Emergent landscape patterns in stream ecosystem processes resulting from groundwater/surface water interactions

The overall scientific objective of this study is to understand how groundwater, supplied to rivers via inter-basin transfers (i.e., from outside the immediate watershed), affects how tropical streams function in the long term (>25 yrs). The project is based in lowland Costa Rica, where solute-rich groundwater account for over half of stream discharge in the dry season. This groundwater is naturally-rich in nutrients such as phosphorus (P), with levels higher than those typically found below sewage treatment plants. Prior research has shown that landscape patterns in stream chemistry (resulting from variation in solute-rich groundwater inputs) reflect rates of primary production and decomposition. This project continues to build a long-term (1988-present) data set on stream solute chemistry, which is the only one for lowland primary rainforests of Central America. The investigators are relating long-term trends in stream chemistry to large-scale climatic phenomena: solute-rich groundwater (also rich in bicarbonates) buffer receiving streams against increases in acidity during periods following El Nino-related droughts, while those streams that do not receive solute-rich groundwater experience dramatic increases in acidity. An outgrowth of the project is the development of an environmental outreach program that focuses on water quality and quantity issues in tropical regions.