Using Bugs and GIS to Assess and Manage Watershed Health

Jennifer Thompson

The University of Texas at Austin

November 18, 2004

What are benthic macroinvertebrates?

• Benthic = bottom-dwelling

• Invertebrates = no backbone

• Macro =visible to unaided eye

Why study benthic macroinvertebrates?

• Sensitive to physical and chemical changes in their environment

• Reflect conditions for a duration of time

• Interact with both sediment and water

• Don’t move or swim away

• Easy to collect

• Relatively inexpensive to monitor

Water Quality Parameters specific to Bug Abundance and

Diversity• Temp

• Conductivity

• TSS

• Flow

• Nitrate as N

• Dissolved Oxygen

Metrics and Biological Indices

• 3 taxa groups: Pollution- intolerant, pollution-intermediate, and pollution- tolerant organisms

• EPT index

• Hilsenhoff Index

• % community as relates to trophic structure

• Aquatic Life Use

Water Scorpion

Damselfly Nymph

6

Caddisfly Larvae

7

Dragonfly Nymph

6

7Crane Fly Larvae

6Water Flea

6

Freshwater Crab

Water Mite

7

Here are the most common aquatic macro-invertebrates that will be found in the Adelaide region. Tick the spaces next to the numbers to indicate which invertebrates

you have found in your samples. The number indicates the sensitivity of the invertebrate, the higher the number, the more sensitive to pollution it is.

Also tick the invertebrates that you find on the ‘Record Sheet’ so you can determine the

stream pollution index.

Mayfly Nymph

8

Stonefly Nymph

9

10

10

Riffle BeetleAdult

Larvae

8

Water Measurer 7

Shrimp5

5

5

PredaciousDiving Beetle

Ad

ult

Larvae

ScavengerBeetle

AdultLarv

ae

5

5

5 5

Whirligig BeetleAdult Larvae

Biting Midge Larvae

5

4

Seed Shrimp

4Copepod

Yabbie4

4

Hydra

Freshwater Mussel

5

Scud

5Water Strider

5

Freshwater Slater5

5

Black Fly Larvae

MosquitoPupaeLarvae

5

Back Swimmer

5

Water Boatman4

Soldier Fly Larvae4

Leech

4

Non-Biting Midge Larvae

3

Flatworm3

Segmented Worm

1

2Springtail

2Water Spider

Round Worm

1

Snail2

Importance to Watershed Managers and Regulators

• Identify areas of concern

• Focus monitoring efforts

• Track success of remediation efforts

Focus: Colorado River Basin

• 22,200 square miles

• Total basin inflow: 10,738,000 acre-feet

• Total basin outflow: 1993: 9,097,000 acre-feet

• Irrigated acreage, 1992: 958,000 acres

• Water quality: typically satisfactory

Primary data source:

•TCEQ TRACS and Surface Water quality databases

Objectives

• Provide a spatial representation of monitoring sites and bug and water quality data using different biological indices for bugs

• Provide a temporal representation of data from 1996-2003

• Compare biological integrity with state criteria (screening and water quality standards) and evaluate how the Colorado River Basin measures in comparison

• Determine what impact urban development has on health of streams

Problem:

• Only 67 bug data entries between 1996 and 2003 for the Colorado River Basin

City of Austin- An example of a comprehensive dataset and the Power

of GIS

• > 1,000 bug data points from ’93-’03• >24,000 water quality data points from ’93-’03• More powerful indices used to prioritize

subwatersheds for addressing CIP projects, monitoring programs, and planning in general (e.g. Ecological Integrity Index)

• More in-depth parameters taken at time of sampling (e.g. flow)

Ecological Integrity Index (EII)

• Composed of 6 sub-indices: water quality, sediment quality, contact recreation, habitat quality, and aquatic life

• Assign a score for each EII site or watershed

• Scores range from 0-100 (very bad to excellent)

City of Austin Watershed Health

City of Austin Watershed Health

What’s next?

• Spatially represent changes in indices or scores over time

• Use linear referencing to assign addresses to streams and creeks

• Depending on frequency of data, use Time Series to show water quality changes over time

• Overly land-use coverages to determine if urban impacts exist

• Statistical analyses with flow• Compare water quality to state screening levels

and criteria