Sediment nutrient concentrations

Low

High

Water column nutrient concentrations

Low

High

Dissolved oxygen levels at the bottom

High

Low

Biological Features

Primary productivity

Low

High

Species diversity

High

Low

Dominant phytoplankton

Diatoms/green algae

Cyanobacteria

Phytoplankton diversity

High

Low

Bloom frequency

Rare

Common

(Source: Shaw, Moore & Garnett, 2004, n.pag)

Oligotrophism is more desirable for sustainability. Here is why: the algae that bloom as a consequence of eutrophication die as they begin to compete among themselves for available nutrients. These dying algal are oxidized by anaerobic bacteria, which deplete oxygen supplies in the water, causing the death of fish and other forms of useful aquatic life (Shaw et al., 2004). Moreover, the increase of anaerobic bacteria in water as a result of eutrophication results in an increase in gases such as methane and hydrogen sulfide, which reduce the quality of water (Shaw et al., 2004).

Question 2: Describe five natural and five human generated point and non-point sources of pollution that lead to eutrophication of water bodies. Of these, which do you believe is the most difficult to regulate?

Eutrophication occurs when pollutant nutrients enter waterways from either diffuse sources or point source discharges (Shaw et al., 2004). This can be as a result of natural occurrences or human activities. One core human source of pollution is industrial effluents -- effluents released by factories into water sources could contain chemicals such as phosphorus, which contaminate the water, promoting the growth of algae. Besides industrial activities, there are also farming/agricultural activities such as irrigation -- irrigation drains carry excess water from farms and plantations, and this water sometimes contains phosphorus, which if released into waterways, could promote algae growth (Shaw et al., 2004). Diaries are another major source of pollution -- the chemicals used in the processing of milk and milk products could contaminate water sources if no effective regulations exist to regulate such release. Feedlots and piggeries are also point sources of pollution -- chemicals used in the fattening of domestic animals could be harmful to water sources if released to the same for prolonged periods. The final source of pollution is sewage treatment plants - waste water treatment plants often carry out the primary and secondary levels of treatment, leaving out the tertiary phase, which is responsible for the elimination of nutrients such as nitrogen and phosphorus. The effluent released from the secondary stage (which contains large amounts of these nutrients) is often used to manufacture commercial fertilizers, which if used on farmlands and washed away into water sources could cause contamination (Malley, Ulrich & Watts, 2009).

A number of natural occurrences could also contribute to the eutrophication process. First, waterways such as lakes are fed by rivers and streams that percolate through organic matter, soils, and rocks (Shaw et al., 2004). These waters carry with them chemicals and nutrients dissolved in rocks and soils, which are transferred into the lake once the flowing waters come into contact with the lake waters (Shaw et al., 2004). A second natural source of pollution is the convention process -- the process by which surface water in lakes or reservoirs mixes with phosphorus-enriched water from deeper layers as a result of temperature changes. The third source is the collapse of stream banks as a result of earthquakes, water saturation or tectonic failure -- when a stream or river bank collapses, it adds fine sediments into the water source. Repeated collapses could cause downstream sediments, which reduce the velocity of flow and affect the river's ability to carry away pollutants. As a result, these pollutants accumulate, promoting algae growth. The fourth source of pollution in this regard is the natural release of nutrients by bottom sediments into the water system. Finally, there is the atmospheric fall-out process -- the process by which airborne particles ejected into the atmosphere as a result of volcanic eruptions, explosions, tornadoes and so on settle back to the ground. If these particles settle inside water reservoirs, they accumulate to form sediments, which contribute to the eutrophication process in the same way as collapsed stream banks.

Of the two groups of sources, natural sources are the most difficult to regulate. The simple reason is that these events occur naturally, and no one can accurately predict when they are likely to occur.

Question 3: Describe the relationship between eutrophication and biological diversity based on the key features of:

i) Water chemistry involving the N/P ratio, biochemical oxygen demand and dissolved oxygen

Nitrogen and phosphorus occur naturally in aquatic systems - when the N/P ratio is favorable, algae grow at a favorable rate. The eutrophication process, however, causes an increase in the levels of nitrogen and phosphorus available in water sources; as a result, the N/P ratio is tampered with and algae multiply at a faster rate than the ecosystem can handle. These algae oxygenate the water as nutrients are assimilated. However, the oxygen produced during the assimilation process is consumed as the macrophytes die and algae senesce. The large numbers of dying algae are oxidized by anaerobic bacteria as they decompose in a process referred to as the biochemical oxygen demand (BOD) (Shaw et al., 2004). The oxidization process consumes large amounts of dissolved oxygen, depleting oxygen levels in the water and making biological life less likely to thrive. As such, the biological diversity levels in eutrophic water sources remain significantly low (Shaw et al., 2004).

ii) Species richness, evenness and dominance

The eutrophication process disrupts the N/P balance, increasing the levels of nitrogen and phosphorus, but not silica (Shaw et al., 2004). Silica is responsible for richness in aquatic species; since the same exists in low levels in eutrophic sources, the species therein are significantly low in richness. Moreover, the low silica levels and high N-P levels cause dominance by cyanobacteria, and not chrysophytes or diatoms as is the case in oligoptrophic systems (Shaw et al., 2004). The species in eutrophic waters are unevenly distributed, with most occurring in the surface waters, where oxygen levels are higher (Shaw et al., 2004).

iii) Food web responses in producers, consumers and decomposers

In the early phases, the eutrophication process causes an increase in the abundance of primary producers in the ecosystem as a result of the increasing nitrogen and phosphorus levels. Moreover, there is an increase in the number of consumers such as fish owing to the increase in food resources. The abundant food resources increase the reproductive ability of consumers, causing them to increase in number. At this point, the high oxygen levels in the ecosystem inhibit the growth of anaerobic bacteria (decomposers), causing them to occur in significantly low numbers. As the eutrophication process progresses, however, the primary producers overgrow and begin to compete among themselves for available nutrients and carbon dioxide. As the level of competition increases, they begin to die in large numbers, causing a decrease in the levels of oxygen in the ecosystem. The consumers also begin to compete for the low levels of oxygen available and they eventually decrease in number. The low oxygen levels, however, favor the growth of anaerobic bacteria, which then increase in number. Thus the decomposers display bottom-top responses as a result of the eutrophication process whereas the consumers and primary producers display top-bottom responses.

Part Two

Question 4: Describe in detail the key features of the Lake Winnipeg watershed that make this lake particularly vulnerable to eutrophication

Two fundamental features of Lake Winnipeg's watershed make the lake particularly vulnerable to eutrophication. First, the Lake Winnipeg watershed is around forty times the lake's surface area (Zubrycki et al., 2015). This, according to the International Institute for Sustainable Development, represents the largest drainage-surface area ratio in the world and makes the lake highly vulnerable to accumulating large amounts of nutrients and pollutants (Zubrycki et al., 2015). The second feature that makes Lake Winnipeg particularly vulnerable to eutrophication is its volume relative to the size of its watershed (the volume-basin index) (Zubrycki et al., 2015). This index is calculated by dividing the lake's volume in cubic kilometers by the size of its watershed (in square kilometers) (Zubrycki et al., 2015). Lake Winnipeg's shallowness coupled with an extensively large watershed makes the lake's storage capacity significantly small (Zubrycki et al., 2015). Lake's Winnipeg's volume: basin index is estimated, for instance, to be 0.000288; Lake Slave has the next smallest index, which is still 7 times larger than that of Winnipeg (Zubrycki et al., 2015). Lake Superior's index is estimated to be 329 times larger than that of Winnipeg (Zubrycki et al., 2015). This low volume in relation to watershed size means that the pressure on the lake is intense (Zubrycki et al., 2015). For instance, high loads of nutrients coming from upstream can increase the levels of nitrogen and phosphorus in the lake more quickly than they would in a deeper reservoir with a smaller basin (Zubrycki et al., 2015).

Besides these, there are also other features of the lake itself that make it susceptible to eutrophication. The first of these is the lake's designation as a hydroelectric power-generation reservoir, which leads to the holding back of water during the productive summer and spring seasons, and hence, the increased mixing of surface waters with phosphorus-rich waters from deeper levels. Secondly, Lake Winnipeg is fed by three large rivers and a series of streams, yet it has only one outflow, through the Nelson River (Zubrycki et al., 2015). This geography facilitates the accumulation of sediments and pollutants fed into the lake by the three rivers.

Question 5: Review water chemistry data for from 1999 to 2010 for three rivers that discharge into Lake Winnipeg

i) Describe the general trends in nitrogen and phosphorus concentrations that occurred over the years of the study

Phosphorus levels in the Saskatchewan River have consistently been below the guidelines for water quality. They dropped significantly between 2001 and 2002, moved on to match the guidelines between 2003 and 2005 and then slightly surpassed the same in 2006. Nitrogen levels, on the other hand, have consistently been above the guidelines, only dropping to guideline levels between 2001 and 2003.

For the Red River, both phosphorus and nitrogen levels have been consistently above the set guidelines and significantly higher than those recorded in the Saskatchewan and Winnipeg Rivers. A major drop in phosphorus levels was recorded between 2001 and 2002, as well as between 2005 and 2007. Nitrogen levels also reduced substantially during these two periods.

The Winnipeg River has recorded the lowest phosphorus levels of the three. Levels have been consistently below guidelines, with a significant drop being reported in 2005. In the same way, nitrogen levels have been below guideline levels, dropping significantly between 2002 and 2004 and again between 2007 and 2008.

ii) Describe the differences in nitrogen and phosphorus concentration between the three rivers

Nitrogen levels in all three rivers are significantly higher than those of phosphorus, with the Red River recording the highest levels of both elements. Moreover, the largest difference in nitrogen and phosphorus concentrations was reported in the Red River. The Winnipeg River recorded the lowest concentrations of both nutrients throughout the study period.

iii) What factors may have contributed to the variability observed in the data?

The variability observed in the data could be attributed to a number of factors. The first of these factors is regulation geared at protecting Lake Winnipeg. Regulations impose upon relevant administrations the responsibility to develop sound policies for reducing water pollution such as charging a fee for harmful nutrient released by companies and private persons into water sources. A second factor is increased public awareness on the need to conserve water sources. These factors have caused the levels of nitrogen and phosphorus released into the three rivers to drop and remain significantly low since 2005.

iv) Based on these results, what conclusion can you make regarding the direction of management goals and priorities for Lake Winnipeg?

I would conclude that this far, the management goals for protecting Lake Winnipeg have yielded positive results, particularly in the case of River Winnipeg and River Saskatchewan. Priority seems to have been given to River Winnipeg compared to the other two rivers, based on its low nutrient levels in comparison to the other two rivers. However, I would expect the conservation authorities to begin placing more effort on the Red River, which up until now appears to have been left out, with nutrient levels consistently above water quality guidelines throughout the study period.

Question 6: Describe how the following strategies offer improvements in water quality within the Lake Winnipeg watershed

i) Riparian Zones

Riparian zones are the lands adjacent or next to water reservoirs. They are recognized as crucial in the conservation of water sources because water quality is determined in part, by what people do on the land. The Manitoba Habitat Heritage Corporation recognizes the importance of riparian zones as buffer areas to protect the quality of water in Lake Winnipeg. The corporation works together with individual farmers to restore the health of riparian zones, educating farmers on strategies of how to rehabilitate their farmlands including carrying out effective irrigation, regenerating cover crops and so on. The aim of this strategy is to correct and eliminate negative human activities and farming practices in the areas surrounding the lake. If individual farmers at the grassroots can understand and play their own conservation efforts in the restoration of Lake Winnipeg, then the effects of negative human activities on the quality of water in Lake Winnipeg would have a lesser effect.

ii) Secondary and Tertiary Wastewater Treatment Options

Wastewater treatment is the process of making grey water from domestic households and the industrial sector suitable for reuse and release into natural aquatic systems (Malley, Ulrich & Watts, 2009). Conventionally, waste water treatment takes place in three stages -- the primary, secondary and tertiary stages. At the primary stage, solids are screened from the waste water and land-filled (Malley et al., 2009). The secondary treatment stage involves using bacteria to degrade the organic/biological content of sewage, which could cause oxygen depletion. Effluent resulting from the secondary level of treatment is significantly low in BOD and could be used in a number of ways including in the making of commercial fertilizer products (Malley et al., 2009). However, this effluent is usually significantly high in phosphorus, potassium, nitrogen and other nutrients present in the original wastewater (Malley et al., 2009). If applied on agricultural land, and washed away by irrigation water into a water reservoir, such effluent could cause eutrophication. Most municipal waste water treatment plans, however, release the same for use this way.

As part of its efforts to restore Lake Winnipeg, the city made it mandatory for wastewater treatment plans in the city to include tertiary treatment in its processes -- an advanced level of treatment where the effluent from the secondary stage is subjected to chemicals that remove nutrients and toxic compounds, particularly phosphorus before being released into the environment. The combination of secondary and tertiary treatment options ensures that effluent reaching the receiving waters contains acceptable levels of nutrients, particularly phosphorus (Malley et al., 2009).

iii) Alternative farming techniques

Commercially manufactured fertilizers contain varying amounts of potassium, nitrogen and phosphorus, which if leached into the soil could cause eutrophication in water sources. This strategy is focused on educating farmers on the use of alternative techniques of increasing their farmlands' productivity. These alternative farming techniques include crop rotation, where the crops planted on a particular piece of land are varied every season so that soils maintain their richness and are not easily blown away by heavy winds; use of organic fertilizers such as manure and so on.