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Scale-dependency and Sensitivity of Hydrological Estimations to Land Use and Topography for a Coastal Watershed in Mississippi - Vladimir J. Alarcon and Charles G. O’Hara
 

Scale-dependency and Sensitivity of Hydrological Estimations to Land Use and Topography for a Coastal Watershed in Mississippi - Vladimir J. Alarcon and Charles G. O’Hara

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Scale-dependency and Sensitivity of Hydrological Estimations to Land Use and Topography for a Coastal Watershed in Mississippi - Vladimir J. Alarcon and Charles G. O’Hara

Scale-dependency and Sensitivity of Hydrological Estimations to Land Use and Topography for a Coastal Watershed in Mississippi - Vladimir J. Alarcon and Charles G. O’Hara

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    Scale-dependency and Sensitivity of Hydrological Estimations to Land Use and Topography for a Coastal Watershed in Mississippi - Vladimir J. Alarcon and Charles G. O’Hara Scale-dependency and Sensitivity of Hydrological Estimations to Land Use and Topography for a Coastal Watershed in Mississippi - Vladimir J. Alarcon and Charles G. O’Hara Presentation Transcript

    • Scale-dependency and Sensitivity of Hydrological Estimations to Land Use and Topography for a Coastal Watershed in Mississippi Vladimir J. Alarcon and Charles G. O’Hara
    • Introduction
      • The spatial variability of the physical characteristics of the terrain influences the flow regime in watersheds.
      • Through Internet, physiographic datasets can be easily downloaded for geo-processing.
        • Topographical and land-use/land-cover datasets are used for the purposes of watershed delineation, land use characterization, geographical positioning of hydro-chemical point sources, etc.
    • Introduction
      • Several previous researches have explored the sensitivity of hydrological estimations to topographical or land use datasets.
      • Few have assessed the sensitivity of hydrological estimations to combined swapping of topographic and land use datasets.
        • Objective : This paper explores the effects of using several different combinations of topographical and land use datasets in hydrological estimations of stream flow.
    • Methods
      • Study area:
        • Two river catchments
          • Jourdan River
            • Drains 88220 ha with an average stream flow of 24.5 m3/s.
          • Wolf River
            • Drains slightly more than 98350 ha with an average stream flow of 20.1 m3/s.
          • Major contributors of flow to the St. Louis Bay, MS, USA.
    • Methods
      • Topographical data:
        • USGS DEM
          • 3 arc-second (or 1:250,000-scale) approx. 300 m spatial res.
        • The National Elevation Data (NED) dataset
          • 1 arc second, approximately 30 m spatial res.
        • NASA Shuttle Radar Topography Mission
          • 30 m spatial resolution near-global topography data product for latitudes smaller than 60 degrees.
        • Intermap’s Interferometric Synthetic Aperture Radar (IfSAR) Digital Elevation Models 1:24,000 scale topographic quadrangle map series, 5 m spatial res.
    • Methods
      • Land Use data:
        • USGS GIRAS
          • Minimum mapping unit of 4 hectares and a maximum of 16 hectares (equivalent to 400 m spatial resolution).
        • National Land Cover Data (NLCD)
          • 21-class land cover classification scheme, spatial resolution of the data is 30 meters.
        • The NASA MODIS MOD12Q1 Land Cover Product (MODIS/Terra Land Cover
          • 1000 m spatial resolution, classified in 21 land use categories, covers most of the globe and is updated every year.
    • Methods
      • Geo-processing
      LAND USE TOPOGRAPHY
    • Methods
      • Data processing : all the datasets were geo-processed for input into the Hydrological Simulation Program Fortran (HSPF).
    • Methods
      • Hydrological Modeling
        • Hydrological Simulation Program Fortran (HSPF).
          • Simulation of non-point source watershed hydrology and water quality.
          • Time-series of meteorological/water-quality data, land use and topographical data are used to estimate stream flow hydrographs and polluto-graphs.
          • The model simulates interception, soil moisture, surface runoff, interflow, base flow, snowpack depth and water content, snowmelt, evapo-transpiration, and ground-water recharge.
    • Methods
      • Processing steps for generating the hydrological model’s data input.
      • BASINS, GEOLEM, ArcGIS, and Arc Info were used.
      • These GIS systems extracted land use and topographical information for input into HSPF.
      • HSPF was launched from within the BASINS system.
    • Methods
      • HSPF models for Jourdan and Wolf watersheds.
      • USGS stream flow gauge stations at:
        • Catahoula (Jourdan River)
        • Lyman, and Landon (Wolf River)
      • were used for hydrological calibration of the models.
    • Results
      • Results of statistical fit between simulated and measured stream flow for Jourdan River watershed
      GIRAS (400 m)
    • Results
      • Results of statistical fit between simulated and measured stream flow for Wolf River watershed
    • Conclusions
        • Scale and spatial resolution of digital land use and topography datasets do not affect the statistical fit of measured and simulated stream flow time-series, when using the Hydrological Program Fortran (HSPF) as the hydrological model recipient of land use and topographical data.
        • When the input to HSPF comes from the coarsest spatial resolution datasets (MODIS land use and USGS DEM topography), HSPF simulated stream flow show equivalent statistical fit to measured stream flow as when finer spatial resolution datasets are combined.
        • This suggests that stream flow simulation is not sensitive to scale or spatial resolution of land use and/or topographical datasets.
    • Conclusions
        • Since HSPF is a lumped-parameter hydrological model, the summarization of physiographic information (before it is input to the model) is a required step.
        • This pre-processing of raw land use and topographical data (re-classification, averaging of data per sub-basin, etc.) may be a factor that explains the insensitivity of simulated stream flow to land use and topographical datasets swapping, when using HSPF.
        • Future studies should explore the effects that this swapping may have when using distributed hydrological models.