LTREB: Emergent Landscape Patterns in Stream Ecosystem Processes Resulting from Groundwater/Surface Water Interactions

本研究的总体科学目标是了解通过流域间转移（即从直接流域外）供应给河流的地下水如何在长期（25年）内影响热带河流的功能。该项目位于哥斯达黎加的低地，在干旱季节，富含溶质的地下水占河流流量的一半以上。这种地下水天然富含磷(P)等营养物质，其含量高于污水处理厂地下的典型含量。先前的研究表明，河流化学的景观格局（由富溶质地下水输入的变化引起）反映了初级生产和分解的速度。该项目继续建立一个长期（1988年至今）的河流溶质化学数据集，这是中美洲低地原始雨林的唯一数据集。研究人员将河流化学的长期趋势与大规模的气候现象联系起来：在厄尔尼诺相关的干旱之后，富溶质地下水（也富含碳酸氢盐）缓冲了接受河流的酸度增加，而那些没有接受富溶质地下水的河流则经历了酸度的急剧增加。该项目的一个成果是发展了一项环境外展计划，重点关注热带地区的水质和水量问题。

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.