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| Titel |
Catchment conceptualisation for examining applicability of chloride mass balance method in an area with historical forest clearance |
| VerfasserIn |
H. Guan, A. J. Love, C. T. Simmons, J. Hutson, Z. Ding |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 14, no. 7 ; Nr. 14, no. 7 (2010-07-13), S.1233-1245 |
| Datensatznummer |
250012366
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| Publikation (Nr.) |
 copernicus.org/hess-14-1233-2010.pdf |
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| Zusammenfassung |
| Of the various approaches for estimating groundwater recharge, the chloride
mass balance (CMB) method is one of the most frequently used, especially for
arid and semiarid regions. Widespread native vegetation clearance, common in
many areas globally, has changed the land surface boundary condition, posing
the question as to whether the current system has reached new chloride
equilibrium, required for a CMB application. Although a one-dimensional CMB
can be applied at a point where the water and chloride fluxes are locally in
steady state, the CMB method is usually applied at a catchment scale owing
to significant lateral flows in mountains. The applicability of the CMB
method to several conceptual catchment types of various chloride equilibrium
conditions is examined. The conceptualisation, combined with some local
climate conditions, is shown to be useful in assessing whether or not a
catchment has reached new chloride equilibrium. The six conceptual catchment
types are tested with eleven selected catchments in the Mount Lofty Ranges
(MLR), a coastal hilly area in South Australia having experienced widespread
historical forest clearance. The results show that six of the eleven
catchments match a type VI chloride balance condition (chloride
non-equilibrium with a gaining stream), with the ratios of stream chloride
output (O) over atmospheric chloride input (I), or catchment chloride O/I
ratios, ranging from 2 to 4. Two catchments match a type V chloride balance
condition (chloride non-equilibrium with a losing stream), with catchment
chloride O/I ratios about 0.5. For these type V and type VI catchments, the
CMB method is not applicable. The results also suggest that neither a
chloride O/I ratio less than one nor a low seasonal fluctuation of
streamflow chloride concentration (a factor below 4) guarantees a chloride
equilibrium condition in the study area. A large chloride O/I value (above
one) and a large fluctuation of streamflow chloride concentration (a factor
of 10 and above) generally indicates either a chloride disequilibrium, or
cross-catchment water transfer, or both, for which the CMB method is not
applicable. Based on regression between chloride O/I values and annual
precipitation for type VI catchments, a catchment with annual precipitation
of 900 mm in MLR has most likely reached new chloride equilibrium, and the
CMB method can be applied if no cross-catchment water transfer occurs. CMB
is applied to one catchment at chloride equilibrium, suggesting a net
groundwater recharge of 27 mm/yr, about 3% of annual precipitation. |
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