Geoscience Reference
In-Depth Information
site for open commentary. They have also been presented to the WCRP Joint Scientific
Committee for comment, and the outcome is what we present here. Three of these GSQs
deal with water and two of them are combined into a more general water resource Grand
Challenge for WCRP that also encompass scientific activities coordinated by the CliC,
CLIVAR and SPARC projects. This is outlined in Sect.
4.1
along with a number of more
specific questions. The third GSQ is part of a WCRP-wide theme of extremes, and those
extremes related to water are discussed in Sect.
4.2
. The other GSQ relates to energy and
processes.
4.1 Grand Challenge on Water Resources
How can we better understand and predict precipitation variability and changes, and how
do changes in land surface and hydrology influence past and future changes in water
availability and security?
These questions focus on the exploitation of improved data sets of precipitation, soil
moisture, evapotranspiration, and related variables such as water storage and sea surface
salinity expected in the next 5 to 10 years. These will allow us to help close the water
budget over land and provide improved information for products related to water avail-
ability and quality for decision makers and for initializing climate predictions from seasons
to years in advance. The improvements will come from ongoing and planned satellite
missions (see below) as well as greater use of in situ observations; their evaluation and
analysis to document means, variability, patterns, extremes and probability density func-
tions; their use to confront models in new ways and to improve our understanding of
atmospheric and land surface processes that in turn improve simulations of precipitation;
and new techniques of data assimilation and forecasts that can lead to improved predictions
of the hydrological cycle across scales, from catchments to regions to the entire globe,
including hydrogeological aspects of ground water recharge. In particular, attention is
needed on the use of realistic land surface complexity with all anthropogenic effects taken
into account, instead of a fictitious natural environment. This encompasses all aspects of
global change, including water management, land-use and land-cover change, and
urbanization. The ecosystem response to climate variability and responsive vegetation to
such changes must be included, as must cryospheric changes such as dynamics of per-
mafrost, thawing and changes in mountain glaciers. The focus on these scientific questions
should lead to improved understanding and prediction of precipitation and water vari-
ability, enhance the evaluation of the vulnerability of water systems, especially to
extremes, which are vital for considerations of water security and can be used to increase
resilience through good management and governance.
The 21st century poses formidable challenges for the sustainable management of water
resources at all levels, from the local, regional to the global scale. Water is a basic
requirement for life, and effective water management is needed to provide some of soci-
ety's most basic needs. However, demand for water resources is increasing, due to pop-
ulation growth and economic development, while water resources are under pressure
globally from over-abstraction and pollution. This is increasingly leading to competition
for water, at local, regional and international levels. Environmental change is adding
additional pressures. Consequently, there are growing issues of vulnerability and acces-
sibility to water, both of which are highly relevant for society. Anthropogenic influences
are changing land and water systems, redefining the state of drainage basins and the rivers
and groundwater aquifers that supply the bulk of renewable freshwater to society. Wide-
spread land-use changes, associated with population increases, urbanization, agricultural
