Chapter 15

Issues in Water Quality

What is Water Quality?• Physical

– Sufficient flow to sustain fish and aquatics– Enough pools and riffles– Riparian zone for woody debris

• Chemical– Enough nutrients for primary production– Not too much nutrients or contaminants

• Biological– No exotics plants or animals– No harmful diseases

Water Quality Laws

• Clean Water Act– Regulates discharges

• Point Sources: Wastewater Treatment Plants

• Nonpoint Sources: Agriculture, Forestry

• Safe Drinking Water Act– Regulates water supplies

• Groundwater => Wellhead protection zones

• Surface Water => Source Water Assessments

Water Resource and Landscape Issues

• Water Quality– Overland flow causes rill and gully erosion – Soils have a strong influence on the chemical

composition of water entering streams and wetlands.

– Soils also influence the suitability of groundwater for drinking water.

• Floods & Baseflows– Soil and vegetative conditions determine how rainfall moves

to streams and thus affect baseflows and flood peaks and volumes.

• Site Productivity– Soil moisture limits tree and crop growth in much of the US.

Some parts of the landscape grow trees or crop better because topographic and geologic conditions cause water to accumulate in those areas.

– But subsurface flows may make an area too wet to grow crops.

• Stormwater Management– Hydrologic alteration by development depends on

the degree to which soils are disturbed, vegetation is altered, and land is covered with pavement.

– Appropriate design of stormwater management and treatment facilities is needed to minimize this change.

• Hillslope Stability– Landslides are largely driven by subsurface flow

conditions. – Seepage areas on steep hillslopes are high landslide

danger areas.

• Stream, Slope, and Wetland Geomorphology– Geologic conditions control hydrologic processes

- but runoff patterns and characteristics alter the landscape.

– Runoff and groundwater flow affect streams and wetlands as well as other landscape features.

– Landscapes are never in equilibrium, but some landscapes change much more rapidly than others.

Landscape Factors Controlling Hydrologic Characteristics

• Climate– Cyclonic fronts, thunderstorms, monsoons, ...– Seasonality of precipitation– Precipitation Type - rain, snow, rain-on-snow– Temperature - Humidity - ET regimes

• Soils and Geology– Depth of soils– Soil layering– Infiltration rates– Hydraulic conductivities– Soil moisture characteristic curves

• Topography– Slopes of ground surface– Presence and abundance of wetlands and lakes (also related to

geology, soils, and climate)– Valley morphology (floodplain storage)

• Vegetation– Interception– Macropore development– Evapotranspiration– Development of humus layer– Soil organic content

Forest Management

• Forest streams have less stormflow and total flow– Forest litter (O-Horizon) increases infiltration– Forest canopies intercept more precipitation (higher

LAI)– Forest have higher evapotranspiration rates– Forest soils dry faster, have higher total storage

Best Management Practices, BMPs

• Used to improve soil and water quality

• Harvesting– High-lead yarding on steep slopes reduces soil

compaction– Soft tires reduces soil compaction– Water is filtered using vegetated stream buffers

(SMZs)– Water temperatures also affected by buffers

High Lead Logging

• Roads– Road runoff can be dispersed onto planar and

convex slopes– Broad-based dips can prevent road erosion

Broad-Based Dips

Road Construction

Roadbed Construction

• Site Preparation– Burning a site increases soil erosion and reduces

infiltration– Leaving mulch on soils increases infiltration– Piling mulch concentrates nutrients into local hot

spots– Distributing mulch returns nutrients to soils– Some herbicides cause nitrate increase in streams

Agricultural Land Management

• Overland flow is a main concern in agriculture– increases soil erosion, nutrients, and fecal coliform

increases herbicides, pesticides, rodenticides, fungicides

• Plowing– exposes the soil surface to rainfall (and wind) forces– mulching and no-till reduces runoff and increases

infiltration– terracing and contour plowing also helps

• Pastures (livestock grazing) – increases soil compaction– reduces vegetative plant cover– increases bank erosion– rotating cattle between pastures and fencing

streams reduce problems

Urban Land Management

• Urban lands have more impervious surfaces– More runoff, less infiltration, recharge, and

baseflow– Very high peak discharges, pollutant loads– Less soil storage, channels are straightened and

piped, no floodplains– Baseflows are generally lower, except for

irrigation water (lawns & septic)

Atlanta, Georgia

“the fastest-spreading human

settlement in history"

Time Magazine

March 22, 1999

Ag/Poultry

Forests

Gainesville

Lake Lanier

Buford Dam

1

10

100

1,000

10,000

0.1 1 10 100

Normalized Discharge, Q / Qo

Su

spen

ded

Sol

ids

Con

cen

trat

ion

, mg/

L

West Fork Little River near Clermont

Chestatee River near Dahlonega

Chattahoochee River at Cornelia

Chattahoochee River at Norcross

Sediment Rating Curve

Nutrient Rating Curve

1

10

100

1,000

10,000

1 10 100 1,000 10,000

Sediment Concentration (mg/L)

Ph

osp

hor

us

Con

cen

trat

ion

(µ

g/L

)

Point Source: Flat Creek

•Vegetated Swales

Drywell

Chap 15 Quiz

Georgia now manages water quality using a watershed perspective.

Does this mean:

1. (True / False) Point sources are permitted without consideration of other dischargers.

2. (True / False) Point sources increase nonpoint sources of pollution

3. (True / False) All nonpoint sources must now be permitted

4. Best Management Practices (BMPs) are now required for:(True / False) forestry

(True / False) agriculture

(True / False) construction

(True / False) homes and businesses