Focal point: Wolfgang Grabs
integrated hydrological observations are the backbone for
improved water management in the light of global change.
GTN-H activities aim to enhance data accessibility and product
development for a large variety of users.
the quality and consistency of data, as well as improving
the understanding of global water processes, is essential
in developing more accurate global and regional water balance
models. This information is vital to manage variability
and change in hydrological regimes, to assess the changing
availability of water resources, and to improve forecasting
accuracy of hydrological extremes.
cycle (source Ramsar)
Global Terrestrial Network for Hydrology (GTN-H) is the
result of the joint efforts of the WMO Hydrology and Water
Resources (HWR) Department, the Global Climate Observing
System (GCOS) and the Global Terrestrial Observing System
(GTOS). GTN-H comprises existing networks, global databases
and global data product centres, and is based around a Coordination
Group that includes:
Runoff Data Centre – GRDC (BfG, Germany, under the
auspices of WMO);
Precipitation Climatology Centre – GPCC (DWD, Germany,
under the auspices of WMO);
Environmental Monitoring System – Water – GEMS/WATER
(UNEP; Environment Canada); and
Systems Research Centre (University of New Hampshire, USA).
the successive identification of participating partners,
the core group is expanding.
objectives and activities
Developing and improving the availability
of hydrological data and information required to address
global and regional climate, water resources and environmental
issues is a prime objective of GTN-H. Benefits will include:
improved weather and climate prediction; hydrological characterization
to detect climate change; ability to predict the impacts
of change; and an understanding of the global water cycle
in an integrated context of weather, water and climate.
Other benefits will be the improved assessment of freshwater
availability and variability, and the greater understanding
of large-scale hydrological processes.
Central to achieving these objectives is
the development of global-scale data products. A major area
of activity within GTN-H aims to develop and implement improved
approaches and tools for data collection, access and management
to support GTN-H objectives, and here GTN-H is a key partner
in implementation of the Integrated Global Water Cycle Observation
(IGWCO) theme of the IGOS partners.
progress in the last biennium included:
1. draft definition
of hydrological metadata standards, based on the WMO core
metadata standards (in collaboration with GRDC);
2. a prototype
online near-real-time river gauge stations data system;
to a first-guess global gridded precipitation product (courtesy
access to the global water quality database of GEMS/Water;
edition of the estimation of freshwater fluxes to the ocean
(in collaboration with the University of New Hampshire and
of the GTN-H Web site and creation of an inventory of hydrological
data and product sources (in collaboration with Environment
Canada and the University of New Hampshire); and
to the Implementation Plan for the Global Observing System
for Climate in Support of the UNFCCC and the implementation
plan of GEOSS.
GTN-H Coordination Panel met in Koblenz, Germany (4–5
July 2005) to review key GTN-H projects; to identify additional
networks; to develop products and plans relevant to global
aspects of hydrology; and to address the need for improved
availability and access to global hydrological data, information
and products to support a wide range of climatic and hydrological
objectives. The tasks and recommendations that emerged from
the meeting included:
to the Arctic and oceanographic communities regarding river
runoff into oceans data;
responsibility for the global harmonization of systematic
observations of water vapour;
support to the planned NASA/ESA surface water interferometry
datasets (in situ and satellite) and research groups to
be included in an international data centre for lakes and
the development of standard observational practices for
relevancy to GEOSS; and
collaboration and synergy with GTOS-TEMS, through the hydrology
figure below shows the current development of GTN-H along
the identification of key partners for the ten selected
variables to be covered by GTN-H.
The core function of GTN-H include:
1. provide users with
timely access to global hydrological data and meta-data;
2. generate relevant
products (including global-scale data products) and related
documentation in a time frame and of a quality that is required
3. promote method standardization
and the use of 'best' practices (including policies, quality
control, data formats, coding and transmission);
4. promote and facilitate
free and unrestricted exchange of data and products within
the existing framework;
5. Promote data integration,
including both multiple platform observations and cross-network
6. evaluate adequacy
7. monitor and evaluate
8. contribute to identifying
the key observational requirements of GTN-H, including requirements
for satellite observations;
9. provide support for
hydrology project will:
develop a joint map product on data availability (near real
time and historical);
develop a state of the system map product;
establish tools (e.g., procedures) for data mining and standardized
produce data and analysis products, including gridded runoff/discharge
fields, BGC fluxes to the oceans, and surface storage fluxes.
TOPC also selected 10 hydrological variables that are relevant
to climate change. These are: 1.
Surface water discharge; 2.
Surface water storage fluxes; 3.
Groundwater storage fluxes; 4.
Relative humidity; 7.
Soil moisture; 8.
Snow water equivalent; 9.
Biogeochemical transport from land to ocean; 10.
Sediment load at large river mouths
Three major networks and global databases have been established
by international organizations:
The Global Runoff Data Centre (GRDC)
The Global Precipitation Climatology Centre (GPCC)
The Global Environment Monitoring Centre on Water Quality