Abstract

From catchment to watershed scale, the critical zone community is asking the question of what to measure—and where to measure it—to constrain models and make informed observations about critical zone processes. One of the primary goals of the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) is to scale-up hydrologic models from the catchment scale at Shale Hills (0.08 km2) and Garner Run (1.21 km2) catchments to the larger watershed scale of Shavers Creek watershed (~120 km2). The increase in drainage area of two to three orders of magnitude provides a challenge of increased spatial heterogeneity when constraining hydrologic models. Shavers Creek watershed drains a variety of lithologies and is overlain by both agricultural and forested land uses. In order to overcome the challenge of spatial heterogeneity in Shavers Creek, several synoptic sampling campaigns have been performed to develop high-spatial resolution datasets of solute fluxes in Shavers Creek. These observations have been used to analyze the most important characteristics (land use, lithology, topography, soils) associated with the export of solutes to surface water. Analysis of the relationships between watershed characteristics and solute export will allow model developers at the SSHCZO to understand what model inputs are most powerful in making accurate simulations or predictions of solute fate and transport in this HUC 10 watershed in a temperate climate and upland regime. In recognition that agriculture is a major land use category in the watershed, hydrologic and solute data have also been gathered from the Cole Farm (0.43 km2) subcatchment in the SSHCZO. Using Cole Farm as a proxy for agricultural land use in Shavers Creek provides insight into the partitioning of solutes between shallow and deep groundwater in the agriculturally developed portion of Shavers Creek. High spatial-resolution synoptic sampling data sets, combined with long-term monitoring data sets from subcatchments show that, from a statistical perspective, lithology is the primary control on the export of several solutes generally associated with agriculture (nitrate, sulfate, etc.). This insight is important for model development and extrapolation to ungauged catchments. The work emphasizes significant role of the subsurface in large-scale solute export.

Citation

Callum Richard Wayman*, Tess A Russo, Jonathan M Duncan, Li Li, Brandon Forsythe, Beth Hoagland, Susan Brantley (2018): Land use and lithology controls on export of nitrate and other solutes from headwaters to HUC10 watersheds. Abstract H13J-1861 presented at 2018 AGU Fall Meeting, Washington, D.C., 10-14 Dec .

This Paper/Book acknowledges NSF CZO grant support.