Paired-Watershed Study of Water and Solute Budgets in a Tropical Rainforest

9903243 Genereux拟议项目是对哥斯达黎加的低地热带雨林水文地质进行的成对流域研究。 拟议项目将使用水文和地球化学测量：1确定Arboleda和Taconazo流域的年度和月度水和溶质预算，2评估我们在研究地点产生径流的概念模型：在Arboleda发现的高溶质浓度是由于地热改造地下水的跨流域转移，而径流则代表了地下水和低-从研究溪流附近的山坡上溶解当地的水。通过测量输入，将构建两个相邻流域的水和溶质预算（来自大气和当地/区域地下水系统）和输出（通过溪流和地下水系统）。 待研究的溶质为CL、SO 4、Na、K、Mg、Ca和总磷。 拟议的30个月项目将给予2整年拟议的研究将利用和建立在哥斯达黎加La Selva生物站独特的新建水文基础设施上（也许是任何雨林研究地点中最好的），使研究能够避免由于水文循环测量不足而造成的巨大不确定性（在许多以前的研究中发现）。 其结果将成为低地雨林流域的首批高质量水和化学品预算。 这些预算将明确包括在拉塞尔瓦发生的重大地下流域间转移（地表地形分水岭下的地下水流）;提出的成对流域方法非常适合于此。 虽然流域间的水转移常常被认为不存在或被认为是一个应避免的“问题”，但许多实地的经验表明，这可能是一种规则而不是例外，因此应直接加以解决。 拟议的项目将作为其他研究地点如何做到这一点的一个例子。 拟议的研究还将提供重要的水文和化学背景信息，需要更大的，跨学科的项目与生态学家在雨林中的碳循环速率和对雨林溪流生态的影响，从地下水排放到流。

9903243Genereux The proposed project is a paired-watershed study of the hydrogeology of lowland tropical rainforest in Costa Rica. The proposed project will use hydrologic and geochemical measurements:1 to determine annual and monthly water and solute budgets for the Arboleda and Taconazo watersheds, and2 to evaluate our conceptual model for streamflow generation at the study site: that high solute concentrations found in the Arboleda are due to interbasin transfer of geothermally-modified groundwater, and streamflow represents a mixture of this groundwater and low-solute local water from hillslpes adjacent to the study streams.Water and solute budgets will be constructed for the two adjacent watersheds by measuring inputs (from the atmosphere, and local/regional groundwater systems) and outputs (via streams and the groundwater systems). The solutes to be studied are CL, SO4,Na,K,Mg,Ca, and total phosphorus. The proposed 30-month project will give 2 full years (24 months) of water and chemical budget data.The proposed study will utilize and build on unique, newly-constructed hydrologic infrastructure at La Selva Biological Station in Costa Rica (perhaps the best at any rainforest research site), enabling the study to avoid the large uncertainty (found in many previous studies) caused by inadequate measurement of the hydrologic cycle. Results will be among the first high-quality water and chemical budgets for lowland rainforest watersheds. These budgets will explicitly include the significant Subsurface interbasin transfer (groundwater flow beneath surface topographic divides) that occurs at La Selva; the paired watershed approach proposed is well suited for this. While interbasin transfer is often assumed not to exist or is considered a "problem" to be avoided, experience at many field sites shows that it is probably the rule rather than the exception and therefore should be directly addressed. The proposed project will serve as an example of how this can be done at other study sites. The proposed study will also provide critical hydrologic and chemical background information needed for larger, interdisciplinary projects with ecologists on the rates of carbon cycling in the rainforest and the effects on rainforest stream ecology from groundwater discharge to the stream.