Rain or Shine: Changes in Water and Mass Fluxes of a Pristine Watershed in Response to Rainfall Events and Regional Drought
Abstract
Small watersheds of first and second order streams are ideal for studying how water and mass fluxes from different sources change over timescales ranging from single storm events to inter-annual climate phenomena. We studied stream sources and fluxes within two nested watersheds: the first order Howler Monkey stream and the downstream Rio Chachagua. These watersheds are located within a tropical montane rainforest in Alajuela province, Costa Rica, which has been experiencing a serious drought that began in November 2018. During July 2018, we measured volumetric and mass fluxes into a 75 m reach along the Howler Monkey stream. We found that the volumetric discharge between the upstream and downstream of this reach doubles while total dissolved solids (TDS) decreases. This results in an overall increase in mass fluxes of major ions. Building on the findings from 2018, we hypothesize that the drought in 2019 increased the concentration of TDS in soil and ground waters by lengthening the contact time between mineral surfaces and recharge water. The delayed start of the 2019 wet season was accompanied by sporadic storm events, which flushed higher elemental fluxes into the stream compared to those measured during the same time of year in 2018. Combining the two years of data enables us to identify mechanisms for streamflow generation in these watersheds using an End Member Mixing Analysis approach. Understanding the response of these two watersheds to storms and drought will help us predict how future climate change will affect the mass fluxes and volumetric discharge of these watersheds.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H43G2066R
- Keywords:
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- 1804 Catchment;
- HYDROLOGY;
- 1806 Chemistry of fresh water;
- HYDROLOGY;
- 1848 Monitoring networks;
- HYDROLOGY;
- 1895 Instruments and techniques: monitoring;
- HYDROLOGY