Non point source pollutant modeling
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Non-Point Source Pollutant Modeling. Analysis and Prediction David Munn. Non-Point Source Pollution. Does not come from a single source Results from pollutants being washed out of large areas during storms Difficult to model without use of GIS or current NPSP models. Goals.

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Non-Point Source Pollutant Modeling

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Non-Point Source Pollutant Modeling

Analysis and Prediction

David Munn


Non-Point Source Pollution

  • Does not come from a single source

  • Results from pollutants being washed out of large areas during storms

  • Difficult to model without use of GIS or current NPSP models


Goals

  • Predicting pollutant runoff loads

  • Defining problem areas within the Watershed

  • Determine what factors effect pollutant loading

  • Determine streams with highest impact

  • Pollutants considered:

    • BOD

    • Suspended Solids

  • Total Phosphorous

  • Total Nitrogen


Study Area

  • Brazos County

  • Buffered boundary


Process Overview

  • Gather data

  • Data preparation

    • Reproject grids and shapefiles

    • Clip themes and set analysis extents

  • Calculate curve numbers

  • Delineate watersheds

  • Calculate pollutant contribution

  • Determine weighted accumulation

  • Analyze data


Data/Themes

  • DEM

    • TNRIS

  • Soil Classification

    • STATSGO

  • County Boundaries

    • ESRI, Tiger files

  • Land Use/Land Cover

    • Txdata, Provided by Dr. Olivera

  • Precipitation

    • Txdata, Annual and Monthly

  • LULC Pollutant Contribution Data

    • Cornell University Hydraulics Study


Reprojecting

  • Reprojected grids using ArcInfo-Workstation

  • Reprojected geographic shapefiles using CRWR-Vector

  • Data Already in a Projection was reprojected using ArcCatalog

  • Final Projection: State Plane 1927

    • Central Texas, Zone 5376

    • Units = feet


CRWR-Prepro

Burned in Streams

Filled Sinks

Determined Flow Direction

Determined Flow Accumulation

Defined Streams

Segmented Streams

Defined Outlets

Delineated Watersheds

Vectorized Grids

Delineating Watersheds


Curve Numbers

  • Used to determine runoff

  • STATSGO data spatially documents soil types (component makeup)

  • Scripts provided by CVEN 689 Website

    • Soilgrp script – calculates % of hydrologic groups per soil type

    • cn script – creates curve numbers based on soil composition


Rainfall given per month (January)

Calculate Run-off (mm) using SCS method

Map Calculator combined formulas with rainfall and CN

Created new grid giving run-off depth per cell

Run-off


Pollutant Contributions

Q (mm)

Cell size (ft2)

Pollutant Concentration (mg/l)

= Mass (mg)

* Map Calculator


Pollutant Flow/Accumulation

  • Weighted flow accumulation

  • Executed in ArcInfo

  • Assigns weights to cells based on a Grid

Weights

Direction

Accumulation


Analysis

  • Determine what land-uses and soil types contribute the largest amount of pollutants

  • Determine what rivers suffer the greatest impact

  • Locate areas that contribute large masses of pollutants


Land Use Relationships (Zonal Summaries)


Soil Type Relationships(Zonal Summaries)


Impacted Rivers

  • Method

    • Map query

    • Changed to shapefile

  • Results too dependent on general accumulation

  • More statistical work needed


Areas of Concern

* TP / TN

* BOD / SS


Conclusions

  • Urban areas contributed the largest mass of BOD and suspended solids per unit area

  • Agricultural areas contributed the largest mass of Nitrogen and Phosphorous / area

  • Rivers > 700,000 cell accumulation were impacted

  • Soil types differed in impact between pollutants

    • Nutrients:

      Crocket-Luling-Benchley & Zack-Zulch-Booneville

    • BOD and Suspended Solids

      Zack-Zulch-Booneville


Future Applications

  • Determining Pollutant Concentrations

    • Calculate run-off volume using weighted accumulation

    • Sum run-off volumes with base flows

    • Calculate in-stream concentrations

  • Better Statistical Analyis of Impacted Rivers


Problems

  • REPROJECTING!!!!!!!

  • Calculating pollutant contributions

    (map calculator)

  • Floating point analysis


QUESTIONS

What up?


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