Comparison of hydrological control in streamwater residence times across headwater catchments
Abstract
The residence time (or transit time) is an important parameter to consider the runoff generation processes and/or biogeochemical processes of the catchments. Many types of tracers and techniques have been applied to estimate the residence time in many studies. However, the estimates can different depending on the applied tracers. This fact implies that the discussion about how the residence time determined is still insufficient. The estimation of residence time with stable isotope is conducted based on the damping and lag of the tracer output signal (groundwater and/or streamwater) compared to the input signal in rainfall through the water transport within the catchment. The long-term and continuous isotope data is necessary to apply this method for precise estimations in each catchment. This fact is sometimes a difficulty for the inter-comparison of residence time between the sites. To overcome this difficulty, the inverse transit time proxies (ITTPs) were proposed by a simple metric of isotopic tracer damping, using the ratio of standard deviation of d18O in streamwater to the standard deviation of d18O in precipitation, and applied in some studies. The smaller ITTPs stand for the longer residence time . In this study, we applied this index for 25 headwater catchments from 8 sites in Japan to compare the controlling factors of streamwater residence time across the catchments considering geomorphic and hydrological parameters.
The relationship between the catchment area and the residence time in streamwater showed that the variation of residence time s were larger among smaller catchment, and it was decreased among larger catchments. This relationship was explained by considering the water balance of each catchment. There were two types in smaller catchments of less than 10 ha; in catchments with low runoff ratios and large losses, recharge to the groundwater was dominant and residence time was short, and in catchments with high runoff ratio and small loss, runoff was dominant and residence time tends to be long. It became clear that the residence time became longer because all the water flowed out when the catchment area became 10 ha or more. Therefore, considering catchment water balance is useful to clarify the control of residence time by hydrological process.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H31O1965K
- Keywords:
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- 1804 Catchment;
- HYDROLOGY;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1839 Hydrologic scaling;
- HYDROLOGY;
- 1847 Modeling;
- HYDROLOGY