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n
Scientific Priorities
Science has developed as a cultural endeavor of value to society
for the enrichment of the human spirit that flows from understand-
ing, as well as for the material benefit to which understanding often
leads. The culture of science draws its strength from the diversity of
interests, experiences, and viewpoints of its individual investigators,
and from its traditional principles of integrity and precision.
Few question the wisdom of public financial support for science,
but most freely acknowledge practical limits to public altruism. Na-
tions and agencies cannot support every scientific proposal, and thus
priorities must be set. Although the political process ultimately determines
what gets funded, it is in everyone's best interest that this process
have the benefit of knowledgeable scientific opinion. Scientists must
learn to formulate and advocate research priorities in their separate
scientific disciplines.
This chapter outlines a rational process by which priorities might
be set to promote a vigorous and beneficial hydrologic science. It
includes a few examples of research opportunities that the committee
believes to be the most important at this time. In addition it names
those developments in education and scientific data viewed as necessary
for the vigor of hydrologic science in the long term.
THE PROCESS
The dilemma in the objective establishment of scientific priorities
is that the criteria for ranking one opportunity with respect to another
are inherently subjective. The 18 members of this committee offered
296
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SCIENTIFIC PRIORITIES
297
10 separate but not necessarily independent measures of worth. Each
member ranked all 10 in descending order of importance by his or
her personal scale of values, and the rankings were averaged across
the committee. The interdependence of many of the 10 measures
allowed consolidation of the averaged rankings to three criteria:
1. Expected contribution to scientific understanding
Including such measures as either breakthrough or incremental
contributions to understanding and reduction of uncertainty, this premier
criterion reflects the dominating objective of science.
2. Support of a viable scientific infrastructure
Maintenance of a cadre of hydrologic researchers and synergistic
stimulation of related sciences are among the measures leading to
this second-ranked criterion.
3. Contribution to problem solving
Social benefits such as the solution of current crises and the opti-
mization of water resources were measures of importance yielding
this third-ranked criterion.
THE PREMISES
The diversity and range of scale of the frontier problems in hydro-
logic science are illustrated clearly by the examples given in Chapter
3. In addressing the issue of priorities among such questions, we
must seek to maintain options and diversity, and to keep avenues
open for innovation and the operation of serendipity. The above
criteria must be augmented with a set of premises:
· It is not possible to make rational priority judgments among
very specific research questions.
For example, which is more important, the effects of chemistry
and biology on soil properties, or how heat and mass flow control
water seepage in frozen media? Instead of such fine-grained comparisons,
we should consider the relative importance of larger classes of prob-
lems, such as land surface-atmosphere interactions versus the generation
of streamflow from precipitation.
· If the number of priority research areas is kept small, the list
need not be ranked.
However, if the categories are too broad they become all-inclusive,
and the sense of direction is lost.
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298 OPPORTUNITIES IN IN THE HYDROLOGIC SCIENCES
· In selecting the priority areas only the primary criterion should
be used.
Satisfaction of the secondary and tertiary criteria should not be
allowed to influence membership on the short list but might be used
to rank order this list if desired.
· The questions with the greatest potential for a contribution to
understanding lie at the least-explored scales and in making
the linkages across scales.
Considering that the historical development of hydrologic science
began at the small catchment scale and has spread both ways (i.e.,
both larger and smaller) over time, rich frontiers lie at the global
scale and the microscale. Finding the scale-bridging laws of hydrologic
similarity will reveal order and pattern.
· Hydrologic science is currently data-limited.
Interest in ever-increasing scale has outrun the financial support
for observation, and the balance of hydrologic science is now seriously
skewed toward modeling. It is important that observation and analysis
proceed hand in hand.
PRIORITY CATEGORIES OF SCIENTIFIC
OPPORTUNITY (UNRANKED)
In keeping with the above premises, the committee suggests the
following five research areas as those now offering the greatest expected
contribution to the understanding of hydrologic science.
· Chemical and Biological Components of the Hydrologic Cycle
In combination with components of the hydrologic cycle, aqueous
geochemistry is the key to understanding many of the pathways of
water through soil and rock, for revealing historical states having
value in climate research, and for reconstructing the erosional history
of continents. Together with the physics of flow in geologic media,
aquatic chemistry and microbiology will reveal solute transformations,
biogeochemical functioning, and the mechanisms for both contamination
and purification of soils and water.
Water is the basis for much ecosystem structure, and many ecosystems
are active participants in the hydrologic cycle. Understanding these
interactions between ecosystems and the hydrologic cycle is essential
to interpreting, forecasting, and even ameliorating global climate change.
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SCIENTIFIC PRIORITIES
299
· Scaling of Dynamic Behavior
In varied guises throughout hydrologic science we encounter questions
concerning the quantitative relationship between the same process
occurring at disparate spatial or temporal scales. Most frequently
perhaps, these are problems of complex aggregation that are con-
founding our attempts to quantify predictions of large-scale hydrologic
processes. The physics of a nonlinear process is well known under
idealized, one-dimensional laboratory conditions, and we wish to quantify
the process under the three-dimensional heterogeneity of natural systems,
which are orders of magnitude larger in scale. This occurs in esti-
mating the fluxes of moisture and heat across mesoscale land surfaces
and in predicting the fluvial transport of a mixture of sediment grains
in river valleys. It arises in attempting to extend tracer tests carried
out over distances of 10 to 50 m in an aquifer to prediction of solute
transport over distances of hundreds of meters to kilometers. It oc-
curs in extrapolating measurements of medium properties in a small
number of deep boreholes (as in the Continental Scientific Drilling
Program) to characterize fluid fluxes at crustal depth.
The inverse problem, disaggregating conditions at large scale to
obtain small-scale information, arises commonly in the parameterization
of subgrid-scale processes in climate models and in inferring the subpixel
properties of remote sensor images.
Solving these problems will require well-conceived field data collection
programs in concert with analysis directed toward "renormalization"
of the underlying dynamics. Success will bring to hydrologic science
the power of generalization, with its dividends of insight and economy
of effort.
· Land Surface-Atmosphere Interactions
Understanding the reciprocal influences between land surface processes
and weather and climate is more than an interesting basic research
question; it has become especially urgent because of accelerating hu-
man-induced changes in land surface characteristics in the United
States and globally. The issues are important from the mesoscale
upward to continental scales. Our knowledge of the time and space
distributions of rainfall, soil moisture, ground water recharge, and
evapotranspiration are remarkably inadequate, in part because historical
data bases are point measurements from which we have attempted
extrapolation to large-scale fields. Our knowledge of their variability,
and of the sensitivity of local and regional climates to alterations in
land surface properties, is especially poor.
The opportunity now exists for great progress on these issues for
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300
OPPORTUNITIES IN IN THE HYDROLOGIC SCIENCES
the following reasons. Remote sensing tools are available from air-
craft and satellites for measurement of many land surface properties.
Critical field experiments such as the completed First ISLSCP Field
Experiment (FIFE) and the Hydrologic-Atmospheric Pilot Experiments-
Modelisation du Bilan Hydrique (HAPEX-MOBILHY), and others under
way and planned, promise to improve both measurement and under-
standing of hydrologic reservoirs and fluxes on several scales. Additional
experiments in a range of environments are needed. Finally, numerical
models exist that are capable of integrating results from regional and
global measurement programs and focusing issues for future experi-
ments.
· Coordinated Global-scale Observation of Water Reservoirs and
the Fluxes of Water and Energy
Regional- and continental-scale water resources forecasts and many
issues of global change depend for their resolution on a detailed
understanding of the state and variability of the global water bal-
ance. Our current knowledge is spotty in its areal coverage; highly
uneven in its quality; limited in character to the quantities of primary
historical interest (namely precipitation, streamflow, and surface water
reservoirs); and largely unavailable still as homogeneous, coordinated,
global data sets. The World Climate Data Program (WCDP) has un-
dertaken the considerable task of assembling the historical and current
data, and the World Climate Research Program (WCRP) is planning
the necessary global experimental program, the Global Energy and
Water Cycle Experiment (GEWEX) (see discussion in Chapter 4), to
place future observations on a sound and coordinated scientific
foundation. Many nations must contribute for this program to be
successful. The United States should play a major role in GEWEX
through the support of key experimental components and accompanying
modeling efforts. Of particular importance in this regard is NASA's
Earth Observing System (EOS) program (see discussion in Chapter
4), which will include observing and data systems as well as scientific
experiments for multidisciplinary study of the earth as a system.
· Hydrologic Effects of Human Activity
For at least two decades hydrologists have acknowledged that humans
are an active and increasingly significant component of the hydrologic
cycle. Quantitative forecasts of anthropogenic hydrologic change are
hampered, however, by their being largely indistinguishable from
the temporal variability of the "natural" system.
Experiment and analysis need to be focused on this question.
Identification of the signal of change within the background noise of
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SCIENTIFIC PRIORITIES
301
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302
OPPORTUNITIES IN IN THE HYDROLOGIC SCIENCES
spatial and temporal variability will require observations at regional
scale and over many annual cycles. Forecasting the course of future
change will be eased by understanding what changes have already
occurred.
DATA REQUIREMENTS
· Maintenance of Continuous Long-Term Data Sets
The hydrologic sciences use data that are collected for operational
purposes as well as those collected specifically for science. Improvements
in the use of operational data require that special attention be given
to the maintenance of continuous long-term data sets of established
quality and reliability. Experience has shown that exciting scientific
and social issues often lead to an erosion in the data collection programs
that provide a basis for much of our understanding of hydrologic
systems and that document changes in regional and global environments.
· Improved Information Management
The increasing emphasis on global-scale hydrology and the increasing
importance of satellite and ground-based remote sensing lead to use
of large volumes of data that are collected by many different agen-
cies. An information management system is needed that would al-
low searching many data bases and integrating data collected at dif-
ferent scales and by different agencies.
· Interpretation of Remote Sensing Data
Effective use of remote sensing data is now too difficult for many
hydrologic scientists, because the interpretation often depends on a
detailed knowledge of sensor characteristics and electromagnetic
properties of the surface and atmosphere. Hydrologic data products
should be made available in a form such that scientists who are not
remote sensing experts can easily use the information derived.
.
· Dissemination of Data from Coordinated Experiments
Special integrated studies, such as HAPEX, FIFE, and GEWEX, that
involve intensive data collection and investigation of the fluxes of
water, energy, sediment, and various chemical species, produce high-
quality data sets that have value lasting far beyond the duration of
the experiment. Optimal use of these data requires broader and more
timely distribution beyond the community of scientists who are involved
in the experiments.
SCIENTIFIC PRIORITIES
303
EDUCATION REQUIREMENTS
· Multidisciplinary Graduate Education Program
The broad range of education inputs to graduate study in hydro-
logic science necessitates the formation of a multidisciplinary program
in the hydrologic sciences. This program should be either a department
unit or a confederation of faculty from host departments that is as-
sured of autonomy and resources by upper-level administration. If it
is the latter type of organization, it may or may not be degree-granting.
The primary purpose of the program would be to educate graduate
students who are considered first and foremost as hydrologists, not
geologists, geographers, or engineers who have some background in
hydrology.
· Experience with Observation and Experimentation
The changing nature of hydrologic science requires the development
of coordinated, multidisciplinary, large-scale field experiments. Graduate
students should be given experience with modern observational
equipment and technologies within their university programs, and
mechanisms should be developed to facilitate their participation in
these experiments, irrespective of their university of study. When
the experiments are planned, the inclusion of a diverse array of studies
should be an integral part of the plan. Undergraduate students of
science should have experience with measurement of natural phenomena,
preferably in field situations as well as in controlled laboratory settings.
· Visibility to Undergraduate Students
Programs should be developed to make hydrologic science more
visible as a scientific discipline to undergraduate students. These
programs should include such elements as research participation, in-
ternships at laboratories and institutes, curricula that introduce the
latest innovations, visiting distinguished lecturers, media development,
and in-service institutes for teachers.
SOURCES AND SUGGESTED READING
Dutton, J. A., and L. Crowe. 1988. Setting priorities among scientific initiatives. Am.
Sci. 76(Nov.-Dec.):599-603.
Press, F. The Dilemma of the Golden Age. Address to the members of the National
Academy of Sciences, April 26, 1988.
