Landscape-Scale Determinants of the Hydrological and Hydrochemical Responses of Mountainous Catchments

定量了解旱地集水区的水化学响应是水文学家和环境化学家的基本目标。需要这种知识，以确定大气中酸和农用化学品的沉积对集水(陆地和水生)生态系统的潜在影响和已实现的影响，气候变化对水质的影响，以及水文学在重金属和其他微量污染物迁移中的作用。特别是，更好地了解控制水源中溶解有机碳(DOC)变化的因素具有科学意义，至少有两个原因。首先，寻求对这些系统的基本科学理解的水生生态学家主要关心的是湖泊系统的总体碳收支。其次，DOC与其他溶解物质(特别是重金属)有很强的相互作用，因此在河流中污染物的传输中起着重要作用。向集水区表面输送的降雨量、土壤性质和植被覆盖率以及入射太阳辐射的不均一性，可在山区集水区的水文反应中发挥重要作用。在影响化学品(例如DOC)如何从陆地集水区输送到溪流方面，这些异质性可能特别重要。完全描述集水区上的非均质性基本上是不可能的，但在整个集水区尺度上描述水化学动力学很可能是不必要的。一个可能卓有成效的假设是，主导集水区响应的异质性是相对较大的规模，因此可以通过现成的数据--地形、航空摄影和卫星图像--结合现场适度的数据收集计划来识别。拟议的工作将探索这一想法。将确定地形、植被覆盖、积雪和融化以及土壤透过率等空间格局对科罗拉多州顶峰县蛇河水化学反应的影响。空间数据将利用地理信息系统中包含的技术进行分析，并在水文模型(TOPMODEL)的背景下综合，该模型将进行修改，以考虑到已确定的景观尺度的异质性。将使用有关降水、流量、水力传导性和溶解成分(特别是硫酸盐和DOC)的现场数据来评估大尺度非均质性、水文学和水化学反应之间联系的工作假说。

A quantitative understanding of the hydrochemical response of upland catchments is a fundamental goal of hydrologists and environmental chemists. Such knowledge is needed to ascertain the potential and realized effects, for example, of atmospheric deposition of acids and agricultural chemicals on the catchment (terrestrial and aquatic) ecosystems, of changes of climate on water quality, and of the role of hydrology in the transport of heavy metals and other trace contaminants. In particular, an improved understanding of the factors controlling the variation of dissolved organic carbon (DOC) in headwater streams is of scientific concern for at least two reasons. First, the overall carbon budget of lotic systems is of primary interest to aquatic ecologists seeking a fundamental scientific understanding of these systems. Second, DOC interacts strongly with other dissolved substances (heavy metals in particular) and therefore plays an important role in the transport of contaminants in streams. Heterogeneities in the amount of precipitation delivered to the surface of a catchment, in soil properties and vegetation coverage, and in incident solar radiation can pay an important role in the hydrological response of mountainous catchments. These heterogeneities may be particularly important in influencing how chemicals (e.g., DOC) are delivered from the terrestrial catchment to the stream. Complete characterization of heterogeneities over a catchment is essentially impossible, but is likely to be unnecessary for descriptions of hydrochemical dynamics at the scale of a whole catchment. A possibly fruitful hypothesis is that the heterogeneities that dominate the catchment response are relatively large scale and hence can be identified from readily available data--topography, aerial photography, and satellite imagery -- in conjunction with a modest data-collection program in the field. The proposed work will explore this idea. The effects of spatial patterns in topography, vegetation cover, snow accumulation and melt, and soil transmissivity on the hydrochemical response of the Snake River in Summit County, Colorado will be determined. Spatial data will be analyzed using techniques embodied within geographic information systems (GIS) and synthesized in the context of a hydrological model (TOPMODEL) that will be modified to take into account the identified landscape-scale heterogeneities. Field data on precipitation, flow, hydraulic conductivity, and dissolved constituents (sulfate and DOC, in particular) will be used to evaluate the working hypothesis of the links between large-scale heterogeneity, hydrology, and hydrochemical response.