Limnology 3-2 (3) PDF

School of Environment and Geomatics ENVR 150 What is a lake?  Lake vs. pond?  No official difference  Does light reach the bottom at the deepest point?  Is the water body relatively uniform?  Waves smaller than 30 cm in height?  Lake vs. river?  Loti...

School of Environment and Geomatics ENVR 150 What is a lake?  Lake vs. pond?  No official difference  Does light reach the bottom at the deepest point?  Is the water body relatively uniform?  Waves smaller than 30 cm in height?  Lake vs. river?  Lotic vs. lentic  Not always easy to distinguish  Lake vs. reservoir?  Reservoir can be combination of lake, river, reservoir  Artificial lake filled by river inflow  Alignment NW to SE Williston Reservoir 1773 km2 Quesnel Lake 610m depth Lakes Size (Morphometry)  Surface Area  Maps or remote sensing  Caspian Sea largest salt-water body  Aral Sea  Lake Superior largest fresh water Lakes Size (Morphometry)  Surface Area  Maps or remote sensing  Caspian Sea largest salt  Lake Superior largest fresh water  Depth  Soundings (weighted line)  Sonar  Bathymetry (map of bottom)  Mean Depth(z)  Volume = (Surface Area)(Mean Depth)  More accurate as sum of area x depth of horizontal segments Hypsographic Curve (depth-area curve) Shows how much of each depth zone is present and therefore the potential for biological reproduction. Surface Area At Depth (m2) Creating a Bathymetric Map Crater Lake, Oregon Mt. Mazama Skaha Lake Bathymetry https://webapp.navi onics.com/?lang=en #boating@6&key=wz %7BkHreemU Okanagan Lake Bathymetry www.ijc.org/ Vanessa Langhorn Kootenay Lake SGRC  Kootenay River Basin 50, 298 km2 Selkirk College  Stream Order of Kootenay River 7  Kootenay Lake Basin 31, 264 km2  Inlets 174  Outlets 1 (Kootenay River)  Discharge of Kootenay River @ KL is 782 m3/s average Kootenay Lake Data  Length 104 km /Width 3-5 km  Surface Area = 421 km2 or 421,730,000 m2  Perimeter = 405 km or 405082 m  Deepest 150 m  Main lake- Average depth 94  West Arm - Average depth 10 m Google Earth Kootenay Lake Calculations Volume = Area x Mean Depth  Volume=421,730,000 m2x 94 m  Volume = 39,642,620,000 m3  Foreshore  Land lying between the high and low watermarks, including beaches.  In BC, foreshore is unceded Indigenous lands or public land (it is not private land) Shoreline Characteristics Reservoirs can have a jagged shoreline because they consist of flooded river valleys Shoreline Regularity Index (SRI)  Measures how the shape of a lake deviates from that of a circle  Minimum is SRI 1.0  Circular lake has the least shoreline  Higher is SRI 4+  Convoluted shoreline of Reservoir  Shoestring shape  Lots of shoreline + shallow = significant littoral zone Kootenay Lake  SRI = Shoreline length/Circumference of Area 405,082𝑚𝑚  SRI = 2 𝐴𝐴𝜋𝜋 405,082𝑚𝑚  SRI = 2√421730,000𝜋𝜋  SRI = 405,082𝑚𝑚⁄72780𝑚𝑚  SRI = 5.56 Hydraulic Residence Time  Flushing Rate  Approximate time any molecule of water spends in a lake.  Important for pollution studies and nutrient regimes HRT (yrs) = Volume (m3) x 1yr Q m3/s 31,536,000 s/yr Or HRT(yrs) = Volume (Lake) (m3) Basin Area (m2) x Avg. Precip (m/yr)x(.85) Kootenay Lake  HRT (yrs) = Volume/Q x 1yr/31,536,000 s/yr  HRT = 39,642,620,000m3/782 m3/s x 1yr/31,536,000 s/yr  HRT = 1.6 years  HRT = Volume/Basin area x precip yr x.85  HRT = 39,642,620,000m3/31,264,000,000m2 x.9m x.85  HRT = 1.66 years Light Penetration  Photic Zone  Surface down to where about 1% of light penetrates  Zone of net oxygen production  Photosynthesis > Respiration  Depth depends on the clarity of the water  Aphotic Zone  Bottom of the photic zone to the bottom of the lake  More carbon dioxide is produced than oxygen  Respiration > Photosynthesis Crater Lake Transparency Secchi Disk Depth Avg 1-10 m Crater Lake 43m D1 – disappearance D2 – reappearance Photic Zone is 2.5 x Secchi Disk Depth