Title slide Wayne Wurtsbaugh & Michelle Baker Utah State University TOPO-MORPHOMETRIC ANALYSIS OF LAKE-STREAM INTERACTIONS IN ALPINE WATERSHEDS Title slide Wayne Wurtsbaugh & Michelle Baker Utah State University

Stream Ecologists are from Saturn… Limnologists are from Mercury Noted Stream Ecologist Normal Lake Limnologist With limited exceptions stream ecologists and lake limnologists don’t talk to each other, despite the fact that the flowing and lacustrine ecosystems are often closely linked in time and space.

Landscape Approaches to Limnology Recent Advances Landscape Approaches to Limnology Kratz et al. 1991, 1997 Soranno et al. 1999 Hershey et al. 1999 Riera et al. 2000 } Lake placement in the watershed Baron and Campbell 1997 Hillbricht-Ilkowska 1999 Kling et al. 2000 Chemical interactions across stream-lake landscapes { Richardson & Mackay 1991 Insect communities & processes at lake outlets Fisher (1997) Wiens (2002) Landscape ecology of streams

An important question: How do complex patterns of lakes and streams influence ecosystem function? Boulder Chain Lakes Watershed, White Cloud Mountains, Idaho A B E C D

Study site Sawtooth Mountains, ID Boise Logan

Glaciated watershed map Glaciated Salmon River Watersheds 1 to 25 lakes Mean inter-lake distance = 2.8 km Glaciated watershed map Sawtooth Mountains, ID

Methods: Morphometric Estimates Lake Volumes Stream Areas, Depths & Volumes Stream Order 1 2 3 4 Width (m) 1.6 3.7 5.8 12.4 Depth (m) 0.09 0.09 0.27 0.36

PHYSICAL COMPARISONS OF WATERSHEDS WITH AND WITHOUT MAJOR LAKES Watershed Volumes Residence Time (1000 m3) @ mean discharge (days) Stream Lakes % lake “Lakeless” (N. Alturas) 6.6 22.8 77.6% 2 Yellow Belly 16 9145 99.8% 101

PHYSICAL COMPARISONS OF WATERSHEDS WITH AND WITHOUT MAJOR LAKES Radiation / airshed Watershed Interaction Interaction Strength Strength Area (ha) Perimeter (km) Watershed Streams Lakes % Stream Lakes % Lake Lake “Lakeless” 9.1 3.9 30% 4.4 0.7 14% ..(N.Alturas) Yellow Belly 5.2 143 96% 31.5 10.0 24% PHYSICAL COMPARISONS OF WATERSHEDS WITH AND WITHOUT MAJOR LAKES

Significance: (1) How do lakes influence watershed temperatures? Yellow Belly L. Stanley Lake X Thermistors Yellow Belly watershed Stanley Creek watershed Brian Heiland, UC Davis

Effect of Lakes on Watershed Temperatures Data of Brian Heiland (UCD) 2000 Yellow Belly Watershed Stanley Watershed

So What? Trout growth: 6°  12°C, +370% (Elliott 1994) Adams et al. 2000 Ecosystems

Yellow Belly Creek Watershed (2) Lakes are dissolved nutrient traps whereas streams are “sources” of dissolved nutrients 16 2.5 2.0 12 Temp 1.5 Temperature (°C) NO3 (µM) ± S.E. 8 1.0 4 NO3 0.5 Yellow Belly Creek Watershed Lake Lake Lake 2 4 6 8 10 12 Distance from inflow of headwater lake (km) Yellow Belly Watershed

(3) When present, lakes dominate aquatic primary production This figure must have an error in it--check Areal production Watershed production - Lake - -Stream “Lakeless” Stream productivity: Minshall et al. 1992 Lake productivity: Wurtsbaugh (unpublished)

Lake seston is removed relatively slowly (4) A large proportion of streams in these watersheds are under the influence of seston exported from lakes Lake seston is removed relatively slowly At 0.35 m3 s-1, Maciolek & Tunzi 1968

Watersheds with more lakes have had higher TN at terminal end The influence of lakes 2003 Baseflow Watersheds with more lakes have had higher TN at terminal end

Summary When lakes are present in watersheds, they dominate water area & volume of the channalized flow, and thus interactions with radiation & gas exchange. The large volumes greatly increase water & nutrient residence times. Streams dominate perimeters & thus interaction with the terrestrial watershed Many ecological functions are dependent on lake-stream interactions The spatial patterning of streams and lakes is thus a crucial factor influencing watershed function

Closing photo