Bottlenecks: A Primer for Discussion
BackgroundConservative projections, based on current information about population growth rates,
pollution, salinization, waterlogging and groundwater overdraft, all indicate a high increase in
the number of countries that will experience significant water stress and scarcity in the near
future. The United Nations system presented a Comprehensive Assessment of the Freshwater
Resources of the World to the nineteenth Special Session of the United Nations General
Assembly in 1997. This assessment made it clear that a "business-as-usual" approach to water
allocation and management is not sustainable. The 2002 World Summit on Sustainable
Development in Johannesburg agreed on specific and time-bound goals for the alleviation ofpoverty, hunger and health; these goals necessitate effective water management policies andstrategies.
The situation for a majority of the world's population has not improved since theComprehensive Assessment of the Freshwater Resources of the World was presented to theUnited Nations in 1997. Still, over a billion people lack access to safe drinking water and almost
3 billion lack proper sanitation. Millions of people die each year from water related diseases andthere are no clear indications that these trends will improve in the near future. The increased useof pollutants associated with the technological development of countries with evolving market
economies, life-style changes all over the world and the increased need to develop sustainable
water resources and infrastructure for growing populations all contribute to the urgency
associated with advancing hydrological sciences and water management strategies. Increased
competition among and within sectors calls for strategies that will help to balance water use forthe multitude of purposes required by humans, while protecting the integrity of the ecosystems.
Some of the statistics are staggering. By 2020, water use is expected to increase by 40 percent,and 17 percent more water will be required for food production to meet the needs of the world’s
growing population.
Over the last decade it has become increasingly clear that if we are to face the water
challenges of the future we must view the Earth as a single, though highly complex, integrated
system. The atmosphere, the hydrosphere and the biosphere extend throughout the globe. They
are very dynamic and highly interactive. Changes that occur in one location can influence theenvironment somewhere else in ways that are not always expected and are frequently poorly
understood. The complicated interactions between the physical and human systems are equally
critical. The scientific and technical community has a very important role to play in this regard.
This role is not only related to scientific monitoring, analysis and interpretation, but also to
guiding future policies and action programs. Effective water management is not purely apolitical problem, a scientific problem, a technological problem, nor a managerial problem; it is acomplex problem that demands interaction between all of these areas. It is clear that to assuage
the impending water crisis, cooperation between the scientific disciplines, as well as thescientific and water policy arenas, must dramatically improve. A directed effort must be taken
now to improve the recognition of the impending water crisis by all stakeholders and to improve1

the understanding of the components involved with the natural system and allocation of its
resrouces.
The Hydrology 2020 group was assembled by IAHS to assess how the discipline ofhydrology should evolve to meet the world water challenges that are expected to prevail by
2020. The hydrology 2020 group has identified what it feels are the most critical "bottlenecks",
or barriers to the advancement of hydrological science, as well as some solutions necessary to
overcome the obstacles. These bottlenecks, which are described below, have categorized into
three areas:• Organizational,• Scientific and• Technical.
At this juncture, the Hydrology 2020 group is soliciting input from the scientific and water
policy arenas to assist in further developing the discussion of "key bottlenecks" and in finding
innovative solutions to the identified problems.
1. Organizational Capacity
Water issues are complex, as water acts as a link between various water uses, land use andecosystems. Calls are often made for integrated water resources management strategies, such as
basin-wide hydrosolaridarity, which focuses on water allocation principles based on equity andefficiency. However, such concepts are still poorly defined and even more poorly understood. It
is clear that effective policies are needed to strike compromises among competing water uses, todevelop sustainable water resource plans, to alleviate and mitigate pollution, and to allay waterrelated disasters. These policies must be driven by scientific knowledge and scientifically based
recommendations, which stem from appropriately directed hydrological research and adequate
funding.
Although water quality and resource management cut across political and nationalboundaries, no strong and well-funded intergovernmental global hydrological organization existsthat can coordinate and fund research and operational efforts within the broad range ofhydrological sciences. A global hydrological intergovernmental organization is needed to serveas the authoritative scientific voice of hydrology and also to organize research efforts toward
world water problems. It could have a role in facilitating integrated approaches to water
development and management and offer a capacity to provide advisory services and implement
and strengthen technical cooperation and investment projects targeting critical areas of water
resource management. Scientific results must be translated into action-oriented recommendations
so that they can be used in national and international policy evaluation, formulation, andplanning. These recommendations should be formulated in terms that are clear, specific andrealistic. With substantial funds and commitment, this organization could be developed anew, or
the hydrology and water management sections of WMO/UNSECO and other UN agencies could
be combined and expanded to meet the organizational needs of the hydrological sciences. The
primary responsibilities of this global organization would include:• Water policy. The organization would both coordinate and contribute to water
policy activities, serving as the central spokes-organization for global hydrology and water
management;2• Coordinated Research Management. A central focus of the organization would be todevelop, fund and coordinate long-term research programs. Included in this task is thecoordination of research programs that are developed by individual countries andorganizations in order to most effectively tackle the existing scientific challenges.
• Testing Centers. The organization would be responsible for establishing linked testing
centers/areas that scientists can use to test models and approaches, to sharedata/instrumentation and to train students or representatives from developing countries. The
centers should work together to establish acceptable data standards, formats and calibration
approaches and to coordinate long-term data acquisition, archiving, and dissemination.
These centers are currently critically needed, yet are too costly to develop by individual
researchers or small groups of researchers.
• Education/Outreach. The organization should establish standards and advocate public
education in hydrological sciences. The organization should oversee outreach efforts toengage young and bright scientists into the discipline, and to make formal connections
between the many sub-disciplines that interact with hydrology.
• Public Awareness. An important component of the organization will be to raise publicawareness about the impending water crisis in a manner similar to how awareness was raised
about climate change and ozone depletion issues. Greater awareness translates into morepolitical support and more funding geared toward hydrological sciences.
• Technology Transfer and Capacity Building. The global hydrological organization would
strive to strike a balance between supporting fundamental research and devoting resources
toward capacity building and toward finding practical solutions to hydrological and water
management problems in developing countries. In many locations, there is a current
disconnect between the state-of-the-art in hydrology (represented by complex researchadvances) and the state-of-the-practice (the tendency to implement the developed approaches
in the field). While many hydrologists in developed nations focus on issues such as
resolution, uncertainty, and accuracy of advanced prediction/estimation approaches, those inless developed nations are enthusiastic about, for example, the development anddissemination of inexpensive treadle pumps that can deliver irrigation water to their crops
using human (cycling) power. Thus, in addition to support of fundamental research (which
will be described below), there also needs to be support and guidance for well-trainedhydrologists and water managers who can focus on solving practical solutions, often in theface of incomplete fundamental theory, using currently available approaches andinstrumentation.
There have been unsuccessful attempts to develop such a global organization in the past. The
attempts met with resistance, not only because of protectionism among existing organizations,but because of the lack of willingness to support additional intergovernmental organizations
among national funding agencies. Water issues are far too often considered to be part of national
security with a strong unwillingness to open up for international cooperation. However, thecurrent situation, typified by a lack of coordination and the duplication of efforts, is not aneffective way to handle the challenges that we face. Water quality and quantity trends are not
auspicious, and no clear solutions are on the horizon. We urge the hydrological sciences andwater policy communities to reconsider the issue of developing a global hydrologicalintergovernmental organization that would serve as the authoritative scientific voice ofhydrology and to organize research efforts toward world water problems.

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2. Scientific Challenges
The Hydrology 2020 group has recognized many fundamental bottlenecks within hydrologicalsciences that must be reconciled in order for hydrology to meet the water scarcity and pollution
challenges of the next few decades. These scientific bottlenecks include persistent obstacles thatcut across many disciplines, such as data integration, scaling, and numerical representation ofcomplex processes. However, some of these bottlenecks are associated with the lack ofunderstanding of fundamental processes, systems, or cycles that are most germane tohydrologists, such as the water cycle and the vadose zone. For some problems, the theory andapproaches within individual subdisciplines are quite advanced, but the links to neighboring
disciplines are often not well established. The individual scientific bottlenecks are described
below.
• Incomplete Understanding of Hydrological Processes
Deficiencies in our understanding of many of the hydrological processes and systems
greatly handicaps our efforts to guide water resource planning, to predict hydrologic
extremes, and to predict contaminant migration. For example, as crucial as the water
cycle is to human and ecosystem existence, there are still many gaps in the understandingof the individual components that comprise the water cycle, as well as the interactions
between these components. Additionally, the vadose zone, which supports ouragriculture, serves as the repository for most of our municipal, industrial and government
wastes and contaminants, and supports our infrastructure, plays a crucial role in both thewater cycle and in contaminant hydrology. In spite of its importance, the understanding
and prediction of flow and transport of water and contaminants through the vadose zone
and across the upper (soil-air) and lower (groundwater) boundaries are inadequate.
Improved understanding of the hydrological processes and system components
can be obtained through nested and coupled experiments replete with field measurements
using several techniques, remote sensing measurements, process investigation, andmodeling. Improved observations of water vapor, clouds, precipitation, evaporation,
surface and subsurface runoff, groundwater, soil moisture, snow and ice using newtechnologies and networks collected over various spatial and temporal scales are needed
to improve our understanding of the water cycle. These measurements must haveenhanced resolution, increased accuracy, and be maintained for long time periods relative
to the currently available data acquisition schemes. These measurements must be
coupled with process studies of the individual components as well as the linkages
between components over various spatiotemporal scales. The measurements and process
studies must be incorporated into improved models (see below). Establishing coordinatedand linked field observations with remote sensing data and modeling efforts over avariety of spatial and temporal scales is necessary for an improved understanding andprediction of water cycle, hydrological extremes, and contaminant infiltration.
Successful implementation of the nested and coupled field experiments will require advances in
our approaches to modeling, data integration, and scaling. These topics are also current
scientific bottlenecks, as described below.

4• Modeling. Many numerical models are based on hydrological principles; these models
range from flow and transport in the groundwater to global circulation models. In mostcases, a combination of both incomplete theory and data exist. Because of theseinadequacies, many different modeling approaches have been developed, ranging fromdeterministic to stochastic and from data-driven to physics-based. Modeling should
continue to be a research topic, with more emphasis on uncertainty assessment, improved
parameterization and data assimilation approaches, standardized validation procedures,
improved frameworks for incorporating indirect data (tracers, geophysics, remote sensing,etc.) and improved numerical representation of coupled processes (such ashydrogeological-biogeochemical) and systems (such as land and atmosphere).
•Data Integration/Calibration. Various data sets, such as tracers, ground-based
geophysics, and remote sensing are becoming increasingly available for use inhydrological studies. More research is needed to fully develop the potential that thesetools have for assisting with hydrological problems. Many current obstacles areassociated with improving the accuracy and resolution of the geophysical and remotesensing measurements. With both data types, a better understanding of data integration
approaches are needed to enable routine calibration (often using data sets that arecollected at different spatial scales) or to facilitate a comprehensive interpretation. With
both ground-based geophysics and remote sensing data sets, we should strive to movebeyond site-specific inference based on spatial patterns toward an improved
understanding of the physics so that the data can be used to more generally andquantitatively estimate hydrological-climatological parameters of interest.
•Scale problems - Issues related to scale are persistent across all aspects of hydrologicalsciences as well as in many other disciplines. Among other topics requiring additional
research include investigation of dominant processes and interactions between processes
that occur at different spatial scales, and reconciling the different spatial scales associatedwith measurements, physical processes and numerical models.
3. Practical/Technological Issues
There are several issues where funding or commitment is the major impediment to progress
rather than development of new theory. These practical/technological bottlenecks are briefly
described below.
• Inexpensive access to data. Many of these obstacles have to do with acquisition of andaccess to data. In order to better assess and manage the world's water supplies and preventhydrological catastrophes, free access to current hydrological data is needed, concomitantwith long-term commitment to establishing and maintaining monitoring networks.
• New Sensors. New sensors are needed to obtain improved data sets. Although
microsensors that are cheap, small, automated, smart, injectable and innocuous are currently
being developed in engineering and biomedical fields, development of such sensors forhydrological sciences has been sluggish. On the other end of the spatial scale, satellite
sensors, which have hydrological applications as the primary goal, should be developed.
These sensors should be improved to offer higher spatial resolution over more specificspectral bands, and should have faster return periods.

5• Water Database development and management. Another practical bottleneck within thehydrological community is lack of a worldwide water resources database. Water resources
cannot be managed unless we know where they are, in what quantity and quality, and how
variable they are likely to be in the future. Development and maintenance of a database using
high quality data is crucial for assessing global water resources and proper planning for theirconservation. The Global Runoff Data Center is currently establishing a data base thatcompiles freshwater fluxes and long term mean monthly discharges from selected monitoring
stations. Databases such as this should be expanded to include complete information of all
significant world aquifers that includes information about capacity, water balances, purpose,and type of runoff control and associated GIS coordinates.
• Technologies for Developing Countries. Development of small-scale technologies andapproaches for dealing with (often nation-specific) water supply and sanitation issues could
dramatically improve conditions in many developing countries. Although development anddeployment of such technologies could be performed with minimal funds, a global
commitment is needed to both identify the needs and to organize the effort.

4. Summary
The bottlenecks described above focus on organizational, scientific, and technological obstacles.
We are at a point in the evolution of hydrology where many of the complex problems that exist
can often only be solved with improved political and organizational support, with more funds
committed over the long term to technological development, research and monitoring, and withand emphasis on coupled, cross-disciplinary, and integrated scientific approaches. The fusion ofdifferent types of information and specialists (including scientists and water policy specialists) tosolve hydrological problems is perhaps a central theme of how hydrology should evolve
scientifically to meet the world water challenges. Although the list of bottlenecks is extensive
and the approaches towards solutions would be costly to implement, the repercussions of not
attacking these obstacles now may be much more costly to future generations. The hydrology
2020 group solicits input from the scientific and water policy communities to assist in further
development of the bottlenecks discussion, and in finding innovative solutions to the identified
problems.

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