Water Quality


How much sediment will be in the water after kids have been playing on the beach. Does this affect the water quality and possibly change ratings on water safety?


Wow, a very insightful question! When we tend to think of water pollution, we think of chemicals in the water itself. However, the sediment that gets into the water from soil during rain storms or resuspended by man or nature is in fact pollution unto itself as it can affect such things as fish quality of life, light penetration and it just does not look very nice. It is also in fact, the sediment particles that often contain the majority of the pollutants as they represent a surface that the chemicals and bacteria can attach too. So yes, sediment resuspended from the bottom of lakes and rivers or delivered to them by overland flow from rain storms, affects water quality, and is an important part of monitoring water quality programs to assess risk to aquatic and human health.

- Ian Droppo



Easter Water


What does Easter Water contain? I’ve been keeping some in my garage, not-heated, for over 10 years and never has it been frozen. This morning I noticed salt like crystals at the bottom of my container. Would this be the key which would explain the virtues of Easter Water?


Thank you for your question. I have been working in meteorology for almost 30 years, and this is the first time I have been asked this question. Easter water is used to bless a house and protect its occupants from potential misfortune. It is soft water from a river, and it contains natural minerals and very little salt. So I do not have an explanation as to why the water did not freeze in the garage in winter. Also, depending on how much water there was, it should have taken much less than 10 years to evaporate. Although science tries to explain how things work, we do not have all the answers.

- René Brunet



Ice Layers


Hello, I am looking for a document that explains the process of formation and growth of ice layers in a lake, a river and oceans (salt water). The purpose is to study the carrying capacity of different kinds of ice layers. Thank you.


Hello. There are a number of publications that may be of use to you, that explain the process of the growth of ice in moving, freshwater and saline water, as well as the bearing capacity of the ice. Most of these should be available through the NRC Canada Institute for Scientific and Technical Information (the national science library), conference internet sites, or online retailers.

For river and lake ice conditions, “River and Lake Ice Engineering”, George D. Ashton, Editor (Water Resources Publications) is generally the text most often found on an engineer’s desk.

For saline ice, the following reference may prove useful to you:

With respect to bearing capacity, Gold pioneered much of the research in this area, for transportation over frozen ice surfaces. Besides the research he carried out through his work at the National Research Council of Canada, he also published an interesting book,

GOLD, L.W. Field study on the load bearing capacity of ice covers, Woodlands Review, Pulp & Paper Magazine Canada, Vol. 61, pp. 153-154, 156-158, 1960

GOLD, L.W. Use of Ice Covers for Transportation, Can. Geotech. J., Vol. 8, pp. 170-181, 1971

Masterson has numerous publications of relevance to bearing capacity, including the following:

MASTERSON, D.M. (2009) State of the art of ice bearing capacity and ice construction. Cold Regions Science and Technology, Volume 59, pp. 99-112, doi:10.1016/j.coldregions.2009.04.002

MASTERSON, D.M. and YOCKEY, K.E. (2000) Field Strength Properties of a Flooded Sea Ice Road, Proc. ISOPE, Paper 2000-JSC-146, Seattle, U.S.A.

The U.S. CRREL website has numerous bearing capacity documents available, many by Nevel: http://www.crrel.usace.army.mil/library/technicalpublications.html

Finally, the new ISO 19906 Offshore Arctic Structures code has a chapter on Ice Engineering, which contains design guidelines for bearing capacity for roads, for example, over ice.

I hope these can be of help to you.

- Anne Barker



Fresh Water vs. Salt Water


At the mouth of a big river like the St. Lawrence, or the Mississippi, where the fresh water meets the salt water of the sea/ocean, is there an area where the ratio of fresh water vs. salt exists where neither a fresh water creature nor a salt water creature cannot exist? And is there a creature that can survive in either pure fresh or pure salt water both?


Areas where freshwater rivers flow into the ocean are called estuaries, and these do provide challenging environments for many types of aquatic animals. However, they are typically rich in nutrients and may have lots of cover, so they can be very important habitats for fish and invertebrates. This is possible because typically the change from freshwater conditions to full oceanic conditions occurs over a gradient rather than as an abrupt transition from one environment to the other. These gradients of increasingly saline (salty, marine) conditions can extend from a few hundreds of meters in some small estuaries to tens or even hundreds of kilometers in large estuaries such as the St. Lawrence or Mississippi, where waters are slightly fresher (less saline) that full marine conditions quite far out to sea. Moreover, with freshwater lighter than saltwater, there is a gradient with depth as well with the surface waters of an estuary typically less saline than deeper waters in the sample place. The tidal effect also has to be considered as more marine waters move up the estuary and often into the river mouth as tides rise, and then move out along the estuary as the tides fall. Together these factors mean there are gradual changes in water conditions in essentially all estuaries.

The fact that the transition in salinity is gradual means that individual fish and invertebrates are rarely required to go abruptly from one extreme fully marine condition to the other extreme fully riverine condition. Moreover, a large number of fish and invertebrate species can tolerate a range of salinities. There may some preferred salinity for a particular species, but they can do almost as well in a range of conditions both more and less saline than their preferred or optimal condition. Hence as one goes out an estuary from fully riverine conditions to fully marine ones, one passes through a gradient of environmental conditions and a gradient of fish and invertebrate species. Well up the river may be freshwater species with very little tolerance for salt in their environment. Their abundance will drop off as one reaches the influence of marine waters, and the abundance of primarily freshwater species with some tolerance for salt in their environment come to dominate. However, marine species that can tolerate low salinities are also beginning to show up, even in quite fresh conditions. These species become more abundant as one moves further out the estuary, with more and more marine species appearing. There are very few species of fish or invertebrates that are purely estuarine in their distributions in fact. Rather, a very large number of species have parts of their life histories closely linked to the highly productive conditions of estuaries, either as feeding grounds for adults, nursery grounds for larvae and juveniles, or important migration points, as for salmon, which do move over their life from fully freshwater, through estuaries to fully marine, back through the same estuary, and into full freshwater to spawn.

- Jake Rice



Freezing Time of Lakes


What types of bacteria affect the freezing time in lakes of western Canada and why?


That is a really interesting question! While biology can drive a lot of physical (erosion control), chemical (chemical transformation, bioremediation) and biological (biofilm) behaviours within aquatic systems, their role in affecting freeze up and/or length of freezing time would be minimal to non-existent. Most bacteria will be dormant, may die or have a reduced metabolism in colder waters. Some bacteria can assist in the formation of ice crystals (e.g. Pseudomonas syringae), but often this will only occur in rain water or within thin films of water such as what may collect on grass.

- Ian Droppo




Are oceans more at risk from acidification than lakes and rivers since the pH level is different?


Thank you for your question.

In general, the pH of oceans would change less than the pH of lakes and rivers, but the answer isn’t really a straightforward ‘yes’ or ‘no’ because lakes and rivers vary considerably in their ability to buffer hydrogen ions (H+), which is what pH is measuring – more H+ means a lower pH.

Over the last number of decades, water acidification has been primarily driven by increasing atmospheric CO2. The rate of change of CO2 in a waterbody will depend on the surface area of the waterbody relative to its depth and its water chemistry, and in particular whether there are carbonates in the water. How is CO2 connected to pH? If you left a glass of distilled water on your kitchen counter, CO2 would dissolve into the water from the air. CO2 combines with H2O to form H2CO3 (carbonic acid), which can then break apart in one step to form H+ + HCO3- (bicarbonate), and in a second step H+ + CO32- (carbonate). The last two steps provide the source of H+ to lower pH and is why pure water in contact with the atmosphere doesn’t have a pH of 7 as many people think, but rather is a bit lower (~5.6).

So, in water, changes in pH are mostly driven by changes in CO2, and its associated forms H2CO3, HCO3- and CO32-. The main addition of CO2 to the oceans, lakes and rivers today is from the atmosphere. The main factor that affects how quickly CO2 dissolves into a waterbody and changes the waterbody’s pH is the surface area relative to the depth. The pH of Lake Superior would change slower than the pH of Lake Winnipeg if CO2 dissolving into the water was the only process that mattered.

However, in watersheds where there is limestone (CaCO3) weathering, such as many areas of western Canada, there is a source of CO32- that is added to the water that will participate in the reactions above and effectively remove H+ from the water. The pH of such a lake is much more resistant to change than a lake on the Canadian Shield where the watershed is primarily granite, weathers very slowly in comparison, and doesn’t add much CO32-. The oceans are rich in carbonates due to weathering of continents and a very long residence time.

CO2 (primarily as HCO3-) is removed from water by algae as they photosynthesize. This also changes pH, but is a rapid process and CO2 may be released back to the water when bacteria decompose the dead algae. If the algae become permanently buried in the sediments, they take the CO2 with them that was used to build their biomass. Oil and gas deposits are the very long term consequences of such deposition and decomposition.

-Leland Jackson

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