Bachelor thesis - Ecosystem water balance and subsurface hydrology
(a) Ecosystems in the AET vs. PET space. (b) Ecosystems in the Bukyko space (AET/P vs. PET/P). Each point represents a site from which flux measurements are available. A selection of sites from which data were used in this and previous chapters are highlighted. AET, PET, and P are multi-year means of annual sums.
Supervision: Prof. Benjamin Stocker
Background
Exchange fluxes of water vapour between ecosystems and the atmosphere are commonly measured using eddy-covariance technique. This gives information about how much water is transpired by plants and evaporated from soil and plant surfaces. Such fluxes are measured across a hundreds of sites globally, data is available and regularly used in our group, and interesting patterns emerge. For example, some sites appear to evaporate a large fraction of annual precipitation. Some even more than annual precipitation. This raises important questions: Is this a data artefact? Or are there topographic and hydrological patterns that can explain differences between sites?
Aim
This thesis will perform data analyses to relate measured annual mean evapotranspiration to site characteristics. Additional data will be prepared for characterising sites in terms of hydrological, topographic, soil, vegetation, and other aspects. The hypothesis to be tested is that sites that exhibit a high ratio of mean annual evapotranspiration over precipitation are located in topographic depressions, where subsurface water flow supplies water for evapotranspiration.
Requirements
- The student is motivated to work with large datasets of the terrestrial biosphere.
- Experience working with R or other data science tools are an advantage.
- The student writes the thesis in English.
Literature
- Land in the Earth System Chapter Ecohydrology
- Williams, C. A., Reichstein, M., Buchmann, N., Baldocchi, D., Beer, C., Schwalm, C., Wohlfahrt, G., Hasler, N., Bernhofer, C., Foken, T., Papale, D., Schymanski, S., and Schaefer, K.: Climate and vegetation controls on the surface water balance: Synthesis of evapotranspiration measured across a global network of flux towers, Water Resources Research, 48, https://doi.org/10.1029/2011WR011586, 2012.
- Thompson, S. E., Harman, C. J., Konings, A. G., Sivapalan, M., Neal, A., and Troch, P. A.: Comparative hydrology across AmeriFlux sites: The variable roles of climate, vegetation, and groundwater, Water Resources Research, 47, https://doi.org/10.1029/2010WR009797, 2011.
