The Full Picture

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phenomena and characteristics of interest for regional

and local water quality monitoring and management. A

key concern among users is ensuring the continuity of

the data both from satellite systems and in situ networks.

There is also a compelling need for new and improved

observations that can help address water quality needs in

these regions, recognizing that tradeoffs will be necessary

in order to accommodate the diverse and challenging user

requirements.

Calibration and validation requirements

– Calibration

and validation (cal/val) are key components required for

satellite remote sensing of properties that contribute to

or impact water quality. Satellite remote sensing of ocean

colour in particular entails very stringent requirements

on the sensor’s radiometric calibration in the visible spec-

tral region due to the significantly low (<10%)

contribution from the ocean (versus atmosphere). A

robust collaborative validation system for the interna-

tional aquatic science community is crucial. The

validation programme serves functions for product quality

assurance, algorithm performance validation, and the

development and refinement of algorithms (especially for

optically complex waters). This also ensures that satel-

lite-derived products meet scientific requirements for both

research and applications.

Data acquisition and distribution

– The impact of satel-

lite sensors (research or operational) for inland or coastal

water studies is dependent on the ability of users to access

appropriate quality data in a straightforward, timely

fashion. Routine water quality management issues (e.g.

beach closures) frequently require the most rapid access

to data to enable an accurate decision to be made in a

timely manner. Key issues to address include the neces-

sary processing level of the data, its quality, how quickly

it is needed, and in what format and by what means.

Others issues include establishing initial access and

resolving limitations on use or redistribution.

Data processing and product development

– A number

of fundamental issues are related to the use of optical

remote sensing data in coastal and inland waters. These

must be addressed to enable applications to make use of

the full potential of these datasets. In many cases these

issues are common to optical remote sensing over any

water body (including the open ocean), but are often

amplified in the coastal and inland waters by their specific

morphological and dynamic characteristics. These issues

include the need for standardized, community-based

open-source radiative transfer (atmospheric and water)

models, the need for standardized algorithmic methods to

be well documented and user-adaptable, and the need for

interoperable data formats, taking into consideration not

only the preferences/ideals of the remote sensing special-

ist but also those of potential end users.

Developing countries

– Developing countries play an

important role as key shareholders of large tracks of coast-

line, large estuarine areas and vital inland ecosystems.

There is, therefore, a need to address issues and needs for

monitoring and management of inland and near-coastal

water quality, which are particular to developing nations,

biogeochemical and ecological parameters such as chlorophyll

concentrations, turbidity/suspended solids, clarity, macrophyte

surveys, and slick and spill detection, and underlying geophysical

parameters such as surface temperature, winds, currents and waves,

bathymetry and flood area. The broad suite of ocean colour para-

meters (e.g. chlorophyll), as well as temperature, currently

represent primary areas of user interest and also research and devel-

opment activities.

GEO workshop brings experts together

The first GEO Inland and Nearshore Coastal Water Quality Remote

Sensing Workshop was held in Geneva, Switzerland on 27-29 March

2007. This seminal gathering of 55 experts from 26 countries was

hosted by the GEO Secretariat as a part of GEO’s activities on water

resources. The goal was to bring together remote sensing data providers

and expert users to improve their ability and capacity to remotely

assess and monitor inland and nearshore coastal water quality. This

was viewed as a forum for a diverse group, from data providers to end

users, to collaboratively chart a course for the future of this emerging

science.

The final report covered six major issues and aspects addressed in

the workshop. For each major issue, the report identified gaps and

issues, and gave recommendations to data providers and GEO

members and participating organizations on short-term priorities for

improving remote sensing capacity and utilization for water quality

assessment and monitoring. In addition, it formulated short and long-

term strategies to identify, enable and implement enhanced capabilities.

The following briefly summarizes the six major issues.

Satellite sensors

– Underlying efforts to generate products and infor-

mation for managers and decision-makers of nearshore coastal and

inland waters are the data streams generated by a suite or virtual

constellation of international satellite sensors, providing different types

of information at different spatial and temporal resolutions. Users

require timely and accurate data at regular intervals over sustained

periods for their particular region that adequately resolve the processes,

Water clarity

A map of water clarity generated from a Landsat image. The area is in the

northern lakes region of Wisconsin, USA

Source: Steven Greb, WDNR

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