Hydrologic Sciences Taking Stock and Looking Ahead (1998) / Chapter Skim
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2 Aquatic Ecosystems: Defined by Hydrology. Holistic Approaches Required for Understanding, Utilizing, and Protecting Freshwater Resources
2 Aquatic Ecosystems: Defined by Hydrology. Holistic Approaches Required for Understanding, Utilizing, and Protecting Freshwater Resources
Pages 44-66
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From page 44... ...
Further, it is critical to maintain and expand networks of monitoring programs that provide long-term records of physical and chemical characteristics of inland aquatic ecosystems. These records allow us to extend current understanding of aquatic ecosystems to the appropriate hydrologic time scales and will allow for resolution of water resource issues through a process of "knowledge-based" consensus at local and regional scales.
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From page 45... ...
As we gain a greater scientific understanding of aquatic ecosystems, it is apparent that the quality of aquatic ecosystems influences not only the resident aquatic biota but also the quality of a water body as a water resource. These interactions can be represented as healthy aquatic ecosystems providing "goods and services" to the other users of water resources, as shown in Figure 1.
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From page 46... ...
In this paper, hydrology is intended to include the study of the hydrologic cycle and physical processes controlling the movement of water in surface and ground waters. Limnology is broadly defined as an integrative discipline applying physics, chemistry, and biology to study inland aquatic ecosystems, which include streams, rivers, lakes, reservoirs, and wetlands.
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From page 47... ...
Further, new conceptual advances were rapidly employed as water resource systems were developed and refined. The most remarkable changes to aquatic ecosystems, as a result of human activity, came with the development of agriculture.
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From page 48... ...
Although limnology is often viewed as a subset of ecology, the two fields developed in parallel (Golley,1993~. While the ecosystem concept is credited to Tansley, limnologists had previously voiced similar ideas that coupled the biota to their physical environment.
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From page 49... ...
In addition to organizations conducting research, the Western Water Policy Review Advisory Commission estimates that there are currently 550 watershed stakeholders' groups in the western United States alone. The RCC was used in the design of the National Water Quality Assessment (NAWQA)
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(1980~. Reprinted, with permission, from Canadian Journal of Fisheries and Aquatic Science.
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From page 51... ...
Another reason for this disparity may be that the time scales over which hydrology controls aquatic ecosystems are so long that these controls are not observed by hydrologists during short-term field studies. However, now that dams have been built and hydrologists are involved in studies of geomorphic and ecological changes associated with the modified flow regimes and lowered water tables, this situation is likely to change.
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From page 52... ...
In general, the hydrologic residence time of water, which controls the transport of solutes, organisms, and suspended particulates, may be short relative to the time scales of dominant ecosystem interactions between organisms or between organisms and their environment. As a result, in many aquatic ecosystems the flux of water, material, and organisms moving through the control volume in a unit of time characteristic of important processes may be large relative to the quantity contained within the control volume.
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From page 53... ...
This hypothesis emphasizes the connection of the stream ecosystem to its floodplain, and implicates flooding as a major control on aquatic biota such as fish. Aquatic ecosystems in the United States have experienced considerable change as a result of flow regulation and other hydrological alterations in rivers.
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From page 55... ...
Grand Canyon has provided scientific understanding that will support new approaches for regulating flow to achieve environmental and power generation
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From page 56... ...
FIGURE 6 Potential effect of climatic changes from a doubling of atmospheric carbon dioxide of the niche volume for fish in selected temperate lakes. Source: Reprinted, with permission, DeStasio et al.
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From page 57... ...
The regional trend of the duration has also been studied using remote sensing data, one of the concrete ways to quantify the changes in freshwater ecosystems that are driven by changing climatic conditions. Beyond the observed trends in the duration of ice cover, a fundamental physical understanding of the processes linking climate and ice cover is critical to predicting the changes in ice cover that might occur in response to the buildup of carbon dioxide in the atmosphere.
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From page 58... ...
different energy flux terms representing the climate/ice cover linkage in the LIMNOS numerical lake ice model (Vavrus et al., 1996~. By using sensitivity analysis, it was shown that the ice-off date was more sensitive to atmospheric
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From page 59... ...
Ground Water Ecosystems Ground water is the largest reservoir of liquid freshwater in the world. It is an important water resource that is affected by a range of human activities (Freeze and Cherry, 1979~.
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From page 60... ...
past several decades that ground water has been studied as an aquatic ecosystem (Ghiorse, 1997~. Ground water ecosystems differ from surface water ecosystems in that the surface area of the solid phases is very high relative to the volume of the water.
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From page 61... ...
Although such field experiments are quite resource intensive, they provide for the coupling of the hydrologic and microbial processes, yielding more definitive information about the process rates in ground water ecosystems. These field-scale experiments are a critical tool for studying ground water contamination and designing in situ ground water remediation.
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From page 62... ...
Regulations coming into effect in the next few years are more sophisticated, addressing the production of harmful chlorinated organic compounds during chlorination of drinking water. While advances were made in some areas of water resources in the midcentury, the quality of many surface waters deteriorated because of municipal and industrial pollution.
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From page 63... ...
Generic water quality standards will be replaced by site-specific or regional aquatic life criteria. Recent first steps in regional assessments include the report on aquatic ecosystems to the Western Water Policy Review Advisory Commission (Minckley, 1997)
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From page 64... ...
For a "knowledge-based" consensus to take hold among different competing interests involved in a water resource issue, some hydrologic records are required to form a basis for interpretation of other information. SUMMARY Aquatic ecosystems are defined by hydrologic processes.
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From page 65... ...
We should not let the budget ax fall now when these data can be used effectively to achieve "knowledge-based consensus" in the management of specific freshwater resources. ACKNOWLEDGMENTS I acknowledge helpful discussions with D
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From page 66... ...
1997. Aquatic Ecosystems Symposium.
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