THE INFLUENCE OF LANDSCAPE STRUCTURE ON STORAGE AND STREAMFLOW GENERATION IN A PIEDMONT CATCHMENT

Streamflow;Catchment Storage;Runoff Generation;Baseflow;Quickflow;Drought;Transport Modeling;Piedmont;Deeply Weathered;Geography & Environmental Engineering

Putnam, Shane MHarman, Ciaran J ;

Johns Hopkins University

关键词: Streamflow;    Catchment Storage;    Runoff Generation;    Baseflow;    Quickflow;    Drought;    Transport Modeling;    Piedmont;    Deeply Weathered;    Geography & Environmental Engineering;   

Others  :  https://jscholarship.library.jhu.edu/bitstream/handle/1774.2/60111/PUTNAM-DISSERTATION-2018.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: JOHNS HOPKINS DSpace Repository

【 摘 要 】

The storage of water and generation of streamflow are fundamental catchment functions. The specific way in which a catchment performs these functions is inextricably tied to the structure of the catchment, including the thickness/texture of soil, depth to impermeable bedrock, and presence of riparian areas with shallow water tables. Accordingly, catchments with different landscape structures will respond differently to hydroclimatic variability. The majority of field investigations into streamflow generation have concentrated on high relief or recently glaciated landscapes where soils are thin and overlie an assumed impermeable bedrock layer. In contrast, relatively little research on streamflow generation has been conducted in deeply weathered regions, such as in the Piedmont Physiographic Province of the eastern United States. Of those studies that have focused on these regions, many have highlighted the potential of deeply weathered landscapes to store large quantities of water, which may be important for maintaining streamflow during droughts.In the research effort reported here, catchment storage and streamflow generation in a prototypical Piedmont headwater catchment were investigated through field data collection and modeling. The analysis aimed to test hypotheses relating hydrologic function to Piedmont landscape structure. The 37-hectare, forested Pond Branch Catchment of northern Maryland was instrumented to collect data on hillslope spring discharge, hydrometeorological data, riparian well water levels, as well as three years of high frequency precipitation and streamflow stable water isotope data. Additional data were collated from other sources on catchment discharge, soil moisture, and remotely-sensed land surface properties. These data were used in combination with recession analysis, water balance models, and transport modeling using StorAge Selection functions to estimate storage and characterize streamflow generation. The storage within the hillslope and underlying weathered bedrock was found to be the main driver of the slowly changing baseflow component of streamflow, which made up 85% of total discharge. In addition, the rapidly responding quickflow component of streamflow was proven to be composed of a combination of direct precipitation and return flow from the toe of the hillslope, which was generated as saturation excess overland flow at the riparian-hillslope boundary. The importance of the storage structure in controlling the emergent catchment response to precipitation variability was revealed when a relatively small reduction in rainfall during early spring (when the deep flow system is typically recharged) of water year 2016 produced what may be a decadal drought in the groundwater level, resulting in persistently low baseflow discharge for at least two years after. The role of the deeply weathered landscape structure of Pond Branch in controlling storage and streamflow generation highlights the importance of studying diverse landscapes with different landscape structures in order to gain understanding into catchment functions.