Download - Salinity of Lakes, Rivers, and Reservoirs
Salinity of Lakes, Rivers, and Reservoirs
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
Saline lake ClassificationName Concentration range
Subsaline 0.5-3‰
Hyposaline 3-20‰
Mesosaline 20-50‰
Hypersaline >50‰
Some Saline Inland WatersName Location Salinity Other
Don Juan Pond Antarctica >400‰ Never freezes
Lake Vanda Antarctica <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
• Don Juan Pond (~400‰)
• Lake Vanda –deep meromictic lake
Lake Assal -Djibouti• Crater lake 155m
below sea level.• Salinity 348 ‰
Dead Sea
337‰ and 378m below sea level
Great Salt Lake
Mono Lake
Major Cations of Surface Waters
Hard Water• Calcium• Magnesium• Sodium• Potassium
Soft Water• Calcium• Sodium• Magnesium• Potassium
Major Anions of Surface Waterscomment on Tables 10-1, 10-3, & 10-4
Hard Water• Bicarbonate• Carbonate• Sulfate• Chloride
Soft Water• Chloride• Sulfate• Carbonate
Salinity due to:
• Substrate (soil, geology)• Total precipitation• Ratio of precipitation to evaporation
Comment on Table 10-2
Aral Sea
Saline lakes form when
• Outflow is restricted• Evaporation rate exceeds inflow or outflow• Inflow equals evaporation plus outflow
Saline Lakes are different from hard water lakes
• Mainly sodium chloride
• Conductivity• Specific conductance
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
Precipitation as a source of ions
• Wind-borne salt• Dust• Acid rain
Calcium
• Essential element for most living things• Soft-water: low Ca• Hard-water: high Ca• Photosynthesis causes decline of Ca• Metabolism causes increase of CaInterpret Figures 10-3, 10-4, & 10-5
Ca & conductivity in Lawrence Lake
Ca in Wintergreen Lake
Magnesium
• Necessary for chlorophyll• Unlike Ca, very soluble and does not easily
precipitateInterpret Figure 10-6 and compare with Figure
10-3
Magnesium in Lawrence Lake
• Sodium, potassium and other minor cations also very soluble
Sodium concentrations
Monovalent: Divalent Cation Ratios
• M:D < 1.5 favors diatoms• M:D > 1.5 favors desmids
Anions, especially halides in surface waters
• Examine Figure 10-8, chloride concentrations in Little Crooked Lake
Chloride in Little Crooked Lake
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