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/ThemesDEM

TNRISSoil Classification

STATSGO County Boundaries

ESRI, Tiger filesLand Use/Land Cover

Txdata, Provided by Dr. Olivera

PrecipitationTxdata, Annual and Monthly

LULC Pollutant Contribution DataCornell 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

Delineating Watersheds

CRWR-Prepro Burned in Streams Filled Sinks Determined Flow

Direction Determined Flow

Accumulation Defined Streams Segmented Streams Defined Outlets Delineated Watersheds Vectorized Grids

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

Run-off

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

Pollutant Contributions     

     

     

     

     

     

     

     

     

Q (mm)

Pollutant Concentration (mg/l)

Cell size (ft2)

= Mass (mg)     

     

     

* Map Calculator

Pollutant Flow/Accumulation

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

 .5 1.0  2.0

1.0  .5  1.0 

.75  1.5  1.5 

.5  .5  1.0 

1.0  .5  1.0

.75 1.0  .5

     

     

     

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

* BOD / SS* TP / TN

Areas of Concern

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?