Challenges and Opportunities in the Hydrologic Sciences (2012) / Chapter Skim
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1 The Hydrologic Sciences
1 The Hydrologic Sciences
Pages 15-44
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. Global population growth has led to increased demand for water to support agricultural, industrial, and drinking water needs, with water withdrawals outstripping water supply in many parts of the world.
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The National Research Council (NRC) report Opportunities in the Hydrologic Sciences, known as the "Blue Book," defined hydrologic science as a distinct geoscience -- "a g eoscience interactive on a wide range of space and time scales with the ocean, atmospheric, and solid earth sciences as well as with plant and animal sciences." However, hydrologic science is also firmly anchored by phenomena that have direct and important relationships with the well-being of humans and natural systems.
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The "Blue Book" envisioned hydrologic science as a distinct geoscience and set forth a corresponding research agenda for the field. In the years following its publication, the document stimulated discussion and various actions, which culminated in the widespread recognition of hydrologic science as a separate field within the Earth Sciences.
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For example, the Royal Netherlands Academy of Arts and Science published a forward-looking agenda in hydrologic sciences for its country and the globe (Royal Netherlands Academy of Arts and Sciences, 2005)
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The talks also presented major breakthroughs in land-atmosphere interactions such as the effect of deforestation on hydrometeorological predictions, advances in generalized scaling theories of floods, the value of remote sensing data of precipitation, vegetation, and soil moisture in improving hydrologic model ing and prediction, new methodologies for characterizing hydrologic uncertainty, advances in data assimilation, advances in coupling geochemical and surface groundwater systems, the role of social sciences in hydrologic prediction, and the need to translate increased scientific understanding into better management of water resources systems. The talks also presented a worldview perspective of water and international efforts in hydrologic science and practice, a renewed educational agenda for hydrologic science at the interfaces of geosciences using community collaboration, and the use of high-performance computing capable of resolving processes at scales of the order of meters in advancing hydrologic predictions in an Earth systems perspective.
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The committee anticipates that the field of hydrologic sciences will use these advances to surge ahead, in part because capabilities in such areas as imaging the Earth, measuring minute quantities of molecules in water and in organisms, performing calculations on amazingly fast computers, and employing techniques developed in microelectronics will enable the community to formulate and answer new questions and to approach recalcitrant old questions effectively. To underscore the advanced state of water science in 2012, the committee highlights four areas where progress has revolutionized hydrologic science -- chemical analytical instrumentation, remote sensing and geophysics, embedded sensor systems, and computation.
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These advances have greatly benefitted the hydrologic science community by helping to answer a wide range of hydrologic questions and providing the information for posing new ones. Mass spectrometry (MS)
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Used with HPLC or UPLC and tandem MS such as triple-quads or quadrupole-time-of-flight MS, this highly selective technique can elucidate complex chemical mixtures such as contaminants of emerging concern in complex environmental matrices. The sophistication of many of these newer techniques and instruments has allowed for more detailed temporal or spatial sampling and analysis, enabling hydrologic scientists, engineers, aquatic geochemists, and envi 2 Seehttp://www-naweb.iaea.org/napc/ih/IHS_resources_gnir.html.
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However, recent breakthroughs in satellite and remote imaging and sensing and ground-based geophysical techniques have provided unprecedented opportunities to break this impasse by collecting and analyzing a massive amount of field data. A few examples are provided, below, to highlight the currently available techniques that have contributed greatly to new ideas but have yet to be fully exploited in advancing hydrologic science.
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, a constellation of spaceborne sensors on board multiple satellite platforms will allow for mapping of global precipitation fields with unprecedented relative accuracy across a larger range of rain rates and with higher spatial and temporal resolutions. Remotely sensed observations of many other land-surface conditions from current and forthcoming sensors on board spaceborne satellites and suborbital aircraft will provide ever greater streams of unprecedented highresolution data on surface soil moisture, soil surface temperature, topography, vegetation structure and health, snow cover, and other variables.
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to launch in 2014, will map global precipitation as part of a constellation R02116 of Earth-observing satellites. One of the main goals of the Surface Water and Ocean Topography mission, Figure 1-1 is under study for launch later 9 which bitmapped, uneditable in the decade, is to provide estimates of surface water extent, elevation, and slopes and therefore storage and storage change in lakes, reservoirs, wetlands, and r ivers (especially flood plains)
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to measure the elevation of the land surface provides the hydrologic community with yet another data source that potentially can change the discipline in fundamental ways. The discovery that water flows downhill is lost in antiquity (undoubtedly it occurred well before written history)
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may be "visible" to geophysical techniques, which allow for creation of images using electrical signals (e.g., Figure 1-3)
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Development of a community hydrologic model or modeling platform (Famiglietti et al., 2008) in a vein similar to the Community Climate Model developed by the National Center for Atmospheric Research has received recent attention and is likely to be pursued by the hydrologic sciences community in the future.
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This kind of detailed information leads to new insights about how critical ecosystem processes such as gross primary production relate to nitrogen uptake at time scales ranging from minutes to seasons and yield insights into the dynamic connections between ecosystem energetics and nutrient kinetics. Hydrologic science is also now utilizing a much wider range of sensors than ever before.
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. R02116 These measurements were used to probe direct and indirect coupling of primary production Figure 1-4and diel nitrate dynamics in a subtropical spring-fed river.
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Distinct steps in stream temperature represent zones of upwelling groundwater, while the variation in both time and space in stream temperature are the result of variations in solar energy input and shading. This figure represents more than 8 million individual data points collected by a single instrument operating remotely and demonstrates the revolution in both spatial and temporal data that can now be collected.
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Soil moisture, increasingly recognized as an important driver of climate along with coupled ocean and terrestrial processes such as monsoon cycles, has long been difficult to measure at the scales necessary for agriculture, meteorology, and hydrologic science. Most sensors to date (e.g., time-domain reflectometry)
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THE INTERDISCIPLINARY INTERFACE As a distinct geoscience, hydrologic science poses many important research questions that will be addressed by work within the discipline. However, the hydrologic cycle is a central element for many environmental disciplines that are neighbors to hydrologic science, and so it is not surprising that meeting many of the present and future challenges and opportunities will require collaboration among hydrologists, engineers, and scientists in other biogeoscience disciplines.
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This interdisciplinary field uses methods of analysis and information from hydrologic science, climate science, botany, and geology. Concern about the impacts of climate variability and change and the corresponding desire for forecasting changes have heightened interest and resulted in increased activity in this area, beginning in the early 1990s (NRC, 1991)
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The linkages between ecology and hydrologic science at the land surface are complex and, like paleohydrology, scientific progress requires interdisciplinary collaboration. Water from the atmosphere as rain, snow, or dew obviously is essential for plants to thrive.
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bitmapped, uneditable with different temperature and humidity relative to, say, a concrete parking lot and so affect the behavior of the atmosphere. Furthermore, soil properties affect how readily water and nutrients can be taken up from the soil by plant roots but again the growth of the roots themselves changes the soil structure, which is relevant to vadose zone hydrology, the subdiscipline concerned with water in soils.
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(For more information, see Box 3-1.) These collaborations are in the spirit of discovering fundamental relationships among physical and biological processes where expertise from the fields of geosciences, hydrologic science, microbiology, ecology, and soil science participates.
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used to promote the foundation's mission.14 In addition, 12 Original language from the study proposal that was included in the grant from the National Science Foundation to the National Research Council authorizing and scoping the study is as follows: "The primary focus of this study will be the NSF program in hydrologic science but given the importance of water issues to the nation, the report should also serve the academic/educational community, other agencies with programs in hydrology and water resources, Congressional staff, the Office of Science and Technology Policy, professional societies, and other entities with missions related to Earth sciences and water resources." 13 The committee interprets the term "modalities" in the statement of task as referring to capabilities within the NSF and other federal agencies used to advance hydrologic research including contracts and research grants, instrumentation and facilities, and so forth. 14 To "promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense..."; see http://www.nsf.gov/about/.
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these capabilities are integral to other agencies and organizations that support research in the hydrologic sciences. The Committee on Challenges and Opportunities in the Hydrologic Sciences met six times, heard presentations from scientists and engineers who work in several areas of hydrologic science and related disciplines, and solicited input from the community at an open town hall meeting at the 2009 Fall Meeting of the American Geophysical Union.
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A discussion of such questions could be organized along many different pathways. This committee chose to write three separate chapters, which stand on their own but are intimately linked, that cover fundamental questions in hydrologic science and related biogeosciences.
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Although the primary audience is the hydrologic community, the challenges and opportunities are intentionally broad, illustrating the necessity of interdisciplinary work needed to face the complex water related challenges of today and tomorrow.15 The signature of a scientific challenge is that it is compelling -- both in the domain of intellectual curiosity as well as in the domain of consequences for human and ecosystem welfare. The following chapters, titled "The Water Cycle: An Agent of Change," "Water and Life," and "Clean Water for People and Ecosystems," outline major areas of opportunity and challenge for hydrologic science.
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1998. Hydrologic Sciences: Taking Stock and Looking Ahead.
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1998. Hydrologic Sciences: Taking Stock and Looking Ahead.
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