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<br />78 <br /> <br />~ <br />~ <br />Q <br />~ <br />o <br />~ 4 <br />::! <br />... <br />~ <br /> <br /> <br />, <br /> <br />\ <br /> <br />~/' <br /> <br /> - <br /> Stream Doainant Sh~ llip.llr1an W.tel~ Water <br /> She Substrate line Streambed Influence Temp. Temp.. <br /> Type 1 Surface Flue.. <br /> t. An~a <br /> Ratio tuatl! <br /> SllLall Coarse High Shaded Lessl!t" Cold <br /> 85% Oail y , <br /> of Boulder Closed Fluet. Cool <br /> Total Rubble Canopy. Water <br /> Mllage Gravel Shading Set.. <br /> (Strong) , <br /> ,762.500 Ground <br /> Water <br /> Effe(:t <br /> - I <br /> Medium Coarse Reduced Noe Greal;er , Transi- <br /> 12% to Shaded Dail~, cion <br /> Fine fluet. Zones , <br /> 390,000 Open Open" <br />: Rubble Less <br /> Gravel (Medium) Ground- <br /> Sand Water <br /> ""~ <br />!Larger Fine Low Open Lesser l.;anz: <br /> 3% Daily \Oater <br /> 91,500 Sand (Weak) Fluet. Streams <br /> Modera- <br /> Hiles Silt tlon <br /> by .l,lrgel <br /> watel, I <br /> volw~e <br /> - <br /> <br />~ <br />IUPARlAN _: <br />VEGETATION <br /> <br />2 STllEAKBA.~ <br /> <br />), <br /> <br />800 M <br />CHANNEL WIDTH <br /> <br />Figure 2. Comparison of the physical habitat of ssall, medium and large streams according co the <br />River Cont1nuua Concept. <br /> <br />than downstream reaches, a coarse substrate composed of boulders, rubble <br />and gravel and a conspicuous absence of finE' sand and ,sediment (with many <br />exceptions). The size of the drainage area and climate strongly influence <br />discharge which may show great variability throughout the year. During <br />non-runoff periods, stream flow is maintainE,d by ground water (overflow). <br /> <br />Headwater feeder streams have the lowest ratio between shoreline <br />length and streambed surface area of the three ecological zones (small, <br />medium, and large). The low ratio permits riparian zone vegetation to <br />form a closed canopy over the channel. In contrast to medium-'size streams, <br />the elimination of sunlight by the vegetative canopy precludes instrenm <br />autochthonous primary production except for a small am,)unt of a1,:"e, moss <br />and periphyton (Figure 3). Autochthonous primary prod'Jction may account <br />for one percent or less of the energy supply of first order streams (Fisher <br />and Likens 1972, 1973). <br /> <br />Temperatures encountered in headwater lltreams reflect ground water <br />temperatures and the natural temperature gnldient from cooler upstream <br />water to warmer downstream water. The rate of change in temperature <br />patterns is affected by many factors including climate, altitude, volume of <br />flow, tree cover canopy, the relationship of volume to surface area, <br />accrual of ground water, melt water from snow and ice, and turbidity. In <br />contrast to downstream reaches, headwater sl:reams maybe characterized as <br /> <br />"'----_._~--,- <br />