 |
| Titel |
Runoff generating processes in adjacent tussock grassland and pine plantation catchments as indicated by mean transit time estimation using tritium |
| VerfasserIn |
M. K. Stewart, B. D. Fahey |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1027-5606
|
| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 14, no. 6 ; Nr. 14, no. 6 (2010-06-24), S.1021-1032 |
| Datensatznummer |
250012340
|
| Publikation (Nr.) |
 copernicus.org/hess-14-1021-2010.pdf |
|
|
|
|
|
| Zusammenfassung |
| The east Otago uplands of New Zealand's South Island have long been studied
because of the environmental consequences of converting native tussock
grasslands to other land covers, notably forestry and pasture for stock
grazing. Early studies showed that afforestation substantially reduced
annual water yield, stream peak flows, and 7-day low flows, mainly as a
consequence of increased interception. Tritium measurements have indicated
that surprisingly old water is present in catchments GH1 and GH2, and the
small headwater wetland and catchment (GH5), and contributes strongly to
baseflow. The data have been simulated assuming the presence of two types of
water in the baseflow, young water from shallow aquifers connecting hillside
regolith with the stream, and old water from deep bedrock aquifers,
respectively. The mean transit time of the young water is approximately one
month, while that of the old water is 25–26 years as revealed by the
presence of tritium originating from the bomb-peak in NZ rainfall in late
1960s and early 1970s. Such a long transit time indicates slow release from
groundwater reservoirs within the bedrock, which constitute by far the
larger of the water stores. Comparison of the results from catchments GH1
(tussock) and GH2 (pine forest) suggests that about equal quantities of
water (85 mm/a) are contributed from the deep aquifers in the two
catchments, although runoff from the shallow aquifers has been strongly
reduced by afforestation in GH2. This study has revealed the presence of a
long transit time component of water in runoff in a catchment with
crystalline metamorphic bedrock. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|