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<br />
<br />H
<br />
<br />I
<br />
<br />Field Studies of Mountainous Terrain
<br />
<br />The steep slopes and rocky characteristics of moun-
<br />tainous terrain make it difficult to determine interactions of
<br />ground water and surface water, Consequently, few detailed
<br />hydrogeologic investigations of these interactions have
<br />been conducted in mountainous areas. Two examples are
<br />given below,
<br />A field and modeling study of the Mirror lake area
<br />in the White Mountains of New Hampshire indicated that
<br />the sizes of ground-water flow systems contributing to
<br />surface-water bodies were considerably larger than their
<br />topographically defined watersheds, For example, much of
<br />the ground water in the fractured bedrock that discharges to
<br />Mirror lake passes beneath the local flow system associated
<br />with Norris Brook (Figure H-1), Furthermore, a more exten-
<br />sive deep ground-water flow system that discharges to the
<br />Pemigewasset River passes beneath flow systems associated
<br />with both Norris Brook and Mirror lake,
<br />Studies in mountainous terrain have used tracers to
<br />determine sources of ground water to streams (see Box G), In
<br />addition to revealing processes of water exchange between
<br />ground water and stream water, solute tracers have proven
<br />useful for defining the limits of the hyporheic zone surrounding
<br />mountain streams. For example, solute tracers such as chlo-
<br />ride or bromide ions are injected into the stream to artificially
<br />raise concentrations above natural background concentra-
<br />tions. The locations and amounts of ground-water inflow are
<br />determined from a simple dilution model. The extent that
<br />tracers move into the hyporheic zone can be estimated by the
<br />models and commonly is verified by sampling wells placed in
<br />the study area,
<br />
<br />Figure H-I. Ground-water flow
<br />systems in the Mirror Lake area extend
<br />beyond the topographically defined
<br />surface-water watersheds, (Modilied
<br />from Harte, p, T., and Winter, T,C"
<br />1996, Factors affecting recharge to
<br />crystalline rock in the Mirror Lake area,
<br />Grafton County, New Hampshire: in
<br />Morganwalp. D, W" and Aronson, D.A.,
<br />eds" U.S, Geoiogical Survey Toxic
<br />Substances Hydrology Program-
<br />Proceedings of Technical Meeting,
<br />Colorado Springs, Colorado,
<br />September 20-24, 1993: U,S, Geolog-
<br />ical Survey Water-Resources Investiga-
<br />tions Report 94-4014, p, 141-150,)
<br />
<br />
<br />A
<br />FEET
<br />2,100
<br />
<br />1,800
<br />
<br />1,500
<br />
<br />1,200
<br />
<br />900
<br />
<br />600
<br />
<br />300
<br />
<br />SEA
<br />LEVEL
<br />
<br />
<br />Chalk Creek, Colorado
<br />
<br />
<br />Mirror lake, New Hampshire. (Photograph by
<br />Thomas Winter.)
<br />
<br /> A'
<br /> FEET
<br /> 2,100
<br /> .
<br /> '0
<br /> '> 1,800
<br /> '5
<br /> .
<br /> co
<br /> .
<br /> 0 , 1,500
<br /> '~ ~
<br /> -c ii:
<br /> .
<br /> u .. 1,200
<br /> . .
<br /> 'to .
<br /> , ~
<br />Mirror '"
<br />I .
<br />Lake ,11> 900
<br />E
<br /> ---- <l:
<br /> Bedrock --- 600
<br /> .
<br />
<br />300
<br />
<br />Lower boundary 01-
<br />bedrock as defined
<br />in model
<br />
<br />SEA
<br />lEVEL
<br />
<br />-400
<br />
<br />-400
<br />
<br />o 1,500 3,000 FEET
<br />I I I
<br />
<br />36
<br />
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