Stream/Ground Water Ecotones: Hydrology, Biogeochemistry and Ecology

河流是复杂的三维生态系统，地表水和地下水是相互作用的，地表和地下之间的界面影响着河流和地下水之间的水和溶质的迁移，并随着气候的变化而变化。这一研究项目的主要目标是量化源头溪流地下水/地表水交错带的水的来源和流动动态，并确定这些相互作用引起的生物、地球化学和生态反应。三个目标是核心。首先，确定地下水/地表水交错带的水文。将对三个不同冲积沉积物类型(细粒到粗卵石)的山地集水区进行测量。将使用以地表传输和与地下交换为特征的水文模型(OTIS)、地下水交错带内的三维流动动力学(MODFLOW)以及从上坡向河流的山坡引水(TOPMODEL)。这些模型将被用来描述水源集水区的瞬时水文性质，并量化地下水/地表水交换的时间变化。其次，将对交错带的三维生物地球化学结构进行研究。它们将描述河流下流(地下水再变化)和上升(地下水排放)段的生物地球化学过程的垂直分布。此外，还将决定浸水或干燥是否会使许多微生物过程重新定位。第三，他们将测量生物群落对水文交换变化的反应。具体而言，将开展研究，以评估底栖藻类组合的群落结构和生物量、初级生产力和呼吸速率，以及对河流-含水层界面藻类群落结构和演替的控制。地表水和地下水之间的交错带极其重要。在陆地部分，河岸带对改善水质和野生动物栖息地至关重要。水生部分包括一个动态的次表层，它调节营养含量和循环。维。T随1996年的反应和排放而变化。

Streams are complex three-dimensional ecosystems in which surface and ground water components are interaction the interface between the surface and subsurface affects the transfer of water and solutes between the stream and ground water and varies in response to variable climate. The main objectives of this research project are to quantify the sources and flow dynamics of water at the ground water/surface water ecotone of headwater streams and to determine biogeochemical and ecological responses resulting from these interactions. Three objectives are central. First, the hydrology of the ground water/surface water ecotone will be determined. Three montane catchments with different alluvial sediment types (fine-grained to coarse cobble) will be instrumented. Hydrologic models that characterize surface transport and exchange with the subsurface (OTIS), three-dimensional flow dynamics within the ground water ecotone (MODFLOW), and hillslope routing of water from the upslope to the stream (TOPMODEL) will be used. These models will be used to describe the transient hydrologic nature of headwater catchments and to quantify the temporal variation in ground water/ surface water exchange. Seco nd, the three-dimensional biogeochemical structure of the ecotone will be investigated. They will describe the vertical distribution of biogeochemical processes in downwelling (ground water rechange) and upwelling (ground water discharge) reaches of streams. In addition, the will determine whether flooding or drying will relocate many microbial processes. Third, they will measure the response of biotic communities to variation in the hydrologic exchange. Specifically, studies will be undertaken to assess the community structure and biomass of benthic algal assemblages, rates of primary production and respiration, and controls on algal community structure and succession in the stream-aquifer interface. The ecotone between surface waters and ground waters is extremely important. The terrestrial portion, the riparian zone is crucial to improving water quality and wildlife habitat. The aquatic component includes a dynamic subsurface that regulates nutrient content and cycling. ve. T varies in response to and discharge verying 1996.