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Non-Point Source Pollutant Modeling

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Non-Point Source Pollutant Modeling

Analysis and Prediction

David Munn

- 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

- 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

- Brazos County
- Buffered boundary

- 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

- 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

- 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

- 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

Q (mm)

Cell size (ft2)

Pollutant Concentration (mg/l)

= Mass (mg)

* Map Calculator

- Weighted flow accumulation
- Executed in ArcInfo
- Assigns weights to cells based on a Grid

Weights

Direction

Accumulation

- 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

- Method
- Map query
- Changed to shapefile

- Results too dependent on general accumulation
- More statistical work needed

* TP / TN

* BOD / SS

- 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

- Nutrients:

- 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

- REPROJECTING!!!!!!!
- Calculating pollutant contributions
(map calculator)

- Floating point analysis

QUESTIONS

What up?