Water Quality; Environmental Assessment; Ecological Processes

Greg Jennings, PhD, PEProfessor & Extension SpecialistBiological & Agricultural EngineeringNorth Carolina State Universityjennings@ncsu.edu

References:1. EPA Watershed Academy Web: http://

cfpub.epa.gov/watertrain/index.cfm

2. A.Ward and S.W.Trimble, ENVIRONMENTAL HYDROLOGY, CRC-Lewis Press Boca Raton,Fl, 475pp, 2004

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

Need to Know:

1. Watershed Principles, Processes, Functions2. Ecosystem Services of Natural Ecosystems:

a. Air and water qualityb. Mitigation of droughts and floodsc. Soil generation and fertilityd. Waste decompositione. Nutrient cyclingf. Biodiversityg. Many others

3. Watershed Ecologya. Physical and biological settingsb. Natural systems conceptc. Structure and functions

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

Need to Know:

1. Flowing (lotic) Systems (e.g. streams, rivers)2. Still (lentic) Systems (e.g. lakes, ponds)3. Watershed Functions:

a. Transport and storage of water & sedimentb. Cycling and transformation of carbon, nutrientsc. Ecological succession

3. Stream Corridor Structure (channel, floodplain, upland fringe)a. Lane’s channel equilibrium:

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

Need to Know:

1. Stream Flow: base flow, storm flow

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

Need to Know:

1. Stream Discharge (Continuity Equation): Q = V A

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

Need to Know:

1. Bankfull Discharge: fills channel and begins to spread onto floodplain

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

Need to Know:

1. Landforms and Deposits:

Meander scroll, a sediment formation marking former channel locations. Chute, a new channel formed across the base of a meander. As it grows in size, it carries more of the flow. Oxbow, a term used to describe the severed meander after a chute is formed. Clay plug, a soil deposit developed at the intersection of the oxbow and the new main channel. Oxbow lake, a body of water created after clay plugs the oxbow from the main channel. Natural levees, formations built up along the bank of some, generally low-gradient streams that flood. As sediment-laden water spills over the bank, the sudden loss of depth and velocity causes coarser-sized sediment to drop out of suspension and collect along the edge of the stream. Splays, delta-shaped deposits of coarser sediments that occur when a natural levee is breached. Natural levees and splays can prevent floodwaters from returning to the channel when floodwaters recede. Backswamps, a term used to describe floodplain wetlands formed by natural levees.

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

Need to Know:

1. River Continuum Concept:

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

Need to Know:

1. Watershed Change & Ecological Impacts: Natural vs. Human2. Nutrient Pollution (Nitrogen & Phosphorus)

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

Need to Know:

1. Watershed Protection Tools:

Tool 1. Land Use Planning Tool 2. Land Conservation Tool 3. Aquatic Buffers Tool 4. Better Site Design Tool 5. Erosion and Sediment Control Tool 6. Stormwater Best Management Practices Tool 7. Non-Stormwater Discharges Tool 8. Watershed Stewardship Programs

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

Need to Know:

1. Agricultural Management Practices for Water Quality:

Conservation Tillage - leaving crop residue (plant materials from past harvests) on the soil surface reduces runoff and soil erosion, conserves soil moisture, helps keep nutrients and pesticides on the field, and improves soil, water, and air quality;Crop Nutrient Management - fully managing and accounting for all nutrient inputs helps ensure nutrients are available to meet crop needs while reducing nutrient movements off fields. It also helps prevent excessive buildup in soils and helps protect air quality;Pest Management - varied methods for keeping insects, weeds, disease, and other pests below economically harmful levels while protecting soil, water, and air quality; Conservation Buffers - from simple grassed waterways to riparian areas, buffers provide an additional barrier of protection by capturing potential pollutants that might otherwise move into surface waters.

EPA Watershed Academy Web: http://cfpub.epa.gov/watertrain/index.cfm

Need to Know:

1. Agricultural Management Practices for Water Quality:

Irrigation Water Management - reducing nonpoint source pollution of ground and surface waters caused by irrigation systems; Grazing Management - minimizing the water quality impacts of grazing and browsing activities on pasture and range lands;Animal Feeding Operations (AFOs) Management - minimizing impacts of animal feeding operations and waste discharges through runoff controls, waste storage, waste utilization, and nutrient management;Erosion and Sediment Control - conserving soil and reducing the mass of sediment reaching a water body, protecting both agricultural land and water quality and habitat.

Sediment

• Natural erosion: – Also referred to as geologic erosion -- is relatively slow– Most rapid along shorelines and stream channel– Vital factor in maintaining environmental balance– Produces about 30% of all sediment in U.S.

• Accelerated erosion:– Refers to erosion occurring at increased rate usually because of

removal of natural vegetation or alteration of ground contour– Accounts for 70% of all sediment generated in U.S.– Construction and agriculture are main causes

• Screens out sunlight/ reduces clarity• Fills channels and reduces capacity

• sediments can fill up ponds and reservoirs• sedimentation can plug culverts and storm drains

• Pollutants attach to sediment particles– legal action– additional costs and penalties– delays in schedule

• Property damage from flooding

Impacts of Sediment

• TSS: Concentration of sediment in water measured in mass per unit volume (mg/L)

• TSS Load: Product of concentration and stream discharge (tons per day)

• TSS can be related to Turbidity for each watershed

Total Suspended Sediment - TSS

Example ProblemIn the Wages Creek watershed, a 2-L sample of water was collected from a stream with a discharge of 10 cfs. The dry weight of sediment in the sample was 48 mg. Calculate TSS concentration and TSS load.

Example ProblemIn the Wages Creek watershed, a 2-L sample of water was collected from a stream with a discharge of 10 cfs. The dry weight of sediment in the sample was 48 mg. Calculate TSS concentration and TSS load.

Given: Volume = 2 L; Mass = 48 mg; Discharge = 10 cfs

Calculate: TSS = 48 mg / 2 L = 24 mg/L

TSS load = 24 mg/L X 10 cfs

= 0.65 tons/day

days

ftL

kgton

mgkg

sft

L mg 400,863.28

9071

000,000,111024 3

3

• An expression of the optical property that causes light to be scattered and absorbed rather than transmitted in straight lines through the water (the measure of relative clarity) measured in NTUs: Nephelometric Turbidity Units

• Turbidity can be related to TSS

Turbidity

Example from Wages Creek

Relationship of Turbidity and TSS(must be determined for each watershed)

Relationship of TSS and Discharge(must be determined for each watershed)

Example ProblemIn the Wages Creek watershed, a 2-L sample of water was collected from a stream with a discharge of 10 cfs. The measured turbidity was 20 NTU. What is the expected TSS concentration? What is the expected TSS load? As the discharge increases to 50 cfs, how does TSS load change?

Example ProblemIn the Wages Creek watershed, a 2-L sample of water was collected from a stream with a discharge of 10 cfs. The measured turbidity was 20 NTU. What is the expected TSS concentration? What is the expected TSS load? As the discharge increases to 50 cfs, how does TSS load change?

From the graphs, we expect the TSS concentration to range from 30 to 60 mg/L and the TSS load to range from 0.1 to 1.0 tons/day. At 50 cfs, the expected TSS load increases to 3 to 10 tons/day.

Nutrients

• Can lead to algal blooms in surface waters which then result in low DO and fish kills

• Can cause drinking water to be unsafe (nitrate)

• Freshwater – usually P limited• Estuarine – usually N limited

Nitrogen

• Nitrogen Forms : Nitrate, Ammonium, Organic N• Total N = TKN + NO3-N + NO2-N• TKN = Organic N + Ammonium-N

– Indicator of animal or human waste• Nitrate: soluble in water

– Unpolluted water <1 mg/L of NO3-N

– Drinking water standard 10 mg/L of NO3-N

Ammonia Concentrations and Fish Kills

• Lethal concentrations of ammonia range from 0.2 - 2.0 ppm– trout most sensitive– carp least sensitive

Aquitard

Nitrate and water movement Nitrate losses

due to buffer

Source: Deanna Osmond, NCSU

Example ProblemFor a 1,000-hectare farm in the Neuse River Basin, it is determined that the total nitrogen loss to the river is 20 kg/ha/year. What is the change in nitrogen load if the farmers installs the following BMPs which?BMP hectares affected

Vegetative Buffer > 30 ft 100

Vegetative Buffer > 20 ft 100

Tree/shrub Buffer > 20ft 100

Water control structures 200

Example ProblemSolution: The current N load is 20,000 kg/year. The total load reduction is calculated in the table below as 5,200 kg/year, or 26%.

BMP hectares % reduction load reduction

Vegetative Buffer > 30 ft 100 65 1300

Vegetative Buffer > 20 ft 100 40 800

Tree/shrub Buffer > 20ft 100 75 1500

Water control structures 200 40 1600

Total 500 5200

Constructed

Wetlands

Bioretention Areas

Source: Bill Hunt, NCSU

Bioretention Areas

Example ProblemWhat is the expected nutrient load reduction if a properly-designed bioretention area is installed to treat runoff from a 10-acre commercial development in central North Carolina where the current loading is estimated to be 20 lb/ac/year of nitrogen and 0.5 lb/ac/year of phosphorus?

Example ProblemWhat is the expected nutrient load reduction if a properly-designed bioretention area is installed to treat runoff from a 10-acre commercial development in central North Carolina where the current loading is estimated to be 20 lb/ac/year of nitrogen and 0.5 lb/ac/year of phosphorus?

Solution:

Current loading is 200 lb/year of N and 5 lb/year of P.

The expected removal efficiencies are at least 40% for N and at least 50% for P, resulting in reductions of at least 80 lb/year of N and 2.5 lb/year of P.

Buffer Width Affects Runoff of P

Example ProblemFor inorganic fertilizer applied to farmland in North Carolina, the expected runoff loss to receiving waters is 0.45 lb/ac/year. What buffer width is needed to reduce this loss to 0.15 lb/ac/year?

Example ProblemFor inorganic fertilizer applied to farmland in North Carolina, the expected runoff loss to receiving waters is 0.45 lb/ac/year. What buffer width is needed to reduce this loss to 0.15 lb/ac/year?

Solution:

The buffer will reduce runoff losses depending on width. To reduce the runoff loss from 0.45 to 0.15, a delivery ratio of 0.33 is required. The minimum buffer width required is 25 ft.