1. Salinity of Lakes, Rivers, and Reservoirs

2. Saline vs. Marine Marine water mainly sodium chloride 35%o
Saline waters vary in dominant ions
Surface waters range from almost pure water to several times the ionic strength of sea water

3. Saline lake Classification
Name
Concentration range
Subsaline
0.5-3‰
Hyposaline
3-20‰
Mesosaline
20-50‰
Hypersaline
>50‰

4. Some Saline Inland Waters
Name
Location
Salinity
Other
Don Juan Pond
Antarctica
>400‰
Never freezes
Lake Vanda
<400‰
Meromictic
Lake Assal
Djibouti (Affar)
348‰
-155m
Dead Sea
Jordan/Israel
337‰
-378m
Great Salt Lake
Utah, USA
50-270‰
Remnant of Lake Bonneville
Mono Lake
California, USA
50-99‰
Highly productive

5. Don Juan Pond (~400‰)
Lake Vanda –deep meromictic lake

6. Lake Assal -Djibouti
Crater lake 155m below sea level.
Salinity 348 ‰

7. Dead Sea
337‰ and 378m below sea level

8. Great Salt Lake

9. Mono Lake

10. Major Cations of Surface Waters
Hard Water
Soft Water
Calcium
Magnesium
Sodium
Potassium
Calcium
Sodium
Magnesium
Potassium

11. Major Anions of Surface Waters comment on Tables 10-1, 10-3, & 10-4
Hard Water
Soft Water
Bicarbonate
Carbonate
Sulfate
Chloride
Chloride
Sulfate
Carbonate

13. Salinity due to: Substrate (soil, geology) Total precipitation
Ratio of precipitation to evaporation
Comment on Table 10-2

14. Aral Sea

15. Saline lakes form when Outflow is restricted
Evaporation rate exceeds inflow or outflow
Inflow equals evaporation plus outflow

16. Saline Lakes are different from hard water lakes
Mainly sodium chloride

17. Conductivity
Specific conductance

18. Sources of ions Direct weathering of rock (e.g. sodium chloride)
ReDox reactions involving iron, manganese, sulfur, nitrogen, phosphorus, and carbon
H+ from carbonic acid, acid rain, humic acids
Influence of groundwater

20. Precipitation as a source of ions
Wind-borne salt
Dust
Acid rain

21. Calcium Essential element for most living things Soft-water: low Ca
Hard-water: high Ca
Photosynthesis causes decline of Ca
Metabolism causes increase of Ca
Interpret Figures 10-3, 10-4, & 10-5

22. Ca & conductivity in Lawrence Lake

23. Ca in Wintergreen Lake

24. Magnesium Necessary for chlorophyll
Unlike Ca, very soluble and does not easily precipitate
Interpret Figure 10-6 and compare with Figure 10-3

25. Magnesium in Lawrence Lake

26. Sodium, potassium and other minor cations also very soluble

27. Sodium concentrations

28. Monovalent: Divalent Cation Ratios
M:D < 1.5 favors diatoms
M:D > 1.5 favors desmids

29. Anions, especially halides in surface waters
Examine Figure 10-8, chloride concentrations in Little Crooked Lake

30. Chloride in Little Crooked Lake

31. Origins of freshwater biota
Bacteria: homiosmotic
Protists: variable, most from marine forms
Plants: from terrestrial groups, few saline plants (e.g. Spartina). Some like Nymphaea primitive freshwater aquatic forms
Animals: Many from marine environments; however, insects from terrestrial groups