Catchment Hydrology in the Wet Dry Tropics – what are the drivers of spring yield variability in East Sumba, Indonesia?

Shallow groundwater systems are a critical water source to communities in resource poor tropical savanna regions. Karstic landscapes in these regions are particularly prone to water insecurity. Many peoples' livelihoods are constrained by the need to travel significant distances from their homes to obtain water for household and productive use. Springs are particularly important sources of perennial household water supply and can also be culturally and spiritually important features in a landscape. It is crucial to understand controls on groundwater availability in these contexts to support sustainable use and to protect high value water sources.
However, there is limited investigation and development of water resources in these areas. The aim of this study is to increase our understanding of landcover and climate as controls on shallow groundwater availability in the case study area of Haharu district, Sumba, Indonesia. The study focusses on two key research questions: 1) What are the source waters for karst springs in the study area and; 2) What are the controls on fluxes in groundwater recharge?
To address these questions the study employs hydrochemical and isotope analyses of rainfall, surface water, groundwater and plant xylem water to study flowpaths and spring recharge processes. In addition, I investigate hydrologic fluxes relevant to landcover change; test differences in infiltration across sites with differing levels of tree cover, and use remote sensing and modelling to study links between climate, vegetation greenness and soil moisture over time. Finally, interviews are conducted to capture the local understanding of the karst savanna landscape function. The findings of this research will have implications for management of landcover in the wet dry tropics at a catchment scale.