Direct Quantification of Groundwater Exports From Headwaters to Higher-Order Streams
Abstract
Groundwater subsidy, defined as out-of-catchment groundwater flow exported from a headwater catchment to higher-order stream, was poorly quantified and characterized in headwater literature. Here we couple a new semi-analytical free-surface integrated flow and transport model with tracer (and hydrometric) observations from the well-studied 4.5-ha M8 headwater catchment in the Maimai experimental watershed, to quantify the magnitude, age, and flow paths of the headwaters groundwater subsidies at the Maimai. Our results show that more than 50% of groundwater recharged in Maimai headwaters subsidizes their parent watershed. The relative proportion of headwaters groundwater subsidies is inversely proportional to recharge rate and/or directly proportional to slope angle. Our results also show that the age of the headwater groundwater subsidies is more than 500 years, almost 9 times older than the age of within-catchment groundwater flow contributions. These findings highlight the need to consider headwaters groundwater subsidies in groundwater management.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H31L2102A
- Keywords:
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- 1804 Catchment;
- HYDROLOGYDE: 1839 Hydrologic scaling;
- HYDROLOGYDE: 1847 Modeling;
- HYDROLOGYDE: 1879 Watershed;
- HYDROLOGY