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

拟议的项目是对哥斯达黎加低地热带雨林的水文地质进行的成对分水岭研究。拟议的项目将使用水文和地球化学测量：1确定Arboleda和Taconazo流域的年度和每月水和溶质预算，2评估我们在研究地点产生径流的概念模型：Arboleda中发现的高溶质浓度是由于受地热改造的地下水的跨流域转移，而Stream Flow是这种地下水和来自研究溪流相邻山坡的低溶质当地水的混合物。将通过测量输入(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)来建立相邻两个流域的水和溶质预算。研究的溶质有CL、SO4、Na、K、Mg、Ca和总磷。拟议的30个月项目将提供整整两年(24个月)的水和化学品预算数据。拟议的研究将利用和建立哥斯达黎加La Selva生物站独特的、新建的水文基础设施(可能是所有雨林研究地点中最好的)，使研究能够避免由于对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)。结果将是低地雨林流域的第一批高质量水和化学品预算之一。这些预算将明确包括在La Selva发生的重大地下流域间转移(地表地形分隔带下的地下水流动)；拟议的成对分水岭办法非常适合这一点。虽然通常认为流域间转移不存在或被认为是一个需要避免的“问题”，但许多外地地点的经验表明，这可能是规则而不是例外，因此应直接加以处理。拟议的项目将作为一个例子，说明如何在其他研究地点做到这一点。拟议的研究还将提供与生态学家合作的大型跨学科项目所需的关键水文和化学背景信息，内容涉及热带雨林的碳循环速率以及地下水排放到溪流对热带雨林溪流生态的影响。

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.