Water Quality Survey in the

Isahaya Bay Using UAV

Haruhiro Hidaka, Susumu Ogawa

Nagasaki University

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背景：諫早湾における汚染過程

Red Tide

Construction of the levee

Background

Blue-Green Algae2 2

Present Problems

1. The number of samples is limited.

2. It is difficult to measure a wide water area.

3. Research depends on the weather.

4. Water quality changes every moment.

3Actual water quality survey 3

Objectives

1. Estimate water quality at high resolution that can not be measured with satellites.

2. Improve limit for the number of sample.

3. Capture changes of water quality in time

series.Phantom4

4 4

Study Area

Tokyo

Levee

Isahaya

Bay

Polluted

Water

5 5

6 6

Methods

PhotoScan

Image

Synthesis

Multivariable

Analysis

Image

Capture

UAV(Phantom4)

Image

Correction PhotoShop

Polluted Water

Water Quality

Measurements

Water

Sampling

Water Quality

Map

Accuracy

Check

500 pictures 7 7

Result on Multivariate analysis

Water Quality Indices DeterministicCoefficient

Evaluation

Chlorophyll-a R² =0.974 Very good

Conductivity R² =0.736 Good

Turbidity R² =0.997 Very Good

pH R² =0.809 Good

Salt Content R² =0.863 Good8 8

Chlorophyll-a in Spring

（May 7, 2016）LOW HIGH

9

Chlorophyll-a in Summer

（Aug 5, 2016）LOW HIGH

10

Discussion

・Only RGB has limit for water quality mapping. Thus, multivariable analysis should be added byinfrared imagery.

・Four multivariable analysis will be needed for every seasons.

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Conclusions

1. Continuous distribution map of water quality was obtained by UAV

2. The temporal and spatial resolution of water quality can be greatly improved with UAV.

3. Turbidity and chlorophyll-a had high correlations with RGB bands. Other water quality will be improved by adding infraredbands.

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